U.S. ENVIRONMENTAL PROTECTION AGENCY
       Annapolis Field Office
      Annapolis Science Center
     Annapolis, Maryland  21401
         TECHNICAL REPORTS
           Volume  4

-------

-------
                      Table of Contents


                          Volume 4



29         Step Backward Regression
31          Relative Contributions of Nutrients to the
           Potomac River Basin from Various Sources
33         Mathematical  Model  Studies of Water Quality
           in the Potomac Estuary
35         Water Resource - Water Supply Study of the
           Potomac Estuary

-------

-------
                            PUBLICATIONS

                U.S.  ENVIRONMENTAL PROTECTION AGENCY
                             REGION III
                       ANNAPOLIS FIELD OFFICE*


                              VOLUME 1
                          Technical  Reports


 5         A Technical  Assessment of Current Water Quality
           Conditions and Factors Affecting Water Quality in
           the Upper Potomac Estuary

 6         Sanitary Bacteriology of  the Upper Potomac Estuary

 7         The Potomac Estuary Mathematical Model

 9         Nutrients in the Potomac  River Basin

11         Optimal  Release Sequences for Water Quality Control
           in Multiple Reservoir Systems


                              VOLUME 2
                          Technical  Reports


13         Mine Drainage in the North Branch Potomac River Basin

15         Nutrients in the Upper Potomac River Basin

17         Upper Potomac River Basin Water Quality Assessment


                              VOLUME  3
                          Technical  Reports


19         Potomac-Piscataway Dye Release and Wastewater
           Assimilation Studies

21         LNEPLT

23         XYPLOT

25         PLOT3D


     * Formerly CB-SRBP, U.S. Department of Health, Education,
       and Welfare; CFS-FWPCA, and CTSL-FWQA,  Middle Atlantic
       Region, U.S. Department of the Interior

-------
                             VOLUME  3   (continued)

                         Technical Reports


27         Water Quality and Wastewater Loadings - Upper Potomac
           Estuary during 1969


                             VOLUME  4
                         Technical Reports


29         Step Backward Regression

31         Relative Contributions of Nutrients to the Potomac
           River Basin from Various Sources

33         Mathematical Model Studies of Water Quality in the
           Potomac Estuary

35         Water Resource - Water Supply Study of the Potomac
           Estuary

                             VOLUME 5
                         Technical Reports


37         Nutrient Transport and Dissolved Oxygen Budget
           Studies in the Potomac Estuary

39         Preliminary Analyses of the Wastewater and Assimilation
           Capacities of the Anacostia Tidal River System

41         Current Water Quality Conditions and Investigations
           in the Upper Potomac River Tidal System

43         Physical Data of the Potomac River Tidal System
           Including Mathematical Model Segmentation

45         Nutrient Management in the Potomac Estuary


                             VOLUME 6

                         Technical Reports


47         Chesapeake Bay Nutrient Input Study

49         Heavy Metals Analyses of Bottom  Sediment in the
           Potomac River Estuary

-------
                                  VOLUME  6  (continued)

                              Technical  Reports

     51         A System of Mathematical Models for Water Quality
                Management

     52         Numerical Method for Groundwater Hydraulics

     53         Upper Potomac Estuary Eutrophication Control
                Requirements

     54         AUT0-QUAL Modelling System

Supplement      AUT0-QUAL Modelling System:  Modification for
   to 54        Non-Point Source Loadings

                                  VOLUME  7
                              Technical  Reports

     55         Water Quality Conditions in the Chesapeake Bay System

     56         Nutrient Enrichment and  Control Requirements in the
                Upper Chesapeake Bay

     57         The Potomac River Estuary in the Washington
                Metropolitan Area - A History of its Water Quality
                Problems and their Solution

                                  VOLUME  8
                              Technical Reports

     58         Application of AUT0-QUAL Modelling System to the
                Patuxent River Basin

     59         Distribution of Metals in Baltimore Harbor Sediments

     60         Summary and Conclusions - Nutrient Transport and
                Accountability in the Lower Susquehanna River Basin

                                  VOLUME  9
                                 Data Reports

                Water Quality Survey, James River and Selected
                Tributaries - October 1969

                Water Quality Survey in the North Branch Potomac River
                between Cumberland and Luke, Maryland - August 1967

-------
                            VOLUME 9  (continued)

                           Data Reports


           Investigation of Water Quality in Chesapeake Bay and
           Tributaries at Aberdeen Proving Ground, Department
           of the Army, Aberdeen, Maryland - October-December 1967

           Biological Survey of the Upper Potomac River and
           Selected Tributaries - 1966-1968

           Water Quality Survey of the Eastern Shore Chesapeake
           Bay, Wicomico River, Pocomoke River, Nanticoke River,
           Marshall Creek, Bunting Branch, and Chincoteague Bay -
           Summer 1967

           Head of Bay Study - Water Quality Survey of Northeast
           River, Elk River, C & D Canal, Bohemia River, Sassafras
           River and Upper Chesapeake Bay - Summer 1968 - Head ot
           Bay Tributaries

           Water Quality Survey of the Potomac Estuary - 1967

           Water Quality Survey of the Potomac Estuary - 1968

           Wastewater Treatment Plant Nutrient Survey - 1966-1967

           Cooperative Bacteriological Study - Upper Chesapeake Bay
           Dredging Spoil  Disposal - Cruise Report No. 11

                            VOLUME 10

                           Data Reports

 9         Water Quality Survey of the Potomac Estuary - 1965-1966

10         Water Quality Survey of the Annapolis Metro Area - 1967

11         Nutrient  Data on Sediment Samples of the Potomac Estuary
           1966-1968

12         1969  Head  of  the Bay Tributaries

13         Water Quality Survey of the Chesapeake Bay in the
           Vicinity  of  Sandy  Point - 1968

14         Water Quality Survey  of the Chesapeake Bay in the
           Vicinity  of  Sandy  Point - 1969

-------
                             VOLUME 10(continued)
                           Data Reports

15         Water Quality Survey of the Patuxent River -  1967

16         Water Quality Survey of the Patuxent River -  1968

17         Water Quality Survey of the Patuxent River -  1969

18         Water Quality of the Potomac Estuary Transects,
           Intensive and Southeast Water Laboratory Cooperative
           Study - 1969

19         Water Quality Survey of the Potomac Estuary Phosphate
           Tracer Study - 1969

                             VOLUME 11
                            Data Reports

20         Water Quality of the Potomac Estuary Transport  Study
           1969-1970

21         Water Quality Survey of the Piscataway Creek Watershed
           1968-1970

22         Water Quality Survey of the Chesapeake Bay in the
           Vicinity of Sandy Point - 1970

23         Water Quality Survey of the Head of the Chesapeake Bay
           Maryland Tributaries - 1970-1971

24         Water Quality Survey of the Upper Chesapeake Bay
           1969-1971

25         Water Quality of the Potomac Estuary Consolidated
           Survey - 1970

26         Water Quality of the Potomac Estuary Dissolved  Oxygen
           Budget Studies - 1970

27         Potomac Estuary Wastewater Treatment Plants Survey
           1970

28         VJater Quality Survey of the Potomac Estuary Embayments
           and Transects - 1970

29         Water Quality of the Upper Potomac Estuary Enforcement
           Survey - 1970

-------
   30


   31


   32
   33
   34
Appendix
  to 1
Appendix
  to 2
    3


    4
                  VOLUME 11  (continued)
                 Data Reports

Water Quality of the Potomac Estuary - Gilbert Swamp
and Allen's Fresh and Gunston Cove - 1970

Survey Results of the Chesapeake Bay Input Study -
1969-1970

Upper Chesapeake Bay Water Quality Studies - Bush River,
Spesutie Narrows and Swan Creek, C & D Canal, Chester
River, Severn River, Gunpowder, Middle and Bird Rivers -
1968-1971

Special Water Quality Surveys of the Potomac River Basin
Anacostia Estuary, Wicomico .River, St. Clement and
Breton Bays, Occoquan Bay - 1970-1971

Water Quality Survey of the Patuxent River - 1970

                  VOLUME 12

               Working Documents

Biological Survey of the Susquehanna River and its
Tributaries between Danville, Pennsylvania and
Conowingo, Maryland

Tabulation of Bottom Organisms Observed at Sampling
Stations during the Biological Survey between Danville,
Pennsylvania and Conowingo, Maryland - November 1966

Biological Survey of the Susquehanna River and its
Tributaries between Cooperstown, New York and
Northumberland, Pennsylvnaia - January 1967

Tabulation of Bottom Organisms Observed at Sampling
Stations during the Biological Survey between Cooperstown,
New  York and Northumberland, Pennsylvania - November 1966

                  VOLUME 13
               Working Documents

 Water  Quality and  Pollution Control Study, Mine Drainage
 Chesapeake  Bay-Delaware  River Basins - July 1967

 Biological  Survey  of  Rock Creek  (from Rockville, Maryland
 to  the Potomac River)  October 1966

-------
                             VOLUME   13   (continued)

                          Working  Documents

 5         Summary of Water Quality  and  Waste  Outfalls,  Rock  Creek
           in Montgomery County, Maryland and  the  District of
           Columbia - December  1966

 6         Water Pollution Survey  -  Back River 1965  -  February  1967

 7         Efficiency Study of  the District  of Columbia  Water
           Pollution Control  Plant - February  1967

                             VOLUME   14

                          Working  Documents

 8         Water Quality and  Pollution Control  Study - Susquehanna
           River Basin from Northumberland to  West Pittson
           (Including the Lackawanna River Basin)  March 1967

 9         Water Quality and  Pollution Control  Study,  Juniata
           River Basin - March  1967

10         Water Quality and  Pollution Control  Study,  Rappahannock
           River Basin - March  1967

11         Water Quality and  Pollution Control  Study,  Susquehanna
           River Basin from Lake Otsego, New York, to  Lake Lackawanna
           River Confluence,  Pennsylvania -  April  1967

                             VOLUME  15
                          Working  Documents

12         Water Quality and Pollution  Control  Study,  York  River
           Basin - April  1967

13         Water Quality and Pollution  Control  Study,  West  Branch,
           Susquehanna River Basin -  April 1967

14         Water Quality and Pollution  Control  Study,  James River
           Basin - June 1967 ,

15         Water Quality and Pollution  Control  Study,  Patuxent  River
           Basin - May 1967

-------
                             VOLUME 16

                          Working Documents

16         Water Quality and Pollution Control  Study,  Susquehanna
           River Basin from Northumberland, Pennsylvania,  to
           Havre de Grace, Maryland - July 1967

17         Water Quality and Pollution Control  Study,  Potomac
           River Basin - June 1967

18         Immediate Water Pollution Control  Needs, Central  Western
           Shore of Chesapeake Bay Area (Magothy, Severn,  South, and
           West River Drainage Areas)  July 1967

19         Immediate Water Pollution Control  Needs, Northwest
           Chesapeake Bay Area (Patapsco to Susquehanna Drainage
           Basins in Maryland) August 1967

20         Immediate Water Pollution Control  Needs - The Eastern
           Shore of Delaware, Maryland and Virginia - September 1967

                             VOLUME 17
                           Working Documents

21         Biological Surveys of the Upper James River Basin
           Covington, Clifton Forge, Big Island, Lynchburg, and
           Piney River Areas - January 1968

22         Biological Survey of Antietam Creek and some of its
           Tributaries from Waynesboro, Pennsylvania to Antietam,
           Maryland - Potomac River Basin - February 1968

23         Biological Survey of the Monocacy River and Tributaries
           from Gettysburg, Pennsylvania, to Maryland Rt. 28 Bridge
           Potomac River Basin - January 1968

24         Water Quality Survey of Chesapeake Bay in the Vicinity of
           Annapolis, Maryland - Summer 1967

25         Mine Drainage Pollution of the North Branch of Potomac
           River - Interim Report - August 1968

26         Water Quality Survey in the Shenandoah River of the
           Potomac River Basin - June 1967

27         Water Quality Survey in the James and Maury Rivers
           Glasgow,  Virginia - September 1967

-------
                             VOLUME  17  (continued)
                           Working Documents

28         Selected Biological  Surveys in the James River Basin,
           Gillie Creek in the  Richmond Area, Appomattox River
           in the Petersburg Area, Bailey Creek from Fort Lee
           to Hopewell - April  1968

                             VOLUME  18
                           Working Documents

29         Biological  Survey of the Upper and Middle Patuxent
           River and some of its Tributaries - from Maryland
           Route 97 Bridge near Roxbury Mills to the Maryland
           Route 4 Bridge near Wayson's Corner, Maryland -
           Chesapeake Drainage Basin - June 1968

30         Rock Creek Watershed - A Water Quality Study Report
           March 1969

31         The Patuxent River - Water Quality Management -
           Technical Evaluation - September 1969

                             VOLUME 19
                          Working Documents

           Tabulation, Community and Source Facility Water Data
           Maryland Portion, Chesapeake Drainage Area - October 1964

           Waste Disposal Practices at Federal  Installations
           Patuxent River Basin - October 1964

           Waste Disposal Practices at Federal  Installations
           Potomac River Basin below Washington, D.C.- November 1964

           Waste Disposal Practices at Federal  Installations
           Chesapeake Bay Area of Maryland Excluding Potomac
           and Patuxent River Basins - January 1965

           The Potomac Estuary - Statistics and Projections -
           February 1968

           Patuxent River - Cross Sections and Mass Travel
           Velocities - July 1968

-------
                            VOLUME  19 (continued)

                         Working Documents

          Wastewater Inventory - Potomac River Basin -
          December 1968

          Wastewater Inventory - Upper Potomac River Basin -
          October 1968

                            VOLUME 20
                         Technical Papers^

 1         A Digital Technique for Calculating and Plotting
          Dissolved Oxygen Deficits

 2         A River-Mile  Indexing System for Computer Application
          in Storing and Retrieving Data      (unavailable)

 3         Oxygen Relationships in Streams, Methodology to be
          Applied when  Determining the Capacity of a Stream to
          Assimilate Organic Wastes - October 1964

 4         Estimating Diffusion Characteristics of Tidal Waters -
          May  1965

 5         Use  of Rhodamine B Dye as a Tracer in Streams of the
          Susquehanna River Basin - April 1965

 6         An  In-Situ Benthic Respirometer - December 1965

 7         A Study of Tidal Dispersion in the Potomac River
          February  1966

 8         A Mathematical Model for the Potomac River - what it
          has  done  and  what it can do - December 1966

 9         A Discussion  and Tabulation of Diffusion Coefficients
          for  Tidal Waters Computed as a Function of Velocity
          February  1967

10         Evaluation of Coliform  Contribution by Pleasure Boats
          July 1966

-------
                            VOLUME  21

                         Technical Papers

11        A Steady State Segmented Estuary Model

12        Simulation of Chloride Concentrations in the
          Potomac Estuary - March 1968

13        Optimal Release Sequences for Water Quality
          Control in Multiple-Reservoir Systems - 1968

                            VOLUME  22
                         Technical  Papers

          Summary Report - Pollution of Back River - January 1964

          Summary of Water Quality - Potomac River Basin in
          Maryland - October 1965

          The Role of Mathematical  Models in the Potomac River
          Basin Water Quality Management Program - December 1967

          Use of Mathematical Models as Aids to Decision Making
          in Water Quality Control  - February 1968

          Piscataway Creek Watershed - A Water Quality Study
          Report - August 1968


                            VOLUME  23
                        Ocean Dumping Surveys

          Environmental  Survey of an Interim Ocean Dumpsite,
          Middle Atlantic Bight - September 1973

          Environmental  Survey of Two Interim  Dumpsites,
          Middle Atlantic Bight - January 1974

          Environmental  Survey of Two Interim Dumpsites
          Middle Atlantic Bight - Supplemental Report -
          October 1974

          Effects of Ocean Disposal Activities on Mid-
          continental Shelf Environment off Delaware
          and Maryland - January 1975

-------
                            VOLUME 24

                           1976 Annual
               Current Nutrient Assessment - Upper Potomac Estuary
               Current Assessment Paper No.  1

               Evaluation of Western Branch Wastewater Treatment
               Plant Expansion - Phases I and II

               Situation Report - Potomac River

               Sediment Studies in Back River Estuary, Baltimore,
               Maryland

Technical      Distribution of Metals in Elizabeth River Sediments
Report 61

Technical      A Water Quality Modelling Study of the Delaware
Report 62      Estuary

-------
    Chesapeake Technical Support Laboratory
             Middle Atlantic Region
Federal Water Pollution Control Administration
        U.S. Department of the Interior
             Technical Report No. 29
                 STEP BACKWARD REGRESSION
                            by
                     Gary I. Seiner*
                       August 1969
               ^Revised by Paul R. Dorn
               Johan A. Aaltos  Chief8  CTSL
       Herbert A. Jaworski,  Chief,  Engineering Section
               Richard Burkett,  Draftsman

-------
                         TABU: OF CONTENTS






                                                              Page



Program  .	°  1



Abstract 	 .......  1



Description	,	2



Restrictions 	  ....  5




Program Run Preparation	  6



JOB card	  7



System Control Cards	.10




Header Card	  . 13



Options	IH




Column Identifier Cards  	 .  	   ...... 15



Row Selector Cards	,	16



Column Selector Cards  	  ... 17



Minimum Number of Variables Card	  .  . 18



Residual Start Card	 19



Output	  . 20



Sample Output  	  .  	  ........ 21

-------

-------
PROGRAM;  STEP BACKWARD REGRESSION






ABSTRACT;  This program performs a multiple regression analysis and



provides related statistics on a STATPAC data matrix or on a subset



of that matrix formed by the selection of rows and columns of the



matrix.  If desired, the regression may proceed stepwise where, at



each step, the least significant independent variable is deleted



from the regression equation.   The regression residuals may also be



computed.

-------
BESTRICTIONS;



     The input matrix may have a maximum size of 99999 rows and



199 columns.  The maximum size of the subset selected for a re-



gression analysis is 99999 rows and 99 columns.

-------
PROGRAM RUE PREPARATION;



     The follawing is a complete deck setup for this program;



1.  JOB card



2.  System control cards



3-  Header card



It-.  Column selector cards*



5.  Row selector cards*



6.  Minimum number of variables card *



T.  Residual start card*



8.  Delimeter






*0ptional--see the individual sections on the various cards.








If more than one run is to be performed, repeat cards 3-7 as



necessary; the final card should "be delimiter card.

-------
 JOB CARD:


      The JOB card cannot be catalogued and  is  installation as well

 as machine dependent.   Below is the  specification  for the 360/Model

 65 located in the Department of the  Interior building,  in Washing-

 ton, D.C.   The structure of the JOB  card changes occasionally,  and

 one should check with  the computer center "before using  the below

 form.


 Card 1 -

 Card Columns                                  Contents


 1-2                    //

 3                        Center Code:
                                     D = Denver, Colorado
                                     F = Flagstaff,  Arizona
                                     I = Crystal Plaza, Virginia
                                     M = Menlo Park, California
                                     R = Rolls, Missouri
                                     W = Washington, B.C.

 4 - 5                    Agency Code

 6-8                    User registration  code.

 9-10                   User's ID,  May be changed  by  the user as
                          desired.  Do  not use  the  same  two charac-
                          ters for  different jobs run during the
                          same day.

11                        Blank.

12 - 14                   JOB (i.e. the word JOB).

-------

-------
Card Columns                                Contents

 1.5                      Blank.

 16                      (   (Left parenthesis)„

 17 - 20                 Program Number

 21                      ,   (Comma)„

 22 - 25                 Auxiliary account number.

 26                      .»   (Comma).

 27 - 30                 Estimated execution time in minutes.  Re-
                         quires four numeric digits.

 31                      ,   (Comma).

 32 - 35                 Estimated lines of print expressed in
                         thousands of lines.  Requires four
                         numeric digits„

 36                      ,   (Comma).

 3? - 1*0                 Estimated number of cards to be punched.
                         Requires four numeric digits.

 41                      ,   (Comma),

 42                      Reserved for future use; must "be a I
                         punch.

 43                      ,   (Comma).

 44                      Reserved for future use; must "be a 1
                         punch.

 4,5                      ,   (Comma).

 46                      Type of Run:
                                      C = Compile only
                                      T = Test of program
                                      P = Production use of program

-------
                                                               9
Card Columns

 47

 48 - 49
                                            Contents
50

51

52

53 -

62

63

64

72
    - 71
                            (Comma),
Number of lines per page.  A value of
zero suppresses page overflow tests „  If
this field (and the preceding comma) is
eliminated, a default option of 6l lines
per page is used.  In this case the
following fields are shifted left 3 col-
umns.  (Except columns 62-72.)

)   (Right parenthesis)„

,   (Comma).

1   (Apostrophe).

Name of the user-

1   (Apostrophe).

,   (Comma).

Blank.

X   (The letter X).
Card 2 -

Card Columns

  1-2

  3 - 15

 16 - 25

 26

 27 - 33

 34 - 72
                        II

                        Blank.

                        MSGEEVEL-1

                        ,    (Comma),

                        CLASS=C

                        Blank.
                                            Contents

-------
                                                              10
SYSTEM CONTROL CARDS;


     Cards 1 & 2;

  (a) If the object deck is used -
1
//"bEXECbLIHKFORT ^REGION. GO=252K /TIME. G0=J
//IKEDoSYSBTbDDb*

where J is the time required to run the program(in minutes).  The
'b' stands for a blank space.  Next comes the object deck (includ-
ing its delimiter).

  (b) If the source deck is used -

1
//bEXECbFORTGCLG, PARM.FORT=' DECK', REGION. GO=252K ,TIMB. G0=J
//FORT.SYSlNbDDb*

where J is as before.  Next comes the source deck (including its
delimeter).
     Cards 3 & ki

  (a) If the data resides on the disc SYSDK -

1                                               PASS
//GO. PT10F001bDDbDSN=&NAME ,UNIT=SYSDY ,DISP=(OLD .>HS][BTE ^DELETE),
//bDCB=(RECFM=VB,IEECL=RRR.,BIKSIZE=BBBB)

where SsNAME is the name of the storage space.  (The '&' signifies
the storage is temporary--it only exists for the extent of the job.)
PASS is used if the data file is used later on; otherwise use DELETE.

The letters 'RRR' and  'BBBB' are computed as follows:

     RRR   » 8M + 2k where M = number of columns in the data matrix.

     BBBB  = K(RRR) + k where K is an integer chosen so that the
             positive difference (7200-BBBB) is as small as possible.

-------
                                                              11
  (b) If the data resides on magnetic tape -

1
                                =( ,SL) ,,VOLUME=( ,HRTAIN, , ,
//bDISP«(OIJ),KEEP) ,DSP=STAPAC

where  'THYYY' in the first tape card represents a six digit in-
put tape number (leading zeros must be given).

The letters  'RRR' and 'BBBB' are as before,

When a tape is used, a tape setup card is required.  Its form is:

Card Columns                                 Contents

  1-9                  /*MESSAGE

 10 - 12                 Blank.

 13 - 20                 The same characters as in columns 3-10
                         of the JOB card.

 21 - 22                 Blank.

 23 - 2?                 SETUP.

 28 - 29                 Blank.

 30 - 36                 The number of the tape used.

 37 - 38                 /9

     If the tape is written on as well as read,, in column 39; place

an R (for ring in).  This card should be placed right after the JOB

card.  (This card's format is particular to the 360/65 in Washington,

B.C.)

-------

-------
                                                                12
     Card 5:

1
//GOoSYSINbDIJb*

-------
HEADER CARDs
                                                             13
Columns
 1-30
Format   Entj
7A4,A2   TITIE
31-38
39-43
VT-56

T3-TT
15


13



1011

15
         INPUT ID
INFJT N
                      INPUT M
OPTION
FROH
T8-8Q
13
PROM
Description

Up to 30 characters of alphanumeric
information used to title the out-
put for this data set.  It is also
used when listing the total number
of plots created.  It is not'used
on the graph.

Up to 8 characters of alphanumeric
information used to identify the
input data set.

The number of rows in the input
data matrix.  (Right justified.)

The number of columns in the in-
put data matrix.  (Right justified,
199-)

See the following sheet.

The number of pairs of row numbers
needed to select the desired rows
of the input matrix.  If blank,
all rows are included„  If not
blank, this number must be right
justified and row selector cards
must be included.

The number of pairs of column num-
bers needed to select the desired
columns in the input data matrix.
(if blank, all columns are inclu-
ded.  If not blank, this number
must be right justified and column
selector cards must be provided.)

-------
OPTIONS -

            0 - No stepwise deletion of variables
OPTION( 1) -}_ _ Deletion of least significant variable occurs
                until the program reaches minimum specified,

            0 - No action taken.
OPTIOW( 2) -JL _ Residual analysis performed starting with all
                variables present; continues until stepwise
                deletion stops.
OPTION( 3) -2 - Residual analysis performed starting with num-
                ber of variables specified on Residual start
                card.

            0 - Indeterminants not allowed in the selected data
OPTION( 4) -i _ observations having indeterminants in selected
                data are skipped.
OPTIONf 5) _° - No action taken
      ^ ^'  1 - Residual analysis doen using antilog transform
                of dependent variable.

OETION( 6) - NOT USED

0!TION( 7) - NOT USED

0!TION( 8) - NOT USED


            0 - Input tape unit is 10.
OPTION( 9) -]__9 Thls is the input tape unit.


            0 - Use the variable identifiers on the STATPAC tape
OPTION(10) -]_ _ Read in new varia-bie identifiers from cards.

-------
COLUMN IDENTIFIER CARDS:




     These cards are used only if OPTION(lO)=l on the header




card.  They permit the user to associate an eight character




identifier with each column in the data matrix.   Ten identi-




fiers can "be used per card; if more then ten identifiers  are




needed, they are continued on another card.   The numbers  above




the eight card column fields indicate the columns in the  data




matrix the identifiers are associated with.   One identifier




must be specified for each column in the output  data matrix.

-------
                                                            16
ROW SELECTOR CARDS;




     These cards are used only if FRON on the header card is




not blank.  The number entered in the field FRON specifies how




many pairs of row numbers are used to select desired rows of a




data matrix.  Each pair specifies the rows FROM and including




the first member of the pair TO and including the last member




of the pair will be selected.  The pairs must be entered




starting in the left most field of the card and continuing a-




cross eight pairs per card   If more pairs are used, continue




on another card.  The first member of the pair is entered under




the word "FROM" and the second member of the pair entered under




"TO."  Except for the selection of a single row (where the "TO"




portion is left blank) the row numbers must form an increasing




sequence, i.e., rows must be selected in the order they appear




in the data matrix.

-------
                                                            17
COLUMN SEUSCTOB CARDS;




     These cards are used only if ERON on the header card is




not blank.  The number entered in the field PROW specifies




how many pairs of column numbers are used to select desired




columns of a data matrix.  The instructions for their use is




identical to the select row cards except that thirteen pairs




per card are used and the columns need not be selected in in-




creasing order.

-------
                                                           18
MINIMUM NUMBER OF VARIABLES CARD;

This card is used if OPTIOH(3,) is non-zero.  It gives the

minimum number of variables (including the dependent variable)

at which stepwise deletion is to cease.

     Its format is:

Columns    Format    Entry    Description

 1 - h       Ik        K      The minimum number of variables
                              (including the dependent variable
                              on which the regression is to be
                              performed.  The stepwise deletion
                              stops when M' is less than K.
                              (K must be punched right justified.)

-------

-------
                                                          19
RESIDUAL START CARD;






     This card is used if OETION(2) is a two,  and OPTION(l)  is



non-zero.  It gives the number of variables (including the de-



pendent variables) at which residual analysis  is to be performed,



Its format is the same as the MINIMUM NUMBER OF VARIABLES CARD.

-------
                                                           20
OUTPUT:



Output to this program is a printed table of means, standard



deviations, variance-covariance,,  the correlation matrix, mul-



tiple correlation coefficients (and degrees freedom), regress-



ion coefficients,, regression weights, regression constants,,




standard errors of the regression weights and tests of signi-



ficance, variables deleted (if any), residuals and sums of



the squares of the residuals if requested, and the standard



error of the estimate of the dependent variable.

-------
                                                                 21
Appendix; Sample Output

-------
Or
«5
>
O
i"
                          a     ~
                         o
                         u
          0
          "' X
          >•- a
          o

-------
                         of  u
                         OJ  LU
                         a;  tr.
                         o  o
                         u.  o
                                           o      c-

                                           LJ      a
                                           o  >  •"..
                                               LU
                                           nor
o
o
o
•n   D
v-  >
o  r>

-------
                         O
                         in
o
o
o
                 o
                 CJ
               o
               o
o
O  rt O CC  O
 I   u. \f\ Uj  rj
UJ  o 
^  D cc rs  10
<  2-   • 2-   .
—•     CJ     O
Cf  "»     ^|
<  o     o
>  tf     or

-------
              O
              O
              O
r     -t     o
       o     o
7.
o  or o UL  r-
•«  in o u *  r J
»-  an o a.'  —
<  )  o y  u^
-J  II -• D  ro
nt
O
              O

-------
                                             i  O

                                               o
                         -•  I
                         o  o

      ' h?

       •3
                                    U


                                    UJ
o

u.
c
   a.  c
1  X     u.     V-  C5
•  o     u     *^
.  —•     uj     S  n
«  u:  O r   o C '  C~
  "C  O O  O <_>  JL -<
)                    j O
•  7*  Uj 7*  u' ^'  u.  |
'<  O  FNJ CJ  O C      U)

.  t/1  l/^ CO  JJ LO  CX °Q
      m i/l  —^ 1/1  < (j-
  u/   »iu   "U-tiir1
      O  X.  O LI  ^*   •
                                       O I
                                       o
                                           C' r?
Q
r*

O

-------
     ee-c-c'C'i-'oc'r  o o o c  o  c
     i   i   i   i   I   i   i   i    i   i   i   i   i    i   i
                                                                           U-> a
                                                                           a  u
C

 I

UJ

IT

C-J

(V,
                                                                           c z
                                                                           V Ul
                                                                           OC »_;
                                                                           < 0
                                                                                       a
                                                                                       •a
                                                iv,  r-   e         i   i   t    i    i    i   i    i    i    i    i   i
u  Ij  1.   u  I'  L  L   U  U   "  U   I.   U   L.   L:  u
 r  u*  C' ^3  ^, f^  ^?  a   fv,  "• •  "^  ^  ^  O  3T c
^TsTi/-  A.  /*-^H^r-rri'-1j-r--^.r-   "^C

"VJ C' tr ^ '  <7  ^  C  fvj  (Y  f^  -   C  ^  — *  i.* -*
Jf-j^C-C^Vy-^-—  f"  rv,  .C  ~  C1  — ^C
            fv.  — ~
                         I    I    I    I    I
                                                                                       O
                                                                                       ,c
o  c  c-  c   •:•  r~-  c-  c   '.'   c~   o  c-   <•   roc   '_  c c
                                                                                      a-

                                                                                      ^T-
                                                                                      o
                                                                                      o
                                                                                      r~
                                                                                      o
                                                                                      a-
                                                                                      o-
                                                                                      a-
                                                                                              LL)  O

                                                                                              C  -J

                                                                                              Z  U-
                                                                                              o
                                                                                              2"  O-

-------

-------
RELATIVE CONTRIBUTIONS OF NUTRIENTS




    TO THE POTOMAC RIVER BASIN




       FROM VARIOUS SOURCES*




     Technical Report No. 31




         January 1970

-------

-------
       Chesapeake Technical Support Laboratory
                Middle Atlantic Region
    Federal Water Pollution Control Administration
            U.S. Department of the Interior
           RELATIVE CONTRIBUTIONS OF NUTRIENTS

               TO THE POTOMAC RIVER BASIN

                  FROM VARIOUS SOURCES*


                 Technical Report No. 31
                   Norbert A.  Jaworski
                           and
                    Leo J. Hetling**

                      January 1970
 * Presented at the Cornell Agricultural Waste Management
   Conference,  January 19-21,  1970,  Rochester, New York

** Director, Research Unit, Division of Environmental
   Health Services, New York State Department of Health

-------

-------
                        TABLE OF CONTENTS

                                                            Page

LIST OF TABLES                                               11

LIST OF FIGURES                                             ill

INTRODUCTION                                                  1

A DESCRIPTION OF THE POTOMAC RIVER BASIN                      2

NUTRIENT SOURCES                                              4

     A.  Sampling Programs                                    It-

     's.  Wastewater Loadings in the Potomac Basin             7

     C.  Land Runoff and Other Sources                        9

     D.  Relative Contribution of Loadings                   18

     E.  Temporal Variations                                 21

     F.  Comparison to Other River Basins in the
           Middle Atlantic Region                            27

     G.  Hudson River Basin System                           31

SUMMARY AND CONCLUSIONS                                      33

REFERENCES                                                   36

-------
                                                             ii
                        LIST OF TABLES
Number                      Table


  I         Nutrient Loadings from Wastewater Discharges       8
              by Sub-Regions

 II         Nutrient Loadings from Watersheds with            12
              Varying Land Use

III         Comparison of Annual Average Nutrient             13
              Concentrations and Loadings

 IV         Estimated Nutrient Loadings from Land             IT
              Runoff - Potomac River Basin

  V         Estimated Total Potomac Basin Nutrient            20
              Loading

 VT         Comparison of Nutrient Loadings in Hudson         32
              and Potomac River Basins

-------
                                                                ill
                           LIST OF FIGURES
Number                         Figure

  1           Major Municipal Wastewater Discharges
                Potomac River Basin                              3

  2           Nutrient Network - Potomac River Basin             5

  3           Chesapeake Bay Nutrient Input Stations             6

  k           Land Use Comparison - Total Phosphorus PO,
                Potomac River Basin  1966                       10

  5           Land Use Comparison - NOp+NO,, as N - Potomac
                River Basin  1966         J                     11

  6           South Branch Potomac River at Petersburg,
                West Virginia - TKN, N02+N0  and PO^ vs
                River Discharge            -*                    15

  7           Potomac River Basin Nitrate Nitrogen Loadings
                at Great Falls, Maryland  19^7-196?             23

  8           Nutrient Loadings and River Discharges -
                Potomac River at Great Falls, Md.  1966         2k

  9           Phosphorus Loadings - Potomac River at
                Great Falls, Md.  1969                          25

 10           Nitrogen Loadings - Potomac River at
                Great Falls, Md.  1969                          26

 11           Chesapeake Bay Nutrient Inputs - Total P0>
                as PO.  - Monthly average                        28

 12           Chesapeake Bay Nutrient Inpurs - N02+N0_ as N
                Monthly average                                 29

 13           Chesapeake Bay Nutrient Inputs - TKN as N
                Monthly average                                 30

-------

-------
                              INTRODUCTION







     The ujper Potomac estuary iz highly eutrophic.  During the




rummer months, large blooms of nuisance blue-green algae, mainly




mlcroc.ystis,  occur in the fresh water portion of the upper estuary.




A relationshii between high nutrient content and the accelerated




eutrophication i •> the Potomac estuary has been established [1].




     To aid in developing the water resources of the Potomac River




ha^;iii, an investigation was initiated in 1906 to determine nutrient




sources including temporal and spaMal distributions.  The analyses




was expanded in 1^)08 to determine the amount of nutrients entering




'he Potomac Basin fron. al^ major wastewater discharges.  The scope




of the program was exjanded to include several other basins in the




Middle Atlantic Region during 1^9-

-------
              A DESCRIPTION OF THE POTOMAC RIVER BASIN


     The Potomac River Basin has a drainage area of 14,670 square

miles and encompasses parts of Pennsylvania,  Maryland, West Virginia,

and Virginia and all of the District of Columbia.  The major sub-basins,

including their drainage areas, are:

          3ub-Basin                            Drainage Area
                                               (square miles)

     (l)  ^henaridoah River                          3,05^
     (2)  South Branch                              lA93
     (3)  North Branch                              1,328
     (k)  Monocacy River                              970
     (5)  Cacapon River                               683
     (6)  Conococheague Creek                         563
     (7)  Opequon Creek                               3^5
     (8)  Antietam Creek                              292

A map of the basin is presented in Figure I.

     Of the 3 million people living in the basin, about 2.5 million,

or 83 percent, live in the Washington, D. C.  metropolitan area.  The

industrial development is primarily concentrated in the North Branch

of the Potomac near Luke and Cumberland, Maryland, and in the South

Fork of the Shenandoah near Front Royal and Waynesboro, Virginia.

     Land use in the sub-basins is either predominately forest, agri-

cultural or urban.  In the entire Potomac Basin, it has been estimated

that the land use is 5 percent urban, 55 percent forest and ^0 percent

agricultural including pasture lands.

     The Potomac and its tributaries are characterized by flash floods

and extremely low flows .  The average discharge of the Potomac River

at Washington, D. C. is about 11,000 cubic feet per second (cfs).

-------
8
3,

-------
                         NUTRIENT SOURCES






A.  Sampling Programs




     During the 1966 calendar year, a ^O-station stream sampling




network was monitored weekly for nitrogen and phosphorus as shown




in Figure 2.  Weekly analyses of nutrients from 13 wastewater




discharges in the upper basin were initiated during the latter part




of l mill iop gallons




per day (mgd) were sampled.




     In 19^'9» a sampling network, as shown in Figure 3j was developed




to determl >, e the nutrient loading Into the Chesapeake Bay.  The




weekly anal/sis included two forms of carbon, three of phosphorus




and four of nitrogen taken at sampling stations just above the




non-tidal portions of the respective basins.

-------

-------
CHESAPEAKE  BAY  NUTRIENT  INPUT  STATIONS
                                                c
    CHESAPEAKE BAY

      SCALE IN MILES

    6  5  10 IS 20 25
 POTOMAC AT
 ODEA
                                               FIGURE  3

-------
     A- o?  "•   ",<•*•;   ,  ' -.ere  were  a •     "o vastewatpr  discharges



Jn the upper Potomac River basin,   Dur: itr 19faP>, 80,^30 Ibs/day of



t otal  /:hoj. . I i^T'is  am] t  •• .  --V lb;./ria',r r.ot.fil K,]nldah2 r.Itroff-n  were



dlschargrd  ' •" *-h« '•.urf'Pcip waters.   As nan be seen in Table T,  the



jRi'ffo^i (-."I- '--p,1;' "MI:  •• .  • '\f Piitoma" c>0  f-r." '.?< from the Washington,,



I;. C. area    r'or  a •,".-. r^d popiilat io:i c^'  2,903,^00, this reduces to




0.02^ and 0.020 Ibs /Capita/day of  phosphorus and nitrogen, respectively.



     Nutr^M  load.J;.y;  from industrial wastewater discharges are



about 7,700 Jbs/day ot  total PO,  and  h/iOC Ibs/day of TKN.   The indus-
                                u


irjal contribution;: to wastewater  nutrient loadings in the basin are
about 10 jtro"',',  or   .re. 4 ota,l PO,  (TFO^ )  and about 7 percent  of the



total nitrogen.   The amount of N0p+N0^  nitrogen in both  the  industrial



and municipal  wastewater discharges  is  insignificant.

-------
                                                                   8
                                 TABLE  I

                  NUTRIENT LOADINGS FROM WASTEWATER  DISCHARGES

                               BY SUB-REGIONS*
Sub-Region Population
Served
North Branch
South Branch and
Upper Region
Opequon
Conococheague and
Upper Middle Region
Antietim and Middle
RegJ OP.
Shenandoah
Ca^octin Creeks
Md. and Va.
Mor.ocacy
Lower Fresh Water
Region
Potomac Estuary 2
TOTAL 2
79,200
17,300
3^,800
26,900
61,500
108,500
5,^00
62,500
7,^00
,500,000
,903,500
LOADING AFTER TREATMENT
BOD TKN TPO^
Ib s /day 1 b s /day Ib s /day
55,300
2,720
3,vro
U.250
7,980
31,800
7^0
U,220
200
130,000
21*0,680
1,750
•370
v-'O
(10
R90
u,8'>0
i i U
1,380
i 00
53,000
63 , 660
M50
460
1,100
1,0-0
2,380
6,360
220
1,830
180
62,000
80,U30
* A Sub-region may include discharges to the small tributaries and
  to the main stem of the Potomac.

-------
C.  Land Runoff and Other Sources




     To determine the amount of nutrients entering the Potomac from




land runoff, analyses of loadings from areas with three distinct land




uses (forest, agricultural, and urban) were made [2].  Using the




Catoctin Creek (Maryland) watershed basin as primarily agricultural,




the Patterson Creek watershed as forested, and Bock Creek watershed




as urban, the effect of land uses on the contribution of nutrients




to surface waters is illustrated in Figures k and 5-  These three




areas receive a relatively small wastewater volume.




     On an annual basis, the concentration of nutrients was consist-




ently higher from agricultural areas.  As summarized in Table IT, it




can be seen that the runoff from agricultural areas yields about




twice the nitrogen and phosphorus as does the forested area.




     Summary of the nutrient data for the major sub-tasins, as




presented in Table ITI, indicates that the phosphorus conc.entra4 ions




were at least three times greater in the Monocacy Fiver, Opequon




Creek, and Antietan Creek sub-basins than in the remaining five sub-




basins.  These three sub-basins, while primarily agricultural, also




receive considerable quantities of municipal wastewater.  These higher




concentrations are also reflected in large PO.  yields of i'rom 3-6 to




^.8 Ibs/day/sq. mi., as shown in Table III.




     The Conococheague, Antietam, Opequon, and Mor.o^a..y sub-basins had




average concentrations of N0?+N0.- nitrogen of 1.1* mg/1 and greater.




The Conococheague and Monocacy sub-basins had nitrine and nitrate




yields of over 10 Ibs/day/sq.mi., almost twofold larger than that of




the remaining four sub-basins.  This is mainly from agricultural drainage.

-------
8

    T
    a  a:
Ul  °
S  J
          2»
                                      "Od
'Od  IViOi
                                                                             Figure 4

-------
Figure 5

-------
12





















M
M
W
PQ
-l
§

B
M
:?
fH efl
W 4'
S3 o{
CO M
$ vo
B VO
'-£ ON
1 - , — |

^"•'
O
F' I

T)
O
g
h-l
&







•H
&
f$ . •
0*
to tn
«! "\
§ ^
w
^j.


fZ -H
W
flj ^^
w
m ^\
i ^
H" id
OJ ~\
O 03
^ n
H
— '


^^
^ -g
0
i-l-j O^
w
V) '~^-.
«5 >>
•S
o •--.
P-l M
^ S,

1) , — .
Kn
QU
03 CS5 -H
a 03 E
•H Sj
cd <4 o^
0) 0)
J2 to
m T) !D
^ rt
o efl -d
4-1 d
S 5




_ ^ [*""• ^~~
odd








O O t—
OJ VD CM











LT\ OO iH

O H H






CT\ CT\ t—
N- 0 t^-
CM H

W X -p -H .'i; • Ai --N
MOJW -POlO 0>C
0)0)0) oai-H aic8
•P ?H £n O JH ^i At JH .^
-POO 4JO5> OU^i
ft — O •— - K — '

-------
                                                                                                             13
co
£5
 is

 8!
•H
K

 O
          £

          fn
          4)
to
a)
!H
O
              as
              CO
              a)
O*
             fi
 OT




I
 CO
                    S

                    o1
             0)

             cs'' aJ
       a1
       m
            •H  C

             W  O

             05  T*

            rO  -P
             I  03

            rQ  -P
             ^  CO

            CO —
-
00
 f-
                             VD


                             OJ
                                       N-
                                       VD
                                       (M

                                       ro
                             CO
                             [--
                             oo
                             OJ
                             ON

                             -H
                             LA
                             LA
                             CM
                             OJ
                             ro
                                      CO
                                      OJ
                                      oo
                          (0
o
-P
          OJ
          LA


          OJ
                    LA
                    LA
                    VD

                    OO
          VC'
          ON
          OJ
                                       LA
                                       CO
                    o
                    LA
                   -4"
                                    O
       O
      CO
                                      £
                                                 ON
                                   -4-
                                    CO
H
oo

LA
                                   on
                                   ON
                                   LA
                   MD

                   OJ
                   VO
                   OJ
                   OJ
                    t-—
                    OJ
                                                ON
                                                VD
                o

                  s

•H •>
K ^d
o
>> -H
(J ^
0) 0)
o tJ
O  H
•H H
K «J

O
o3 -P
fa flj
O 0)
-P fn

PH ^—--
                                                                                                             •H
                                                                                                             H
                                                                                                             &
                                                                                O

                                                                                ca
                                                                                                             i
                                                                                o>
                                                                                03
                                                                                05

-------
     The large variations in NOp+NO- nitrogen can be attributed to




high mobility of NO  ion as reported by Wadleigh [3] and Bailey O].




Figure 6 for the South Branch station at Petersburg demonstrates




that the concentration of nitrates is directly related to river




discharge while concentrations of TKN and PO.  are indirectly related




     For the 35 stations in the non-tidal portion of the basin,




regression analyses were made using both linear and lo>/ transforms




The lop branr;forms appeared to yield the best correlation resulting




in the following expression:




                              C = aQb




where:




          C - concentration of PO, , TKN, or N0_+N0  (mg/l)




          Q = stream flow (cfs)




          a = a constant




          b = an exponent




Usjny the slope of the concentration-discharge relationship (the




exponent b) and knowing the specific location of the sampling point




in reJatiou to the municipal or industrial waste outfalls, a quanti-




zation of the sources of the nutrients can be obtained.  For example,




all stations,except one below an industrial outfall discharging




nitrates, had a positive slope ranging from about 0.3 to 0.7 with an




average of 0.L) suggesting that most of the inorganic nitrogen comes




from land and other sources and not from wastewater discharges.

-------
lO.Or
  SOUTH  BRANCH  POTOMAC  RIVER
                  AT
     PETERSBURG, WEST  VIRGINIA
TKN. N02+N03 and P04 V».  RIVER  DISCHARGE
                                                    1000
                                                                             10.000
                                  RIVER DISCHARGE ef»
                                                                          Figure 6

-------
                                                               16
     The concentrations of phosphorus'and TKN for most of the non-




tidal stations had either slightly positive or negative slopes




indicating a diluting effect.  The correlation coefficients for these




two parameters were low, probably due to seasonal and flushing effects




which were not incorporated into the regression studies.




     A review of the slopes of the coneentration-flow relationships




for stations above and below waste outfalls definitely supports the




finding:; oi.' Bailey [k] who indicated that (l) nitrate nitrogen has




high mobilii,;/ in soil, (2) PO, and TKN are not readily leached, and




(3) nutrient concentrations appeal- to be ai't'ected by stream transport




mechanisms.




     Using tre same land use designations that the U. S.  Corps of




Engineers developed in their 19t>8 stud,/ [6], the nutrient loading from




land runoff was determined (Table IV) .  It should be noted that the




largest contribution of nutrients, at out ;'-'5 percent, is  from  agri-




cultural r.r.olM even though only 38 percent of the basin  is farmed or




in pasture lands.

-------
                                                                                                     IT
 C
•H
•H ON
« H
O
-p





fr;
CO
a5
J§
EH









H,
to
Oj
oo
o
£^
+
g™





O
°3
$
6^
&


0)

1



0)
to
!=>

£3
(rt
t— i
•H
fi

0*
to

, — „
•g
0*
CO
t>.
«5
id
to
f
<-\
%
"a
^-
to
o
H

•rH


C71
07
t
w
H
CO
CO
o
*x
-*




t"-
o




0
o
-
ir\
CO





O
^O

^
4

H
" — '
•H
H
to
§
CO
H
81
LT\
^



en
H


^1 °
1 CO
W| LTN
*
0)
^






-P
1
0
•H
H
S)
<
o
~3"
OJ

m




-4-
o




8
OJ
*s
\^Q
H





O
OJ


0
o
-4-



LT\
O


8
H
co"




•P
to
^
o
fc
H
H
LT\






r-
o




0
ON
H
•-.
OJ






O
m


8
CO




H
rH


o
on
t—






0)
£>
^

ON
CO
CO
•s
K 	



m
LfN
O




O
no
^j-
»s
ro
l/N




CO
ON
-*'


OJ
-3-
sf



^
0


o
M3
-^
H

c!
•H
q5
m
•d
-p
o
EH
 §
-p
 I
•o
 cd
                                                             O
                                                             fn
                                                             O
                                                             -P
                                                             O
                                                             W
                                                             0!
                                                             O
                                                             d
                                                             0)
                                                             to
                                                             o
                                                             •H
                                                             !n

-------
                                                               18






D.  Relative Contribution of Loadings




     Utilizing the wastewater data of 1968 and stream flow conditions




of 1966, the total nutrient loadings to the surface waters of the




basin have been estimated as presented in Table V.  The delineation




of the sources indicates the following:




     1.  Of the 92,872 Ibs/day of total phosphorus as PO,,




         87 percent was from wastewater discharges.




     2.  About 67 percent of the total phosphorus was from




         wastewater discharges in the upper Potomac estuary.




     3-  The total loading of nitrogen as N was about 125,000




         Ibs/day, of which approximately ;?! percent or




         63,i->80 Ibs/day originated from wastewater discharges.




     H.  About ^3 percent of the total nitrogen loading was from




         wastewater discharges in the upper Potomac estuary.




     The above delineation clearly indicates for the Potomac River




basin  the ma.'iOr sources of phosphorus is from wastewater.  The major




source of nitrogen in 1966 was also from wast-ewater discharge.  Land




runoff from the agricultural areas had the nighest yield of nitrogen




per square r..;ie.  Moreover, the concentration of nitrate-nitrogen




appears also to be greatly affected by stream flow conditions.




     Data i'or the first eight months of 19'"'9 indicate that over




Bo percent of phosphorus and (~>6 percent of the nitrogen entering the




Potomac estuary was from wastewater discharges in the Washington, B.C.




area [7]-  Even though the first six months of 19^9 had stream flows

-------
                                                               19





below normal with the latter period having above or normal flow



conditions, the data supports the 1966 findings that the major



source of nutrients in the Potomac is from wastewater discharges.

-------
                                                                                                           20
                         -p
                         o
                         -p
                                  ON
                                  00
               o
               o
               H
                  3
                        1
O
00
MD
                                 vo
ON
en
oo
                                                ir\
                                                  •s

                                                pi
                        -p
                        O
                        -P
                                        O

                                        O
                                                                   -p
                                                                    o
                                                                   •H
en
55 \O
FQ \D
a\
O r-H
<£
£
fe

CQ
0}
oo
§

,, — s
>>
^
~-^^
w
rQ
H


O
oo
^t-
* »,
or^
ITS
0
oo
J-

OO
LT\
P4




I
H

O
W
El
B
M
                                t--
                                oo
                                               O
                                               O
                                                                   •


                                                                    g,

                                                                   •H

                                                                    W
                                                                    0)
                                                                   0)

                                                                   I
                                                                   -p
                                                                   w
                                                                   0)
O x-s
^ b
05
D'J Tj
03 ~^.
CO
-* ^3
S d
rH v — ^
EH

O CM
r>o ^J-
-* J-
•s »\
eg SI
CO
f-
oo

CM
ON

                0)
                o
                o
               CO
                                0)
                                -p
                                0)
                               -p
                                to
                                a]
                                      Vl
                                       o
                                       c
                                       s
                                      K
             C

             •H

             M
                                                                   O

                                                                   ?H

                                                                  •P

                                                                  •H

                                                                  S


                                                                    f

                                                                  O

                                                                  fe

                                                                  +
                                                                  O

                                                                  -p

-------
                                                               21






E.  Temporal Variations




     An important aspect of the nutrient control problem is the




annual variation in nutrient contributions from the various sources,




especially from land runoff.  The nitrate-nitrogen loadings from the




years 1947-196? for the Potomac River at Great Falls show a definite




seasonal pattern (Figure 7)•  The seasonal loading variations closely




parallel those of river discharge that is high in the spring months,




low in the summer and fall, and somewhat higher than fall in the




wi nter months.




     The relationship between river discharge and nutrient loadings




is vividly demonstrated in Figure 8 for the Potomac at Great Falls.




During the high discharge rate in February and March of 1966, the




N0p+N0~ and TPO,  loadings were also the largest while in August,




when the flow was very low, the nutrient loadings were likewise




smalJ .




     In mid-September of 1966, there was considerable precipitation




throughout the basin.  This resulted in a high nutrient loading in




September as also seen in Figure 8.




     An important aspect of -the temporal variations in nutrient




loadings is nutrient transport.  This is especially pronounced for




phosphorus.  As can also be seen in Figure 3, during August, less




than 100 Ibs/day of TPO,  entered the estuary even though over




1
-------
                                                               22
onto sediment particl-es or utilized by aquatic life.   At times of




high stream flows, much of the phosphorus is re-suspended and trans-




ported downstream.




     The high loadings of TPO; • in mid*September were due to flushing




of the river channel system by.the high stream flows.  The high




inorganic nitrogen loadings in September can be readily attributed to




flushing of the land as previously indicated.




     The various forms of phosphorus and nitrogen for the Potomac




River at Great Falls during the first 10 months of 19&9 are presented




in Figures 9 and 10.  Figure 9 shows that only about 25 percent of




the total phosphorus is in the dissolved reactive form.  This suggests




that most of the phosphorus originating from the upper basin was or




has become attached to silt particles.




     Similar to Figures 6 and 7,  the N0p+N0_ nitrogen as shown in




Figure 10 demonstrates the dependence of this form of nitrogen on




river discharge.  Fraction analyses of the TKN form indicates that




over 50 percent is in the particulate state.




     The wide variations in nutrient loadings in the Potomac River




at Great Falls demonstrates the need to sample at various river




discharges continuously over an annual cycle before a delineation




of nutrient sources can be made.   Moreover, as shown in Figure 8,




sampling only during summer flow conditions can yield misleading




conclusions as to the temporal distribution, relative sources and




transport mechanism of nutrients.

-------
CON
                     Figure 7

-------
                        NUTRIENT  LOADINGS  and  RIVER DISCHARGES
                                POTOMAC RIVER a* GREAT FALLS. Md.
-*-
                                                                                 Figure 8

-------
Id
5
                                                                        g  5



                                        'I'  39MVHDSIO M3AIM
                                                                                                FIGURE - 9

-------

                                                                                                                     z
                               r
n  i  i   i   i
                                      I IT  i  rt




                                     <3
                                                                                                           HOUSE - 10

-------
                                                              27






F.  Comparison to Other River Basins in the Middle Atlantic Region




     Figures 11, 12 and 13 present a six month comparison of nutrient




concentrations for five river basin systems as part of a nutrient




input study of the Chesapeake Bay system.  The mean monthly concen-




tration of phosphorus is highest for the Patuxent Basin and lowest




for the Susquehanna with the Potomac being second highest (Figure ll).




Except for the Patuxent, all have concentrations usually less than




0.5 rug/I.




     In terms of N0p+N0_ nitrogen, the Patuxent is the highest




(Figure 12).  This is mainly due to high ratio of sewage to stream




flow in this small basin.  The concentrations, usually less than




0.5 mg/1, were the lowest for the Rappahannock Basin with Potomac




being comparable to the other basins of its size, ranging from about




0.5 to 0.75 mg/1.




     TKN nitrogen concentrations in the Patuxent were the highest




with the Potomac being second highest.  For the three remaining basins,




the concentration varied from about 0.3 to 1.0 mg/1.

-------
I/)
                                                                                                        CE
                                                                                                        uj

                                                                                                        i
                                                                                                        UJ

                                                                                                        I
                                                                                                        00

                                                                                                        O


                                                                                                        U

                                                                                                        O
                                                                                                        1
                                                                                                        10
                                                                                                        O
                                 q

                                 •*'
q

o
                                                         0d
                                                                                                       FIGURE-  II

-------
 a
 z
P   s
=>    c
Z  O
CO


UJ
U
a
UJ
I
U
            UJ
<

>

I
I-
2
                                                                                                                     U  cr


                                                                                                                        i
                                                                                                                        LJ
                  in
                  (Vj
                          q
i/)


N
                                                                 o
                                                                                    10
                                                                                    ci
                                                                                                                         cc
                                                                                                                         uj
                                                                                                                         UJ
                                                                                                                        cr
                                                                                                                        UJ
                                                                                                                        m
                                                                                                                        U
                                                                                                                        o
                                                                                                                        I/)
q
o
                                                                                                                      FIGURE- 12

-------
 I
 a
 z

 i-
 z
 UJ
 i  3
          o
          UJ
>  *-   -J
<  *   I
CD  K   Z
          O
U       ^
ui
a
UJ
X
u
                                                                                                        a:
                                                                                                        ui
                                                                                                        GO
                                                                                                        O
                                                                                                        o
                                                                                                      UI
-, 	 1 	 , 	 r 	 ,
ui o
OJ N
\ 	 1 	 ' — 1
in
r — ' 	 1 	
Q
— i 	 r^ 	 1 	
m
o'
-4
c
                                                                                                     FIGURE- 13

-------
                                                               31






G.  Hudson River Basin System




     In order to determine if the relatively high percentage of




nutrients from wastewater in the .Potomac Basin vas unique or




whether it Js more generally true that wastevater discharges are




the most significant contributors of nutrients to the aquatic




ecosystem in the Middle Atlantic Region, a comparison of the




nutrient sources was made for the Hudson River Basin.  This basin




Is relatively comparable to the Potomac in size, land use patterns




and population (both over-all density and distribution).   It is




also more highly industralized.




     A complete description of the Hudson River Basin and its




nutrient loading was recently presented by Tofflemire and Hetling




L8].  As a result of this study, it was estimated that the total




phosphorus as PO.  discharged to the Hudson Rive.r Basin above the




New York City line is approximately 72,000 Ibs/day,  73% of which




is from wastewater discharges.  The corresponding total for nitrogen




as N is 125,570 Ibs/day with 63/0 coming from wastewater.




     A comparison of the Hudson River estimates with those found




for the Potomac is given in Table VI.  The Hudson results give




added support to the Potomac findings that, for the large river




basins in the Middle Atlantic Region, the major source of nutrients




is wastewater discharges.

-------
Source


Wastewater
Land Runoff
Total Basin


Source
Wastewater
Land Runoff
Total Basin
              TABLE VI
   COMPARISON OF NUTRIENT LOADINGS
  IN HUDSON AN)  POTOMAC RIVER BASINS
       Total Phosphorus as PO,
Potomac Basin
  (Ibs/day)	4
  80,430         87
  12,442         13
  92,872        100

         Total Nitrogen as N
Potomac Basin
  63,680         51
  61,269         49
 124,949        100
Hudson Basin
  '(Ibs/day)     %

   52,000      73
   19,420      37
   71,600     100


Hudson Basin
   78,500      63
   47,070      37
  125,570     100

-------
                                                                33
                      SUMMARY AND CONCLUSIONS
     Results of the initial phase of the nutrient investigations




in the Potomac River system, which have been expanded to include




other river basins and which are being continued by the CTSL, are




summarized below:




     1.  The annual average concentration of phosphorus as PO,  in




the major sub-basins varied from a minimum of 0.09 mg/1 in the




South Branch to a maximum of 1.9 mg/1 in the Antietam watershed.




     2.  The annual average concentration of N02+N0  nitrogen as N




in the major sub-basins varied from 0.3 mg/1 in the South Branch to




2.2 mg/1 in Opequon Creek.




     3-  The annual average concentrations of phosphates, total




Kjeldahl nitrogen (TKN) and NO + NO  nitrogen in the freshwater




stream flow entering the estuary near Washington, D. C., were 0.3,




0.3, and O.y mg/1, respectively.




     k.  About 92,700 Ibs/day of total phosphorus as PO, entered




the surface waters of the Potomac in 1966, of which 87 percent




resulted from wastewater discharges.



     5.  The average 1966 loading of total nitrogen as N from all




sources to the surface waters of the basin was about, 125,000 Ibs/day,




of which 63,680 Ibs/day, or 5! percent, were from wastewater discharges.




     6.  Seasonal variations in inorganic nitrogen loadings are much




more pronounced when compared to phosphorus.  This is mainly attributed

-------
to.a direct relationship between stream flow and inorganic nitrogen




concentration for the stations in the non-tidal portion of the basin




while phosphorus generally has an inverse relationship.




     J.  Prom an analysis of watersheds with varying land uses and




receiving little or no wastewater discharges, the average annual




yields per square mile for the entire basin was 0.8 Ibs/day of




phosphorus PO, , 5-0 Ibs/day of NCL+NO  nitrogen as N, and 0.5 Ibs/day




of TKN.




     8.  Of the 6l,2TO Ibs/day of total nitrogen from land runoff,




about 35>000 Ibs/day or 65 percent,  were from agricultural areas which




comprise only 38 percent of the total drainage area in the basin.




     9-  Nutrient yields were over twofold greater from areas which




were predominately agricultural than from forested areas.




    10.  Similar to 1966 findings, data for the first eight months




of 1969 corroborate that the major source of nutrients is from waste-



water discharge with the largest contribution originating in the




Washington, D.  C. area.




    11.  During low flow conditions a significant proportion of the




phosphorus entering the surface water from the various sources in




the upper basin is retained in the stream channel.  At high stream




flow, it appears that a large proportion of this phosphorus is




"flushed" out of the stream channel and transported downstream.




    12.  The wide variation in nutrient loadings clearly demonstrates




the need to sample more frequently over a vide range of stream flows




before a precise identification of nutrient sources can be made.

-------
    13.  In the Hudson River Basin,  wastewater discharge contributes



about 73 percent of the phosphorus and 63 percent of the nitrogen.



    lU.  A comparison of sources of nutrients in the Hudson River



Basin to those found in the Potomac supports the contention that for



large drainage basins in the Middle Atlantic Region the major source



of nutrients to the aquatic ecosystem is from wastewater discharges.

-------
                                                               36
                             REFERENCES
1.  Jaworski, N.A.,  Lear, D.W.,  and Aalto,  J.A.,  "A Technical
    Assessment of Current Water  Quality Conditions and Factors
    Affecting Water Quality in the Upper Potomac Estuary,"
    Technical Report No. 5, CTSL, MAR, FWPCA, March 1969.

2.  Jaworski, N.A.,  Villa, 0., and Hetling, L.J., "Nutrients in
    the Potomac River Basin/' Technical Report No. 9,  CTSL,  MAR,
    FWPCA, May 1969.

3.  Wadleigh, C.H.,  "Wastes in Relation to Agriculture and
    Forestry/' U.S.  Department of Agriculture, Washington, D.C.,
    March 1968.

k.  Bailey, G.W., "Role of Soils and Sediment in Water Pollution
    Control, Part One," Southeast Water Laboratory, FWPCA,
    March 1968.

5-  Jaworski, N.A.,  "Nutrients in the Upper Potomac River Basin,"
    Technical Report No. 15, CTSL, MAR, FWPCA, August 1969.

6.  U.S. Army Corps of Engineers, "Potomac River Basin Report,"
    Volume 1, Part 1, North Atlantic Division, Baltimore,  Md., 1963.

7.  Jaworski, N.A.,  "Water Quality and Wastewater Loadings Upper
    Potomac Estuary During 1969," Technical Report No. 27, CTSL,
    MAR, FWPCA, November 1969.

8.  Tofflemire, T.J. and Hetling, Leo J.,  "Pollution Sources and
    Loads in the Lower Hudson River," presented at the Second
    Annual Symposium on Hudson River Ecology, New York University
    Medical Center, Institute of Environmental Medicine, Sterling
    Forest, New York, October 3969.

-------
                                                               35
    13.  In the Hudson River Basin.,  wastewater discharge contributes



about 73 percent of the phosphorus and 63 percent of the nitrogen.



    lU.  A comparison of sources of nutrients in the Hudson River



Basin to those found in the Potomac supports the contention that for



large drainage basins in the Middle Atlantic Region the major source



of nutrients to the aquatic ecosystem is from wastewater discharges.

-------
                                                               36
                             REFERENCES
1.  Jaworski, N.A., Lear, D.W.,  and Aalto, J.A.,  "A Technical
    Assessment of Current Water Quality Conditions and Factors
    Affecting Water Quality in the Upper Potomac Estuary,"
    Technical Report No. 5, CTSL, MAR, FWPCA, March 1969-

2.  Jaworski, N.A., Villa, 0., and Hetling, L.J., "Nutrients in
    the Potomac River Basin," Technical Report No. 9, CTSL, MAR,
    FWPCA, May 1969.

3.  Wadleigh, C.H., "Wastes in Relation to Agriculture and
    Forestry," U.S. Department of Agriculture, Washington, D.C,,
    March 1968.

^.  Bailey, G.W., "Role of Soils and Sediment in Water Pollution
    Control, Part One," Southeast Water Laboratory, FWPCA,
    March 1968.

5.  Jaworski, N.A., "Nutrients in the Upper Potomac River Basin,"
    Technical Report No. 15, CTSL, MAR, FWPCA, August 1969.

6.  U.S. Army Corps of Engineers, "Potomac River Basin Report,"
    Volume 1, Part 1, North Atlantic Division, Baltimore,  Md., 1963.

7-  Jaworski, N.A., "Water Quality and Wastewater Loadings Upper
    Potomac Estuary During 1969," Technical Report No. 27, CTSL,
    MAR, FWPCA, November 1969.

8.  Tofflemire, T.J. and Hetling, Leo J.,  "Pollution Sources and
    Loads in the Lower Hudson River," presented at the Second
    Annual Symposium on Hudson River Ecology, New York University
    Medical Center, Institute of Environmental Medicine, Sterling
    Forest, New York, October 1969.

-------
                       Annapolis Field Office
                             Region III
                   Environmental Protection Agency
            MATHEMATICAL MODEL STUDIES OF WATER QUALITY

                               IN THE

                          POTOMAC ESTUARY



                         Technical Report 33

                            March 1972



                             Leo J. Clark

                         Kenneth D. Feigner*
*Environmental  Protection Agency, Office of Water Programs,
 Washington, D.  C.

-------
                              PREFACE
     During 1969, two independent but coordinated studies were under-
taken by the U. S. Department of the Interior, (FWQA)* and the Corps of
Engineers to ascertain the feasibility of using the upper Potomac Estuary
as a supplemental water supply source for the Washington Metropolitan Area.
Another of the primary requirements for the FWQA study was determination
of maximum allowable pollutant loadings to achieve and maintain the adopted
water quality standards.  Current water quality conditions in the upper
estuary have been adequately defined by extensive sampling, but prediction
of the effects of large freshwater withdrawals and the corresponding
increases in wastewater flows on water quality was also required.
     The Chesapeake Technical Support Laboratory (CTSL)** has employed
mathematical modeling techniques to predict water quality behavior in the
Potomac Estuary for various hydraulic conditions and wastewater loading
schemes.  While existing estuary models have proven to be flexible and
versatile tools, verification for a particular system was necessary
before reliable predictions could be made.  This report presents CTSL's
findings based upon simulation studies in the Potomac Estuary using two
of the more commonly known mathematical models:  (1) DECS III***, and
(2) the FWQA Dynamic Estuary Model.  The former model employs an average
tidal solution whereas the latter is based upon a real-time solution.
  * Now the Environmental Protection Agency
 ** Presently known as Annapolis Field Office
*** Hereafter referred to as the Thomann Model

-------
                         TABLE OF CON-TENTS

                                                            Page

PREFACE	        iii

LIST OF TABLES	        vii

LIST OF FIGURES    	       viii

Chapter

   I.  INTRODUCTION	          I -  1

       A.  Purpose and Scope	          I -  1

       B.  Acknowledgements 	          1-3

  II.  SUMMARY AND CONCLUSIONS	         II -  1

 III.  DESCRIPTION OF STUDY AREA	        Ill -  1

  IV.  DESCRIPTION OF MATHEMATICAL MODELS  ....         IV -  1

       A.  Thomann Model	         IV -  1

       B.  Dynamic Estuary Model	         IV -  5

   V.  MATHEMATICAL MODEL SIMULATIONS OF 1969-1970
       DYE RELEASES	          V -  1

       A.  Thomann Model	          V -  1

           1.   Simulations and Verification   ...          V -  1

               a.   Potomac Dye Study	          V -  1

               b.   Anacostia Dye Study	          V - 12

       B.  FWQA's  Dynamic Estuary Model  	          V - 19

           1.   Simulations and Verification   ...          V - 19

               a.   Potomac Dye Study	          V - 19

               b.   Anacostia Dye Study	          V - 28

                                  iv

-------
                         TABLE  OF  CONTENTS

Chapter                                                    Page

  VI.   OTHER MATHEMATICAL MODEL SIMULATIONS  	     VI -  1

       A.   Simulation of 1965 Dye  Release	     VI -  1

           1.  Thomann Model	     VI -  1

           2.  Dynamic Estuary  Model	     VI -  6

       B.   Chloride Simulations -  1966  and  1969    ...     VI -  11

           1.  Thomann Model	     VI -  11

       C.   Simulation of 1965 Chlorides	     VI -  16

           1.  Dynamic Estuary  Model	     VI -  16

 VII.   COMPARATIVE SENSITIVITY  EVALUATIONS  - THOMANN  AND
       DYNAMIC ESTUARY MODELS    	     VII -  1

       A.   Decay Rate of Pollutant	     VII -  1

       B.   Segment Length	     VII-5

           1.  Thomann Model	     VII-5

           2.  Dynamic Estuary  Model   	     VII-5

       C.   Dispersion Coefficient	•  VII -  10

           1.  Thomann Model	     VII -  10

               a.  Point Discharges	     VII -  10

               b.  Chloride Distributions	     VII -  15

           2.  Dynamic Estuary  Model	     VII -  18

               a.  Point Discharges	     VII -  18

               b.  Chloride Distributions	     VII -  20

       D.   Advective Transport	     VII -  25

           1 .  Thomann Model	     VII -  25

           2.  Dynamic Estuary  Model	     VII -  28

-------
                          TABLE OF CONTENTS

Chapter                                                     Page

 VII.  COMPARATIVE SENSITIVITY EVALUATIONS -  THOMANN AND
       DYNAMIC ESTUARY MODELS (Continued)

       E.  River Flow and Dispersion Coefficients (Thomann
           Model)	VII  -  30

       F.  Manning Coefficient and Tidal  Effects  (Dynamic
           Estuary Model)	VII  -  33

VIII.  ENGINEERING CONSIDERATIONS 	   VIII  -   1

       A.  Dispersion and Advection	VIII  -   1

       B.  Model Comparison	VIII  -   5

APPENDIX	      A.-   1

       A.  Potomac Dye Study - 1969	      A  -   1

           1.  Release Conditions	      A  -   1

           2.  Monitoring System	      A  -   4

               a.  Longitudinal  Stations  (Slack Tide)  .  .      A  -   4

               b.  Lateral  and Vertical  Stations  ....      A  -   4

           3.  Presentation of Data	      A  -   6

               a.  Tidal  Conditions and  Hydrology   ...      A  -   6

               b.  Dye Movement	      A  -  12

               c.  Loss Rate Determination	      A  -  20

       B.  Anacostia Dye  Study - 1970	      A  -  23

           1.  Release Conditions	      A  -  23

           2.  Monitoring System	      A  -  24

           3.  Presentation of Data	      A  -  26

               a.  Tidal  Conditions and  Hydrology   ...      A  -  26

               b.  Dye Movement	      A  -  28

               c.  Loss Rate Determination	      A  -  32

BIBLIOGRAPHY

                                  vi

-------
LIST OF TABLES
Number
VII -
Appendi








1
X
1
2
3
4
5
6
7

Effects of Manning Coefficients on Tides

Dye Injection Data, Blue Plains, November
1969 	 . . . . .
Longitudinal Sampling Stations, Potomac
River 	
Longitudinal Sampling Stations, Anacostia
River 	
Summary of Dye Concentration Data - Potomac
Estuary, November 1969, High Slack Tide Data
Summary of Dye Concentration Data - Potomac
Estuary, November 1969, Low Slack Tide Data
Summary of Dye Concentration Data - Anacostia
River, April-May, 1970, High Slack Tide Data
Summary of Dye Concentration Data - Anacostia
River, April-May, 1970, Low Slack Tide Data
Page
VII

A
A
A
A
A
A
A

- 33

- 2
- 5
- 25
- 34
- 35
- 36
- 37
       Vll

-------
LIST OF FIGURES
Number
I -
III -

III -

III -

V -

V -

V -

V -

V -

V -

V -

V -

V -

V -

V -

V -


1
1

2

3

1

2

3

4

5

6

7

8

9

10

11

12

Description
Potomac River Tidal System 	
Cross-sectional Area vs Distance, Potomac
Estuary, Mean Water Data 	
Accumulative Volume vs Distance, Potomac
Estuary, Mean Water Data . 	
Accumulative Surface Area vs Distance,
Potomac Estuary, Mean High Water Data
Thomann Mathematical Model Segments, Potomac
Estuary 	
Thomann Model Dye Simulation and Verification,
Uoper Potomac Estuary, November 6, 1969
Thomann Model Dye Simulation and Verification,
Upper Potomac Estuary, November 7, 1969
Thomann Model Dye Simulation and Verification,
Upper Potomac Estuary, November 10, 1969
Thomann Model Dye Simulation and Verification,
Upper Potomac Estuary, November 12, 1969
Thomann, Model Dye Simulation and Verification,
Upper Potomac Estuary, November 17, 1969
Temporal Dye Profiles, Upper Potomac Estuary,
Thomann Model 	
Thomann Model Dye Simulation and Verification,
Anacostia River, April 23, 1970 	
Thomann Model Dye Simulation and Verification,
Anacostia River, April 27, 1970 	
Thomann Model Dye Simulation and Verification,
Anacostia River, April 29, 1970 	
Thomann Model Dye Simulation and Verification,
Anacostia River, May 4, 1970 	
Thomann Model Dye Simulation and Verification,
Anacostia River, May 7, 1970 	
Page
I -

III -

III -

III -

V -

V -

V -

V -

V -

V -

V -

V -

V -

V -

V -

V -

2

3

4

5

2

6

1

8

9

10

11

13

14

15

16

17
       vm

-------
LIST OF FIGURES
Number
V -
V -


V -


V -


V -

V -

V -

V -

V -

V -

V -

VI -

VI -

VI -


13
14


15


16


17

18

19

20

21

22

23

1

2

3

Description
FWQA Dynamic Estuary Model Dye Simulation and
Verification, Upper Potomac Estuary, November 6,
1969 ... 	
FWQA Dynamic Estuary Model Dye Simulation and
Verification, Upper Potomac Estuary,
November 10, 1969 	
FWQA Dynamic Estuary Model Dye Simulation and
Verification, Upper Potomac Estuary,
November 12, 1969 . . . ....
FWQA Dynamic Estuary Model Dye Simulation and
Verification, Upper Potomac Estuary.
November 17, 1969 	
Temporal Dye Profiles, Upper Potomac Estuary,
FWQA Dynamic Estuary Model (High Water Slack Data)
Temporal Dye Profiles, Upper Potomac Estuary,
FWQA Dynamic Estuary Model (Low Water Slack Data)
FWQA Dynamic Estuary Model Dye Simulation and
Verification, Anacostia River, April 23, 1970.
FWQA Dynamic Estuary Model Dye Simulation and
Verification, Anacostia River, April 27, 1970. •.
FWQA Dynamic Estuary Model Dye Simulation and
Verification, Anacostia River, April 29, 1970.
FWQA Dynamic Estuary Model Dye Simulation and
Verification, Anacostia River, May 4, 1970.
FWQA Dynamic Estuary Model Dye Simulation and
Verification, Anacostia River, May 7, 1970.
Thomann Model Dye Simulation and Verification,
1965 Dye Release, June 14, 1965 	
Thomann Model Dye Simulation and Verification,
1965 Dye Release, June 22, 1965 	
Thomann Model Dye Simulation and Verification,
1965 Dve Release, June 26, 1965 	
Page
V


V


V


V

V

V

V

V

V

V

V

VI

VI

VI

- 21


- 22


- 23


- 24

- 25

- 26

- 30

- 31

- 32

- 33

- 34

- 2

- 3

- 4
          IX

-------
                         LIST  OF  FIGURES
Number
VI -
VI -
VI -
VI -
VI -
VI -
VI -
VI -
VI -
VII -
VII -
VII -

4
5
6
7
8
9
10
11
12
1
2
3
Description
Thomann Model Dye Simulation and Verification,
1965 Dye Release, July 1, 1965 	
FWQA Dynamic Estuary Model Dye Simulation and
Verification, 1965 Dye Release, June 14, 1965 .
FWQA Dynamic Estuary Model Dye Simulation and
Verification, 1965 Dye Release, June 26, 1965 .
FWQA Dynamic Estuary Model Dye Simulation and
Verification, 1965 Dye Release, July 1, 1965
FWQA Dynamic Estuary Model Dye Simulation and
Verification, 1965 Dye Release, July 8, 1965
Thomann Model Chloride Simulation and Verifi-
cation, 1966 Chloride Data, Potomac Estuary at
Possum Point, Va 	
Thomann Model Chloride Simulation and Verifi-
cation, 1969 Chloride Data, Potomac Estuary at
Nanjemoy Creek 	
Thomann Model Chloride Simulation and Verifi-
cation, 1969 Chloride Data, Potomac Estuary at
Wicomico River 	
FWQA Dynamic Estuary Model Chloride Simulation and
Verification, Potomac Estuary, July-December 1965
Effects of Decay Rates, Dynamic Estuary Model
Effects of Decay Rates , Thomann Model ....
Effects of Segmentation, Thomann Model Dye
Page
VI
VI
VI
VI
. VI
VI
VI
VI
VI
. VII
. VII

- 5
- 7
- 8
- 9
- 10
- 1?
- 14
- 15
- 17
- 2
- 3
           Simulations,  November  6,  1969	VII -  7

VII -  4   Effects  of Segmentation,  Thomann Model Dye
           Simulations,  November  12,  1969	VII -  8

VII -  5   Effects  of Segmentation,  Thomann Model Dye
           Simulations,  November  17,  1969	VII -  9

-------
                          LIST OF FIGURES

Number                     Description                         Page

 VII -  6   Effects  of  Dispersion Coefficient, Thomann
            Model  Dye Simulations, November 6, 1969   .   .   .    VII - 11

 VII -  7   Effects  of  Dispersion Coefficient, Thomann
            Model  Dye Simulations, November 12,  1969  .   .   .    VII - 12

 VII -  8   Effects  of  Dispersion Coefficient, Thomann
            Model  Dye Simulations, November 17,  1969  ...    VII - 13

 VII -  9   Effects  of  Dispersion Coefficient, Thomann
            Model  Chloride Simulations,  Potomac  Estuary  at
            Nanjemoy Creek	    v II - 16

 VII - 10   Relationship of Dispersion Coefficient to
            Chlorides Based upon  1969  (3,000  - 5,000  cfs)
            Data	    VII - 17

 VII - 11   Effects  of  Dispersion Constant  (CiJ  on Dynamic
            Estuary  Model  Simulations, Point  Discharge   .   .    VII - 19

 VII - 12   Effects  of  Dispersion Constant  (Cj  on Dynamic
            Estuary  Model ,Chloride Simulations	    VII - 21

 VII - 13   Effects  of  Advection  Factor  (a),  Thomann  Model
            Dye Simulations, November  6, 1971	    VII - 26

 VII - 14   Effects  of  Advection  Factor  (a),  Thomann  Model
            Dye Simulations, November  12, 1969	    VII - 27

 VII - 15   Effects  of  Advective  Solution Technique,
            Dynamic  Estuary Model,Chloride  Simulations   .   .    VII - 29

 VII - 16   Dispersion  Coefficient vs  Flow, Thomann Model,
            Upper Potomac Estuary	    VII - 31

Appendix

   A -  1   Tidal  Data, Potomac  Estuary  at  Washington,
            November 1969	      A -   7

   A -  2   Tidal  Data, Potomac  Estuary  at  Washington,
            November 1969	      4-8

   A -  3   Tidal  Data, Potomac  Estuary  at  Washington,
            November 1969	      A ~   9


                                  xi

-------
                          LIST  OF  FIGURES

Number                                                        Page

   A -  4   Freshwater Flows, Potomac  River at Great Falls,
            November 1969	     A - 10

   A -  5   Dye  Isopleth,  Upper Potomac  Estuary, Low Slack
            Data,  November 1969	     A - 14

   A -  6   Dye  Isopleth,  Upper Potomac  Estuary, High Slack
            Sampling Data, November  1969	     A - 15

   A -  7   Transect Dye Sampling  Summary, Upper Potomac
            Estuary, November 11,  1969	     A - 16

   A -  8   Transect Dye Sampling  Summary, Upper Potomac
            Estuary, November 18,  1969	     A - 17

   A -  9   Transect Dye Sampling  Summary, Upper Potomac
            Estuary, November 20,  1969	     A - 18

   A - 10   Dye  Loss Rate, Upper Potomac Estuary, November
            1969	     A - 21

   A - 11    Freshwater Flows, Anacostia  River, April-May
            1970	     A - 27

   A - 12   Dye  Isopleth,  Anacostia  River, High Slack
            Sampling,  April-May 1970	     A - 29

   A - 13   Dye  Isopleth,  Anacostia  River, Low Slack
            Sampling,  April-May 1970	     A - 30

   A - 14   Dye  Loss Rate, Anacostia River, April-May 1970   .     A - 33

   A - 15   Transect # 1 - Key  Bridge	     A - 38

   A - 16   Transect # 2 - 14th Street Bridge	     A - 39

   A - 17   Transect * 3 - Mains Point	     A - 40

   A - 18   Transect * 3A  - Hunter Point	     A - 41

   A - 19   Transect * 4 - Bellevue	     A - 42

-------
                          LIST OF FIGURES



Number                      Description                        Page



   A - 20   Transect # 4A - Goose Island	      A - 43



   A - 21   Transect # 5 - Woodrow Wilson Bridge  ....      A - 44



   A - 22   Transect # 5A - Rosier Bluff	      A - 45



   A ,. 23   Transect # 6 - Broad Creek	      A - 46



   A - 24   Transect # 7 - Piscataway Creek	      A - 47



   A - 25   Transect # 8 - Dogue Creek	      A - 48



   A - 26   Transect # 8A - Gunston Cove	      A - 49



   A - 27   Transect # 9 - Hallowing Point	      A - 50



   A - 28   Transect # 10 - Indian Head	      A - 51
                                  XI 1 1

-------
                                                                     I - 1
                             CHAPTER I



                           INTRODUCTION



A.  PURPOSE AND SCOPE



     Mathematical models are becoming an increasingly important "tool"



for predicting, under a variety of conditions, water quality behavior



in an estuary.  The purpose of this report is to present recent CTSL



studies on use of these models in the Potomac Estuary, specifically,



the Thomann Model (time-dependent version) and the FWQA Dynamic Estuary



Model.



     Numerous computer runs were made with both models in an attempt to



make a reasonably accurate simulation of dye profiles observed in the



Potomac Estuary following a 13-day continuous release during November 1969



and of observed dye profiles in the Anacostia River following a 7-day con-



tinuous release during April 1970.  In addition to model verification,



consideration was given to:  (1) a comparison of modeling approaches,



(2) the limitations of each model, (3) input data requirements, and (4) a



detailed sensitivity analysis to determine which input parameters had the



greatest effect on model output.  Hopefully, investigations of each of



these factors will assist in future modeling efforts by defining the



limitations and applicability of each model  and also by indicating where



expenditures for necessary data refinement are warranted.



     While mathematical models have been developed for the entire Potomac



Estuary, most studies in this report pertain to the 40-mile reach of the



upper estuary extending from Key Bridge to Sandy Point (Figure 1-1).

-------
        POTOMAC  RIVER TIDAL  SYSTEM









               lEOtNO



              A USGS STREAM GAGl



              D USC & GS TIDAL GAG£
           SCAL£ N HLCS
POTOMAC    ESTUARY
                                        FIGURE

-------
                                                                    I - 3
B.  ACKNOWLEDGEMENTS



     The assistance and cooperation extended by the personnel  at the



District of Columbia's Blue Plains Sewage Treatment Plant, the Washington



Suburban Sanitary Commission, and the U.  S.  Geological  Survey, Washington,



D. C. contributed to successful  completion of this study and is gratefully



acknowledged.

-------
                                                                    II  - 1
                             CHAPTER II
                      SUMMARY AND CONCLUSIONS
     In its continuing study of the Potomac Estuary,  the Chesapeake
Technical  Support Laboratory (CTSL) has utilized mathematical  models
to predict water quality response to given hydrographic, demographic,
and other physical, chemical, and biological  constraints.   In  the course
of model application, many problems associated with verification became
evident almost immediately.   The findings and conclusions  which evolved
during CTSL verification studies of both a nontidal model  (Thomann) and
a tidal or real-time model (FWQA Dynamic Estuary) for the Potomac are
reported as follows:
     1.  The primary model verification effort involved simulation of a
13-day continuous dye release during November 1969 in which 4,454 pounds
of diluted (6 percent) Rhodamine WT dye were discharged into the Potomac
Estuary at the District of Columbia's Blue Plains Sewage Treatment Plant.
     2.  Using dispersion coefficients varying from 2.0 mi^/day to 5.0
mi^/day, the Thomann Model appeared to simulate the 1969 Potomac dye study
satisfactorily in terms of peak concentrations and longitudinal dye dis-
tribution.  Shortcomings found in the Thomann Model simulations were pro-
nounced "peaking" during the early phase of the release and insufficient
movement of peak dye concentration.  Both of these problems were probably
caused by the basic analytical (nontidal) solution employed by this model
since refinement in the segmentation did not appear to overcome them.

-------
                                                                     It  -  2
     3,   A comparison of observed  spatial  profiles  and  those  obtained
from the Dynamic Estuary Model  indicated that,  except for  minor
differences in peak dye concentrations  near the release point and  the
rate of downstream transport, the  Dynamic Estuary Model was also ade-
quately verified using the 1969 Potomac dye study data. For  this
verification, the dispersion coefficient ranged from about 1.0 to
2.0 mi2/day depending on the existing tidal velocities  and depths.
     4.   In order to define the mass transport  characteristics of  the
Anacostia Tidal River better and also to provide data upon which confir-
mation of dispersion rates and other model input for this  tidal  system
could be based, a 7-day continuous dye release  was  conducted  during
April 1970 at the Bladensburg Marina, above the D.  C.-Maryland line.
     5.   With the exception of inadequate downstream movement of the
simulated peak concentration, both the Dynamic  Estuary and Thomann Models
appeared to be capable of closely predicting the observed  dye distribution
in the Anacostia River.
     6.   A Potomac dye study conducted in 1965  was  successfully simulated
with both the Dynamic Estuary and Thomann Models.  The substantially lower
freshwater inflows which occurred during this study resulted in the use of
lower dispersion coefficients  (1.0 - 2.0 mi^/day) for  the Thomann Model.
The dispersion coefficients  remained the same in the DEM.

-------
                                                                 II - 3
     7.  Based on all of the dye simulation studies, it can be concluded
from the standpoint of model verification that, in general, maximum
difficulty was experienced in the immediate area of the release point.
However, this could have been expected since complete mixing had not yet
occurred in the prototype but had to be assumed in both of the models
(neither model can treat vertical concentration gradients), and because of
the difficulty in selecting representative sampling points.
     8.  Chloride profiles observed in the Potomac Estuary during 1966
and 1969 were simulated using the Thomann Model.  Historical station
data, showing annual fluctuations in observed and predicted chlorides,
indicated very good agreement when dispersion coefficients ranged
between 1.5 - 14.0 mi^/day during relatively low-flow periods and 2.0 -
20.0 mi^/day during the higher flow periods of 1966 and when they ranged
between 2.0 - 16.0 mi^/day for the entire year of 1969.
     9.  The following conclusions can be drawn based upon the chloride
simulations performed with the Thomann Model:
     a.  A considerable range in the dispersion coefficients can be
expected where there are great salinity increases in a longitudinal
direction.  The pronounced gradients, rather than the actual salinity
concentrations, require much larger dispersion coefficients for the
Thomann Model if meaningful  data are to be obtained.
     b.  Dependence of dispersion coefficients on freshwater inflow rates
was not as evident for chloride as it was for dye simulations.  In fact, an
apparent anomaly appeared since maximum chloride intrusion occurred in the

-------
                                                                  II  -  4
Potomac Estuary during low-flow periods whereas the use of high dis-
persion coefficients normally associated with high-flow periods was
required in the model  to produce similar results.   Thus, the dispersion
term in the Thomann Model may have to be evaluated and related to flow
in a different manner for constituents dispersing  upstream than for
those dispersing primarily downstream.
     10.  The observed chloride data, measured longitudinally during  a
period of relatively steady-state flow (July-December 1965), were
simulated in the Dynamic Estuary Model.  Special problems involving  both
the advection and dispersion components arose, probably as a result  of the
unusually high concentration gradients.
     11.  The following conclusions can be drawn based upon the chloride
simulations performed with the Dynamic Estuary Model:
     a.  The dispersion term employed in the Dynamic Estuary Model (C4)
must be increased over an order of magnitude in the seaward portion  of the
model network to reflect the increasing chloride concentration gradients
and to obtain sufficient mass transfer across the seaward boundary.   The
approximate range in dispersion coefficients used for simulation of
chlorides was from 1.0 mi^/day to 20.0 mi^/day for representative depths
and tidal velocities.
     b.  Determination of the proper amount of constituent advected  from
one node to another in the model becomes quite critical in areas with high
concentration gradients.  The quarter-point solution method for advective
transport, which generally produces acceptable accuracy and low numerical

-------
                                                                II - 5
mixing, did not yield satisfactory comparisons for chloride simulations



in the Potomac.  The use of a third-point advective concentration within



a given channel was found to yield more favorable results.



     12.  Undoubtedly, many of the difficulties associated  with application



of either the Thomann or Dynamic Estuary Model to simulate  the movement of



chlorides are the result of representing a three-dimensional  stratified



system with a one-dimensional model.  This further points out the importance



of hydrodynamic behavior and the fallacy of using a model to  solve a problem



for which it was not designed.



     13.  In order to determine where additional  refinement of model input



may be warranted, a detailed sensitivity analysis of several  factors



pertinent to the Thomann and/or Dynamic Estuary Models was  performed.



     14.  Based upon the results of this sensitivity analysis with the



Thomann ,Model, the following represent a listing, in decreasing importance,



of the sensitivity of each variable:



     a.  Dispersion coefficient (K),



     b.  Decay rate,



     c.  Segmentation, and



     d.  Proportionality factor (a) used for advective transport.



     15.  Of the various input parameters investigated for  the Dynamic



Estuary Model, the decay rate and the solution technique for  advective



transport appeared to be the most sensitive in affecting the  model's



predictions.  With the exception of simulating salinity (chlorides),



the least sensitivity was identified with the dispersion coefficient.

-------
                                                                  II  -  6
While the hydraulic solution was  relatively sensitive to the Manning
roughness coefficients, the quality predictions  were insensitive to them
as well as to the tidal range specified at the seaward boundary.  Based
on limited data, it appeared that the Dynamic Estuary Model  was con-
siderably more sensitive to network detail than  the Thomann  Model.
     16.  Utilizing an approach where simulated  data from both tidal and
nontidal models were compared, relationships of  dispersion coefficients
(as used in the Thomann Model) to freshwater flows were formulated for
the Potomac Estuary.  For the flow range investigated (930 cfs ^o 20,000
cfs) it was determined that dispersion coefficients (K) varied directly
with flow in accordance with the following equations:
     Upstream from B1ue P1 aJ ns
              K = 0.195 Q°'34
     Blue Plains to Occoquan Bay
              K = 0.027 Q°-63
     where:
              K = dispersion coefficient  (mi^/day) and
              Q - freshwater flow (cfs).
     17.  The primary disadvantage of the Thomann Model or any nontidal
model is the greater significance of dispersion coefficients for an
estuarine system and the need to relate them to freshwater flows, sal in;
gradients, and other factors.
     18.  Another deficiency encountered with the Thomann Model, as evi
denced by certain chloride simulations and the sensitivity analysis was

-------
                                                               II - 7
the apparent deemphasis of both tidal and nontidal advective transport
as a result of the model's strong dependence on dispersion.   Moreover,
the fact that a flow sequence is routed through the system instantaneously
indicates that the hydraulic conditions influencing advection are based
strictly on a velocity (Q/A) relationship and not on volume  displacement.
     19.  Other important disadvantages of the Thomann Model are its
inability to (1) branch in a lateral direction and (2) link  more than two
constituents.
     20.  Significant advantages of the Thomann Model over the FWQA Dynamic
Estuary Model as both models are presently programmed are (1) its less
stringent input requirements, (2) its ability through the Namelist I/O
option to change input variables, such as flow on a daily basis, and
thereby readily simulate interseasonal conditions, and (3) the capability
of running several alternative data decks back-to-back with  a minimum of
effort.  In short, one can generate considerably more data in much less
time with the Thomann Model.
     21.  In addition to more demanding input requirements,  another dis-
advantage of the Dynamic Estuary Model is the fact that it is quite costly
and time consuming to link different hydraulic conditions if simulation of
seasonal or annual quality characteristics is desired.

-------
                                                                II - 8
     22.   Because the  Dynamic  Estuary  Model  is a  "real-time" system, it



can predict the effect of tidal  exchange  and excursion on  the distribution



of a pollutant as well as other  intratidal  cycle  variations in water



quality and it is significantly  less dependent on an empirically derived



dispersion term.   Other major  advantages  of this  model are its ability to



branch in a lateral  direction  and  thereby allow simulation of water quality



behavior within embayments and to  consider six separate  constituents



either dependency or  independently of one another.

-------
                                                              Ill  - 1

                            CHAPTER III
                    DESCRIPTION OF THE STUDY AREA
     The Potomac River Basin,  draining 14,170 square miles,  is the
second largest watershed in the Middle Atlantic States.   Its tidal
portion begins at Little Falls in the Washington Metropolitan Area
and extends 114 miles southeastward to the Chesapeake Bay.   The
section of the estuary discussed in detail in this report is the
40-mile reach extending from Key Bridge  in Washington to Sandy Point
which is located downstream from Quantico, Virginia (Figure  1-1).
     The estuary is less than  200 feet wide near its upper end at
Chain Bridge and widens to approximately 4,000 yards at Sandy Point.
A shipping channel with a minimum depth of 24 feet is maintained from
Washington to the Chesapeake Bay.  The major embayments along the  upper
Potomac Estuary and their surface areas  are:
     Embayments               Surface Area
                                      PI    ?
     Occoquan-Belmont Bays    218 x 10  ft
     Mattawoman Creek          75 x 106  ft2
     Gunston Cove              65 x 106 ft
     Piscataway Creek          36 x 106 ft2
     Anacostia River           31 x 106 ft
     Quantico Creek            30 x 106 ft2
Except for the main channel and a small  reach below Chain Bridge where
depths up to 80 feet occur, the estuary is relatively shallow with an
average depth of about 15 feet.  The embayments generally have average
depths of 5 feet or less.

-------
                                                               Ill - 2
     The upper 20 miles of the study reach (Chain Bridge to Marshall
Hall) contain fresh water whereas the lower 20 miles (Marshall  Hall to
Sandy Point) form the transition zone from fresh to brackish water.
The average tidal range at Washington is 2.9 feet, with high and low
water occurring about +6 and +7 hours respectively.*
     Physical data for the entire Potomac Estuary are summarized in
Figure III-l (cross-sectional area versus distance below Chain Bridge),
Figure III-2 (accumulative volume versus distance below Chain Bridge),
and Figure  III-3 (accumulative surface area versus distance below Chain
Bridge).  More detailed information was recently published by CTSL  in a
separate report  [1].
* Referenced to Piney Point  (River Mile 99)

-------
= V3MV TVNOU33S SSOiD

-------
8
                                                      -o
                                                        a
                                                        o
                                                      -8z
                                                      -8

-------
o
                                                          -8

-------

-------
                                                            IV - 1
                             CHAPTER  IV
                DESCRIPTION OF  MATHEMATICAL MODELS
A.  THOMANN MODEL
     The Thomann Model  [4] was  originally  developed  in  1963 as a one-
dimensional, steady-state, BOD-DO  model  specifically for  the  Delaware
Estuary.  A time-dependent version of this model  [5] and  a chloride
model [6] were developed in 1966-1967 by General  Electric under con-
tract to the Federal  Water Pollution  Control  Administration.* Each of
the above models was  applied to the Potomac Estuary  shortly after
development.
     The time-dependent Thomann Model employs a  segmented network of
the water body under  consideration and utilizes  a finite  difference
approach to solve the basic mass balance equations.   For  the  case of
BOD and DO, these equations can be written as follows:
     nan a,] + c^-.] = EJ,]
     HAH [c,] t [£.] - [r, cs,  * P,  - d, L,]
where [I JJ denotes a square matrix of order  n and  [ ]  denotes a column
vector of dimension n (n is equal  to  the number  of  segments in the system),
     The total number of equations and unknowns  equals  2n.  The components
of matrices A and B are defined as:
                        a. Q  + E
     A       = R      -  '  J    i
     V i-i   Bi, i-r    M.
                           V.
  Now Environmental  Protection Agency

-------
                                                                 IV  -  2
                                               dj
      A         -           -  Ei  + 1  "*1  *
      A
       i ,  i  + 1     i ,  i  + 1           \Tj




 The remainder of the  terms  are  defined  below:


      L   =   BOD


      C   =   DO


      J-   =   forcing  function or loading in section i


      r.   =?   reaeration  coefficient
       J

      C   =   saturation  value of DO


      d.   =   decay coefficient
       J

      P..   =   other sources and sinks of  oxygen


      V.   =   volume of segment i


      Q.   =   net flow
       \J

      E.J   =   eddy exchange coefficient


a.  •  <(>.   =   advection factors
  I J 5  I


      Of special importance are the eddy exchange coefficient and the


 advection factors.  The eddy exchange coefficient is used to describe the


 tidal and other nonadvective effects on the transport of a constituent.


 Between sections i and i + 1, it can be computed as follows;



      F     =  i , J x  i , j                ,

       i, j    1  /.   .  ,      v x 27.878 x 10°

              2  ai   Li + 1;

-------
                                                                IV - 3
where:


     K.  .  =  eddy diffusion coefficient between sections i  and i  + 1
      "i > J

              (mi2/day)


     A.  .  =  cross-sectional area at the boundary of segments i  and
      ' > J

              i  + 1,  and


        L.  =  length  of segment i



     The purpose of the advection  factor is to serve as a means of com-


puting the  concentration of a constituent at the interface of two  segments


by "weighing" the concentrations in these two adjacent segments.   In order


to guarantee positivity in the solution, the advection factor takes on the


following definition:
Ei - 1 ' Ei '
Qi - 1 , J ' Qi , J

'i > J
     if .  .  > 0.5 then .  .  = 0.5
          < i J              ' >  J
     for the first section:
     in which case a =  1.0 (pure advection).   If the concentrations in


the adjoining sections are to be weighed equally (pure dispersion both c


and a are 0.5.

-------
                                                                IV  -  4
     The simultaneous,  linear,  first-order differential  equations
employed by the Thomann Model express  the time  rate  of change  of
pollutant concentration as a function  of the advection and  dispersion
components at each segment interface and sources  and sinks  within  each
segment.  These equations are numerically integrated by a  fourth-order
Runge-Kutta procedure whereby the truncation error is kept  within  some
preset allowable value by constant adjustment of  the time  step size.
The solution yields a mean tide concentation of a particular consti-
tuent for every segment.
     Since the Thomann Model does not have a "real-time" solution  where
tidal movement is explicitly considered in the mass  transfer equations,
the dispersion coefficient (K)  must be an "all-inclusive"  term that can
grossly represent tidal behavior.  Another source of uncertainty is
numerical dispersion which is introduced by the assumption of a completely
mixed finite volume.

-------
                                                             IV  - 5
B.  FWQA DYNAMIC ESTUARY MODEL

     The DEM represents the two-dimensional  flow and mass transfer within

an estuary by a network of interconnecting junctions and channels.

Uniformity must be assumed only in the vertical  direction.   The hydraulic

component of the model  essentially solves  the equations describing the

propagation of a long wave (tidal) through a shallow water system.  When

the tidal conditions such as amplitude, period,  etc. existing at the sea-

ward boundary are known, this solution can be obtained from the one-

dimensional form of the equations of motion and  continuity.  The equation

of motion is:


     3u     3u  „, ,     3H
     3t = ~U97 -K/U/U -9 a?


     where:

         u = velocity along x axis

         x = distance along x axis

         H = water surface elevation

         g = acceleration of gravity

         K = frictional resistance coefficient

         t = time

The equation of continuity can be expressed as:


     
-------
                                                                  IV - 6
      The  equation  of motion  is applied to the channel elements to predict
 velocity  and  flow  and  the continuity equation is associated with the
 junctions and accounts  for tidal fluctuations in the water surface elevation
 (head)  and corresponding changes in volume.  Both of these differential
 equations are converted to finite difference form and solved by numerical
 integration techniques  (predictor-corrector method) to yield a "real-time"
 hydraulic solution.  The time  step used  is normally very  small, i.e.,  1-5
^minutes,  as dictated by the  network and  by numerical stability.  The solution
 will  converge for  a given set  of boundary conditions (including tides  and
 freshwater flow rates)  to a  dynamic equilibrium having velocities, flows,
 and heads repeated at  intervals equal  to the specified tidal period.
      The  quality component of  the FWQA model incorporates the  two basic
 transport mechanisms;  namely,  advection  and diffusion, and requires  the
 dynamic steady-state hydraulic solution  as input.  Advective transport is
 primarily a hydraulic  mechanism that moves the constituent in  the direction
 of flow.   It can be represented by the following  two equations:
      3C _ ,. 3C
      at     3x
 or in terms of mass and in finite difference form
      where:
      c* = concentration in advected water
      U  = channel velocity, and
      A  = channel area

-------
                                                                IV - 7
The determination of c* can present special  problems  such as computa-

tional instability and "numerical  mixing."  Previous  studies have

indicated that an advected concentration equal  to that at one-quarter of

the channel length, measured in the direction of decreasing gradient,

generally proved satisfactory.

     Diffusion (eddy) is represented in the  model as  a physical-chemical

transport mechanism dependent only upon concentration gradients.   Mathe-

matically, it can be expressed as:

     l£ = % 32C
     3t     3x^"

or again in terms of mass

     AM _ v. Ac
     At ~ ™ x

where:

     Ac =  concentration gradient within a channel

      x =  channel length, and

      K =  diffusion coefficient

     The diffusion coefficient has a dimension of length squared over

time and can be defined by the following equation:

      K =  Ci,/U/R

where:

     C4 =  a constant

     U  =  mean channel velocity, and

     R  =  hydraulic radius of channel.

-------
                                                                IV  -  8
     As currently programmed,  a  maximum of six constituents  can be
handled simultaneously in the  FWQA model.   They may be either conser-
vative or nonconservative and  may be interrelated in any mathematically
describable fashion.  Recent modifications have enabled this model  to
quantitatively consider terms  other than carbonaceous BOD oxidation and
reaeration in the DO budget.  For example, nitrification, benthic oxygen
demand, and phytoplankton photosynthesis and respiration have also been
included.
     The model will compute constituent concentrations throughout the
system by means of a numerical integration solution of the above finite
difference equations describing advection and diffusion as well as those
expressing degradation and the constituent's other sources and sinks.
While maintaining mass continuity, the solution proceeds from channel  to
channel and junction to junction performing the appropriate transfers
over a specified time step.
     In order to minimize "induced dispersion" or numerical  mixing, ample
consideration should be given  to the network layout and to selection of the
time step.  Ideally, the ratio of fluid displacement  (LJAt) to the channel
length (x) should approach unity.

-------
                                                                 V  -  1





                             CHAPTER V



      MATHEMATICAL MODEL SIMULATIONS OF 1969-1970 DYE RELEASES



A.  THOMANN MODEL



1.  Simulations and Verification



     a.   Potomac Dye Study



     It should be noted at the outset that all  mathematical  model  verifi-



cations  involving the 1969 dye release data were based upon  a dye  loss



rate of 0.03 per day as computed in Section A-3c of the Appendix.   While



other values for loss rate were considered in the Thomann and Dynamic



Estuary models, the most favorable output was obtained with  the 0.03  per



day rate.   Moreover,si nee neither background nor boundary data were



collected prior to this dye study, the upper and lower boundary concen-



trations as well as a uniform background concentration of 0.1 ppb  were



arbitrarily specified in both models to compensate for differences  between



observed and discharged dye quantities.  An evaluation of the sampling



data collected from areas where dye was nonexistent and from background



data collected during the 1965 Potomac dye study provided some insight



into the magnitude of these concentrations.



     The expanded segmented network used for the Potomac Estuary Thomann



Model is shown in Figure V-l.  Model simulations discussed in this  section



were made using the upper 35 segments between Chain Bridge and Mattawoman



Creek.



     During the simulation and verification studies, special consideration



was given to the following:



     1)   Advection factors (, a), and



     2)   Dispersion coefficient (K).

-------
A/
                     THOMANN MATHEMATICAL MOOtl SI .McN'S
   ORIGINAL 28 SEGMENTS



   EXPANDED 73 SEGMENTS
                         SCAU N ML£S
              POTOMAC    ESTUARY
                                                       FIGURE V-i

-------
                                                                 V - 3
     As described previously, the advective proportionality factors are
used to determine the constituent concentration at a segment interface
as a function of the concentrations in the adjoining segments.   This
concentration, when multiplied by a net flow across the interface, yields
the quantity of constituent advected from one segment to another.   Theo-
retically, a must range between 1.0 (nontidal or pure advection system)
and 0.5 (pure tidal system with no net adve,ctive flow).  In the original
Thomann time-dependent model,  was computed from the ratio E/Q, where
E is the eddy exchange coefficient (ft^/day) and Q is net flow and a was
equal to 1 - .  Since there was no stipulation on the magnitude of a, a
program modification was made to maintain its value between these specified
limits.  A sensitivity analysis of cc on model predictions is presented in
Chapter VI.
     The major problem involved with verifying the Thomann Model was esti-
mating the longitudinal dispersion coefficient (K).  This is a complex
parameter affected by  (1) freshwater inflow rates, (2) salinity gradients,
(3) estuary geometry, and (4) tidal conditions.
     The relationship between freshwater flow rates and dispersion coeffi-
cients is presented in Chapter VI.  Salinity has a very pronounced effect
on dispersion due to density gradients causing significant changes in the
boundary shear velocity distribution.  As reported by Harleman [7], dis-
persion coefficients calculated for freshwater and high salinity areas  in
a constant area estuary (Rotterdam Waterway) were 0.5 mi2/day and 40 mi^'
respectively.

-------
                                                                 V  -  4
     The geometry of the channel  and the tidal  conditions  also affect the

extent of dispersion although quantitative relationships among the  three

have not been determined in this  report.  A sensitivity analysis  of the

dispersion coefficient in the Thomann Model is  presented in Chapter VI.

     In an attempt to verify the  Thomann Model, several  runs were made

using the 1969 dye release data,  each with different dispersion coeffici-

ents.  The most favorable agreement between observed and simulated

spatial profiles was noted utilizing the coefficients shown below:

       Segment                      Time Period
       Numbers             November 1-5     November 6-30

 1 - 13 (upstream of
          discharge)        K  =   2.0        K  =  3.0*

14 - 37 (downstream of
          discharge)        K  =   3.0        K  =  5.0*

* Dispersion coefficients were increased after November 5, to reflect
  the increased freshwater inflows and were increased farther down-
  stream to reflect geometry and  salinity changes.

     The simulated spatial profiles obtained from the Thomann time-

dependent model and the observed  profiles at high-  and low-slack tide

are shown in Figures V-2 through  V-6 for 5 different days  of the study

period.  Major emphasis during model verification studies  was placed

upon closely simulating dye peaks, both spatially and in magnitude, and

achieving similarly shaped curves.   It was also important  that simulated

profiles generally fall within high- and low-slack  water observed data

since they do  represent mean tide conditions.  As can be seen in these

figures, acceptable agreement between prototype and model  data was

-------
                                                                 V - 5
generally obtained but certain discrepancies  did arise.   The  primary



shortcoming in the Thomann Model  simulations  appeared to be the



pronounced "peaking" that occurred during the early period of the



study.   The simulated profiles for November 6 (Figure V-2), November 7



(Figure V-3), and November 10 (Figure V-4) show extremely sharp and



somewhat greater peaks as compared to prototype data.  Another diffi-



culty encountered with some of the Thomann Model simulations  was



insufficient downstream movement  of peak concentrations.  This is



evident in Figures V-3, V-5, and  V-6.



     A refinement in the estuary  segmentation did not resolve the above



problems.  Increasing the dispersion coefficient lowered the  peaks but



the configuration of the curve was adversely  affected for model verifi-



cation.  It appeared that all of  the problems associated with simulation



of dye peaks were created by the  nontidal approach or the analytical



mathematical solution of the basic equations  employed by the  Thomann



Model.



     A station history or temporal verification of the dye release data



with the Thomann Model simulations discussed  previously is shown for four



selected sampling stations in Figure V-7.

-------
                                                            r
                           15

y
LL
cr
   I
   2

   Q;
   UJ

   Q.
                               \
                                                      X


B ^




1 i
§ S




i i i
*J "1 *
d d d
(qdd)
31Q


3




OJ
d


\
\
\
\
\
d i



-------
s
                     d
                    (<*")
                    3AO
3          §

-------

-------
                                                                             1-3
9   >•
I   2
S    <  ;
i    I  s
*    2  8
                                 S



                                I

                                I

                                I

-------
      O
m    2

-------
5?
      UJ

o  *
2  a
5  &
UJ  D
I-
                     cr
                     CD


                     z
                     O
                     to
                     d   o
                    in   uj


                    i   5

                    P   a

                    §   >
                    CO   (T
                 r
                 q
                                r  ONOO
CO
z o
< o
I <0
1 :
fO "> i.
^ s.
z - /
0 z /c
t- QC
< y <
H >
to tr ^ ,
<]
0

O

3
i
c

c
3
1 1
q - c


- 0
CM

tf>
5
a
11
UJ
Z
. g t-



)
>
    O
    z

    $
    o
                                                                                   a<

                                                                                   to
                                                                                   M
    CTi   uj


    5   i
    l-   tr
 r
o
                                                                                          ; ONOO
                                                                                                                                r-
                                                                                                                                 l

                                                                                                                                H
                                                                                                                                UJ
                                                                                                                                (T
                                                                                                                                n
                                                                                                                                o
                                                                                                                    o
                                                                                                                    (M
                                                                                                                         I
                                                                                                                         Z

                                                                                                                    O   (-
                            qdd•ONOD
                                                                                                                         10
                                                                                                                         UI

                                                                                                                         Z

-------
                                                                 V  -  12





     b.  Anacostia Dye Study



     The segmented network applied to the Anacostia tidal  system for



modeling purposes is presented in Figure V-l.   The problem of veri-



fying the Thomann Model  based upon 1970 Anacostia dye study data was



again essentially one of evaluating a dispersion coefficient to yield



the best agreement between observed and simulated data.   The dye loss



rate was specified as 0.05 per day for all simulation runs.  After



several trial runs, it appeared that a K value of 0.7 mi^/day produced



the most satisfactory results.  Attempting to vary the dispersion



coefficient longitudinally or relating it to freshwater flow, as was



done with the Potomac, did not seem to improve the simulated data.



     Observed spatial profiles and simulated data from the Thomann  Model



are shown in Figures V-8 through V-12.  An analysis of these figures



indicates that the basic configurations of the two curves  are generally



similar for various times in the study, especially those portions



representing the leading edge of the dye cloud.  Moreover, relatively



close agreement was obtained between observed and simulated peak dye



concentrations insofar as magnitude was concerned.  Again, a major



shortcoming of the Thomann Model predictions, which can be seen in



several of the figures,  was an insufficient rate of longitudinal peak



movement.



     The net advective transport of the dye cloud's centroid was not



accurately simulated with the range of dispersion coefficients investi-



gated.  As was noted with the Potomac dye study, the effects of such



factors as extreme and "flashy" flow variation and unusually high or

-------
          THOMANN  MODEL  DYE  SIMULATION AND VERIFICATION
                               ANACOSTIA  RIVER
                                  APRIL 23. 1970
 9-
 8-
 7 -
  6-
a.
a.
Jjg
O
 4-
  3-
 2-
         	 LOW SLACK (OBSERVED)
          	 HIGH SLACK (OBSERVED)
         	MEAN TIDE (PREDICTED)
                                    456
                                   MILES  FROM  POTOMAC
	1	
 FIGURE .Z-8

-------
        THOMANN  MODEL  DYE  SIMULATION  AND VERIFICATION

                             ANACOSTIA  RIVER

                                APRIL  27, 1970
10-
 9-
8-
 7-
 6-
 4-
 3-
 2-
LOW SLACK (OBSERVED)

HIGH SLACK (OBSERVED)

MEAN TIDE (PREDICTED)
                  I
                  2
             I
             3
 r       i        i
 456
MILES FROM  POTOMAC
  I
 7

FIGURETT-9
I
8

-------
          THOMANN  MODEL  DYE  SIMULATION  AND  VERIFICATION

                                ANACOSTIA  RIVER

                                   APRIL 29. 1970
             -LOW SLACK (OBSERVED)
 lO-i
  9-
  8-
  7-
 6-
-o
a
a
'5-
 4-
 3-
 2-
         	HIGH SLACK (OBSERVED)

         	MEAN TIDE (PREDICTED)
                                                               \
                             I
                            3
 I        I         I
 456
MILES FROM  POTOMAC
I
9
                                                              FIGURE 1- 10

-------
 9-
 8 -
 7-
 6-
  5-
Q
 4-
 3-
 2-
         THOMANN  MODEL DYE SIMULATION  AND VERIFICATION

                            ANACOSTIA  RIVER

                                 MAY 4. 1970
10-1
LOW SLACK (OBSERVED)

MEAN TIDE (PREDICTED)
                          \        I        I       i
                          3456
                                MILES FROM POTOMAC
                                           I
                                           7

                                        FIGURE 3C- I

-------
         THOMANN  MODEL DYE SIMULATION  AND VERIFICATION


                             ANACOSTIA  RIVER


                                 MAY 7. 1970
 10-1
 9-
 8-
 7-
 6-
>- 5
o
 4-
 3-
 2-
  I-
HIGH SLACK (OBSERVED)


MEAN TIDE ( PREDICTED )
                                  I        I        I

                                  456

                                MILES FROM POTOMAC
                                                        FIGURE 3T-I2

-------
                                                                 V - 18
low tides with the corresponding changes in tidal  excursion and advection



which generally accompany a long-term study are not adequately incorpo-



rated in the nontidal  model and while the dispersion coefficient does



exert considerable influence, there are limitations present.

-------
                                                                 V - 19
B.  FWQA's DYNAMIC ESTUARY MODEL



1.  Simulations and Verification



     a.  Potomac Dye Study



     The network of junctions comprising the Dynamic Estuary Model for



the main Potomac are basically the same as those shown in Figure V-l.



The simulation data presented herein pertain to the 35 junctions



upstream from Occoquan Bay.



     The verification of the Dynamic Estuary Model based upon 1969 dye



study data initially required a reliable representation of the hydro-



dynamics during the study period.  For sake of convenience, only two



hydraulic conditions were simulated.  The period from November 1-5



assumed an average flow of 1,886 cfs.  The remainder of November was



assigned an average flow of 3,974 cfs.  The actual tidal record at



Piney Point, Maryland, (near the seaward boundary) was obtained from the



U. S. Coast and Geodetic Survey for the month of November.  A somewhat



typical tide, having a period of 12.5 hours, was selected and assumed  to



recur continuously throughout the study period.  Hydraulic runs using



different Manning coefficients were tried until the simulated tidal data



at Washington, including ranges and phasing, compared favorably with



corresponding observed data.   Predicted tidal data at intermediate



stations throughout the estuary were also compared with observed data  for



hydraulic verification.

-------
                                                                 V - 20
     Insofar as the quality program is concerned, consideration was
given to (1) appropriate dye loading rate, and (2)  dispersion  term
C4*.  Since dye loading rates were computed fpr each 4-hour interval
of the 13-day release period, a similar procedure was used in  the model.
Simulations were based on varying the dye concentrations in the effluent
every 4 hours until the 13th day when the dye release was shut off
entirely.  While the dispersion coefficient is relatively unimportant
in this model as compared to the Thomann Model, the initial value of
2.5 used for Ci» was considered too low and was subsequently increased an
order of magnitude to 25.  For a tidal velocity of 1.5 ft/sec  and a
channel depth of 15 feet, a d, of 25.0 would translate to a dispersion
                     2
coefficient of 1.7 mi /day.  This value yielded better results and
additional  refinement in the dispersion coefficient did not appear
warranted.
     The simulated dye profiles obtained from the Dynamic Estuary Model
for the conditions and assumptions described above are shown in Figures
V-13 through V-16.  Also shown are high- and low-slack water sampling
data for the same 4 days of the study period.  The spatial profiles
depicted in these figures indicate that the model was predicting dye
movement and concentration buildups satisfactorily.  While simulated
  As indicated previously, the actual  dispersion coefficient is computed
  internally from the relationship
                                   E i C^ U d
  where C4 is a constant, U is the mean velocity, and d is the depth

-------
l±J

§1
2 5
fc£
  CC f- o>

  LJ «« 5
  ^> Ul »
ft Q
UJ z

  <

O ^
O 
-------
                                                                                                                                                                                         o
                                                                                                                                                                                        "•*
U  2
                                                   s
                                                   Q

                                                   6
I      1     I

3      3     *
«      in     ">

i      *     1
                                                   o     Q
                                                   C     U
                                                                  =
                                                          «)      ^     2
                                                          as      Z     2
                                                          O      (/)!/)
                                                                                                                                                                                            O
                                                                                                                                                                                            o
                                                                                                                                                             \
                                                                                                                                                                 \
                                                                                                                                                                    \

-------
g " fc s
fc 5" a-
w *" ~

y z 1 i
5 92 i
^ i- Q- Sr
  - 5
a
                                          -3AQ

-------
IN
5 £i
4 S
             ill 1
                * ^
             5 a ^ sj
             5 3 9J 5i
             B in


             Hll

                Q 0
             Q Q Ul "
               I
                                          \
                                             I
                                             o
                             -3AQ

-------


CO
UJ
_J
\J_
2
a.
UJ
>
TEMPORAL D












>
ae
<
D
Si
UJ
0
^2
§
O.
a:
UJ
|












_i
2
•^
i
UJ
FWQA DYNAMIC










WOODROW WILSON BRI
1
V 	
f
(V
V
— 1 1
-8
" I
O
~f\J
UJ
K
_0


z
<
X
\;
17
\?
^
'(
O
n
i«
>
<
0 Q
o
oj
|
^

_o
'
\ i
o o o
        t-



        I
                                                 UJ
                                                 
-------
      g
      £
                             _o
                              f)
      O

      g
              I
              o


             '   3NOD
                                  i
                                                 2
                                                 o
                                                 z

                                                 1
                                                                                 o
                                                                                 "n
         i
        >
                                                                                               UJ
                                                                                               cc

                                                                                               o
                                                                              o

                                                                              o
                             _o
                                           I
                                           o
                          2
                                            oo
                                        in  O
                                                      qdd •
      O
      a
to
2

<
 I
o
I
o
                                  10


                                  I
                                                               uj
                                                               Ul
                                                               cc.
                                                               u
                                                 i
                                                 o
                             _O
                             _o
                                                                          o
                                                                         "n
     i
_0
  \l
     UJ
                                                                                       _o
                                                   I
                                                   o
            qdd
                                                    qdd  '

-------
                                                                 V - 27
maximum dye concentrations were generally higher than prototype data,



they were not characterized by the pronounced "peaking" which occurred



with Thomann Model simulations and their spatial position agreed



favorably with observed data.  The other consistent difference between the



observed and simulated profiles was the insufficient downstream dye trans-



port by the model over a given time interval.  It is interesting to note



that a "real-time" solution permitted the effects of a short term dye



slug to be simulated as can be seen in Figure V-15.  Considering the



difficulty of model  verification by a comparison of spatial  profiles for



specific slack-tide periods, the Dynamic Estuary Model has demonstrated



the capability to simulate the hydraulic and quality behavior in the Potomac



acceptably utilizing 1969 dye study data.  Similar agreement between model



and prototype data can be shown when temporal variations are considered.



Data of this type (station histories) are presented in Figures V-17 and



V-18.

-------
                                                                 V - 28
     b.   Anacostia Dye Study

     The physical  network of junctions applied to the Anacostia tidal

river for the Dynamic Estuary Model  is shown in Figure V-l.   This network

is identical to the one used in the  Thomann Model and is comprised of 15

junctions with lengths averaging approximately 1/2 mile.

     For all hydraulic simulations during the study period,  an average

Potomac  tide (12.5-hour period) was  estimated from data recorded by the

U. S. Coast and Geodetic Survey at Piney Point.  Some degree of hydro-

dynamic  verification was lacking due to the absence of tidal gaging

stations in the Anacostia River.  Visual observations of the tidal range

near the point of dye release and the model's tidal range predictions

appeared to be of similar magnitude; however, it could not be deter-

mined whether the simulation of tidal phasing and duration of rise and

fall throughout the Anacostia, or even the assumed Manning roughness

coefficients were accurate.

     The dye study period was divided into four separate hydraulic

components as follows:

                                Average                  Average
     Time Period              Potomac Flow             Anacostia Flow
     April  20-28                 30,000                     180

     April  29-May 11              15,000                      83

     May 12-18                    7,800                     145

     May 19-28                    6,800                      72

-------
                                                                 V - 29
     The quality program for the Anacostia study was based on a constant



dye loading rate of 8.1 Ibs/day, a dye loss rate of 0.05/day and a uni-



form background concentration of 0.10 ppb.  Moreover, the dispersion



term, d*, was assigned a value of 25.0.  The dye profiles observed during



various days of the study and corresponding simulated data from the



Dynamic Estuary Model are shown in Figures V-19 through V-23.  While the



general longitudinal dye distribution predicted by the model compared



favorably with prototype data, several figures were characterized by



insufficient downstream movement of simulated peak concentrations.  On



one occasion (Figure V-19), the magnitude of the simulated peak was



excessive.  A further evaluation of the input factors which may have



influenced these differences such as network geometry or dye loading



rates was made but with no apparent success.  It appeared that a lack



of tidal data during the study period may have been partially respon-



sible, otherwise a better hydraulic representation would have been



obtained.  Another possible cause of the differences noted could have



been the flow averaging concept used for each hydraulic simulation.



This averaging may tend to disregard or minimize the effects of the



"flashy" flows that occurred during the early phase of the study.



     Improved agreement may have been realized in both models had trans-



ect sampling data been collected to correlate mid-channel concentrations



with cross-sectional averages.  Normally, the differences resulting from



this omission would be especially acute near the release point where



incomplete mixing could be expected and where most of the model verifi-



cation difficulties were encountered.

-------
   10-
   9-
   7-
a.
a.
O
                        FWQA   DYNAMIC ESTUARY  MODEL
                         DYE SIMULATION  AND  VERIFICATION
                                    ANACOSTIA   RIVER
                                     APRIL 23.  1970
                   OBSERVED LOW  SLACK DATA
                   OBSERVED HIGH SLACK DATA
                   SIMULATED LOW SLACK DATA
                   SIMULATED HIGH  SLACK DATA
                              T	1	1	T
                               3456
                                     MILES  FROM  POTOMAC
                                                                    FIGURE  V-19

-------
-Q
a
a
I
U
   10-
   9-
   8-
   7-
   6-
5-
   4-
   3-
   2-
    I-
                        FWQA  DYNAMIC  ESTUARY  MODEL
                         DYE  SIMULATION  AND  VERIFICATION
                                     ANACOSTIA   RIVER
                                      APRIL 27,  1970
              •- OBSERVED LOW SLACK DATA
                   OBSERVED HIGH  SLACK DATA
                SIMULATED  LOW SLACK  DATA
                   SIMULATED  HIGH SLACK DATA
                                        1         1         I
                                        456
                                      MILES  FROM   POTOMAC
                                                                    FIGURE V-20

-------
   8-1
                       FWQA  DYNAMIC  ESTUARY  MODEL

                        DYE  SIMULATION  AND  VERIFICATION
                                   ANACOSTIA   RIVER
                                    APRIL 29,  1970
        	 OBSERVED  LOW  SLACK DATA
                  OBSERVED HIGH SLACK DATA
                  SIMULATED  LOW  SLACK DATA
                  SIMULATED HIGH SLACK DATA
   7-
   6-
I   5-
   4-
   3-
   2-
                                       I        I         I
                                       456
                                     MILES FROM  POTOMAC
                                                                  FIGURE  V-21

-------
                      FWQA   DYNAMIC ESTUARY  MODEL
                       DYE SIMULATION  AND VERIFICATION
                                  ANACOSTIA   RIVER
                                   MAV   4 . 1970
                           	OBSERVED LOW  SLACK DATA
                           	 SIMULATED LOW SLACK DATA
  3-1
  2-
a
a
                                     456
                                   MILES  FROM  POTOMAC
                                                                FIGURE  V-22

-------
                       FWQA  DYNAMIC ESTUARY MODEL
                        DYE SIMULATION  AND  VERIFICATION
                                   ANACOSTIA   RIVER
                                    MAY  7 . 1970
                                  OBSERVED HIGH SLACK  DATA
                                  SIMULATED HIGH SLACK  DATA
  3-1
  2-
I
LJ
Q
                                      4        5
                                    MILES  FROM POTOMAC
                                                                  FIGURE  V-23

-------
                                                                VI - 1




                             CHAPTER VI



                OTHER MATHEMATICAL MODEL SIMULATIONS



A.  SIMULATION OF 1969 DYE RELEASE



     The 1965 dye release data were incorporated in a series of model



runs for verifying both the Thomann and Dynamic Estuary mathematical



models under a different hydraulic regime than that which occurred



during the November 1969 dye study.  The freshwater inflow rates during



the 1965 study period (June 10-July 15) averaged about 2,000 cfs, or



approximately one-half of the average November 1969 flows.  Because of



this lower flow, the appropriate dispersion coefficients required to



verify the Thomann Model were expected to be significantly different.



1.  Thomann Model



     Figures VI-1 through VI-4 show the observed high- and low-slack



water sampling data for various days and the corresponding simulated



mean tide data using the Thomann Model.  A dispersion coefficient of



2.0 mi2/day was used initially when flows were relatively high, and 1.0



mi2/day for the remainder of the study period when flows were much



lower.  Although other dispersion coefficients and different spatial



variations were investigated for model verification, the above values



appeared to yield the closest agreement.  It should be noted that these



coefficients were considerably higher than those obtained by Hetling and



O'Connell [3] using an analog computer solution based on temporal  or



"station history" verification.  Their computed dispersion coefficients



varied between 0.2 - 0.6 mi2/day for a similar reach of the upper Potomac



Estuary.

-------
                                                                                                                                         . in
                                                                                                                                          (M
                                                                                                           V3
 2
Q 3
(O
O)
1
1
1 1












O
I
I-
          00

          d
ID

O

-------

o
cc
Id



O
       UJ
2     «£
o     g

§     £

i     *
<7>     Q
•  i     *n
uj     (o
^     o>
            ID


            *

            (VI
            (M

            LJ

            z

                         o
                         I
                            y  S
                      00

                      (M
                                   <\J
A
(VJ
                                                                                                                 f-fO
                                                                  •«§
                                                                      cr
                                                                      o
                                                                      3
                                                                  .ID UJ
                                                                   — CD
                                                                                                                 _<*)
                                                                                      oo

                                                                                      O
o

o

-------
o
L_
LJ
>

Q
Z
^

z
o
^
	 1
K^
z>
s
co

LxJ
£T


s
s
/
/
1
1
1
UJ | /
(0 /
< 1 /
UJ \ 1
-1 jOl 1
LJ $' \
QC -.\ \
10 v \
PO \ >
£s \/
Q- /\
/ \
s /
O> /
«•>
 I
a;

o

-------
                           *
                           o
o  *
                                  3
                           I   3  Z
                           i   o
<
o
U.

CC
I—

<
u
O
                                                                                                                             -Ol

                                                                                                -  9

                                                                                                   00


                                                                                                CD  z





                                                                                                P-  5




                                                                                                "I
                                                                                                to  uJ
                                                                                                -  00



                                                                                                   lij

                                                                                                _  —I

                                                                                                   i
                                                                                                                             .<*>
                                                                                                                              -.
                                                                                                                                         t


                                                                                                                                         H
                                                                                                                                         UJ
                                                                                                                                         cr

                                                                                                                                         O

-------
                                                            VI  - 6
2.  Dynamic Estuary Model



     Two separate hydraulic conditions were assumed for the Dynamic



Estuary Model when attempting to simulate the 1965 dye study data.



Prior to June 23, the freshwater flow was assigned an average value of



2,687 cfs.  The second hydraulic condition, which represented the



remainder of the study period, was based on a constant flow of 1,451



cfs.  In general, a steadily declining flow was experienced during  this



dye study.



     The simulated 1965 dye profiles (high- and low-slack water)  that



resulted from using the Dynamic Estuary Model along with observed data



are shown in Figures VI-5  through VI-8 for several days of the study



period.  An examination of these figures showed relatively close  agree-



ment in the spatial position, shape, and peak dye concentrations  between



the prototype and model data.  However, in order for the observed and



simulated dye mass characteristics to compare favorably, it was necessary



to treat the dye as a conservative substance since applying a decay rate



of either 0.034/day or 0.02/day in the model reduced the dye concentrations,



and thus the mass, beyond  an acceptable level.  As will be pointed  out in



a subsequent chapter, the  effects of decay rate are quite significant.



The reason that this problem occurred in the mass balancing of prototype



and model data cannot be explained except that the indeterminate  fluores-



cent contribution from algae may have been responsible.

-------
                                                                                                                   r
                                                                                                                   k
                                                                                                                     (O
                                                                                                                   "^
5  2
O  b
2

>-  ^
0^  Q;
<  Ul UJ

£><


LJ  Z £


O     £
Q  D
    2

<  ^

a  ui
                 o
                 00
2
o
_J
I/)
o
_J
Q
Ul
UJ
in
CD
O


1
1
•«».
\-
O
|
tf>
O
I
0
Ul
w
m
O
1
1
I
1
1
g
o
§
-J
in
!
Q
Ul
_l
2



I
x:
^
_
i/>
i
c
I
Q
S
_
i?



                                                       O           o           O
                                                       in           ^           r»)


                                                     <1dd - NOI1VH1N3DNCO  3AQ
                                                                                            PJ
                                                                                                                    "
                                                                                                                     ro
                                                                                                                    "
-------
£   t
<   £
—5   -T   LJ
.-*'>(/)
t—         <
tO   Q   UJ
UJ   Z   CJ
      <   
                                                                                                                                                          (M


                                                                                                                                                          
o
oq
d
                                                                                                     r-.
                                                                                                     O
                                                                                                  
-------
Q  O
O  p

25
>-  u.
5  c
<  i
D  :
    Z o: 2
U

M
z  b
                                                                                                             r-
                                                                                                       Uo
                                                                                                        CO
                                                                                                          UJ
                                                                                                          O
                                                                                                          cr
                                                                                                          OQ
                                                                                                          I
                                                                                                          O
                                                o     o     o    o    o
                                                qdd -NOIiV«iN3DNOO  3AQ
                                                                                           ra    —.     q
                                                                                           c>    °     o

-------
_ NOIlVaiN3DNOD 3AQ

-------
                                                                VI - 11








B.  CHLORIDE SIMULATIONS - 1966 AND 1969



1.  Thomann Model



     Further simulation and verification studies with the Thomann Model



were made using 1966 and 1969 chloride data from the Potomac Estuary.



It was believed that chloride data would provide a sound basis for



estimating dispersion characteristics throughout the entire estuary



rather than just the upper portion for which dye data was available.



Moreover, the effects of density gradients created by varying chloride



concentrations on dispersion rates could be evaluated.



     The most complete temporal record of 1966 chloride concentrations



in the Potomac was provided by the Virginia Electric and Power Company



generating plant at Possum Point.   These data along with the simulated



chloride profiles at two representative model segments are shown in



Figure VI-9.  Observed and simulated profiles show reasonable agreement



except for the almost continuous cyclic variation in the observed data.



Two sets of dispersion coefficients were used in the Thomann Model for



the 1966 chloride simulations.  One set ranging from 2.0 - 20.0 mi^/day



was selected for the period January-May when freshwater inflows were



usually between 11,000 and 14,000 cfs.  The other set which ranged from



1.5 - 14.0 mi^/day was used for the remainder of the year for 1,000 -



7,000 cfs inflows.  The high range, of course, applied to the seaward



portion of the estuary where maximum density differences could be



expected.

-------
o
                  l/&»-S30IH01HO

-------
                                                                VI - 13








     Chloride concentrations at the upper boundary (Chain Bridge) were



determined from D. C. Department of Sanitary Engineering sampling data.



Seaward boundary values were correlated to U. S. Coast and Geodetic



Survey data collected at Solomons, Maryland.  Supplemental sampling



data were obtained from a Potomac nutrient study conducted by the



Chesapeake Bay Institute.  The concentration of chlorides in wastewater



discharges was assumed to be 40 mg/1.



     A comparison of simulated and observed profiles showing 1969 chloride



distributions is given in Figures VI-10 and VI-11  for sampling stations



in the middle and lower reaches of the Potomac Estuary.  The data as



presented in these figures indicate relatively close agreement between model



predictions and observed chloride profiles, again  except for the day-to-day



fluctuations in the observed data.  Various sets of dispersion coefficients



were tried in verifying the 1969 chloride data and the best agreement was



obtained by using one set of coefficients ranging  from 2.0 - 16.0 mi'2/day.



It should be noted that use of a single set of coefficients departs from



previous Thomann Model simulation studies discussed in this report wherein



dispersion was found to be directly related to freshwater flow rates.



While flows varied greatly during 1969, attempts to refine the dispersion



coefficients to reflect these flow changes did not prove successful.

-------
                                                          If

                                                          3 Q
                                                          t >
                                                          5 IT
                                                          D ^
                                                          3 £
    O


    o
UJ
UI
cr
O
I  8       S
i  5   g   j

z  z   o   ^
1  g   ^   >
i  ^   °   I

         o>
         
-------
                                                    I
o
0
o
o
o
o
8
§ 1
o c
§ ?
5 °
> §
	 1 	
O
§
i
o
o.
— h
o
•» -saaiac»D

-------
                                                                VI  -  16








C.  SIMULATION OF 1965 CHLORIDES



1.  Dynamic Estuary Model



     To demonstrate the Dynamic Estuary Model's  capability of simulating



changing salinity conditions in the Potomac Estuary,  an historical  period



(July-December 1965) was selected for which sufficient data were available



to establish the salinity distribution throughout the system at two



different points in time and for which flow rates were relatively uniform.



The mean Potomac River flow over Great Falls remained near 1,300 cfs



during this 5-month period with the mean monthly flows varying between



1,018 and 1,585 cfs.  Data were available to establish the salinity pro-



file in the main stem of the Potomac near the start of the period



(July 7-8, 1965) and also near the end (December 1-2, 1965).  These data



were converted to chloride concentrations and were then utilized to



establish visual "best fit" profiles for these two points in time as



illustrated in Figure VI-12.  No attempt was made to  relate any specific



data point to the tidal phase at the time of sampling, e.g., high-  or low-



slack water conditions; hence, the concentrations were assumed to be



representative of the mean concentration over a  full  tidal cycle.



     The profile for July 7-8, 1965, was specified as the initial profile



in the model.  For this simulation, the network  extended to Piney Point,



near River Mile 99.  The specified chloride concentration at the seaward



boundary was changed during the simulation to correspond to the change



noted in the prototype during the same period, i.e.,  the concentration

-------
   II. 000-,
   10,000-
    9000-
    8000-
    7000-
J   6000-
O   5000-
_j

u

    4000-
    3000-
    2000-
    1000 -J
                FWQA  DYNAMIC  ESTUARY  MODEL

            CHLORIDE  SIMULATION  AND  VERIFICATION

                         POTOMAC ESTUARY

                       JULY—DECEMBER , 1965
                           MILES BELOW  CHAIN  BRIDGE
                                                  FIGURE VI - 12

-------
                                                                VI  -  18






was increased from 8,400 mg/1  to 10,930 mg/1  in increments  of 55 mg/1



every 3 days.  A uniform flow of 1,300 cfs  in the Potomac  River was



maintained in both the hydraulic and quality  simulations.



     The chloride profile predicted by use  of the model  after the



147-day simulation period is illustrated in Figure VI-12 along with that



measured in the prototype.  As can be seen, the upstream movement of the



"salt wedge" and the spatial chloride distribution in the  Potomac Estuary



were successfully simulated for this 5-month  condition.



     In the course of model verification, certain unexpected problems



arose which were related to the basic transport mechanisms, advection,  and



dispersion.  These problems were evidently  the result of simulating a  con-



stituent having an extremely high concentration gradient.   For example,



the standard one-quarter point method, i.e.,  the assigning  of an advective



concentration equal to that at one-quarter  of the channel  length measured



in the direction of decreasing gradient, did  not prove adequate.  Although



this solution technique for advective transport is acceptable in terms  of



numerical mixing, accuracy, and stability when simulating  dye or other



constituents with a small concentration gradient, the one-third point



method yielded the best results with chlorides.  A discussion of the



Dynamic Estuary Model's sensitivity to the  advective transport solution  is



included in Chapter VII.



     The chloride simulation presented in Figure VI-12 was  based on d+



values of 15.0 (above River Mile 55), 80.0  (River Mile 55 to River Mile  70)



and 250.0 (River Mile 70 to River Mile 99).  Unlike previous simulations

-------
                                                                VI - 19

where the rate of dispersion was considered constant throughout the system,
it appeared that a strong relationship existed between dispersion rates
and increased salinity gradients as suggested by Harleman [7].   A dis-
cussion of this aspect is also presented in Chapter VII.
     It should be noted that an improved representation of the  chloride
distribution with less difficulty in defining the transport components
of the model, including the transfer of chlorides across  the seaward
boundary, might have been realized had the  model  network  been more refined
in the lower portions of the Potomac Estuary.  Almost all  channels in  this
area were much wider than they were long, a distortion which could con-
ceivably influence the chloride predictions obtained using the  Dynamic
Estuary Model.

-------
                                                                 VII  -  1

                            CHAPTER VII
                COMPARATIVE SENSITIVITY  EVALUATIONS
                THOMANN AND DYNAMIC ESTUARY MODELS
A.  DECAY RATE OF POLLUTANT
     The purpose of investigating the role of decay rate during  mathe-
matical modeling studies in the Potomac  was essentially twofold:   (1)  to
ascertain the effects of decay on the simulated distribution (steady
state) of a pollutant by using both the  Thomann and Dynamic  Estuary Models
and (2) to compare profiles from the two models for similar  loading rates
and freshwater flows for determining whether the predicted results  agree,
and what effect, if any, does decay rate exert on this agreement.
     Figures VII-1 and VII-2 present steady-state simulated  profiles  from
the Dynamic Estuary and Thomann Models,  respectively,  for decay  rates
varying from 0.0 to 0.4/day (base e), for a constant loading of  100,000
Ibs/day, and for a flow of 4,430 cfs. As can be seen  in these figures,
each model's predictions are highly sensitive to the magnitude of the
decay rate and each behaves similarly, i.e., lower peak concentrations
and less mass transport, particularly downstream, as the decay rate
increases.  The major change in profiles occurs between decay rates of
0.0 (conservative) and O.I/day.  A further increase diminishes the  effects
of the decay rate in both models.
     By comparing Figures VII-1 and VII-2, it is clearly evident that
many similarities existed in the predictions from both models.  Of
particular importance was the close agreement obtained in peak magnitudes

-------
(0
o

u.
UJ
                                 2 o

-------
UJ
*!
(/> O
UJ

-------
                                                            VII  -  4







for each of the decay rates investigated.   Moreover,  the general  shape



and position of the profiles did not differ appreciably over this  com-



plete range in decay rates, indicating that either model can be  used



to simulate a given constituent regardless of its decay rate. As  was



noted previously when simulating dye data, the major  difference  between



the two models' predictions was the pronounced peaking with the  Thomann



Model whereas the DEM "smoothed" the gradients considerably in the area



of maximum concentration.

-------
                                                               VII  -  5








B.  SEGMENT LENGTH



1.  Thomann Model



     A certain degree of refinement in the  segmentation  and the associ-



ated physical  data of an estuary is necessary;  however,  the CTSL studies



in the Potomac using the Thomann Model suggest  that overrefinement  of the



geometry may be a  wasted effort.  Figures VII-3,  VII-4,  and VII-5 show



simulated 1969 dye data for two separate networks that were applied to the



Potomac Estuary.  According to these figures,  there is relatively low



model sensitivity  to the length of segments.   The original  28-segment sys-



tem, from which 15 segments were used for this  analysis, produced basically



the same profiles  as the expanded system for  3  different days during  the



dye study period.   The only differences noted  were (1) slightly higher peak



concentrations, and (2) slight downstream displacement of entire profile.



The foregoing results remain true for decay rates of either 0.03 or 0.3



per day.



     The effects of "induced dispersion" due  to averaging concentrations



throughout the larger volumes and longer distances in a  coarse network



appeared to be minimal.



2.  Dynamic Estuary Model



     A detailed investigation was not undertaken  to determine the sensi-



tivity of the Dynamic Estuary Model to network  detail.  In fact, the



114-node network used for all DEM simulations  throughout this report  was



initially laid out for the Thomann Model.   In  order to avoid the time-



consuming task of developing the additional data  required for a new

-------
                                                            VII - 6

network, the original segmentation, except for embayments,  was used with-
out basic change in the DEM.   Subsequent simulations have indicated that
this degree of refinement was adequate to reproduce the hydrodynamic and
quality behavior in the prototype.   A single run based upon a 28-node
network, also specifically designed for the Thomann Model,  showed that a
network with this coarse detail could not accurately simulate tidal move-
ment in the Potomac Estuary.

-------
M
ui     G
z     z
?,     £

-------
                    If
                    H K
                    UJ UJ
                    2 Z
                    2 ft
_


II
1 ^

2 S
B
  z


LLJ <




t I

U I
                                1 -3AQ

-------
Z
O   o
     in  ?
»   °S
u.   ui 5
o   a 2
u

H-   z
U-   o
UJ   ±
                                                       *     *


                                                       I     1
                                                       UJ     UJ

                                                       I     5
                                                                                                                             I
                                                                                                                             
-------
                                                               VII  -  10

C.  DISPERSION COEFFICIENT
1.  Thomann Model
     a.  Point Discharges
     Of the various input parameters  investigated,  the Thomann Model
appeared to be most sensitive to the  dispersion coefficient (K),
especially when simulating constituents having low  decay rates.  The
importance of this term is evident from an examination of Figure  VI1-6,
VII-7, and VII-8 wherein simulated 1969 dye profiles  are shown for  K
values ranging from 0.5 mi^/day to 10.0 nn'2/day for all segments.  The
higher dispersion coefficients indicated greater upstream and downstream
dye movement.  Moreover, higher coefficients greatly decreased concen-
tration peaks to compensate for the additional mass of dye at the leading
and trailing edges.  On November 17 (Figure VII-8), for example,  dye  peaks
of 0.8 ppb, 0.7 ppb, 0.5 ppb, and 0.4 ppb were predicted for dispersion
coefficients of 0.5, 2.0, 5.0, and 10.0 respectively.  The remaining  2 days
of the study for which data were plotted indicated  similar results.
     The spatial position of peak concentrations was also affected  by the
dispersion coefficient.  As can be seen in Figures  VII-7 and VII-8,
 increased dispersion coefficients resulted in a lower rate of downstream
movement of the concentration peak.
     The range in dispersion coefficients selected  for this sensitivity
 analysis may have been extreme, but it nevertheless showed that a
 relatively accurate estimate of the dispersion coefficient was required
 for the Thomann Model either by conducting a dye study or by using some

-------
 o
-S  >
    u
    3
    8
-s

-------

-------
rS
I  tO  1
r- m  4:

-------
                                                               VII  -  14

natural tracer.  The relationship of dispersion coefficient to fresh-
water inflow, salinity, and possibly the physical  characteristics  of  the
system should also be defined prior to extensive model  use.
     For nonconservative constituents such as BOD, the  effects of  decay
somewhat overcome the influence of dispersion coefficient in the Thomann
Model.

-------
                                                               VII - 15



     b.  Chloride Distributions


     The effects of using three different sets of dispersion coefficients


in the Thomann Model  to simulate the annual  (1969)  chloride distribution


at Nanjemoy Creek are shown in Figure VII-9.   Increasing the previously

                                                  P
verified dispersion coefficients of 2.0 to 16.0 mi^/day by an order of


magnitude resulted in a profound change in chloride concentrations.


Instead of the model  predicting chloride concentrations between 3,000


and 5,000 mg/1, which were comparable to observed values, the chloride


levels were generally in the range of 7,000  to 9,000 mg/1.  Similar


differences could be  expected at most other  locations along the Potomac


Estuary.


     The third profile shown in Figure VII-9,  based on a constant dis-


persion coefficient of 2.0 mi^/day, indicates  the considerable effect


that changing chloride gradients exert on Thomann Model simulation


studies.  Under this  assumption, a minimal amount of chlorides


(< 500 mg/1) were transported up the Potomac  Estuary from Chesapeake Bay.


It can be concluded that the Thomann Model's  sensitivity to dispersion


is at least equally as great for simulating  chlorides as it is for point-


source discharges.


     The relationship of dispersion coefficient and chloride concentrations


established from Thomann Model simulations and actual data collected in


1969 during a relatively steady-state flow period (3,000 cfs-5,000 cfs)


can be seen in Figure VII-10.

-------
                                                                                                                                              I

                                                                                                                                              o
    CO
       z
       UJ
    o

52     ^
Q  _) <
       g
                             I     ,'
                  I
                 o

                 8
                 8
                 q

                 d

-------
                                -J.N3IDUJ3O?  NOISM3dSIO
UJ
O
o
o
     <
     o
z   -5
y   §
u.   m
u.
u   I
O   o
     §
z   2
(T  «
UJ
a  z
  o
5  %
u.  o
O  »
o
5
                                                                                                           K
                                                                                                           D
                                                                                                           O

-------
                                                               VII  -  18

2.   Dynamic Estuary Model
     Studies with the Dynamic Estuary Model  in the  Potomac  Estuary
indicate that the quality solution is relatively insensitive to the
dispersion constant (C4) when considering point discharges  in the
freshwater portion of the system.   On the other hand, the simulation
of salinity intrusion with this model indicated a significantly
greater sensitivity to the dispersion term.   The difficulty encountered
with proper assignment of the dispersion term in high salinity areas  is
due in part to representing a vertically stratified system with a one-
dimensional model.
     a.  Point Discharges
     The effect of the dispersion constant,  d,, on the steady-state
distribution resulting from a point discharge of 100,000 Ibs/day at
Blue Plains is indicated in Figure VII-11.  These studies were con-
ducted with a 4,430 cfs freshwater inflow and mean tidal conditions.
As would be expected, increasing the dispersion constant generally
lowers the peak concentration and reduces the concentration gradient
somewhat.  These comparisons indicate that the predicted distribution
resulting from a point discharge is relatively insensitive to the dis-
persion term in the Dynamic Estuary Model.  Because this model simulates
advective transfers and mixing resulting from tidal action, there is
significantly less dependence on a dispersion term than  that shown with
the Thomann Model.

-------
~   z
 2
S    g
 III
 o   o    5

         K
 £E   >    Z


 SI    5
 —       ^,
 O   uj    <

 0   z
 UJ   O
                                     o
                                     o

                                  •s§
                                  o  9
                                                       o   9

                                                       iri   o
                                                       Aj   u)

-------
                                                               VII  -  20

     b.   Chloride Distributions
     As  a second test of the  significance  of the  dispersion  term  C4 in
the Dynamic Estuary Model,  an attempt  was  made, as  discussed in the pre-
ceding chapter, to simulate changing salinity conditions  in  the Potomac
Estuary during the July 1965  to  December  1965 period.
     The profiles representing prototype  conditions for July 7-8, 1965,
and December 1-2, 1965, are shown  in Figure  VII-12.  The  initial  simu-
lation was completed with the dispersion  constant Ci» equal  to 2.5 for
the entire system (labeled  model  prediction  number 1 in Figure VII-12).
A second simulation with d* increased  to  25.0 (model prediction number  2
in Figure VII-12) resulted  in only a slightly better agreement.  From
these two simulations, it was apparent that  the model  was significantly
misrepresenting the rate of chloride  incursion as well  as the chloride
distribution through the system.   The  discrepancies could be attributable
to any of several causes, including:
     1)  Network layout - a brief discussion of  the effect of network
         layout on model predictions  is presented in other sections of
         this report.  No further attempt to determine the effect of the
         network layout on chloride intrusion was made.   It remains as  a
         possible significant cause of the poor  simulation agreements.
     2)  Prototype data - insufficient and/or inadequate  data to
         establish prototype  behavior  can present appreciable problems
         in model verification.   For this comparison, however, the data

-------
12,000-1
10,000-
 8000-
 6000-
  O

  i
  UJ
  Q
  CC

  3
  X
  o
 4000-
 2000-
           EFFECTS  OF  DISPERSION   CONSTANT ( C4 )  ON

           DYNAMIC  ESTUARY  MODEL   CHLORIDE  SIMULATIONS




If 1 1 1 1
40 50 60 70 80 90




1 1
100 HO
                              MILES  BELOW CHAIN BRIDGE
                                                       FIGURE  VII-12

-------
                                                              VII - 22

        were considered sufficient to adequately define the profiles
        and to dismiss the prototype data as a major cause of the
        discrepancies.
     3)  Advective  transport  techniques - the techniques utilized for
        advective  transport  within the quality model can significantly
        affect the rate of movement and the profile of any quality
        constituent but particularly one which has steep concentration
        gradients  such as salinity.  This "numerical mixing" phenomenon
        is  discussed in detail  in the DEM Documentation Report  [8].
     4)  Dispersion - although  previous applications [8] of the  Dynamic
        Estuary  Model  indicated that transport due to dispersion was
        relatively insignificant when compared to advective transport,
        recent studies by Harleman  [7] demonstrated that the dispersion
        term  can be very  important  in those portions of an estuary with
        vertical or longitudinal concentration gradients.  For  this
        reason the sensitivity of the dispersion  term on model  pre-
        dictions was further investigated.
     The studies  by Harleman  [7] indicate  that dispersion in areas with
perceptible  salinity gradients  is many times greater than dispersion  in
areas with uniform salinity.   To evaluate  the  significance  of  this
phenomenon in  the Dynamic  Estuary Model,  it was necessary to  incorporate
the ability  to vary the constant C4  with  distance  from  the  seaward  boun-
dary.  For this  study, the estuary was divided  into  three zones  With  a
different  constant for each.   The C4  constant  was  assigned  a  relatively

-------
                                                               VII - 23








low value in both the upstream and middle reaches but was increased



substantially in the seaward reach.  In one simulation (labeled model



number 3 in Figure VII-12) C4 was assigned a value of 2.5 in the upper



40 miles of the estuary, 25.0 in the next 20 miles, and a value of 250.0



between River Miles 60 to 96 (the seaward boundary for the model).  This



simulation demonstrated the marked effect of increasing the dispersion



term.  The final simulation presented (model number 4 in Figure VII-12)



was a result of utilizing a d, value of 15.0 in the upper 55 miles of



the estuary, 80.0 in the next 15 miles, and 250.0 in the downstream



29 miles (River Miles 70-99).  Further refinement and adjustment of



these dispersion terms undoubtedly would have resulted in even more



favorable agreement between model and prototype behavior.  However,



because of uncertainties in the prototype data base, the uncertainty of



the model network effect and other factors, further refinement in this



one aspect of the model did not appear warranted.  The conclusion



reached from this study was that a significant transfer of chloride



across the seaward boundary above and beyond that entering the model via



the advective transport mechanism is necessary to adequately simulate



chloride distributions in the Potomac.   This was demonstrated in this



study by substantially increasing the dispersion term in the downstream



portions of the estuary.   Thus the dispersion term appears to be the



important factor in predicting the distribution and rate of transfer of



a water quality constituent having the  ocean as its major source such



as chlorides.  It should be kept in mind that no specific study was

-------
                                                               VII - 24







conducted to determine the effect of the network layout on the rate of



advective transfer across the seaward boundary.   Whether or not this



is a significant factor in the case of the Potomac system has yet to be



demonstrated.



     It is also possible that the dispersion constants determined in this



analysis are applicable only for the flow and tidal  conditions existing



at the time.  No specific analysis was conducted to  determine whether



these constants are appropriate for other freshwater flow conditions.

-------
                                                               VII - 25

D.  ADVECTIVE TRANSPORT
1.  Thomann Model
     As mentioned previously, the advective proportionality factor (a)
should theoretically range between 0.5 and 1.0 depending on the relative
importance of dispersion and advection for a given estuary.  In the
Thomann Model, it is computed as a function of the eddy exchange coef-
ficient and flow.  Simulated dye profiles based upon a values of 0.5,
0.75, and 1.0 for all  model segments with other variables held constant
are shown in Figures VII-13 and VII-14.  As can be seen in both of these
figures, the three profiles almost coincide indicating that the model is
quite insensitive to a.  Decreasing a results in slightly higher peak
concentrations accompanied by less upstream movement.  The configuration
of the profile's leading edge is unaffected.
     In addition to dye simulations, the effects of a on chloride
modeling was also investigated.  The considerably higher concentration
gradient found in the longitudinal chloride distribution did not appear
to increase the Thomann Model's sensitivity to the advective component
of mass transport as was noted with the dispersion component for similar
conditions.
     Based upon the above discussion, it would seem that the advective
transport mechanism plays an insignificant role in the Thomann Model.

-------
r°
  

-------
f- 3AC

-------
                                                              VII  -  28

2.  Dynamic Estuary Model
     The effectiveness of  the method utilized  for  advective  transport
determination in the Dynamic Estuary Model  was demonstrated  by simu-
lating a somewhat shorter  historical salinity  incursion  period than that
utilized to demonstrate the effect of the dispersion term.   For  this
analysis, the chloride conditions in the Potomac during  the  period
October 19 through December 2, 1965, were used as  a  basis  for comparing
two different solution techniques.  The effect of  changing the concen-
tration in the advected water from that computed at  a channel's  quarter
point to that computed at  the upstream third point is illustrated in
Figure VII-15.  As can be  noted, the quarter-point method  significantly
increases the predicted upstream incursion and tends to  flatten  the
gradient more than the third-point method.   While  the third-point method
produces the more favorable comparison with prototype behavior, it should
not be interpreted as the  "best" the model  can do  since  the- comparisons
could have been improved by use of appropriate dispersion  constants
throughout the estuary (as discussed in a previous section).  The curves are
included only to illustrate the effect of the advective solution technique.
It is apparent that the model predictions are sensitive to the method used
for advective transport; however, the effect is more pronounced for water
quality constituents with substantial concentration gradients such as
chloride.  For other water quality  constituents with less  significant
gradients, the predictions are much less sensitive to the solution technique
used.

-------
2000-1
10000-
8000-
6000
  D>
  a.
  O

  I
  u
 4000
2000-
            EFFECTS  OF ADVECTIVE   SOLUTION  TECHNIQUE


                       DYNAMIC  ESTUARY   MODEL


                          CHLORIDE  SIMULATIONS
              OCT. 19-20, 1965(OBSERVED)




     	 •- DEC 1-2 , I965(OBSERVED)




     	1/4 POINT (PREDICTED)




     	 1/3 POINT (PREDICTED)
            30
                    40
 \        ITT
50       60      70      80
    MILES  BELOW CHAIN BRIDGE
                                                            90



                                                           FIGURE VII-15
                                                                    100
                                                                             \
                                                                             HO

-------
                                                            VII  -  30

E.  RIVER FLOW AND DISPERSION COEFFICIENTS  (THOMANN  MODEL)
     To increase the predictive reliability of the Thomann  Model  in  the
upper Potomac Estuary,  the effect of freshwater inflows  on  dispersion
coefficients was investigated.  The simulation of November  1969  and
June 1965 dye study data indicated that a direct relationship existed
whenever flows were between 1,400 and 4,000 cfs.  The increased  inflows
which occurred during the study periods required higher  dispersion
coefficients in order to obtain a satisfactory agreement between proto-
type and model data.  Moreover, a study in  the Delaware  Estuary  by
Paulson [9] also indicated that dispersion  increased directly with flow.
This relationship may be partly due to the  dissipation of the larger energy
levels associated with greater flows.
     The approach adopted for this analysis was a comparison of  simulated
data from the tidal and nontidal models for the upper 30 miles of the
Potomac Estuary.  The data generated by the "real-time"  tidal model  was
used as a basis for determining when the most favorable  predictions,
hence most applicable dispersion coefficients, occurred  with the Thomann
Model.  Four separate flow conditions, ranging from 930  cfs to 20,000 cfs,
were investigated.  For each inflow, an arbitrary loading at Blue Plains
of 100,000 Ibs/day with a decay rate of O.I/day (base e) was assumed.
Initial and boundary concentrations were set to zero in both models and
simulations continued in time until steady-state conditions were observed.
     The dispersion coefficients yielding the best data with the Thomann
Model are plotted as a function of flow in Figure VII-16.

-------
Q
to    >•
>    a

*dl
Z  Q to
UJ  O u

y2^
^  -^ Ld

If |

cr

Q.
      o
      o
        I — I - 1 - 1   I   T
                                       —i—i—i—i—r
                                        o
                                                                            o
                                                                            o
                                                                            o
                                                                            o
                                                                            q
                                                                            o
                                                                               i

                                                                               g
                                                                            o

                                                                            8
                         AVa/S3-|m'DS (X) 1N3IDIJJ30D NOISdldSIO
                                                                       FIGURE  VI! -16

-------
                                                              VII  -  32

     As can be seen in Figure VI1-16,  there  were  two different K
versus Q relationships—one applied  to the model  segments  upstream
from the discharge point and the  other to the  segments  between the
discharge point and the Occoquan  Bay.   The effects  of flow on the
dispersion coefficient were more  pronounced  in the  downstream direction
but nevertheless a direct relationship between the  two  existed upstream
as well.  For the higher flow conditions, it appeared that the increased
downstream advective movement overshadowed the effects  of  upstream
dispersion resulting from the higher coefficients.

-------
                                                               VII - 33







F.  MANNING COEFFICIENT AND TIDAL EFFECTS (DYNAMIC ESTUARY MODEL)



     Studies were made with the Dynamic Estuary Model  to ascertain the



effects of Manning's roughness coefficient (n) on the  steady-state



hydraulic solution and its subsequent effects on the quality program.



Moreover, two different tidal  conditions (mean annual  and mean spring



tide) were simulated hydraulically to determine the sensitivity of tidal



input on quality predictions.



     The following table contains various sets of Manning coefficients



for the main Potomac and the corresponding dynamic steady-state tides



predicted at Washington.  For purposes of comparison,  the mean tide



which was used for this investigation had an average range at Washington



of 2.9 feet and phasing differences referenced to Piney Point of 6.4 hours



and 7.1 hours for high and low water, respectively.  At Piney Point, the



average tidal range was 1.4 feet.




                            Table VII-1



              Effects of Manning Coefficients on Tides

"n"

(decreasing downstream)
.023 -
.020 -
.025 -
.025 -
.020 -
.020 -
.020 -
.019
.020 -
.022 -
.017 -
.017 -
.016

.017
.020
.015
.014
Tidal
Range
TftTJ
2.60
2.23
2.48
2.13
2.73
2.85
High and Low
Lag Times
(hrs.
5.80 -
6.05 -
5.80 -
6.10 -
5.85 -
5.90 -
.)
7.00
7.10
7.00
7.15
7.00
7.00

-------
                                                               VII  -  34

     It is evident from the above data  that tidal  range was more
sensitive to channel  roughness than tidal  phase.   The greater roughness
values slowed the tidal movement and thereby produced greater lag times
and lower ranges.  The best agreement was  obtained with "n" ranging from
.020 to .014.  While the hydraulics were relatively sensitive to Manning
coefficients, quality program output based upon two different sets  of
coefficients indicated that simulated concentrations were essentially
unchanged.  An attempt to overrefine Manning coefficients does not appear
warranted from the standpoint of required  predictive capability.
     In addition to the use of mean tidal  figures previously discussed,
numerous simulation studies were made for  the Potomac using the mean
spring tidal figures.  This particular  tide has a range of 1.6 feet at
Piney Point and 3.3 feet at Washington.  The most favorable simulation
of the spring tide again occurred with  Manning coefficients varying from
.020 to .014.  The predicted quality data in the upper Potomac Estuary
resulting from the use of mean spring tidal figures did not differ
appreciably from a mean annual tide hydraulic condition.  Maximum concen-
tration differences were less than 10 percent.

-------
                                                              VIII  -  1





                            CHAPTER VIII



                     ENGINEERING CONSIDERATIONS



A.  DISPERSION AND ADVECTION



     The mathematical  model  simulation studies  discussed in this  report



indicated that dispersion coefficients were particularly significant



when a "tidal-averaging" concept was used.   Since lateral  differences



in tidal velocities are the  predominant driving force in physical  dis-



persion, a nontidal system must include a gross term approximating  the



total effect of various individual  dispersion components.



     The dispersion coefficient employed  in the Thomann Model  was  hard



to evaluate.  Two large scale dye studies were  conducted in the upper



Potomac Estuary in an attempt to characterize dispersion,  but  the  results



appear to contain discrepancies.  The 1969  dye  study yielded dispersion



coefficients of 2.0 and 3.0  mi2/day for 1,900 cfs and 3.0 and  5.0  mi2/day



for 4,000 cfs.  For a similar reach of the  Potomac, values of  2.0  mi2/day



(3,200 cfs) and 1.0 mi2/day  (1,600 cfs) provided the best agreement



between observed and simulated 1965 dye study data.  While it  can  be



concluded that dispersion coefficients in the Thomann Model for a  point-



source discharge appeared to be directly related to freshwater inflow



rates, the probable magnitudes to be assigned for predictive studies  using



fairly conservative constituents are difficult to determine.  It should be



noted that the aforementioned dye studies produced only approximate values



of dispersion which have limited application.  When constituents exhibiting



significant degradability are simulated,  i.e.,  K > O.I/day, the effects of

-------
                                                              VIII  -  2

dispersion in the nontidal  modeling  approach  will  be  decreased because
the natural  decay process dominates  the effects  of transport and  pri-
marily governs the constituent distribution.
     Simulation of chloride data also created problems  because
dispersion coefficients appear to be greatly  influenced by salinity
gradients.  The 1966 and 1969 chloride simulations, as  presented  in
Chapter VI,  again indicated wide variation in dispersion coefficients
both spatially and temporally.  From the dispersion standpoint, the 1966
chloride simulations yielded results comparable  to those of the dye
studies, i.e., dispersion coefficients were found  to be directly  pro-
portional to freshwater inflow.  However, the 1969 chloride simulations
showed a different relationship.  In order to realize basic agreement
between simulated profiles and observed data, dispersion coefficients
were held constant for the entire year of simulation regardless of fresh-
water inflow rates.  Not only did this approach  differ with the direct K
versus Q relationship developed in Chapter VII for a point discharge but
with the logical definition of dispersion as  applied to chloride intrusion
as well.  It would appear that the true dispersion coefficients for a
tracer discharged into the upper reaches of the  Potomac Estuary and
dispersing primarily in a downstream direction are directly proportional
to inflow rates because advection and diffusion  forces have accumulative
effects.  Dispersion coefficients for chlorides  and other constituents
dispersing upstream should then be inversely proportional to flow;
although this was not reflected in the Thomann Model simulations presented

-------
                                                              VIII  - 3








in this report.  Since chloride intrusion is in  an  upstream direction



and the forces of advection and diffusion oppose each other, it is



reasonable to assume that during low-flow periods,  maximum intrusion



would result.  To duplicate similar performance  in  the model,  high



dispersion coefficients were necessary to simulate  the downstream



movement of the chloride wedge.



     Discrepancies in the interrelationship between dispersion, advec-



tion and flow on the hydrodynamic behavior and the  relative insensitivity



of the advective proportionality factor suggest  that tidal and nontidal



advection is deemphasized in the Thomann Model.   The method by which



this model handles incoming flows may be responsible for deficiencies



in the basic transport mechanisms of dispersion  and advection.  A given



flow sequence, for example, is assumed to occur  instantaneously through-



out the system, indicating that the hydraulics are  strictly a  function



of velocity  (Q/A) and not volume displacement.  It  can be concluded



that continual refinement of the dispersion coefficient and a  sound



understanding of how it is affected by various factors within  a given



system are mandatory when applying the Thomann Model to any great extent.



     The simulations for a point-source discharge conducted using the



Dynamic Estuary Model indicated that a much more accurate representation



of advection and dispersion can be expected.  The insensitivity of this



model to the dispersion component and the relative  importance  of tidal

-------
                                                              VIII  - 4

and advective forces were indications that the DEM more realistically
approximates the hydrodynamic behavior of the prototype.
     In the case of chlorides or other constituents entering the Potomac
Estuary from the Chesapeake Bay, caution must be exercised when assigning
the dispersion term C4 in areas with large concentration gradients.  The
chloride simulations performed with the DEM showed that dispersion  can
be directly related to the concentration gradient and furthermore that the
advective concentration is quite important.  Whether this can be attributed
to the coarse network used or some other peculiarity in the solution tech-
nique has not been adequately determined.  Since this model employs a
"real-time" system, it is essential that the total quantity of constituent
crossing the seaward boundary over a complete tidal cycle be accurately
represented, even if this is done by drastically increasing dispersion.

-------
                                                               VIII  -  5

B.  MODEL COMPARISON
     As discussed in previous sections  of this  report,  the  primary dis-
advantage of the Thomann Model,  or any  other nontidal model,  is the
difficulty in selection of appropriate  dispersion  coefficients.  Costly
dye studies and field data collection can provide  an  approximation of
this coefficient but the accuracy necessary for various predictive water
quality studies will probably remain to be developed.   Other  important
disadvantages of the Thomann Model are  its inability  to (1) branch in  a
lateral direction, (2) link more than two constituents, and (3) simulate
the effects of tides on the distribution of a constituent.
     The major advantages of the Thomann Model  over the FWQA  Dynamic
Estuary Model as presently programmed are (1) less stringent  input require-
ments, (2) its ability through Namelist I/O option to change  input
variables, such as flow on a daily basis, and thereby readily simulate an
entire year's or season's characteristics, and  (3) the  capability of
running several different data decks "back-to-back" without having to
resubmit the whole program.  In  light of the above, one can investigate
many more alternatives in much less time with the  Thomann Model which  is
important when time is critical.
     Except as noted earlier, the Dynamic Estuary  Model does  not appear
to be very sensitive to the dispersion  coefficient since tidal  effects
are included.  Furthermore, the  short time step which can be  used in the
real-time quality solution enables this model to make a better prediction
for constituents having a relatively fast reaction rate.  Nitrification

-------
                                                              VIII  -  6

analysis, for example, may be better investigated with the  Dynamic  Estuary
Model.  Recent refinement in the quality program has  added  several
additional  source and sink terms in DO budget analyses.   The effects  of
algal photosynthesis and respiration based upon conversion  of inorganic
nitrogen to chlorophyll a_, nitrogenous oxygen demand, benthic oxygen
demand, and modifications to the reaeration term have been  programmed into
the model and should definitely increase its capability in  predicting DO
concentrations in eutrophic estuarine waters.  Another recent innovation
was the expansion of the first-order reaction system to any order system.
This was the outcome of preliminary phosphate simulation data analysis
which indicated that a second-order reaction was more applicable.  A
report currently being prepared by CTSL [10] describes such nutrient
and DO simulation studies.  Source and sink terms in the DO budget have
not been delineated to this extent in the Thomann Model nor can chloro-
phyll levels be simulated by linkage with the nitrogen cycle.
     When initially applying the Dynamic Estuary Model to a given system,
reasonable care is required in simulating the hydraulics to avoid major
errors in the quality predictions.  The values assumed for Manning rough-
ness coefficients are particularly important since they influence both
the tidal range and phasing.  An optimum set of coefficients with verifi-
cation based upon USC&GS tidal data should be determined by trial and
error procedures prior to any quality simulations.  Another factor
warranting consideration in the hydraulic model is the time step used
for the  solution.   In order to minimize hydrodynamic  instability, a

-------
                                                              VIII  -  7

stability criterion which relates  channel  length,  wave  celerity,  and  tidal
velocity to the time step, must be satisfied.   Once the stability criterion
is met, selecting shorter time intervals would  not improve  the hydraulic
predictions significantly.
     A discussion of both models'  sensitivity  to the physical  network
detail was previously presented.   The Thomann  Model, possibly  because of
its averaging effect over long time periods, does  not appear to be  very
sensitive to degree of segmentation.   For  the  Potomac Estuary, segment
lengths of 1 to 3 miles were adequate.   The Dynamic Estuary Model appears
to be considerably more sensitive  to the  refinement of  the  network  based
upon limited data pertaining to the two networks originally developed for
the Thomann Model.  However, it should be  recognized that input require-
ments and computer time and output increase in  proportion to the number of
channels and junctions selected.   Time and resource restraints must be
weighed against accuracy of data required  before an evaluation of the
required network can be made.
     Practically all of the prototype dye  data  were reasonably simulated
with the Thomann and Dynamic Estuary Models.   With sufficient manipulation
of dispersion coefficients, it was possible to make reasonable simulations
of the 1966 and 1969 Potomac Estuary chloride  distributions using the
Thomann Model and of a 5-month transient chloride condition (1965)  using
the DEM.  From an engineering viewpoint,  it is  preferable to refine the
hydrodynamics of a system by utilizing a  real-time solution (such as  the
Dynamic Estuary Model) rather than to represent a gross tidal  mixing

-------
                                                               VIII  -  8







phenomenon with an empirically derived  dispersion  coefficient  appli-



cable only over a narrow range of prototype  conditions.   This  is



particularly significant when attempting to  predict water quality



behavior for future conditions significantly different from any



experienced historically and for which  the validity of the dispersion



coefficients is uncertain.   From a practical standpoint, however, the



Thomann Model does offer expediency with minimum effort.

-------
                                                                A - 1
                             APPENDIX



A.  POTOMAC DYE STUDY - 1969



     1.   Release Conditions



     A 6-percent solution of Rhodamine WT dye was  discharged continu-



ously into the upper Potomac Estuary from November 2-14,  1969,  via the



District of Columbia's Blue Plains Sewage Treatment Plant outfall.  This



outfall  extends to the main shipping channel  approximately 900  feet from



the eastern shore at a point 10.4 miles downstream from Chain Bridge.  The



dye solution was discharged into the elutriation washwater discharge sump



which drains directly to the outfall.  Initially,  dye was pumped at a rate



of 120 ml/min but a pump failure occurred during the second day of the



study.   It was therefore decided to use a siphoning procedure for the



remaining 12 days.



     Due to the imprecision of siphoning, it was necessary to recalibrate



the discharge rate of 120 ml/min several  times each day.   As an additional



check, the rectangular tank in which the dye solution was mixed was



accurately measured to determine changes in the volume of dye.   Volume



changes for each 4-hour period of the study were recorded and subsequently



converted to a mass basis.  Table 1 presents volumes, discharge rates and



related factors for the 13-day release period.  Except for November 3 when



a pump failure occurred and November 11-12 when a line became clogged, the



dye injection rates (as shown in Table 1) were relatively uniform.  During



this release period, a total of 269 pounds of pure dye (4,454 pounds of



6-percent dye solution) was discharged to the Potomac Estuary.

-------
   O  C
O n

.S
   V
II
   CO
 -  tl o1
•< 5 •
    tl
    +>


    fl
tHOOO    OJ O «H  -O O »T\   C^\-vTiHOrHC\J
r-\ r^ f\ ry    o O irv CO -N* to   u^ CO O O O 00

r*-\ r^ f\ r'N    O O rH OJ vo f\j   fN r\j c»\ c*\ t- rH
                                                                            J f"\ O O1- "*   r- r-l *0 <\| O 0s    O
                                                                             f\ CO f\ W    ^CvVO'T'^^O    f\ tf\ O»-  Ol H ^
                                                                                        v r"\ ->f f\ r-\ CO    -4- C\J m,
                            <*\ O »Tv >* O OJ    -* O C
              -*>t^f^-   ir\ Q o r- T^ r-    co r-
              ir\ ur\ ir\ ITN   rH O O NT O •>*    '"
                                                           rH OJ

                                                            *O
^- -\o vo eo
o w  H r-i p
rHrHi-ifu
                                                      - r- \o c-
                                                      - to r- 6
                                                                        to c- to o  o «>
                                                                        rn o w H o >»
                                                                        r-lfHiHr-lr-IN
                                                                                                                              «o r- C~ ^9 ?M S
                                                                                                                              cr S to >B *\ o
                                                                                                                                           -
                \ O CO *T»   OJ O OJ t
                r ^ r^ r*>   o    rH •
                r ^ •< -^   ^*    o (
               tf\m«fstf\    rHOO>ArHtfN    ^O>f\^OKOr-lt*\   tKifN^fScO^    v^>VOt-^25>T\^J    Co^COOJ^CSO    l

               O O O O    O O C\J O fH O    O O O O i-I O   O O O O O  O    O CD O O O f4    tD O i-J O O C3     <
                                                3

-------
rH O


g*

             Vi O
              o •
             •
             a -
                ^3

                to
                s't:
                i -H
                I!
y*
C5'
                                                        ~*f 0s vO OJ Oj O    O O O £- OJ f*\    OJ
                                                        r*"\ "*i rH r^ r^- o    o o o to t^- Nf    f- i

                                                        - -tf <*>    rH  »
                                                                                  I  O   OOO-*i-CTvOj    rH(
                                                                                                    i  C"v O CVI «%    r\CM OJ <
                                                                                                    ^  oj H H o    o o^ o t
                                                                                                        rH rH rH
                                                                     oOrH^r^o   o o o
                                                          t^O^O    0s f\ ^ rH rH Q   Q Q Q "^ O °J    rHPAOJCr-°J
                                                          rHojoj    ojo^ojojo   ooocor--^    ojvosta^cj
                                                          rHrHrHrHrH                           rH               rHOJ
                                                                                                              OJr>>fCT*rH»r\    rH^TsOCT^

                                                                                                                                  r- \Q \o  S"
                            \ CO rH Co  M*\ OJ    CO •
                          P?5j!
                          rH rH CO
                                                                     &\O
                                                                     CO OJ r
                                                         _  . J f\ rH rH
                                                        03  «0 O r^t^
                                                               I  O C"\ P4
                                                                 »T\ O f\J
                                                                 <\l V O
                                                                 i-H OJ
                                                                                                rH OJ O
                                                                                                H C*\ OJ (
                                                                                                 -
                                     - tf\ r^

                                     I  fo Ki
r- to o 1-1
•*f*\r\ c\i
?J rg (\i oj
                          CT^ O^ C~ CO -^ 0s   ^ (7* ^O rH C^ *fN ^    y~* f\J C^ OJ CvJ O    O O O O O "^    OJ t^~  ""* C^- O C^    O O O C^-
                          yDVOQOC^O^yD    \OlO"Ar^\r^f<^    r^rHrr\rHrHO    OOO>TNOOJ    rHf'NOJrHOJrH    OOOOO

                          O O O O O O    O O O O O O O*    O rH O O O O    O O O O rH O    O O  O rH rH rH    rH rH rH O
                                            r*- oj ^    &* oj ifv <*\ oj               o (*\ co    v^ -^ cu ^D *«o ^o    r^- co o ^
                 -     ,....    ___     <*\r\OJ    rHrHOOCjl      I   I   lOCJ^CQ    tQCOOOr^^O»fN    ^C^f^NOj
            •f\tr\«~\tf\tf\tf\    if\'*-4'^*tfNtf\>r\    ir\»fNirvtr\tf\i      i   i   i if\ >*•><•    •^sr^>4'>t''^'
            OJOJOJOJOJOJ    OJOJOJOJOJOJOJ    OJOJOJOJOJ               OJOJOJ    OloJOJOJOJOl
i-4-cor-    cooc^-'^oojco    oj
kO>OJ-**    r^-rH-NtO^jOrHC'N
                                                   < CO CO PMT\ OJ    rH O (
I O    O O O V\ O 1
V ifN    if\ tfN lf\ C\J f\ 1

* O^    O^ O^ ^ (J* CO I
                                                                                                                                  888SJ
                                                                                                                        t *f>  -rf-   f*> OJ rH O
                          OOrHrHCUOJ     OOrHrH    OJOJ    oSHrHOjo5    OOrHrHOJOJ    OOrHrHOJCM    OOHi

                                                I  I  I  I     II      I   I  I  I  I   I      I   I  I  I  I  I      1   1   1   I   I   I     III

                                                    8O Q    Q Q    o O O O O O    O O O O O Q    O O O  O O C
                                                    o o    o o    o o o o o o    o o o o o o    o o o  o o c

                                               5OOrH    rHOJ    OOOrHrHOJ    OOOrHrHOJ    OOOrHrHCV
                    188!
                    » OJ vo (
                                                                                                  188!
                                                                                                  13%:
                                               o

                                               rH
                                                 I      7
                                                        OJ
                                                        T

-------
                                                                A  -  4
2.   Monitoring System
     a.   Longitudinal  Stations  (Slack  Tide)
     Longitudinal  sampling in the  Potomac  Estuary from Key Bridge  to
Sandy Point during high- and low-slack tide  periods  was  conducted  by
CTSL.  Data from 10 low-slack sampling runs  and eight high-slack runs
were obtained during the period November 3-December  1.  A tabulation  of
the data as analyzed by the U.  S.  Geological  Survey  is included in this
appendix.
     Surface samples at mid-channel  were collected from 18 stations for
longitudinal monitoring of the dye release.   A listing of these stations
is given in Table 2.
     b.   Lateral and Vertical Stations
     To determine the lateral and vertical mixing of the dye, transect
sampling was conducted by CTSL at 14 stations, all of which coincided
with the longitudinal sampling stations.  These transect stations  are
shown in Table 2.
     Five transect sampling runs were made during the period November
4-20.  Due to the considerable amount of time required for transect
sampling, it was not possible to limit sampling to slack-tide periods.
Cross-sectional area profiles showing the sampling grids used for each
station are presented in the appendix.  As can be seen from these profiles,
eight to 17 samples were collected at each station.   It should be noted
that many of  the transects  extended into the major embayments.

-------
                              Table 2

                   LONGITUDINAL SAMPLING STATIONS
                           Potomac River

Station                                                      Miles Below
Number                        Location                       Chain Bridge

  1  *                   Key Bridge                               3.35

  1A                    Memorial  Bridge                          4.85

  2  *                   14th Street Bridge                       5.90

  2A                    Buoy N "6"                               6.70

  3  *                   Hains Point              .                7.60

  3A                    Hunter's  Point                           8.70

  4  *                   Bellevue                                 10.00

  4A*                   Goose Island                            11.05

  5  *                   Woodrow Wilson Bridge                   12.10

  5A                    Rosier Bluff                            13.55

  6  *                   Broad Creek                             15.20

  7  *                   Piscataway Creek                        18.35

  8  *                   Dogue Creek                             22.30

  8A*                   Gunston Cove                            24.30

  9  *                   Hallowing Point                         26.90

 10  *                   Indian Head                             30.60

 11                      Possum Point                            38.00

 12                      Sandy Point                             42.50



* Also transect stations

-------
                                                                 A - 6
3.  Presentation of Data
     a.   Tidal  Conditions and Hydrology
     The tidal  conditions in the upper Potomac Estuary at Washington,
D. C. are monitored routinely by the U. S.  Coast and Geodetic Survey.
Figures  1, 2, and 3 present actual  tidal  data at Washington for
most of November 1969 and the mean  tidal  height at this station for the
entire period of record.
     As can be seen in Figures 1 through 3, there were three dis-
tinct tidal conditions during November.  The first 3 days of the month
were characterized by atypically high tides with considerable fluctuations
in the tidal range.  The predominately northwesterly winds which occurred
on November 3-6 were responsible for the steadily decreasing tidal levels
shown during this period.  These extremely low tides had a pronounced
effect on the downstream movement of dye.  The remaining 3 weeks showed
generally normal tidal ranges with  average heights approximating the
mean-tide condition.  The slight decrease in tidal levels on November 19-21
was again attributed to high northwesterly winds.
     Average daily flows measured at Great Falls during November 1969 are
shown in Figure 4.  Freshwater  inflows to the upper Potomac Estuary,
like tides, were influenced greatly by climatological conditions.  As
indicated in Figure 4, two separate flow regimes occurred.  The period
November 1-5 had an average flow of 1,886 cfs whereas during the remainder
of the month, the average flow  was 3,974 cfs.  Daily flows within each
period were uniform, however.

-------
                                        - 00
iJ - 1HOI3H
                                   FIGURE  - A I

-------
FIGURE - A 2

-------
I
      O)
      to
      Ol
                                                                                                             _ r-
                                                                                                              (VJ
      cc
      Ul
      CO
                                                                       u
I
O.
                             I
                            Ol
 I
CO
 I
(O
 I
10
                                                            - 1H9I3H
                                                                                                               o
                                                                                                               f>J
                                                                                                             _ Ol
                                                                                                            o
                                                                                                      FIGURE - A 3

-------
   5000-
                          FRESHWATER  FLOWS


                      POTOMAC RIVER AT GREAT  FALLS

                                NOVEMBER. 1969
O
_j
u.
o

z
•<*
ui
Z
   4500-
   4000-
   3500-
   3000-
   2500-
   2000-
   1500-
    1000-
    500-
      0--
          i  i  I  I

                5
rill

      10
 I  I  I  I  I  1   I  I

     15         20


NOVEMBER   1969
I  I  I  I  I  I  T

  25         30
                                                              FIGURE - A 4

-------
                                                                 A -  11
     Freshwater inflows account for the net advective downstream move-



ment in a tidal system.  They can also greatly affect its  dispersion



characteristics.   Because of their importance, freshwater  flows  must be



defined and incorporated into the hydrodynamics of a  tidal  system if



mathematical model simulation studies are to be successful.

-------
                                                                A  -  12
     b.   Dye Movement
     The upper Potomac  Estuary dye  data  obtained  from  longitudinal
sampling stations between Key Bridge  and Possum  Point  are  presented  in
isopleth form in Figure 5 (low-slack  data)  and Figure  6  (high-slack
data).   Although dye was discharged at River  Mile 10.4,  Figure  5
indicates that maximum  dye buildup  occurred between  River  Mile  14  and
15.  Dye concentrations between 1.0 and  2.0 ppb  were observed  in this
area on  November 5, three days after  dye was  initially discharged.   The
fact that dye peaks were located 5  miles downstream  from the discharge
point may have been due to (1) dye  injected at a  14-foot depth  with
samples  collected at the surface, (2) freshwater inflows which  caused
net downstream advective movement,  (3) sampling  performed  at low-slack
tide when maximum downstream movement could be expected.  The  effects
of item (3) are evident when Figures  5 and  6  are compared.  The high-
slack tide data shown in Figure 6 indicate  that  maximum  dye concentrations
(> 1.0 ppb) occurred between River  Mile  8 and 11, or approximately a
complete tidal excursion range upstream  from  the low-slack tide peaks.
     Longitudinal dye movement can  be readily identified in the two
isopleths.  The dye cloud spread rapidly between Hains Point and
Piscataway Creek as shown in Figure 5.   In  3  days, it  moved approxi-
mately 5 miles upstream beyond the  14th  Street Bridge  and approximately
14 miles downstream to  Gunston Cove.   This  represented movement rates  of
1.7 mi/day and 4.7 mi/day, respectively.  The especially high  downstream
movement can be attributed to the very low tides observed during this

-------
                                                                 A -  13
period (see previous section).   Downstream movement rates  beyond
November 5 can be estimated from the slopes of the concentration lines
shown in Figures 5 and 6.   The  rates generally range from  approximately
0.8 mi/day to 1.2 mi/day with an average of 1.1  mi/day.  These rates
apply only to a freshwater inflow of 4,000 cfs.
     Dye was initially detected at Indian Head on November 15  and at
Possum Point on November 19.   Both time periods  yield an average down-
stream movement rate of approximately 1.6 mi/day.  An instantaneous  dye
release study conducted in the  upper Potomac Estuary by  the U. S.
Geological Survey in August 1965 [2] showed the  average  velocity of  net
downstream movement of the dye  mass centroid to  be 0.6 mi/day.  It should
be noted, however, that the tides were relatively stable during the  USGS
study and that freshwater flows at Great Falls varied between  700 and
1,200 cfs, considerably smaller flows than those encountered during  the
1969 dye study.  The rates of movement of the leading edge and the centroid
of the dye mass may also differ appreciably.
     Data collected from the three complete transect runs—November  11, 18,
and 20--between the 14th Street Bridge and Indian Head are plotted in
Figures 7, 8, and 9.  The ranges in dye concentration at each  transect
station and in the major embayments, mean concentrations at each transect
(excluding embayments), and mid-channel concentrations are shown in  these
figures.  Mid-channel stations  correspond with the longitudinal sampling

-------
                                                                 A - 14
stations discussed previously.   The stations comprising a  transect
were selected in such a way that each would have about equal  weight
in terms of the cross-sectional  area and the flow represented.
     In most cases, the total  dye concentration range for  a given
transect was within 0.3 ppb which indicated that considerable lateral
and vertical mixing had actually occurred.   According to Figures 7 and
9, the dye concentration ranges  measured in Broad Creek, Piscataway
Creek, Dogue Creek, and Gunston  Cove were generally representative of
data collected at comparable main-channel stations.  The extent of dye
intrusion into these embayments  was substantial, further indicating that
tidal exchanges between the main channel and adjoining embayments should
definitely be considered and, if possible,  incorporated in mathematical
modeling studies.
     To assist in the interpretation of simulated and observed data for
model verification purposes, an  analysis was made of the average concen-
tration for transect and mid-channel (surface) values.  Figures 7, 8, and
9 generally show relatively small differences  (< 0.5 ppb)  between these
two sets of data.  Therefore, it would appear  to be valid to compare the
model predictions for a given segment with the results obtained from
longitudinal sampling within that segment.   Where larger deviations between
mean and mid-channel concentrations were noted, no significant conclusions
could be drawn concerning their relative magnitudes.

-------
                                            3
JDOIdB NIVHD  MO138  S31IW
                                                                FIGURE  - A 5

-------
                                                                 -8
30
-------
                  TRANSECT  DYE  SAMPLING  SUMMARY

                         UPPER  POTOMAC ESTUARY
                                NOVEMBER II. 1969
 -O-i
 .9-
 .8 -
  .7-
  .6-
S.5H
 .4-
 .2-
        Q— CONCENTRATION RANGE FOR  TRANSECT
        Q — CONCENTRATION RANGE FOR  EMBAYMENT  ONLY
        X—MEAN CONCENTRATION (EXCLUDING EMBAYMENT)
        A— MID-CHANNEL CONCENTRATION
                        0
                   n
                             6
             (D
                                    o
             (i

             a
                          9
                          {2
                          t)

                          C)
            I
            4
I
12
      T        I         I
      16       20       24
MILES  BELOW CHAIN BRIDGE
28      32

 FIGURE - A 7

-------
                       TRANSECT  DYE SAMPLING  SUMMARY

                               UPPER  POTOMAC ESTUARY
                                     NOVEMBER 18, 1969
 1.0 -I
O—CONCENTRATION  RANGE  FOR TRANSECT
Q—CONCENTRATION RANGE FOR EMBAYMENT ONLY
X—MEAN CONCENTRATION (EXCLUDING EMBAYMENT)
A—MID-CHANNEL CONCENTRATION
 .9-
 .8 -
 .7-
 .6-
o.
Q.
i -H
 .4-
  .3-
  .2
                             Q

                                           o

i
12
                                      I
                                      16
                                                       I
                               MILES
       I
       20      24
.OW  CHAIN BRIDGE
                                                       I
                                                      28

                                                     FIGURC - A 8
 I
32

-------
                  TRANSECT  DYE  SAMPLING  SUMMARY

                          UPPER  POTOMAC  ESTUARY
                                NOVEMBER 20. 1969
 I.O-
  .9-
 .8 -
  .7 -
  .6-
£.5-
o
 .4-
 .3 -
 .2 -
CONCENTRATION RANGE  FOR  TRANSECT
CONCENTRATION RANGE  FOR  EMBAYMENT ONLY
MEAN  CONCENTRATION (EXCLUDING EMBAYMENT)
MID-CHANNEL CONCENTRATION
                                
                                    []

                                    
                                    (\
                                                       ()
                                8
                                          8
                                                                    o
                                                                    *
             i^
            4
                   I  IJ     I         I        I
                   12       16       20      24
                     M  _b BELOW  CHAIN BRIDGE
 I        I
28      32

FIGURE - A 9

-------
                                                                 A - 20
     c.  Loss Rate Determination
     The dye loss rate considers not only a decay or adsorption phenomenon
but also reflects the inability to detect dye at low concentrations.   It
was estimated by computing the rate of change in the total  dye mass as
measured throughout the upper estuary during an 18-day period immediately
following the dye release.  Longitudinal  sampling data, supplemented  by
two sets of transect data, were converted from concentrations to mass
loadings per lineal foot of estuary according to the following equation:
     Mass (Ibs/lineal ft.) = C x ^Qg 62'4
     where:   C    = dye concentration (ppb) for a given sampling station
             A    = cross-sectional area (ft2) at the sampling station
             62.4 = mass of 1 cubic foot of water, and
             1()9  = conversion factor
     The mass loadings obtained were plotted as a function of distance and
fitted with smooth curves.  The areas under these curves were planimetered
to determine the total dye mass observed at a given time.  As shown in
Figure 10, all such dye masses for the 18-day period appear to follow
a first-order reaction.  The slope of the resulting line, which is the dye
loss rate, was calculated to be 0.030 per day (base e).  A 1965 upper
Potomac Estuary dye study by Hetling and O'Connell [3] yielded a dye loss
rate of 0.034 per day (base e) which was calculated utilizing a similar
approach.

-------
                                                                 A - 21
     The dye masses computed from measured data were always greater



than the actual masses discharged during the release period.   By the



end of the release period (November 14), approximately 350 pounds of



dye were computed to be in the estuary whereas only 269 pounds had been



discharged.  This 80-pound difference, excluding dye losses to November



14, can perhaps be attributed to (1)  naturally occurring background



fluoresence which was not defined quantitatively, (2) possible unrepre-



sentative sampling, especially near the injection site, or (3) inaccuracy



in analysis.  For purposes of computing dye loss rate, these factors



should have a uniform relationship over the entire sampling period.

-------
                                                                                                                O)
                                                                                                                (M
      CC
      h-
      to
      LJ
           10
           01
      O
O    O
Ld
s
      o
      Q.

      DC
      LJ
      Q.
      a
            a:
            LJ
            CD
            z
            LJ

            O
                                                                                                                   I
                           I
                           O
                           o
                           O
                                                    I
                                                   o
                                                   o
                                                   in
                                                                                                              -CO
o
o
                                                                         3xa
                                                                                            FIGURE  - A 10

-------
                                                                 A - 23
B.  ANACOSTIA DYE STUDY - 1970
     1.  Release Conditions
     A 20-percent solution of Rhodamine WT dye was discharged continu-
ously into the Anacostia River from April 22-28, 1970, to determine the
advective transport characteristics of the Anacostia tidal system and to
provide additional data upon which mathematical model verification studies
could be based.  The dye was discharged into the main channel of the
Anacostia River approximately 1  foot below the low water surface at the
Washington Suburban Sanitary Commission's marina in Bladensburg, Maryland
(River Mile 8.1).  This area exhibits an average tidal range of approxi-
mately 3 feet but nontidal conditions exist 1/2 mile upstream.
     A diaphragm type controlled volume pump, precalibrated to discharge
40 Ibs/day, was utilized for this study.  The container of dye was placed
on a scale so that weight could  be read and recorded several times each
day as a further check of the actual mass pumped.   A total of 280 pounds
of the 20-percent dye solution or 56 pounds of pure dye was discharged
to the Anacostia during this study.

-------
                                                                 A - 24
2.  Monitoring System
     Longitudinal  monitoring of the dye cloud was  performed daily during
periods of high- and low-slack water.   Coverage extended from the conflu-
ence of the Northeast and Northwest Branches to the mouth of the Anacostia
River at Mains Point.  Thirteen high-slack and 10  low-slack water
sampling runs were made during the period April 22-May 27.  All  samples
were analyzed by CTSL using a Turner fluorometer modified with a high
sensitivity kit to obtain concentrations as low as 0.1 ppb.  The sampling
data is shown in this appendix.
     There were 19 stations routinely sampled.  All samples were collected
at mid-channel and within 1 foot of the surface.  A description of these
stations is presented in Table 3.
     In addition to the stations given in Table 3, several samples were
collected within Kingman Lake to determine the effect of tidal exchange
between this embayment and the main stem Anacostia River.  -However, neither
lateral nor vertical sampling was  routinely performed at any of the sampling
stations.  As was discussed in a previous chapter  on model verification, the
lack of transect data raised some  doubt as to the  representativeness of
those stations actually sampled.

-------
           Table 3

LONGITUDINAL SAMPLING STATIONS
      Anacostia River
Station
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
16
17
18
19
20
Location
Ha ins Point 	
Mouth of Washington Channel ....
Opposite U. S. Naval Station ....
Upstream from Buzzard Point ....
Douglass Bridge 	
Opposite Washington Naval Yard
llth Street Bridge 	
Sousa Bridge 	
Southern Entrance to Kingman Lake
East Capitol Street Bridge 	
Benning Bridge 	
Northern Entrance to Kingman Lake
Opposite Kenilworth Aquatic Gardens .
Route 50 Bridge 	
Upstream from Unnamed Tributary
Southern Edge of Marina 	
Bladensburg Road Bridge 	
Northwest Branch at Rhode Island Avenue
Bridge 	
Northeast Branch at Baltimore Avenue
Bridae 	
Miles Upstream
from Mouth
0.00
-
0.55
1.00
1 .45
1.95
2.45
3.10
3.75
4.35
4.90
5.65
6.25
6.90
7.45
7.95
8.45

9.00

-------
                                                                 A - 26
3.  Presentation of Data



     a.  Tidal  Conditions and Hydrology



     There are  no tidal  monitoring stations in the Anacostia River and



consequently detailed tidal  data during the dye study were not obtained.



It has been reported by the  U.  S.  Coast and Geodetic Survey that the



mean tidal range at both Benning Bridge and Anacostia Bridge is 2.9 feet.



The observed tidal  range at  the Bladensburg marina, which is farther



upstream, was also  estimated to be approximately 3 feet.   Time differences



for Benning Bridge  referenced to the Washington gage average +16 minutes



for high water and  +04 minutes  for low water.



     Average daily  flows entering the tidal portion of the Anacostia



River were measured by USGS  gaging stations on the Northwest Branch



at Hyattsville and  the Northeast Branch at Riverdale.  The flows for the



study period are shown in Figure 11.  Except for the initial 9 days when



flows averaged 180  cfs, the  freshwater inflows were generally between 60



and 100 cfs.  Unusually high flows, i.e., 200-500 cfs, also occurred



during the study but they were  "flashy" in nature.

-------
                                                                 A - 28
     b.  Dye Movement
     The Anacostia River dye data obtained from the sampling stations
outlined previously are presented in isopleth form in Figure 12
(high-slack data) and Figure 13 (low-slack data).   As can be seen in
Figure 12, maximum dye concentrations were observed at River Mile 7.5
on April 27-28, which were the last two days of dye discharge.   Concen-
trations in this area were initially 6 to 7 ppb but as the study
progressed, dye concentrations exceeded 10 ppb.  Figure 13 also showed
a maximum dye buildup of similar magnitude on April 27-28 but at River
Mile 6.9.  Evidently, the 0.6 mile difference can  be attributed to the
tidal excursion between slack water periods.  The  relatively high fresh-
water flows that occurred prior to April  28 were probably responsible
for the net advective downstream movement of the dye peak from River Mile
8.1 to River Mile 7.5 or 6.9, depending on the tidal phase.
     The longitudinal dye movement occurred quite  rapidly between the
point of injection and the southern entrance to Kingman Lake.  Under
low-slack conditions, when maximum downstream movement could be expected,
dye concentrations exceeding 1.0 ppb were observed at that downstream
station the second day (April 23) after discharge  started.  This trans-
lates to a velocity of approximately 2.5  mi/day.  The rate of dye movement
decreased farther downstream due to a significant  increase in the volume
of the Anacostia River.  From April 23 to May 4, the average rate of
downstream movement based upon the slopes of the concentration lines
shown in Figure 13 was approximately 0.3  mi/day for the existing flows.

-------
L
_| U
   CE   5?
1°
is
C/) 2
UJ <
o:
       Q.
                                           E

1



1
1 1 1 1 1 1
o o o o o o
^ 00 
-------
                                                                 A - 29
During this period, the leading edge of the dye cloud progressed down-
stream to the mouth of the Anacostia River.
     As shown in Figures 12 and 13, there was very little upstream
movement of the dye which is attributable to the fact that tidal effects
do not extend much above the discharge point.  Moreover, the trailing
edge of the dye cloud appeared to move downstream at a slightly greater
rate than the leading edge.  The samples collected within Kingman Lake
indicated that comparable amounts of dye were present there as in
adjacent reaches of the main stem Anacostia River.  The tidal  and mass
exchange between these two bodies of water therefore appears to be quite
significant.

-------
       O      ^     O
ID      10      ui     in
  3DN3mjNOD   DVWOlOd
m
(M
                                                                 o
                                                           FIGURE - A 12

-------
                               DYE  ISOPLETH

                             ANACOSTIA RIVER
                              LOW  SLACK  SAMPLING
                               APRIL-MAY , 1970
Z2
                   APRIL
                                        1970
                                                         MAY
                                                                FIGURE - A 13

-------
     c.  Loss Rate Determination



     An estimate of the dye loss rate in the Anacostia River was obtained



using a method similar to that discussed previously for the Potomac dye



study.  The total quantities of dye observed during a 25-day period



following the release are shown in Figure 14.  The dye loss rate for the



Anacostia study which again followed first-order kinetics was computed to



be 0.050/day.



     Although 56 pounds of dye were discharged during the study period,



the initial mass of dye observed .in the Anacostia River was approximately



63 pounds.  A relatively higti natural background concentration (0.1 - 0.3



ppb) was measured prior to dye injection and may be responsible for this



7-pound difference.

-------
lOO-i
                                   DYE LOSS RATE
                                   ANACOSTIA RIVER
                                     APRIL-MAY, 1970
                                            SLOPE  (D)-- 0.050 DAY — BASE t
                                                                 FIGURE - A 14

-------









*
CTi
<-O
cn
S_
OJ
_p
s
_^.
o
•--
'
i-.'
rr*
-^
Lu

,~ "
"' ra
O O
o a.)
Tf Q_ -o
• f~ ,- •
UJ 1 1 — jQ
,Q n; .v Ci
rr) 4-> c •--'
J — • T <"O
t — ^ ^_
L/-I
e
• -- "c->
*•' 'C
;? ~L
t_>
ctr
r
-.,
r )
OJ
"V
en

O

;>>
i.
rn
c:'
£s
1 o


















i—


O





e^£
00



CO









 o
4-> ~^
Q •—









CO
o

0
CM
r—
•
0
LD
CO
0
CM
LO
0

t-~
I"-;
0

r^
r—
•
•—

O
co
o

0
CO
CD

O
"3]
O

,_
0

CD

i —
O
•
CD

, 	
O
o
,_
o
•
0
1
1
1
'




oo
o
"^

o
CM
0
r—
CM
0
0
CM
0
^.
CM
•
O
LO
LO
•
0
CM
CO
o
CM
co
o

LO
co
o

, —
CO
•
o

o
co
0

0
co
o

CO
CO
CD

^.
LO

0

CTI
r^
•
O

LO
•— ;
o
^
t—
•
0
CO
i —
•
0




o
^-~
x^-


I—
0
^-
o
o
CO
o
o
t
r~
•
o
LO
r—
•
0
0
LO
o
LO
LO
0

LO
U3
0

LO
LO
•
o

LO
•*
o

CO
LO
o

LO
LO
o

01
CM
•
CD

CM
o
•
o

CO
•— ;
o
, 	
o
•
o
1
1
1
1




CM
^~
^














o
CM
•
0
01

o
o

o

CO
^o
o

co
LO
•
o

LO
LO
o

r^
o
, —

o

0

LO
r—
•
0









CO
0
•
0
1
1
1
1




^3-
^~
"^

CM
o
o
LO
l—f
o
LO
CM
o
CTi
CO
•
o
CTi
CO
•
o
LO
CO
o
CTI
LO
o

o
uO
0

CO
CM
•
0

CM
CM
o

LO
<—
0

p^
CD
o

CO
CD

O

CM
O

0

, 	
0
o












f*^
^~
""•»

1
1
'
CM
CM
0
l
CO
o
00
CO
•
o
o
LO
•
o
1 	
LO
o
•3-
LO
o

LO
**•
o

, 	
CO

o

^J-
CM
o

LO
1—
o

CO
r—
0

LO
o

o

CM
o

o

«;:j-
0
o
CO
o
.
0
CM
0
•
o




CTi
r—
"^

o
r—
c
Li
0
c
«;
o
c
r-
c-

c
c
o

c
c
r—
c
o
c
c

t—
c
c











































r™
c
•^,
r\

0

3
3
J
3
1-
J
3

si
*
3
3
J
•
3
3

3
0
3
3


3
3

































(A
'!/>
j*
fO
C
n3
OJ
-Q

00

3 OO
•^ ^..".-3
j


-------

CM
i —


r—
i 	


0
i —



en

•X
en
LO 
UJ
O O3
O •*— ' e^C
E 03 LO
0 Q
i ^
O Ol
LO O- "O
•r— ' — *
CD 1 1 — J3 LO
r— Q.
-0 03 -*: Q.
03 4-> O - — -
^"** 'O f"O
Q r— 
o
c~ 
O)

t — \
ro
14-
0
^
S- 
ro
CO
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i

i
p
i
i
i
i
I
1

i
i
i
i

LO
ro
0

CM
ro
•
0

VO
r—

O


o
1 —
•
o


CM
f—

CD

1
1
1
1

1
1
1
1

1
1
1
1

CM
0

0
CM
0
o
CM
CM
•
0



ro
0) o


i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
1

i
i
i
i
_
ro
•
O

0
CTl
•
o

^t-
0
CM

ro
ro

•—

LO
CO
.
O


ro
r^
•
, —


r*^
^o

0

f—
ro
•
1 —

CJ1
CM
.
O

co
1 —
•
o

LO
1 —
•
o
o
CM
o
«.,.
CM
•
O



LO
o
1 —

i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i

i
i
i
i
i
i
i
i

0
ro

CD

*3"
cc
o

CO
CTi

O

CM
CTl
•
O


CM
LO
•
O


r^.
r\

0

r--
o
•
0

o
i —

0

CM
r—
•
0

CO
o
•
o
(^
f~^
o
00
o
•
0



<*D
0
"•^









co
o
•
o
CM
o

0

LO
o
•
o
CM
CM

0

1 —
LO

O

CM
CO
o

en
* —

0

CTl

<^"
•
0

^o
ro
•
CD
CTi
(Ni
-
o

<^-
r-~
•
o

LO
"—
o

CTi
CM
•
o

LO
CM
•
o


*^3~
CM
•
o


I—
CM
•
0

^J-
CM
•
CD

cc
ro
•
0

LO
ro
•
o

co
CM
•
o










LO
CM
~-^














































































to
to
fO
c
03


-------

























CO
^ «=f
fO r— ~
J
£ 00
Q. i—
•=!!
1
s- oj
O) r—
•r—
Oi
ro i —
•i— ro i —
4-* 4-*
in ro
0 Q
O
ro O) CD
C -0 i—
£ -Q
1 O-
_*: o_
ro O — - cn
4-> ro
ro r—
Q CO
C -C:
O CTl CO
•1 — *l —
rO
$_
4-*
C
cu r~~
c
o
o
CO
ru
o
t-
O LO

rO
E

CO

CO

00

1 —

in
c:
0
4J
ro
4-J
CO
•x * co
r~.
•X -X r—
•x * i—
CO r— CO
LO CO CO
O OO O
co r*~^ co
LO ID O
r— CD 00
i — ^f" CO
CO LO O
OO ^3- OO
i— co

r- «* O
oo r-. co
00

CO O O
i— CO i—
00


LO LT) O
i — CO O
, 	


•3- o o
r— OO CO

^ co «a-
i— i— CO


CO LO i —
i—r—00



«^J~ CO ^J~
i—i—OO

•^- oo co
I— r— i—

1 -X -X


1 -X -X

1 -X -X

1 * *




 OO CVJ OJ
ro ^^^ "*-~» **^*
O "st" «=!• ^3"
o
1 —
CO
^1
CO

o
CO
o
co
00
o
cn
CO

o
oo
CO

o
CO
00


o
r-.
co


o
LO
—
00



cn
CO



co
OJ

co
oo

OJ
•~;

•X

-X

^




LO
oo
•^^^
*3"
1

1
-X
CD
LO
CO
cn
o

CO
o
CD
,3-

o
CO
CO

LO
cn
OJ


o
CO
00


o
o
oo
LO
oo
, 	

o
o
, 	


oo
LO

^
r~~

00
00

r—
OJ
^
OO
CO
OJ



r-^.
OJ
^^^
«d-
,

'
•X
r^
r-.
CO
[H
LO
^
LO
^
co
«^-

0
o
^j-

rv^
cn
00


CO
•—
oo


cn
•—
OJ
cn

, —

cn
•—
,_


OJ
LO

LO
CO

r^.
•— ;

•x

^.
•~;
^.
i —



CO
OJ
-* —
<^-
,

1
•X
r^

co
•—
o
CO
LO
OJ
CO
LO

, —
CO
,3-

co
CO
CO


^J-
LO
CO


o
CO
oo
cn
OJ
oo

, 	
0
oo


o
i —

,_
•^-

CO
00

•X

_
CO
•X




cn
oo
•-. 	
«d~
(

i
•X
-X

1 —
•—
CO
CO
CO
co
r^-
CO

co
cn
CO

CO
co
CO


CO
CO
oo


^j-
co
00
00
CO
, —

oo
cn



i —
CO

oo
00

C1
•-;

-x

•X

-X




CD
CO
^•^
«sf
(

1
-X
r—

OO

o
CO

,-J.
LO


O
O
,_

CD
CO
,_


cn
i —
,_


o
LO
•-
^.
LO
,—

r~^
•*
r—


OO
0
—
co
^

i —
"^

to
*"]
o
00
,_
• —



CO
CD
--^
LO
t

1
1
-X

•X

cn
r—

CO



cn
CO


oo
co



cn
CO



oo
oo
r~
CO
CO
, —

,3-
CO
i —


CO
cn

CO
CO

00
LO

CO
r—
^
00
CO
00



f^
0
•* —
LO
1 1 1

1 1 1
' * '
•x oo -x

•x oo oo

LO cn o
OO i — OJ

^i-oo
CO OO OO


LO r- CO
•Bj- CVJ i —


CD co cn
LO OO r—



r- •— 00
CO OJ r—



CO O OO
CO 00 r—

O CD 4:
r-^ oo


oo t-~~ -x
CO r-



^J" «^- ^C
«^- 1 —

LO 1— *
CO i—

LO -X -X
00

-X -X -X

r— -X -X
oo
-X -X *




oo oo r^-
i— OJ 00
~*h-> ^^- ^^-
LO LO LO






















































"
c-
ro
4->
(/)
i/l
0)
	 1
.
"^

-------

























f^».

QJ
»—
.0
(O
^~


































O
CM
cn
co

r^
"~
0
cn to
r\
% *t
(
•r-
i.
CL co
 ro
O ro O
U Q i—
ro
c~ cLJ x — ^
«=t -0 -0
•r- Q-
i 1— Q. cn
—
ro ^
•*-* O
ro ro
Q •—
00 CO
C
0 2
•r- O
ro
i— r*"^>
4_}
c:
CD
O
c
O to
o
Q
LO
M-
O
ro ^-
E
oo
CO

CM

^

to
o
£>
ro
1 *
OO
* cn i
"""]
-K CO 1
-K CM *

CM O «»•
tD LO CO

LO 00 to
CO ^J- f —
O i— 00
co co o

co r^. CM
CM ^3- LO

LO •* O
• . •
co r-~ to
CM o r-.
• * .
CM LO ^T

oo o LO
r-. LO o

co ^J-


^j- •cj- LO
CM cn CM
• . •
i — CO


LT) CM CM
i — to to
...
CM

LO i — tO
i— CO O1
...
r—


to oo co
"""I """I """I

LD tO O
i— i— cn
• • •
LD LO i —
i — i — tO

•3- CO r—
i — i — LO
* * *

* * cn
•~;


cu CM co r^
•»-> CM CM CM
O _,. «* *J-
1

1
o
-^
LO
LO

O
tO
r-
CM

oo
LO

O
•
^
crv
.
LO

co
CO
•
LD


r—
CM
.
«^-


CM
CM
•
CO

«^-
CM
•
CM


00
LD

CO
O
r-^
oo
LO

,3-
LO
CO
r~-
^.
CM


oo
CM
^"


1
-K

-K


.-

CO


0
LO

cn
.
LO
CM

to

^J.
cn
.
LO


«^J-
co
.
^j-


to
CM
.
CO

co
«=}-
.
CM


f^
CO

LO
o
r-^
CM
LO

LD
^
O
CM
O
CO


cn
CM
.3-


1
*

*


*

r-


o
CM

00
.
ro
cn

CM

^
LD
•
CO


0
O
.
^j-


LD
r-^

CO

to
to
.
CM


cn
CO

en
CO
^
cn
^

r^.
LD
00
CO

•~;


o
CO
^J-
1

'
1

r-


r—

CM


CO
i —

^f-
•
CO
r—
.
CM

«^-
CM
•
CM


CM
to
*
CM


CO
CO
.
CO

CO


CM


to
cn

CM
CO
*
to
to

CM
LO
cn
CM
*



, 	
CD
LO
1

1
, 	

*


*

1—


^J"


CO
.

CO
•


CM
LD
•



CO
o
.
1 —


o
f^
.
•—

CM
01
.
r—


^J-
oo

CM
to
r-'
CM
CO
"~
cn
cn
LO
cn
^
^;


^.
o
LD


'
, 	
CM
*


*

,-


CO


cn
•

^
•


CM
to
•



LO
cn
»



o
LO
•
•—

r*>^
LO
.
f—


i-~
to

to
CO
^
LO
cn

CM
oo

LD
co
CM


LD
O
LD


1
1

r~


r-

CM


CM


CO
•

CM
.


,_
CM
•



O
CM
•



cn

•


0
CM
•



px.
•"";

CM
CM
*
oo


,-j.
1
LO
•"^
CM



O1

LO
 d)
_J

*

-------
              o
              O
              a
              5
                          a
                          5

-------
UJ
O
9

a:
CD
UJ
UJ
a:


CO
                 I/)
 (D
 Z
 _
 Q.

 2

 <
 in
OJ
O
ui
in
z
<
a:
i-
LJ
a:
                                 r
                                o
                                I
                                CO
 I
•

                                                                                                      I
                                                                                                -O
                                                                                              (\J
                                                            1J - Hld3Q
                                                                                        FIGURE  A-16

-------
                             Q

                             2
               O
               _
               a
               5
2
<
h-
u
UJ
co
Z
<
cc
LJ

QC
                                             i
                                             GO
                                                           T

                                                           •
-------
          I/)
          z
          o

          I
          IO
          o
          z
          _l
          Q.
Q

2
O
Q.
CC
LJ

t-
h-
u
UJ
cc
h-
         <
         UJ
                          r
                         o
                                             I

                                             •*
                                             OJ
                                                                             O
                                                                            •s
                                                                                                     o
                                                                                                    .o
                                                                                                     o
                                                                             o
                                                                            -o
                                                                             00
                                                                                                     O
                                                                                                    -o
                                                                                                         I/)
                                                                                                         Q
                                                                                                         I
                                                                                                         I-
                                                                                                         Q

                                                                                                         s
                                                                             o
                                                                             o
                                                                                                     o
                                                                                                     o
                                                                                                     (VI
                                                   UJ - Hid3Q
                                                                                            FIGURE   A-18

-------
          IO
          z
          o
                                                                                                        o
                                                                                                       -8
          Q.
          2
UJ
I-
o
UJ
cr
I-
UJ
cr
h-
to
a
          O
          Z

          (J
                                                                                                        o
                                                                                                       .o
                                                                                                        o
                                                                                                        o
                                                                                                       -o
                                                                                                        00
                                                                                                        o
                                                                                                       -o
                                                                                                            co
                                                                                                            Q
                                                                                                  I

                                                                                                  I
                                                                                              O
                                                                                             -o
                                                                                                        o
                                                                                                       -o
                                                                                                        fVJ
                                                        I
                                                        to
                                                              I
                                                             •*
                                                             (VJ
                                                                                      (M
                                                         - Hld3C]
                                                                                               FIGURE   A-19

-------
               z
               o
              13
              Z


              a
a
z
CO
CO
O
O
(D
U
LL)
CO
Z
<
a:
LJ
a

CO
a
              u
                              I
                             o
                                            I

                                            VO
                                                                                         O
                                                                                        -o
                                                                                         o
                                                                                        -o
                                                                                       1-8
                                                                                         o
                                                                                        •o
                                                                               I

                                                                               I
                                                                           o
                                                                           o
                                                                           (VJ
                                                                                         o
                                                                                         o
                                                      - Hld3Q
                                                                                FIGURE   A-ZO

-------
z
o
o
a:
Q
O

i
              lO
              z
              o
              O

              Z


              a
u
Ul
              LJ
              tr
              1>



              (D
              Z
                                                                                        o
                                                                                       .o
 o
.o
 o
                                                                                      u
.8
 IO
                                                                                           I

                                                                                           fe
                                                                                           $
                                                                                        o
                                                                                       • o
                                                         <£>
                                             UJ - Hld3Q
                                                                               FIGURE   A-21

-------
            o
       a
D


CO
a:
UJ


O
cc
o
UJ
cr
UJ
a:

to
a
       Z

       o
                                                                                                  o
                                                                                                  o
                                                                                                  o
                                                                                                  o
                                                                                                 •
                                                                                                 .8
                                                                                                  o
                                                                                                  o
                                                                                                  O
                                                                                                  co
                                                                                                     >

                                                                                                      I

                                                                                                     I
                                                                                                  o
                                                                                                 •o
                                                                                                -8
                                                                                                  o
                                                                                                  o
                                                                                                  (\J
                                                                                                -o
             o
                           I

                           CO
                                  I
                                  10
                                                                    (M
                                                  - Hid3Q
                                                                                          FIGURE   A-22

-------
                                                                                                         to
             -z.
             o
                                                                                                         o
                                                                                                        -O
             <
             i/l
                                                                                                         o
                                                                                                        _o
                                                                                                       *^00
                                                                                                         (M
UJ
LU
o:
U
                                                                                             O
                                                                                             O
                                                                                           ^•*
                                                                                             (\J
CD
(O

*



U
U
cc.
h-
<
Ul
cc

CO
Q.

D


O
Z

U
                                                                                                         0
                                                                                                       \~°
                                                                                                       r
-------
UJ
UJ
tr
O
I
£
U

-------
              to

              o
              O
              z
              _
              a
Ul
LJ

(T

U
LJ
Z>

O
O
Q
00
A



U
UJ
i/>
Z
<
a:
                                                                                     L8
                                                                                       CO
                                                                                       M
                                                                                      .8
 CVJ
• <
 00
              LJ
              a:
              a.
              D
              o
              2

              U
                                           i
                                           CO
                                                         <0
                                                       - Hld3Q
                                                                       •
-------
             o

             £
             10
             z

             a
5
u
z
D
<
00
U
Ul
                                                                                                      o
                                                                                                      .o
                                                                                                      o
                                                                                                      -8
                                                                                                      o
                                                                                                     _o

                                                                                                      C\J
                                                                                                      O
                                                                                                      o
                                                                                                      •QO
                                                                               I

                                                                              fe
            Ul
            
-------
I-
z

2
z

o
            10
            z
            o
            o
            z
            _1
            a
            2
O)
(J
UJ
cc
h-
            UJ
            cr
                                                                                                       I

                                                                                                       I
                                                   - Hid3Q
                                                                                           FIGURE   A-27

-------
            a


            I
LJ
I
a
z
O


*
a:
h-
u
cr

to
a
                                                                                                  o
                                                                                                  .o
                                                                                                  o
                                                                                                  o
                                                                                                  o
                                                                                                  to
                                                                                                  I
                                                                                                       o
                                                                                                       >-
                                                                                                       I
                                                                                                       I-
                                                                                                       Q
                                                                                                  O
                                                                                                  -O
                                                                                                  00
                                                                                                 -o
                           I
                           o
                                         00
                                           I
                                           IO
I
Tt

(VI
                                                           - Hld30
                                                                                     FIGURE   A-28

-------
                             BIBLIOGRAPHY


 1.   Jaworski,  N.  A.,  L.  J. Clark,  "Physical Data Potomac River Tidal
     System Including  Mathematical  Model Segmentation," CTSL, MAR,
     FWQA,  1970.

 2.   U.  S.  Geological  Survey,  "Movement of a Solute in the Potomac River
     Estuary at Washington, D. C. at Low Inflow Conditions," 1969.

 3.   Hetling,  L.  J., R.  L. O'Connell,  "A Study of Tidal Dispersion in
     the Potomac  River,"  CTSL, MAR, FWQA, 1966.

 4.   Thomann,  Robert V.,  "Mathematical Model for Dissolved Oxygen,"
     Journal  of the Sanitary  Engineering Division, ASCE, Vol. 89. No. SA5,
     October 1963.

 5.   Jeglic, J. M., "Mathematical Simulation of the Estuarine Behavior,"
     Contract  to  FWQA  by  General  Electric, 1967.

 6.   Jeglic, J. M., "Mathematical Simulation of the Estuarine Chloride
     Distribution," Contract  to  FWQA by General Electric, 1967.

 7.   Harleman,  D.  R. F.,  "One-Dimensional Mathematical Models in State of
     the Art of Estuary  Models,"  Contract to FWQA by Tracer, Inc., 1971.

 8.   Feigner,  K.  D. and  H. S.  Harris,  Documentation Report, FWQA Dynamic
     Estuary Model, FWQA, July 1970.

 9.   Paulson,  R.  W., "Variation  of  the Longitudinal Dispersion Coefficient
     in  the Delaware River Estuary  as  a Function of Freshwater Inflow,"
     Water  Resources Research, Volume  6, April 1970, Number 2.

10.   Clark, L.  J.  and  N.  A. Jaworski,  "Nutrient Transport and Dissolved
     Oxygen Budget Studies in  the Potomac Estuary," CTSL, MAR, FWQA,
     (In Preparation).

-------
Chesapeake Technical Support  Laboratory
          Middle Atlantic  Region
           Water Quality Office
    Environmental Protection  Agency
  A WATER RESOURCE-WATER SUPPLY STUDY


                 OF THE


            POTOMAC ESTUARY


          Technical Report  35


              April 1971



         Norbert  A. Jaworski

             Leo  J. Clark

         Kenneth  D. Feigner*
 *EPA,  WQO,  Washington,  D.  C.

-------
                         TABLE OF CONTENTS
LIST OF TABLES 	

LIST OF FIGURES   .   .  .	

Chapter

   I       INTRODUCTION 	        1-1

  II       SUMMARY AND CONCLUSIONS	       II - 1

 III       STUDY AREA DESCRIPTION	      Ill - 1

           A.  Potomac fiiver Tidal System	      Ill - 1

           B,,  Hydrographic Analysis	      Ill - 5

           C.  Proposed Reservoir Development   .   .   .      Ill - 8

           D,  Water Resource Uses	      Ill -12

               1. Water Supply Use	      Ill -12

                   a.  Municipal    	      Ill -12

                   b.  Industrial	      Ill -13

               2.  Recreation and Boating	    -  III -15

               3o  Commercial Fisheries	      Ill -17

  IV       WASTEWATER LOADINGS AND RUNOFF CONTRIBUTIONS       IV - 1

           A.  Wastewater Loadings and Trends   ...       IV - 1

           B0  Potomac River Water Quality above
                 Great Falls	       IV - 7

           C0  Suburban and Urban Runoff	       IV -12

           D.  Summary and Comparison of Nutrients,
                 BOD, and Carbon Contributions  ...       IV -14
                                 ii

-------
                         TABLE OF CONTENTS (Continued)


Chapter                                                      Page

   V       WATER QUALITY CONDITIONS AND TRENDS ....      V - 1

           A.  Bacterial Densities    	      V - 2

           B.  Dissolved Oxygen    	      V - 6

           C.  Silt and Debris	      V -13

           D.  Nutrients and Algal Growths	      V -21

               1.  Nutrient Concentrations in the Potomac
                     Estuary .	      V -21

               2.  Mathematical Models for Nutrient
                     Transport	      V -27

               3.  Ecological Trends as Related to
                     Nutrient Loadings   	      V -35

           E.  Effects of Eutrophication on Water Quality      V -42

               1.  Increase in Organic Oxygen Demanding
                     Load    	      V -42

               2.  Algal Oxygen Production and Respiration     V -43

               3.  Unfavorable Physical and Aesthetic
                     Characteristics of Algal Blooms .  .      V -48

               4.  Algal Toxicity	      V -49

  VI       DISSOLVED OXYGEN ENHANCEMENT	     VI - 1

           A.  Study Approach	     VI - 1

           B.  DO Criteria	     VI - 8
                                iii

-------
Chapter

 VII
VIII
              TABLE OF CONTENTS (Continued)




ALGAL GROWTH RESPONSE TO NUTRIENT CONTROL

A.  Eutrophication Control Objectives .
VII - 1

VII - 2
B.  Nutrient Requirements to Prevent
      Excessive Standing Crops of Blue-green
        Algae    	      VII - 5

    !„  Algal Composition Analysis ....      VII - 8

    2.  Analysis of Data on an Annual Cycle
          and Longitudinal Profile Basis .  .      VII -11

    3o  Bioassay Studies  .  „	      VII -16

    4,  Nutrient and Algal Modeling   .  .  .      VII -18

    5.  Comparison With a Less-stressed
          Estuary	      VII -22

    6.  Review of Historical Nutrient and
          Ecological Trends in the Potomac
            Estuary    	      VII -24

C.  Controllability of Various Nutrients .  .      VII -25

D.  Nutrient Criteria	      VII -30

CONTROL CONSIDERATIONS FOR BACTERIAL DENSITIES,
  VIRUSES, HEAVY METALS, AND OTHER WATER
    QUALITY PARAMETERS	     VIII - 1

A.  Bacterial Densities	     VIII - 1

    1.  Indicator Organisms	     VIII - 1

    2.  Bacterial Standards	     VIII - 3

B.  Viruses	     VIII - 4

C.  Heavy Metals	     VIII - 7
                                 IV

-------
                         TABLE OF CONTENTS (Continued)


Chapter                                                      Page

VIII       CONTROL CONSIDERATIONS FOR BACTERIAL DENSITIES,
             VIRUSES, HEAVY METALS, AND OTHER WATER
               QUALITY PARAMETERS (Continued)                VIII - 1

           D.  Other Water Quality Indicators ....     VIII -10

               1.  Thermal	     VIII -10

               2.  Carbon Chloroform Extraction  .  .   .     VIII -10

               3.  Chlorides and Total Dissolved Solids      VIII -12

               4.  Pesticides and Herbicides  ....     VIII -15

  IX       POPULATION AND WASTEWATER PROJECTIONS ...       IX - 1

           A0  Population Projections   ......       IX - 1

           B.  Water Supply Requirements	       IX - 6

           C.  Wastewater Loadings	       IX - 9

   X       WATER QUALITY SIMULATIONS	        X - 1

           A.  Water Quality Simulation Models   ...        X - 1

           B.  Alternative Wastewater Treatment Systems         X - 5

           C.  Wastewater Management Zones and Stream-
                 flow Criteria	   .        X -16

           D.  Ultimate Oxygen Demand   	        X -20

           E.  Phosphorus   .  „	        X -26

           F.  Nitrogen	        X -33

           G.  Chloride and Total Dissolved Solids
                 Simulations	        X -37

               1.  Estuary Water Supply Withdrawal  .   .        X -37

               2,  Direct Reuse of Treated Wastewater            X -47

-------
                         TABLE OF CONTENTS  (Continued)


Chapter

  XI       WASTEWATER TREATMENT FACILITIES  AND COSTS         XI  - 1

           A.  Treatment Considerations	        XI  - 1

           B.  Wastewater Treatment Costs   ....        XI  - 3

 XII       IMPLEMENTATION TO ACHIEVE WATER  QUALITY
             STANDARDS    	        XII  - 1

           A.  Seasonal Waste Treatment	        XII  - 1

               1.  Ultimate Oxygen Demand   ....        XII  - 1

               2.  Phosphorus	        XII  - 2

               3.  Nitrogen	        XII  - 5

           B.  Location of Wastewater Discharges   .   .        XII  - 8

               1.  Wastewater Assimilation  Versus
                     Salinity Intrusion	        XII  - 8

               2.  Wastewater Discharges to the
                     Embayments    	        XII  - 9

           C.  Flow Regulation for Water Supply and
                 Water Quality Control	        XII  -10

ACKNOWLEDGEMENTS

REFERENCES
                                 vi

-------
                           LIST OF TABLES


Number                                                       Page

 III - 1    Zones of the Upper and Middle Reaches  of
            the Potomac Estuary  ........        Ill - 4

 III - 2    Magnitude and Frequency of Low Flows,
            Potomac River near Washington, D.  C.,
            1930-1966 Water Years	        Ill - 7

 III - 3    Reservoir Projects, Storage,  and Cost,
            Potomac River Basin  	        Ill -10

 III - 4    Low-flow Frequency Analyses for Various
            Reservoir Systems, Potomac near Washington        III -11

 III - 5    Maryland and Virginia Landings Fish and
            Shellfish, Potomac River and  Tributaries,
            1969  .............        Ill -19

  IV - 1    Wastewater Loadings to the Upper Potomac
            Estuary and Tributaries, Great Falls to
            Indian Head,  1970	         IV - 2

  IV - 2    Wastewater Loading Trends, Washington
            Metropolitan Area 	         IV - 3

  IV - 3    Upper Potomac River Basin Contributions
            (Above Great  Falls),  February 1969 through
            February 1970	         IV - 9

  IV - 4    Nutrient and  BOD Contributions from the
            Upper Potomac River Basin above Great
            Falls,  Maryland	         IV -11

  IV - 5    Urban and Suburban Runoff Contributions  to
            Upper Potomac Estuary (Great  Falls to
            Indian Head)	         IV -13

  IV - 6    Summary of Contributions of Nutrients, BOD,
            and Carbon	         IV -15

   V - 1    Sediment Data,  Potomac River  Basin Below
            Confluence of Monocacy River	         V -14

   V - 2    Sediment Data,  Northwest Branch Anacostia
            River near Colesville,  Maryland ....         V -15
                                VII

-------
                           LIST OF TABLES

Number                         Title

   V - 3    Oxygen Production and Respiration Rate
            Survey, Upper and Middle Potomac Estuary,
            1970	         V -44

   V - 4    Oxygen Production-Respiration Balances .   .         V -45

 VII - 1    Subjective Analysis of Algal Control
            Requirements	       VII - 4

 VII - 2    Algal Composition Study, Upper Potomac
            Estuary, 1970	       VII - 9

 VII - 3    Nitrogen Bioassay Summary, Potomac Estuary,
            1970  .............       VII -16

 VII - 4    Summary Data, Upper Rappahannock Estuary,
            1970  0  ............       VII -23

VIII - 1    Heavy Metal Analyses of Sediment Samples,
            August 18 - 20, 1970, Potomac Estuary  .   .      VIII - 9

  IX - 1    Data Summary Facility Service Areas ...        IX - 2

  IX - 2    Water Supply Requirements, Washington
            Metropolitan Area	        IX - 7

  IX - 3    Various Water Supply Demands, Washington
            Metropolitan Area	        IX - 8

  IX - 4    Present Wastewater Loadings, Washington
            Metropolitan Area	        IX -10

  IX - 5    1980 Wastewater Loadings, Washington
            Metropolitan Area	        IX -11

  IX - 6    2000 Wastewater Loadings, Washington
            Metropolitan Area 	        IX -12

  IX - 7    2020 Wastewater Loadings, Washington
            Metropolitan Area	        IX -13
                                Vlll

-------
                           LIST OF TABLES

Number                         Title                         Page

   X - I    Wastewater Facilities and Projected Flows,
            Alternative I	         X-5

   X - 2    Wastewater Facilities and Projected Flows,
            Alternative II	         X -12

   X - 3    Wastewater Facilities and Projected Flows,
            Alternative III	         X -13

   X - 4    Zones of the Upper and Middle Reaches of
            the Potomac Estuary  ........         X -17

   X - 5    UOD Loadings for Potomac Estuary ....         X -21

   X - 6    Phosphorus Loadings for Potomac Estuary.  .         X -27

   X - 7    Intrusion Times for Phosphorus into Estuary
            Water Intake	         X -32

   X - 8    Nitrogen Loadings for Potomac Estuary  .  .         X -34

   X - 9    Time, In Days, To Reach Indicated Concen-
            tration of Total Dissolved Solids in
            Estuary at Proposed Water Intake near
            Chain Bridge	         X -45

   X -10    Time, In Days, To Reach Indicated Concen-
            tration of Total Dissolved Solids in
            Estuary at Proposed Water Intake near
            Chain Bridge	         X -46

  XI - 1    Total Wastewater Treatment Cost, 1970-2020,
            Alternative III	        XI - 7

  XI - 2    Initial Capital Construction and Operation
            and Maintenance Costs, 1970-1980, 1980-
            2000, and 2000-2020 Time Periods ....        XI - 8
                                 IX

-------
                           LIST OF FIGURES


Number                         Title

 III - 1    Potomac River Tidal System  ......      Ill - 3

 III - 2    Planned Development for the Proposed Seven
            Reservoir System, Potomac River Basin   .   .      Ill - 9

  IV - 1    UOD Loading Trends to Potomac Estuary From
            Washington, D. C. Metropolitan Area  ...       IV - 5

  IV - 2    Nutrient Concentrations , Potomac River at
            Great Falls  .  .  .........       IV - 8

   V - 1    Total Goliform Organisms, Upper Potomac
            Estuary, 1938-1970 Summer Averages   ...        V - 3

   V - 2    Fecal Coliform Densities, Upper Potomac
            Estuary   .  .  .  .  ........        V - 4

   V - 3    Dissolved Oxygen Concentration, Upper Potomac
            Estuary, 1938-1970 .........        V-8

   V - 4    DO Profiles, Upper Potomac Estuary, 1969            V - 9

   V - 5    Dissolved Oxygen Concentration, Potomac
            Estuary at Woodrow Wilson Bridge, 1965  ..        V -10

   V - 6    Dissolved Cbcygen Concentration, Potomac
            Estuary at Woodrow Wilson Bridge, 1966  .        'V -11

   V - 7    DC Contour (mg/l) Piscataway Embayment-
            Potomac Estuary, June 22, 1970 .....        V -12

   V-8    Benthal Uptake, Potomac Estuary   ....        V -19

   V - 9    Chemical Oxygen Demand of Sediments, Potomac
            Estuary   ......  ......        V -20
   V -10    Inorganic Phosphate Concentration as    .
            Potomac Estuary, 1969-1970  ......        V -22

   V -11    Nitrate and Nitrite Nitrogen as N, Potomac
            Estuary, 1969-1970 ...  ......        V -24

   V -12    Ammonia Nitrogen as N, Potomac Estuary, 1969-
            1970   .............        V -26

-------
                           LIST OF FIGURES


Number                         Tj,tle                         gage

   V -13    Phosphorus Concentration, Potomac Estuary,
            September 28 - October 27, 1965  ....         V -28

   V -14    Phosphorus Concentration, Potomac Estuary,
            January 25, 1966	         V -29

   V -15    Nitrogen Concentration, Potomac Estuary,
            September 6-13, 1966	         V -30

   V -16    Nitrogen Concentration, Potomac Estuary,
            August 19 - 22, 1968	         V -31

   V -17    Effect of Temperature on Phosphorus
            Deposition Rate, Potomac Estuary ....         V -32

   V -18    Effect of Temperature on Nitrification Rate,
            Potomac Estuary	         V -33

   V -19    Effect of Temperature on Rate of Nitrogen
            Utilization by Algae, Potomac Estuary  .  .         V -34

   V -20    Waste-water Nutrient Enrichment Trends and
            Ecological Effects, Upper Potomac Tidal
            River System	         V -36

   V -21    Chlorophyll a, Potomac Estuary, Upper Reach,
            1965-1966, 1969-1970	'        V -39

   V -22    Chlorophyll g., Potomac Estuary, Middle and
            Lower Reach, 1965-1966, 1969-1970   ...         V -40

   V -23    DO Concentrations, Potomac Estuary,
            August 19 - 22, 1968	         V -47

  VI - 1    A Schematic Diagram of Dissolved Oxygen
            Interrelationships for the Three Major
            Biological Systems   	        VI - 2

  VI - 2    DO Concentrations, Potomac Estuary,
            September 22, 1968	        VI - 4

  VI - 3    DO Concentrations, Potomac Estuary,
            August 12 - 17, 1969	        VI - 5
                                 XI

-------
LIST OF FIGURES
Number
VII

VII

VII

VII

VIII

VIII
IX

IX

X

X

X

X

X

X

X

- 1

- 2

- 3

- 4

- 1

- 2
- 1

- 2

- 1

- 2

_ -j

- 4

- 5

- 6

- 7

Title
Nutrient -Chlorophyll Profiles, Potomac

Chlorophyll Concentration, Potomac Estuary,
August 19 - 23, 1968 	
Chlorophyll Concentration, Potomac Estuary,
September 6-7, 1966 	
Carbon, TKN and Phosphorus in Sediments,
Potomac Estuary, August 19 - 20, 1970 . .
Carbon Chloroform Extract, Potomac Estuary,
1963-1968 . . 	
Chloride Concentration, Potomac Estuary.
Wastewater Service Areas, Washington
Metropolitan Area 	
Population Projections, Washington

Schematic of Potomac Estuary for FWQA
Dynamic Model ... 	
Schematic of Water Flow, Water Quality
Simulation . 	
Wastewater Treatment Systems, Upper Potomac
Estuary, Alternative I 	
Wastewater Treatment Systems, Upper Potomac
Estuary, Alternative II . 	
Wastewater Treatment Systems, Upper Potomac

Wastewater Treatment Systems, Upper Potomac
Estuary, Alternative IV 	
Wastewater Treatment Systems, Upper Potomac
Estuary. Alternative V 	
Page

VII

VII

VII

VII

VIII
VIII

IX

IX

X

X

X

X

X

X

X


-13

-20

-21

-29

-11
-14

- 4

- 5

_ ^

- 4

- 6

- 7

- 8

- 9

-10
      Xll

-------
                           LIST OF FIGURES


Number                         Title

   X - 8    Wastewater Discharge Zones in Upper Potomac
            Estuary	       X -18

   X - 9    Observed Chloride Profiles for Low Flow
            Conditions	       X -38

  XI - 1    Activated Sludge Cost	      XI - 4

 XII - 1    Annual Phosphorus Profiles, Potomac Estuary
            at Indian Head	     XII - 4

 XII - 2    Simulated Annual Nitrogen, Potomac Estuary
            at Indian Head	     XII - 6
                                xiii

-------
                                                                   1-1





                             CHAPTER I



                            INTRODUCTION



     At the third session of the Conference on the Matter of Pollution



of the Interstate Waters of the Potomac River and Its Tributaries in



the Washington Metropolitan Area held April 2, 3, 4 and again on



May 8, 1969, the conferees agreed upon 15 recommendations to enhance



the water quality of the Potomac and to assure adequate sewerage




services for the area.



     At the progress evaluation meeting of the conference held on



November 6-7, 1969, a technical advisory committee was established



to determine the studies required to evaluate water quality management



needs of the upper estuary.



     In November 1969, the Assistant Secretary of the Interior also



requested a study of the water supply potential of the upper Potomac



Estuary.  Incorporating both the suggestions of the Potomac Enforcement



Technical Advisory Committee and the request of the Assistant Secretary



of the Interior, a detailed water quality-water resources study of the



Potomac Estuary was undertaken by the Chesapeake Technical Support



Laboratory.



     The study included (l) an evaluation of pollution sources including



nutrients, (2) the development and refinement of mathematical models to



predict the effects of the various pollutants on water quality, (3) the



projection of water supply needs and wastewater loadings, (4) an evalu-



ation of the estuary as a potential water supply source,  (5) the



determination of the maximum pound loadings by zone for the various

-------
                                                                    1-2






pollutants under various flow conditions, (6) an investigation of



alternative waste treatment plans, and (7) an estimate of the cost



of wastewater treatment required to maintain water quality standards.



     During this study, close cooperation was maintained with the



North Atlantic Division of the U. S. Army Corps of Engineers who were



investigating the water supply potential of the upper Potomac Estuary



as part of their Northeast Water Supply Study (NEWS) for the Washington



metropolitan area0

-------
                                                                  II-1



                            CHAPTER II



                      SUMMARY AND CONCLUSIONS



     A detailed study of the interrelationships among wastewater



discharges, water supply withdrawals, freshwater inflow, and water



quality in the Potomac Estuary was undertaken in November 1969.  This



study had two purposes:  (l) to refine the allowable oxygen demanding



and nutrient loadings previously established for Zones I, II, and III



of the upper Potomac Estuary and (2) to determine the feasibility of



using the estuary as a municipal water supply source.  The latter



study was conducted in cooperation with the U. S. Army Corps of



Engineers.  The study findings as related to wastewater management



are presented below:



     1.  The Potomac River Basin has a drainage area of 14,670 square



miles.  The average discharge rate of the Potomac River at Great Falls



is 10,780 cubic feet per second (cfs) with a minimum of 610 cfs and a



maximum of over 484,000 cfs.



     2.  Of the present 3.3 million population in the Potomac River



Basin, 2.8 million live within the study area which encompasses the



entire Washington metropolitan region.



     3.  The present municipal water use within the study area is



370 mgd with 72 percent (265 mgd) supplied from the Potomac River



above Washington.  The industrial water use is 2,750 mgd with cooling



water for electric power production accounting for 99 percent.

-------
                                                                   II-2


     4.  Recreational facilities on or near the Potomac Estuary include

a national park, three state parks, seven fish and game areas and 226

county recreational sites.  A recent study by the Bureau of Outdoor

Recreation indicated that the recreational potential of the 637 miles

of shoreline has barely been developed.

     5.  In 1969, approximately 17-million pounds of fish, crabs, clams,

and oystere were taken from the Potomac tidal system with a dockside

value of some $4.7 million,  A study in 196l indicated that about $0.6

million was spent during 6 months of sport fishing in the Potomac

Fstuary,  There are approximately 95 marina facilities in the tidal

Potomac which accommodate over 5,200 recreational watercraft.

     60  Effluents from the 18 major wastewater treatment facilities

and combined sewer overflows, with a total flow of 325 mgd, contribute

450,000, 24,000, and 60,000 Ibs/day of ultimate oxygen demand (UOD*),

phosphorus, and nitrogen respectively to the waters of the upper

Potomac Estuary„

     7»  Under low-flow conditions, the ultimate oxygen demand, phos-

phorus, and nitrogen loadings from the upper basin and local runoff

were estimated as 66,000, 1,000, and 2,300 Ibs/day, respectively.

     8.  The major sources of nutrients and ultimate oxygen demand in

the Potomac Estuary are the local wastewater discharges.  Under low-

flow conditions approximately SB, 90, and 96 percent of the ultimate

oxygen demand, nitrogen, and phosphorus are from treated waste effluents,
* UOD - Ultimate Oxygen Demand is defined as the sum of 1.45 times the
  5-day biochemical oxygen demand and 4.57 times the unoxidized nitrogen.

-------
                                                                   II -3





At median freshwater inflows, approximately 62, 60, and 82 percent



respectively are from these wastewater discharges.



     9.  Since the first sanitary surveys in 1913, the water quality of



the upper Potomac Estuary has generally deteriorated.  This is attributable



to the increased pollution originating in the Washington area.



    10.  Fecal coliform densities have recently proved an exception to



the general degradation as shown by the water quality indicators.  Since



the summer of 1969, the high fecal coliform densities previously found



near the waste discharge points have been significantly reduced by con-



tinuous wastewater effluent chlorination.  At present, the largest



sources of bacterial pollution in the upper estuary are from sanitary



and combined sewer overflows, where at times about 10 to 20 mgd of



untreated sewage enters the estuary because of inadequate sewer and



treatment capacities„



     To achieve the adopted fecal coliform water quality standards,



there must be both continuous disinfection of wastewater effluents



and elimination or drastic reduction in overflows from sanitary and



combined sewers.



    11„  The most pronounced effect of thermal discharges is in the



Anacostia tidal river where a five-degree rise above ambient water



temperature frequently occurs and readings as high as 33°C have been



recorded during the summer months.



    12.  Since 1938, dissolved oxygen levels in the upper estuary had



been decreasing.  A slight upward trend occurred in the early 1960's

-------
                                                                   II-4





due to the provision of a higher degree of wastewater treatment.   However,



with increasing population, the amount of organic matter discharged has



increased to a record high in 1970 resulting in a critical dissolved



oxygen stress in the receiving water.  In recent years, dissolved oxy-



gen concentrations of less than 1.0 mg/1 have occurred during low-flow,



high-temperature periods.



    13.  Mathematical model simulation of the dissolved oxygen budget



including carbonaceous, nitrogenous, benthic, and algal demands indicate



that the nitrogenous demand is the greatest cause of dissolved oxygen



deficit in the critical reach near the wastewater discharges and that



algal growths have the greatest effect on DO from Piscataway to Indian



Head, at times depressing it below 5.0 mg/1.



    14.  On the average, approximately 3-billion pounds per year of



sediments enter the Potomac Estuary of which 2.2-billion pounds per



year originate in the upper Potomac River Basin.  The sediment yield



from the Washington area on a Ibs/sq mi/yr basis is about seven times



greater than that from the upper basin.



    15 o  Since 1913, the wastewater discharge quantities have increased



over sevenfold from 42 to 325 mgd, the phosphorus load increased 22-fold



from 1,100 to 24,000 Ibs/day; nitrogen ninefold, from 6,400 to 60,000



Ibs/day; and carbon approximately twofold, from 40,000 to 100,000



Ibs/dayo  When ecological plant successions from a balanced toward



an unbalanced system (primarily one dominated by blue-green algae) are



related to wastewater loading trends, it can be concluded that the

-------
                                                                   II-5





 ecological successions are the result of increases in nutrients.



 Moreover, it appears that the ecological changes are due primarily



 to the large increases in phosphorus and nitrogen.



    16.  In recent years, large populations of blue-green algae, often



 forming thick mats, have been observed in the Potomac Estuary from the



 Potomac River Bridge (Route 301) to the Woodrow Wilson Bridge during



 the months of June through October.  In September of 1970, after a



 period of low-stream flow and high temperatures, the algal mats



 extended upstream beyond Hains Point and included the first nuisance



 growth within the Tidal Basin.  The effects of the massive blue-green



 algal blooms in the middle and upper portions of the Potomac Estuary



 are (l) large increases of over 490,000 Ibs/day in total oxygen demand,



 (2) an overall decrease in dissolved oxygen due to algal respiration in



 waters 12 feet and greater in depth, (3) creation of nuisance and



 aesthetically objectionable conditions,  and (4) reduction in the feasi-



 bility of using the upper estuary as a potable water supply source



 because of potential toxin, taste, and odor problems.



    17,  To reduce the effects of excessive algal blooms on water



 quality and designated beneficial uses,  it has been determined that



 during the summer months, the standing crop should be reduced to a



minimum of 75 to 90 percent of the current level or to a chlorophyll §.




 concentration at or below 25 ug/1.



    18.  From six independent methods of analysis,  it appears that if



the upper concentration limit of inorganic nitrogen is maintained bet-



ween Oo3 and 0.5 mg/1 as  N and the upper limit of total phosphorus at

-------
                                                                  II-6

0.03 to 0.1 mg/1 as P, the algal standing crop can be maintained below
nuisance levels under summer conditions.  The lower limits of nutrient
concentration apply to the embayments and middle portion of the estuary
where growing conditions are more favorable, whereas the higher concen-
trations are applicable to the upper portion of the estuary where lack
of light penetration limits algal growth.
    19.  Significant accumulations of various heavy metals in sediments
have been detected near the major wastewater discharges.  A study of the
possible long-term toxic effects of these heavy metals on the biota of
the Potomac Estuary, especially shellfish, is essential.
    20.  Population and water supply needs have been projected as
follows:
                                            Water Supply Needs
lear
1969
1980
2000
2020
Populat ion
2,700,000
4,000,000
6,700,000
9,300,000
Yearly avg.
(mgd)
370
570
1010
1570
Maximum Month
(mgd)
470
720
1310
2040
Maximum Daily
(mgd)
660
1000
1820
2820

-------
                                                                   II-7


    21.  Even with the seven proposed upper Potomac River Basin reser-

voirs operational, the following withdrawals will be required from the

estuary or from direct wastewater reuse to meet the water supply

requirements:

Low-flow Characteristics Before     Withdrawal from the Potomac Estuary
     Water Supply Diversion	   	or from Direct Reuse*
Recurrence
Interval
(years)
5
20
50
Minimum Monthly
Fresh Inflow
(mgd)
1.300
1170
910
1980
For a 720
mgd Need
(mgd)
none
none
none
2000
For a 1310
med Need
(mgd)
210
340
600
2020
For a 2040
med Need
(mgd)
940
1070
1330
* Withdrawal based on minimum 30-day low flow concurrently with a
  maximum 30-day water supply withdrawal and a 200 mgd minimum base
  flow over Great Falls into the estuary.

    22,  The projected wastewater volumes and loading characteristics

before treatment are as follows:
Year
1969
1980
2000
2020
Flow
(mgd)
325
475
860
1,340
BOD
(Ibs/day)
483,500
823,500
1,463,500
2,195,000
Nitrogen
(Ibs/day)
63,500
95,600
155,700
215,600
Phosphorus
(Ibs/day)
27,300
43,100
70,300
97,400
    23.  To aid in determining the allowable pollutant loadings from

wastewater discharges, mathematical models have been developed and

verified for predicting (l) phosphorus transport, (2) nitrogen trans-

port and assimilation, (3) effects of benthic, carbonaceous, and

nitrogenous oxygen demand, including the effects of algal photosynthesis

-------
                                                                   II-8






and respiration on the dissolved oxygen budget, and (4) chloride and



total dissolved solid intrusions from the Chesapeake Bay, and their



buildup as a result of water supply withdrawals from the estuary.



    24.  Based upon the study of projected wastewater quantities and the



recently adopted metropolitan Washington wastewater treatment implemen-



tation schedule, the following can be concluded:



     (1)  Between the years 1980 and 2000, the Potomac (Dulles) Interceptor,



with its current capacity of 65 mgd, will be overloaded,



     (2)  To provide for future wastewater collection and treatment



facilities in areas currently projected to be served by the Potomac



Interceptor, either the capacity of the interceptor would have to be



significantly increased or additional wastewater treatment facilities



constructed on the Potomac River above Washington.



     (3)  With the Blue Plains wastewater treatment capacity limited



to 309 mgd, a need exists not only for one or more facilities to



serve the Anacostia Valley but also to serve a portion of the upper



Potomac area currently served by Blue Plains via the Dulles Interceptor.



     (4)  Large wastewater volumes are projected in the Occoquan and



Pohick watersheds in the Virginia counties downstream from Washington,



indicating a need for long-range water resources planning in this area.



    25.  Three basic alternative wastewater treatment systems were



investigated to determine the effects of the discharge locations on

-------
                                                                  II-9






receiving water quality including chloride and total dissolved solid



intrusions, as follows:



     (l)  Alternative I consisted of the following plants: Pentagon,



Arlington, Blue Plains, Alexandria, Piscataway (also serving Andrews



Air Force Base), Lower Potomac (serving Pohick, Accotink, Dogue, and



Little Hunting Creek watersheds including Fort Belvoir), Mattawoman,



Neabsco (serving the Occoquan watershed), and Port Tobacco.



     (2)  Alternative II consisted of the nine treatment plants as in



Alternative I plus a facility serving the Anacostia Valley and located



just above the Maryland-D. C. Line, and



     (3)  Alternative III consisted of the same facilities as Alternative



II plus an upper Potomac plant discharging near Chain Bridge and serving



the upper Potomac region.



     Two other systems designated as Alternatives IV and V were also



investigated.  These were identical to III, except that for Alternative



IV, all effluents were assumed to be discharged into the main channel



of the Potomac; while for Alternative V, all effluents were assumed to



be conveyed downstream to a common discharge point below Indian Head,



Maryland.



    26.  Data from the chloride,  total dissolved solids, and other



simulations where the estuary was used as a potable water supply source



indicate the following:



     (1)  The position of the salt wedge with respect to intrusion



from the Chesapeake Bay is a function of (a) duration and magnitude

-------
                                                                  11-10


of any selected flow, (b) location of the wastewater treatment facility

discharges, and (c) consumptive losses in the water distribution system.

     (2)  Even with no water supply withdrawals from the estuary, for

comparable flow conditions, intrusion of chlorides and total dissolved

solids from the Chesapeake Bay will occur farther upstream in the future

as a result of the greater percentages of wastewater discharged down-

stream into the salt wedge and the projected increases in consumptive

loss, with the latter having the most pronounced effect.

     (3)  The number of days during which the estuary can be used for

water supply depends upon (a) the position of the wedge prior to the

withdrawal, (b) magnitude of the withdrawal, (c) freshwater inflow

during withdrawal, (d) location of the wastewater discharges, and

(e) the increase in chlorides and total dissolved solids as a result

of water use.

     (4)  The maximum possible number of days that the estuary could

be used for a water supply source was determined by using a t6tal

dissolved solids concentration in the blended water of 500 mg/1 maxi-

mum as a criterion since this parameter was determined to be more

critical than chlorides,  TDS water use increments* of 40 and 240 mg/1
* Water use increment is the amount that the concentration of TDS or
  any other parameter is increased from the point of water intake to
  the point of discharge as a result of water supply treatment,
  municipal use, and wastewater treatment.

-------
                                                                  11-11

were applied at both the upstream and downstream location extremes of

the saltwater wedge to give the results in the table below:

                           Alternative I
                   Maximum Days of Use of Estuary

                              Upper Position         Lower Position
        Water Withdrawal         of Wedge               of Wedge
Year      From Estuary      Water Use Increment    Water Use Increment

1980
2000
2020
(cfs)
500
1250
2000
40 mg/1
>166
90
45
240 mg/1
>166
35
15
40 mg/1
>166
140
95
240 mg/1
>166
45
20
     (5)  For the year 2020 and using the upper position of the wedge

(as observed in early September 1966—the lowest flow on record),  the

number of days that the estuary can be used as a water supply and  yet

maintain a maximum 500 mg/1 total dissolved solids standard in the

blended water is given below as a function of freshwater flow before

water supply diversions:

                   Maximum Days of Use of Estuary

                           Alternative I           Alternative V
Freshwater Flow         Water Use Increment     Water Use Increment
(cfs)
400
1100
1800
40 mg/1
(days
45
>166
>166
240 me/1
( days )
15
42
>166
40 mg/1
(days)
18
>166
>166
240 mg/1
( days )
18
41
>166
     (6)  Since the projected water supply needs  for the year 2020

cannot be met completely either by withdrawals  from the estuary or

-------
                                                                  11-12





from the seven proposed upper basin reservoirs for drought periods



extending over a month, both sources will eventually be needed to



meet the future water requirements for the Washington metropolitan



area.  It appears that an increase of approximately 860 cfs (from 940



to 1800 cfs) in the Potomac River discharge at Washington will be



required to maintain an acceptable blended water with respect to



total dissolved solids for a 240 mg/1 water reuse increase.  If the



increase is less than 240 mg/1, the flow regulation requirements will



decrease„




     (7)  While other aspects of water supply requirements such as



viruses and carbon chloriform extractables need to be considered in



more detail, it appears that the estuary can be used as a supplementary



water supply source if wastewater discharges and water supply withdrawals



are subjected to adequate treatment.



    27.  Direct reuse of the renovated wastewater is another solution



to meet water supply needs.  This alternative has numerous advantages



over withdrawals from the estuary because:



     (l)  Any need for consideration of salt intrusion from the



Chesapeake Bay for water supply purposes is eliminated,



     (2)  Localized runoff and combined sewer overflows will not



degrade the high quality renovated water,



     (3)  The need for flow regulation from upstream reservoirs to meet



the projected Washington area water supply requirements is reduced to



a total flow of approximately 1100 cfs (before water supply diversion)



or an increase of about 150 cfs above unregulated conditions.

-------
                                                                  11-13


     Excluding the psychological objections to treated wastewater reuse

and the problems of physical transport of the wastewater to the water

intake, the major disadvantage, especially from the technical viewpoint,

would be the need to maintain the present maximum total dissolved solids

buildup of 140 mg/1 through the water supply treatment, water use, and

wastewater renovation processes whenever more than 80 percent of the

water supply is taken directly from renovated wastewater.

    28.  When the water resource needs of the entire basin are considered,

the long-range solution to the water supply-wastewater disposal problem

may initially be a combination of water supply withdrawals from the

estuary and flow regulation, with direct reuse becoming increasingly

feasible by early in the 21st Century.

    29.  The maximum allowable ultimate oxygen demand loadings have

been determined as given below for various zones and subzones of the

upper estuary for a 29°C temperature, a freshwater inflow after water

supply diversion of 300 cfs, a DO of 6 mg/1 in the treated effluent,

and based upon maintaining 5 mg/1 DO in the receiving waters.

              MAXIMUM UOD LOADINGS FOR POTOMAC ESTUARY

     Zone                                         Allowable UOD*
                                                    (Ibs/day)

       I-a   (Upstream from Hains Point)               4,000

       I-b   (Anacostia River)                         3,000

       I-c   (Hains Point to Broad Creek)             75,000

      II     (Broad Creek to Indian Head)            190,000

     III     (Indian Head to Smith Point)            380,000


* These loadings are the maximum allowable loadings for each zone assuming
  adjacent zones are loaded to their maximum capacities.

-------
                                                                 II-U






    30.  For the three freshwater inflows (before water supply with-



drawal) investigated, i.e., 1800, 1100, and 400 cfs, the maximum UOD



loadings were not affected significantly except for Alternative III



which included a treated waste discharge in Zone I-a near Chain Bridge,



     When the DO in the effluents in mathematical model simulations was



decreased from 6.0 to 2.0 mg/1, the most pronounced effect was in Zone I-c



in which the UOD loading decreased from 75,000 to 56,000 Ibs/day.



    31o  Allowable UOD loadings for the Piscataway and Gunston Cove



embayments have been developed for the projected wastewater volumes



and conditions specified in Number 29 and are given below:




     MAXIMUM UOD LOADINGS FOR PISGATAWAY CREEK AND GUNSTON COVE
Piscataway Creek
Wastewater Maximum
Flow UOD Load
(mgd) (Ibs/day)
24 10,000
49 11,000
79 12,000
Gunston Cove
Wastewater Maximum
Flow UOD Load
(mgd) (Ibs/day)
50 7,000
103 ,11,000
170 16,000
    32.  Since nitrification (the conversion of ammonia nitrogen to



nitrate nitrogen) has little effect on the oxygen resources of the



estuary at temperatures below 15°C, nitrogen removal from the waste-



water effluents to meet IX) standards will be required whenever the



water temperature is above 15°C, usually during the months of April



through October.

-------
                                                                   11-15


     In order to prevent formation of sludge deposits, to eliminate

objectionable floating matter, and to prevent low DO concentrations

during periods of ice cover, a minimum of 70-percent UOD removal and an

effluent concentration of less than 15 mg/1 suspended solids are required

year-around for all discharges.

    33.  Using an average freshwater inflow of 300 cfs to the Potomac

Estuary after water supply diversions, the allowable loadings of phos-

phorus by zones were determined based on maintaining an average maximum

of 0.067 mg/1 as P in Zones I and II, and 0.03 mg/1 as P in Zone III for

algal control.  The allowable loadings are presented below:


          MAXIMUM PHOSPHORUS LOADINGS FOR POTOMAC ESTUARY

     Zone                                     Allowable Phosphorus
                                                   (Ibs/day)

       I-a   (Upstream from Hains Point)               200

       I-b   (Anacostia River)                          85

       I-c   (Hains Point to Broad Creek)              900

      II     (Broad Creek to Indian Head)             1500

     III     (Indian Head to Smith Point)             2000

-------
                                                                  II-16





    34.  Allowable phosphorus loadings for the Piscataway and Gunston



Cove embayments for phosphorus concentration in the receiving waters of



0.03 mg/1 as P are shown below as a function of wastewater flow:




                 PHOSPHORUS LOADINGS TO EMBAYMENTS



            Piscataway Creek                   Gunston Cove
Wastewater
Flow
(mgd)
24
49
79
Maximum
Phosphorus Load
(Ibs/day)
35
50
65
Wastewater
Flow
(mgd)
50
103
170
Maximum
PhosjchoTus Load
(Ibs/day)
35
60
140
    35.  To prevent excessive algal growth and to enhance the water



quality in the upper and middle reaches of the estuary, it appears that



it will be necessary to remove phosphorus on a continuous or a year-



around basis for discharges into the upper estuary.  Moreover, the



control of at least 50 percent of the phosphorus load originating in



the upper Potomac River Basin appears necessary if the aforementioned



phosphorus criteria are to be achieved.  To accomplish this reduction,



the current phosphorus loading from all wastewater discharges in the



upper Potomac River Basin must be decreased from 6100 to 700 Ibs/day.

-------
                                                                  11-17


    36.  Using a freshwater inflow of 300 cfs and average maximum

inorganic nitrogen concentrations of 0.5, 0.4, and 0.3 mg/1 in Zones I,

II, and III, respectively, for algal control, the maximum nitrogen

loadings for warm temperature conditions were determined as follows:


               NITROGEN LOADINGS FOR POTOMAC ESTUARY

     Zone                                  Allowable Total Nitrogen
                                                 (Ibs/day)

       I-a   (Upstream from Hains Point)            1000

       I-b   (Anacostia River)                       300

       I-c   (Hains Point to Broad Creek)           3400

      II     (Broad Creek to Indian Head)           5800

     III     (Indian Head to Smith Point)           9000


    37.  Allowable total nitrogen loadings for the Piscataway and

Gunston Cove embayments based upon maintaining 0.3 mg/1 of inorganic

nitrogen under warm temperature conditions and for varying wastewater

flows follow:


                  NITROGEN LOADINGS TO EMBAYMENTS


            Piscataway Creek                   Gunston Cove
     Wastewater          Maximum       Wastewater          Maximum
        Flow          Nitrogen Load       Flow          Nitrogen Load
        (mgd)            (Ibs/day)        (mgd)            (ibs/day)

          24                120             50                130

          49                170            103                270

          79                270            170                460

-------
                                                                  11-18






    38.  Considering the present difficulty in controlling nitrogen in



the upper basin and its transport characteristics in the estuary,  it



appears that the need for nitrogen removal for algal control at waste-



water treatment plants will be limited to those periods when the water



temperature exceeds 15°C, normally from April through October.   With



the large projected increases in nitrogen from wastewater discharges,



there may be a need for year-around nitrogen control by the year 2000.




    39.  Because of the lack of transport and assimilative capacity in



the upper portions of small tidal embayments and also because of ideal



algal growing conditions, maximum concentrations of UOD, phosphorus and



nitrogen in effluents discharged to these areas should be less  than 10.0,



0.2, and 1.0 mg/1, respectively.  A detailed analysis for each embayment



is required to determine the minimum cost of either extending the  dis-



charge outfall to the main channel of the Potomac or discharging within



the embayment and providing a very high degree of wastewater treatment,



approaching ultimate wastewater renovation.  Unless this high degree of



removal is provided, effluents from Alexandria, Arlington, Piscataway,



and the Lower Potomac facilities should be discharged into the main



channel of the Potomac Estuary.



    40.  The present worth cost of additional wastewater treatment



from the year 1970 to 2020, including operation, maintenance, and



amortization costs, has been estimated to be $1.34 billion with a



total average annual cost of $64.8 million.  The unit treatment pro-



cesses assumed include activated sludge, biological nitrification-



denitrification, lime clarification, filtration, effluent aeration,



and chlorination.

-------
                                                                  11-19
    41.  The cost of wastewater treatment on a per capita basis is

as follows:


         Item               1970-1980        1980-2000        2000-2020

Average Population          3,350,000        5,350,000        8,000,000

Initial Capital
Cost/Person/Year              $17.0            $ 4.90           $ 7.30

Operation and Maintenance
Cost/PersonAear              $ 7.50           $ 8.60           $ 9.10


Total Cost/PersonAear        $24.50           $13.50           $16.40

-------
                                                                 III-l



                            CHAPTER III



                       STUDY AREA DESCRIPTION



A.  POTOMAC RIVER TIDAL SYSTEM



     The Potomac River Basin, with a drainage area of 14,670 square



miles, is the second largest watershed in the Middle Atlantic States.



From its headwaters on the eastern slope of the Appalachian Mountains,



the Potomac flows first northeasterly then generally southeasterly in



direction some 400 miles to the Chesapeake Bay.



     Above Washington, D, C., the Potomac traverses the Piedmont



Plateau to the Coastal Plain at the Fall Line.  Below the Fall Line,



the Potomac is tidal and extends -114 miles southeastward to its dis-



charge point into the Chesapeake Bay.



     The tidal portion is several hundred feet in width at its upper-



most reach near Washington and broadens to nearly six miles at its



mouth.  A shipping channel with a minimum depth of 24 feet is main-



tained upstream to Washington.  Except for this channel and a few



short reaches with depths up to 100 feet, the tidal portion is



relatively shallow with an average depth of about 18 feet.



     The mean tidal range is about 2.9 feet in the upper portion near



Washington and about 1.4 feet near the Chesapeake Bay.  The lag time



for the tidal phase between Washington and the Chesapeake Bay is



about 6.5 hours.



     Of the 3.3 million people living in the entire basin, approxi-



mately 2.8 million reside in the Washington metropolitan area.  The

-------
                                                                 III-2





remaining area of the tidal portion, which drains 3,216 square miles,



is sparsely populated.



     For purposes of discussion and investigation, the tidal portion



of the Potomac River has been divided into three reaches as shown in



Figure III-l and described below:
Reach
Upper
Middle
Lower
Description
From Chain Bridge to
Indian Head
From Indian Head to
Rte. 301 Bridge
From Rte. 301 Bridge
River Mile
114.4 to 73.8
73.8 to 47.0
47.0 to 00.0
Volume
cu.ft.xlO9
9.3
36.2
175.4
                 to Chesapeake Bay



     The upper reach, although tidal, contains fresh water.  The



middle reach is normally the transition zone from fresh to brackish



water.  The lower reach is saline with chloride concentrations near



the Chesapeake Bay ranging from about 7,000 to 11,000 mg/1.



     To facilitate determination of water quality control requirements,



the upper and middle reaches of the estuary have been segmented into



15-mile zones of similar physical characteristics beginning at Chain



Bridge.



     River mile distances from both the Chesapeake Bay and Chain Bridge



for the three upper zones are given in Table III-l.  This zone concept



was adopted by the conferees at the Potomac Enforcement Conference on



May 8, 1969.

-------
CHAIN BRIDGE
    A/
                                                      .CHESAPEAKE
                                                        BAY
           POTOMAC  RIVER TIDAL SYSTEM
                                                     FIGURE III -1

-------
0)
r-t
o

cd
     tsi
                0)
                c
            CH  O
             O  1X1

             0)  *•
                                                         CO
                                            O
                                              •

                                            O
                                                                          o
                                                                            *
                                                                          ITN
                                       •sl-
                                       rH
                                       H
                                                              CO
                                       O

                                       O
                                                         O
                                                              O

                                                              O
                                       QJ  0)
                                       bp <1)
                                       •3^ ^
                                       •H o
                                       FH
                                       « TJ
                                             o
                                            •p -a
                                                cd
                                            >4 (1)
                                                         o
                                       •H
                                          cq
                                                               0)

                                                              W
                                                               CS
                                                              13  CO
                                                               Pi

-------
                                                                 III-5



B.  HYDROGRAPHIC ANALYSIS



     The major source of freshwater inflow into the Potomac Estuary



is from the upper Potomac River Basin.  The average flow, measured



at Great Falls before diversions for municipal water supply for the



period from 1930-1968, was 10,768 cfs with a minimum flow of 610 cfs



that occurred on September 10, 1966.



     The monthly flow characteristics for the Potomac at Great Falls



are tabulated below for the reference period of 1931-1960.

Month
January
February
March
April
May
June
July
August
September
October
November
December
25 Percent
Quart ile

7,600
8,700
13,900
12,800
8,800
6,100
3,500
2,700
2,000
2,000
3,000
3,800
Mean
Flow
(cfs)
13,600
16,600
21,100
20,000
14,500
8,700
5,500
6,000
4,700
6,300
6,600
9,900
75 Percent
Quart ile

17,200
24,600
24,400
26,900
17,900
10,300
6,400
7,400
6,800
6,400
9,600
13,100
     In water resource management, especially for the water quality



aspects, low-flow frequencies are used to determine assimilation and



transport capacities of receiving waters.  The low-flow frequency

-------
                                                                 III-6
utilized for water quality control in the Potomac Estuary as set by
the State of Maryland and the District of Columbia is the seven-
consecutive-days -of -low-flow with a recurrence interval of once-in-10-
years.  For the Potomac at Washington, this is 954 cfs (before the
diversions for water supply).  See Table III-2 for complete analyses
of low-flow frequency information.

-------
            Table III-2
MAGNITUDE AND FREQUENCY OF LOW FLOWS
POTOMAC RIVER NEAR WASHINGTON, D. C.
       1930-1966 WATER YEARS
  (Before Water Supply Diversions)

Period


(Consecutive days)
7
14
30
60
90
120
183


1.02
years

3,440
3,8^0
4,470
6,620
8,630
8,770
11,200
Discharge

2.0
years

1,620
1,700
1,890
2,300
2,660
3,110
4,280
for indicated recurrence interval

5.0
years
(cfs)
1,150
1,210
1,340
1,540
1,740
2,060
2,800

10.0
years

954
1,000
1,130
1,260
1,420
1,670
2,220

20.0
years

814
862
976
1,070
1,210
1,400
1,830

50.0
years

670
730
8/.0
900
1,000
1,150
1,480

-------
                                                                 Ill-8

C.  PROPOSED RESERVOIR DEVELOPMENT

     In 1956, the U. S. Army initiated a study of the water resources

of the Potomac River Basin.  The result of this study was a plan for

development of water and related land resources of the basin including

(l) water supply, (2) water quality, (3) flood control, and

(4) recreational needs.

     The plan recommended a l6-reservoir system to provide for orderly

development, conservation, and utilization of the basin water resources

to meet the needs of the next 50 years [1].  To provide additional

water supply resources for the Washington metropolitan area, three

alternative reservoir systems were suggested.  These three systems

were:

     System

        I          Bloomington

       II          Bloomington, Verona, and Sixes Bridge

      III          Bloomington, Verona, Sixes Bridge, Town Creek,
                   North Mountain, Sideling Hill, and Little
                   Cacapon

The locations of the seven reservoirs in System III plus the two

existing impoundments are shown in Figure III-2.  The initial cost of

the seven impoundments based on the 1967 cost index would be $204.4

million.  See Table III-3 for individual reservoir cost.

     Using data from 1929 to 1968 and a river-flow mathematical model,

the U. S. Army Corps of Engineers simulated the effects of the three

reservoir systems on river flows over Great Falls.  The low-flow

frequency analysis for the three systems is given in Table III-4.

-------
FIGURE   III - 2

-------
Project



Bloomington

Staunton

Sixes Bridge

Town Creek

North Mountain

Sideling Hill

Little Cacapon


Total
                                    Table III-3
                       RESERVOIR PROJECTS,  STORAGE, AND COST*
                                Potomac River Basin
Total Storage   Total Initial
Allocated Cost
(acre-feet)
137,500
143,000
103,000
96,800
195,000
75,000
82,500
832,800
Cost ($)
90,400,000
22,870,000
20,510,000
13,190,000
24,450,000
13,600,000
19,350,000
$204,370,000
Downstream
Water Supply
30,000,000
756,000
1,112,000
2,039,000
3,953,000
2,753,000
3,872,000
$44,485,000
Preserve Stream
($) Environment
36,800,000
3,473,000
5,005,000
4,136,000
7,312,000
5,557,000
7,857,000
$70,140,000
  Based on data supplied by the U. S. Army Corps of Engineers,  Baltimore
  District, September 1970

-------
                       Table III-4
LOW-FLOW FREQUENCY ANALYSES FOR VARIOUS RESERVOIR SYSTEMS
              Potomac River near Washington

                     Reservoir System
                         Number I
Period
(days)
30
60
90
120

30
60
90
120

30
60
90
120
Discharge
(5 years)
1600
1900
2100
2600

1900
2000
2200
2600

2000
2150
2300
2800
in cfs l"or Indicated
(10 years)
1200
1600
1700
2000
Number II
1700
1900
2100
2200
Number III
1800
2000
2200
2300
Recurrence Inter^
(50 yea]
1000
1050
1100
1500

1200
1400
1500
1600

MOO
1500
1600
1700

-------
                                                                111-12


D.  WATER RESOURCE USES

1.  Water Supply Use

     a.  Municipal

     The municipal water supply needs of the Washington metropolitan

area are obtained from five major sources.  The largest source is the

Potomac River above Washington, D. C.  For 1969-1970, water withdrawal

data for the five sources are presented below:

                Source                      Withdrawal
                                              (mgd)

     Potomac River above Great Ealls           265

     Patuxent River near Laurel                 46

     Goose Creek                                 6

     Occoquan Creek                             42

     Wells and other minor sources              11


     Total                                     370

Currently, there is no municipal water withdrawn from the freshwater

portion of the Potomac Estuary.  However, during the drought in the

summer of 1969, an emergency estuary intake would have been constructed

and used had the lows flows continued.

-------
                                                                111-13
b.  Industrial

     In the Washington metropolitan area, the amount of water used for

manufacturing is insignificant.  The major industrial use is as cooling

water.

     There are currently six major cooling water users in the Potomac

River tidal system with another being proposed near Sandy Point.  The

total cooling water use is 2,748 mgd as follows:
       Facility
PEPCO at Benning Rd.
(Washington, D. C.)

PEPCO, Buzzard Point
(Washington, D. C.)

Virginia Heating
(Arlington, Va.)

PEPGO Generating Station
(Alexandria, Va.)

VEPCO, Possum Point
(Quantico, Va.)

PEPCO, Sandy Point
PEPCO, Morgantown
(Charles Co., Md.)
Water
Usage
(mgd)
568
570
40
450
400
Receiving Water

Anacostia River
Anacostia River
Boundary Channel of
Potomac Estuary
Potomac Estuary
Potomac Estuary
                                    Remarks
                                 Also Uses
                                 Cooling Towers
720
Potomac Estuary


Potomac Estuary
Proposed
Facility

Ultimate Usage
to be 1440 mgd
Total                      2,748

     Navigational use of the Potomac Estuary waters is primarily to pro-

vide commercial transport via river barges.   Two commercial firms

presently transport various petroleum products from tank farms located

-------
                                                                111-14





in the lower Potomac and in the Chesapeake Bay proper to the Washington



metropolitan area.



     Sand and gravel mining is also a water related industrial use of



the estuary bed.  Currently, dredging for this purpose is being con-



ducted in the estuary below Indian Head, Maryland.

-------
                                                                111-15
2.  Recreation and Boating



     Aside from enhancing the suburban environment, the water and land



resources of the Potomac Estuary and its tributaries contribute to the



aesthetics of the nation's capital.  From Washington, where large



numbers of tourists visit the numerous monuments, museums, public



buildings, and parks, to the remote park at Point Lookout near the



Chesapeake Bay, the Potomac's amenities are widely used.  These include



freshwater and tidal sport fishing, boating, hunting, swimming, camping,



and picnicking„



     At the present time, there are approximately 95 marina facilities



in the Potomac River tidal system.  These marinas offer slips and moorings



to accommodate over 5,200 recreational watercraft.  They also provide



boat rentals and launching areas for small craft.



     Expanses of open water below Washington with large populations of



several popular species have stimulated the growth of sport fishing



in the Potomac Estuary.  A study in 1959-1961, estimated that 101,000



angler trips produced approximately 1,200,000 fish weighing almost



642,000 pounds [2].



     The most popular fish caught are striped bass, bluefish, spot, and



perch„  For a 5-month period during the 196l survey, an estimated



$594,000 was spent by Potomac Estuary anglers [2].



     A recent study by the Bureau of Outdoor Recreation indicated the



following regarding recreational facilities and the potential of the



Potomac Estuary [3]:

-------
                                                                111-16






     1.  Of the 637 miles of shoreline and 207,000 acres  of water sur-



face, which are rich in natural resources, the recreational potential



has barely been touched.



     2.  At the present time, there is one national park, three state



parks, three state forests, seven game and fish areas,  and 226 county



recreation sites in the estuary drainage area.  Most of these areas



are located inland without direct access to the water.



     3.  The recreational potential remains relatively undeveloped



because of poor access to many shoreline areas and because extensive



acreage is controlled by private and government interests.



     4.  There are few public beaches, but lack of such development



is probably due more to poor water quality and the hazard of stinging



jellyfish than to a lack of suitable locations.

-------
                                                                Ill-17
3.  Commercial Fisheries

     The Potomac River tidal system supports a substantial commercial

fishery.  There are approximately 160 species in the Potomac Estuary

ecosystem of which the anadromous* and the semi-anadromous** species

such as striped bass, shad, white and yellow perch, winter flounder,

and herring are the most significant economically.

     Another group of commercially important fish species spawns and

winters outside of the Chesapeake Bay in the Atlantic Ocean and utilizes

the Potomac for a nursery area and feeding ground.  Included in this

group are the menhaden, croaker, silver perch, sea trout, and drum.

     Oysters are indigenous to the lower reaches of the Potomac Estuary.

These reaches are considered prime shellfish waters.

     Soft clams, like oysters, are indigenous to the Chesapeake Bay and

occur in the same general areas.  Only in recent years, however, have

they been harvested commercially and the resource far exceeds the demand.

     The lower Potomac is a favorable habitat for the growth of blue crats,

As juveniles, the young crabs feed and grow in the estuary before com-

pleting their life cycle at the mouth of the Chesapeake Bay.


*  Anadromous - fish which spend most of their lives in the ocean and
   ascend freshwater streams and rivers to spawn

** Semi-anadromous - fish which spend most of their lives in a brackish
   water and ascend freshwater streams to spawn

-------
                                                                Ill-18






     In 1969, approximately 9 million pounds of fish, 1.9 million



pounds of crabs, 1.4 million pounds of clams, and 5.3 million pounds



of oysters were harvested from the waters of the Potomac and its



tributaries  [4].  The dockside value of the 1969 harvest was computed



to be over $4.6 million.  See Table III-5.



     There are  currently about 29,000 acres of oyster beds in the



Potomac Estuary and its embayments.  Of these, approximately 970



acres, mainly in the embayments, are closed because of high bacterial



densities resulting from domestic sewage pollution.



     Numerous fish kills have occurred in the Potomac Estuary in recent



years.  IHIhile the cause of many of these kills is unknown, several have



been attributed to low dissolved oxygen concentrations resulting from



domestic waste discharges such as the large kill near Washington during



May 1969.

-------
                                        Table III-5
                    MARYLAND AND VIRGINIA LANDINGS OF FISH AND SHELLFISH
                               POTOMAC RIVER AND TRIBUTARIES
                                            1969

                	Maryland	       	Virginia	      	Total	„
Species         Pounds        Value       Pounds        Value      Pounds         Value
Fish
Crabs -
Hard
Soft & Peeler
Clam
Oyster
1,250,668

628,702
20,348
1,090,140
2,923,275
$ 183,563

75,686
8,260
389,292
1,771,812
7,780,549

1,249,774
28,000
322,092
2,457,770
$ 347,974

142,460
11,659
114,331
1,642,866
9,031,217

1,878,476
48,348
1,412,232
5,381,045
$ 531,537

218,146
19,919
503,623
3,414,678
Total          5,913,133   $2,428,613   11,838,185    $2,259,290   17,751,318   $4,687,903

-------
                                                                   IV-1



                             CHAPTER IV



            WASTEWATER LOADINGS AND RUNOFF CONTRIBUTIONS



A.  WASTEWATER LOADINGS AND TRENDS



     In the upper reach from Great Falls to Indian Head, Maryland, a



domestic wastewater flow of approximately 325 mgd is discharged into



the Potomac River tidal system.  Eighteen facilities currently serve



approximately 2.5 million people in the Washington metropolitan area



with the largest facility being the Blue Plains Plant of the District



of Columbia (Table IV-1).  Of the 325 mgd, 41.5, 23.1, and 35.4 percent



come from Maryland, Virginia, and the District of Columbia respectively.



     An analysis of the loading trends since 1913 indicates that waste-



water volumes have increased eightfold, from 42 to 325 mgd.  Similar



trends have occurred for total nitrogen and phosphorus with 10-fold



and 24-fold increases respectively (Table IV-2).



     Of major significance has been the increase in ultimate oxygen



demand (UOD) loadings.  The carbonaceous UOD increased from 84,000



Ibs/day in 1913 to about 297,000 Ibs/day in the late 1950's.  With



the construction of the secondary treatment facilities, including



completion of the Blue Plains Plant of the District of Columbia, the



carbonaceous loading was reduced to 110,000 Ibs/day.  The nitrogenous



loading has increased steadily from 1913 to the present loading of



254,000 Ibs/day, which exceeds the current carbonaceous loading of



204,000 Ibs/day.

-------
                           S
                               I
                                                      O  O
                                                      OJ  vj-
                                                                     rH    >n
                                                                             OJ  OJ OJ
                                   Q O O

                                   VO «0 V£>
                                                                 <*N  OJ    O
                                                                                                          f-

                                                                                                          c"N
sphoru
reated
                     &
                     (-H
                     ?S
   a
   EH
                                   m  o  O
                                   \O  U"N  C—

                       O
                      !fc
                      I rH
Solids
Tte
Suspended
rea
FH

t)
rH

•3
H
                               ^— *
t
                 O  O  O
                 rH  O  O
                 C"\  <^\  f-
&  8  8  8
•3   rH  -J-  f-
                                      fc
                     O
                     H I
   g

   I
                               'b
                                Bf
                               •O
        885
                                CQ
                                rQ
S  1-0
 '  Iff
       r^\  vr\

       ON  CVJ
                                   8O O O T\
                                   O g CVJ >*"
§
                          8  8
                          VD  OJ
                                                            O  O  O  •*    O  O  O
                                                   OJ  OJ  «0
                                                   O  rH
                                                            Q  O  O
                                                            O  C^  to
                                                  O
                                                  -*
                                                  rH
                        .  A
                          8f\  O
                          l-t  rH
                                              O  O  O
                                              to  i-t  i-H
                                              to  O  H
                                          ff- rH OJ  §
                                                   8
                                                  O
                                                  iH
                                                  r-t
                                                                          O
«
                                                8 8
               m    O O O O
                    SvS o r- rH
                    MD c^ in to
                                                            >T\  O  O  O
rH  O  O
•*  o  ><•
^T  VO  f*N

oj'  d  oJ
                                                         8
                                                             8 8
                                                             VD >!•
        O  c^ CO
        H  V rH
           OJ
                    O  O
                    t*N  CT^
                    tO  rH
                                                         -*
                                                         if
                                                       drlrlt)B*
                                                                     M  M  !>
                                                                     M  M  M
                                    3"
                                         CO Q
                            C««H     &  *PP  •««s»>fli!aSi'2       M
                            Ba°43l&§§  iilJiegsf.?....
                            •S-stJ^ISfiBollA-i^  igw^^ss
                                 •H  §!3"  s  KB  a  a««accotowoj
                            iHttrlSCdECr-l-^VltH          +J  H  rl  O  C  C  ^ H  r.  r. f>  f>  h  1C) -H
                            S--H  01  10-H  CO  •§  -5  > •  -ri  Tl  It  T<  1-1  >13
                            s£«d«si3j*fi«tS££a*5
                                                                                                              o S +»
                                                                                                              bo* o
                                                                                                             H "O m

                                                                                                              § § 8

-------
       18888888888
       ^s.   MOO*r\^oOwrH   rH    O
                                            8
       J"^


  *I|   888888
   « «\   •*   -»   O   f-   «r\   w

   ba.8
           vo   iH   f\

                rH   CM
                            rA  r.
                            »*\  N\
              R
«
 .  *> z
 I  *>
H3a
  g5
              •-f   O   
                                                            Q   T)
                                                            O   0)
                                                            fi   H
                                                                 -H

                                                                 &T>
                                                                 •H

                                                            •a   H
                                                                    M


                                                                   t^
   q
   o

  S'S
r—1  I





&«
                         g   §
                         c-\   \o
                                       OJ   OJ    OJ   OJ
                                                        w   -t^   T"
                                                        •Qgfl

                                                        5   JH   5
                                                               g

-------
                                                                  IV-4
     As can be seen in Figure IV-1, the current total oxygen demanding
carbonaceous and nitrogenous loading is over 450,000 Ibs/day, the
highest loading rate ever discharged into the estuary although the
percent removal of 5-day BOD has remained at about 70 percent.  Since
I960, the increase in wastewater volumes and the continual increase
in nitrogenous UOD has resulted in a total oxygen demanding load to
the estuary similar to that which occurred before the secondary treat-
ment facility at Blue Plains was completed in the late 1950's.
     There are 82 wastewater point source discharges into the middle
and lower reaches of the Potomac Estuary and their tributaries.  The
estimated BOD, total phosphorus as P, and nitrogen as N are 4,000, 500,
and 1,000 Ibs/day, respectively.
     The major sources of domestic wastewater discharges are listed
below:
Mannassas Park No. 1
Mannassas Park No. 2
Manassas
Greenbrier
Fairfax-Flatlick
Greater Manassas S. D.
Lorton Reformatory
Marumsco
Featherstone, Va.
Marine Corps Schools
(Quantico, Va.)
Naval Weapons Laboratory
(Dahlgren, Va.)
Wastewater
Volume (mg d)
   0.109
   0.221
   0.786
   0.214
   0.111
   0.700
   0.410
   1.000
   0.300
   1.400

   0.350
    Receiving
      Water
Bull Run
Bull Run
Bull Run
Bull Run
Flatlick Run
Bull Run
Giles Run
Marumsco Creek
Farm Creek
Potomac Estuary

Upper Machodoc Creek

-------
400,000-
3 00,000-
200,000-
100,000-
                           UOD LOADING  TRENDS
                                       TO
                              POTOMAC  ESTUARY
                                      FROM
                       WASHINGTON D C  METROPOLITAN AREA
         TOTAL OF CARBONACEOUS AND NITROGENOUS
                                             NITROGENOUS UOD
     1910
1920
1930
 I
1940

YEAR
 7
1950
 I           I
I960        1970

      FIGURE  IV-

-------
                                                                  IV-6
     Compared to the upper reach, which has a population served of



approximately 2.51 million, the middle and lower reaches serve a



population of approximately 50,000.  Most of the discharges in this



area are into tributary or embayment waters.

-------
                                                                  IV-7
B.  POTOMAC RIVER WATER QUALITY ABOVE GREAT FALLS
     Detailed analyses of the freshwater inflow from the upper Potomac
River Basin at Great Falls were conducted during 1969 and 1970.  During
the period of February 1969 to February 1970, the following were the
average measured concentrations of BOD^ and nutrients :
            Parameter                    Concentration
            BOD5                              2.60
            TKN as N                          0.6l
            N02 + N03 as N                    1,00
            T0 Phosphorus as P                0.13
     The observed data, as shown in Figure IV-2, show the wide range of
nutrient concentrations for the period of June 1969 to July 1970.  The
river discharge was considerably higher during the 6 months of 1970 than
for the last 7 months of 1969.  This resulted in higher N02 + NO-^ concen-
trations „  Concentrations of TKN and phosphorus appeared to decrease
during the higher flow periods except during periods of intense runoff [5]
     The contributions from the upper basin in Ibs/day during the period
of February 1969 through February 1970 are presented in Table IV-3,  For
the 13 -month period, the average daily contributions of nutrients were
tabulated and are given below:
            Parameter                    Contribution
                                           (Ibs/day)
            T. Phosphorus as P                4,580
            Inorganic Phosphorus as P         2,650
            TKN as N                         22,410
            NH3 as N                          4,590
            N02 + N03 as N                   36,700

-------
    I/)
3  -
    -
^  K
Z  o

o  \-
z  <
O  Q,
O  ui
    >
h~  ^

UJ  U
•o:  <
                                                                                                   O
                                                                                                   r~
                                                                                                   01
                                                                                                ^  a>
                                                                                                a.  
-------










o o
5 — 1 C"°~
t-l ON
& rH
S &
O 10 £l
0 rH ,0
| ft)
i— "1 U/
fc*' CO ^i
P§ «j P
«D 0) O
rH pi f-! £
Q pfj p^f Cj
m F> -P
HMO)
W > ON
OVO
0 ,0 ON
|j <^rH
P «J
O . r~{
g
P4 .O
0 Q)
P_j fjr_j
!=>









f\ *— «
O £»
53 o
+ * \.
^s,
CO W
AJ rrt .C
0 r-
x—.
Cfl
co

s-l
CO
§5
C 	 | s 	 S


Oi
CQ
C> 
•U p -C
tlD «H ^^N,
h O W
O & ^Q
fj fi^ (--
rH 03 •---
O





p ^~
0 ">
rd CC

TO ^v
o to a
H
SCO
CM
EH ^


i

oooooooo
tOt>ir\HONt>rr\->l-
oc*N,r^cJNtQONOO
C>-\if\rHl>OJ-VOVO xtOJVO
OJVOOJHI>tOVO^t
OJ CM OJ H CM rH





OOOOOOOO
[>- ^~ CM O C'A ^" O WA
OCMrHON-^UAOO
** »s ^ »V **
CM 0^ CM CM H










UAOOOOOOO
ONO^tC^vVOOrHCM
^^" IA f^- £^- VfN. [^- C*™\ ON
^l-ir\^}-OJrHHifNOJ

OOOOOOOO
OOOOOOOO
r^ ^t" o ON CM ^i~ O O'N,
votoc^r^ojojtoxr

f-,
& ^|
M O "H d) r*5 p -P
^3r>GrH&)P(

O
3
CVN


O
OJ
OJ

CM
to





o
CM












§
VO
rH

O
O

CM


October

o
to
vo


o

C'N

O
O
to
rH
rH





O
H
to












O
UA
OJ

g
VO
c^


November

o
o
-sf
ON
O'N,

O
o
rH
ir\

0
ON
to
CM





O
to
ON
•v
OJ










O
CM
ITN

O
o

C--


December

o
to
vo
to

o
ir\
ON
VO

O
!>
to
to

VO
C^>

o
ON
-
-------
                                                                 IV-10
     A regression analysis of the river discharge and contribution

loadings was made.  Utilizing the flow duration curve for the Potomac

River near Washington and the regression equation between river dis-

charge and loadings, the contribution of phosphorus, nitrogen, and

BOD/, was determined for three frequency periods: 5%, 50%, and 95% of

the time (Table IV-4).  Based on this analysis, 50 percent of the time,

which corresponds to a median river discharge of 6,470 cfs, the nutrient

loadings into the Potomac from the upper basin are as follows:

            Parameter                    Median Loading
                                           (Ibs/day)

            BOD5                             89,390

            TKN as N                         16,850

            N02 + N03 as N                   19,830

            Phosphorus as P                   4,350

            Total Carbon as C               480,000

     Data for the 5-percent duration or 34,000 cfs, as also given in

Table IV-4, show higher loading rates and thus higher total loadings.

Conversely, for the 95-percent duration of the 1200 cfs discharge rate,

the loading rates are lower as are the loadings.  For water quality

control purposes, the 50- and 95-percent duration times are more

applicable since they occur under critical summer conditions.
* Frequency percent is percentage of time in which a given parameter
  is equalled or exceeded

-------
aj      o
                O      O






















-sf
1
FH
rH
£>
cd
EH







































IZ5
M
ro
^n
pQ

pj
P

rt
o


$3
PI

@
Pn
P-i
t=>

g
EH

6

§
0
M
1

a
&
o
Q
§

£-^
5s

Q
O
«

Z

CO
CO VO (^ 0s
f> H TO rH
rH C*N
•g
CO
\ vo to j>
CO
cd o o o
~\ tf\ to o^
CQ - -v *
^3 TO VO >!•
rH O H
cd

J2
S
EH






•H
S

CO
\ 0 i> c^
^ . . .
T3 to H O
CO
^




S5

CO
cd
>j O O O
cd vo c^\ vo
TJ if\ to OJ
'*\^ *v *s *«
CQ £> O^ rH
rO D^ rH
rH OJ

ol'a
+ j CO
1 j OJ !> rH
cd
T3 >t rH O
\ OJ
CO
H

P-.
CO
 •>
£> O --t
rH H
^
fj
o
^
8

E
<
EH

•H
e

CQ
\ TO CO to
tVO c^ O
rH O O
^N^
CQ
rH


•a CD
O b
-p h f
cd CD ct
*H I> ,C
O -H O
O p"I 0
CQ -r
^


8O O
!> O
H
£


U> O if\
u^\ 0^



exceeded

^
O

•o
0)
H
H
%

cu
CQ


•rH

CT1
1

rrj
\^
CQ
ft
rH

•0
H

•H
cT

O
•H
.g
*

^
O

0)
5
-p

C,_(
O
-p
C
OJ
o
CO
p(

0)
X!
EH
*

-------
                                                                 IV-12

C.  SUBURBAN AND URBAN RUNOFF

     An analysis similar to that used for the Potomac at Great Falls was

applied to data on Rock Creek and the Anacostia River.  Based on these

regression studies and flow duration curves,  yield rates in terms of

Ibs/day/sq mi were determined as given in Table IV-5.  These rates were

used for the suburban areas in Virginia and Maryland.

     For the District of Columbia, data on stormwater and urban runoff

were obtained from a study of Washington overflows [6],  The rates and

flow frequency percentages based upon the Rock Creek and the Anacostia

River drainage areas were used.

     The median loadings contributed from urban and suburban areas to

the upper Potomac Estuary are tabulated below:

            Parameter                    Loadings
                                         (Ibs/day)

            BOD5                           12,500

            TKN as N                        2,560

            N02 + N03                       1,510

            T. Phosphorus as P                850

     The total loadings (Ibs/day) of BOD and  nutrients from suburban and

urban runoff were fairly small when compared  to those from the upper

Potomac Basin.  However, yield rates (Ibs/day/sq mi) for the urban and

suburban area, except for nitrites and nitrates, were significantly

higher (Table IV-5).  This indicates that as  population in an area

increases, the BOD, phosphorus, and TKN loadings from urban runoff will

probably also increase.

-------
                                                                     I   8    8    8

                                                                     5   8
                                                                     o1
                                                                     a   o   \o
                                                                                                                CM    O

                                                                                                               MD    rH

      o   O    H       o    \f>   to      oo
      r^rHCV       rH    C>   i-l      M3    >A
                                                                     s    O   rH
                                                                                                                                  o    ^o    to
                                                                                                                                         ••
0" O O O O C
>> O f\ O O r-
.§ ^ '"X
SO O O f1- to c^
O^ <— I 
8
                                           8    8
                                           r-    >»•
                                                                     O"   lf\   rH    O
                                                                     m   \O   t-    cu
                                                                             CM


                                                                                             >f\   rH   O
     8    S      8
                                                       •s
                                                        0)
                                                        u
                                                        H

                                                        S



                                                       I
                                                                    rH    CM_

                                                                    CM"    o
                                                                                                                                  8    8
                                                                                                                                  C"\    SO
                                                                                                                                                    •o

                                                                                                                                                    ^

                                                                                                                                                    "o

                                                                                                                                                    g
           8
o   o    o
r-v   O    rH

r^   r-I    O
                                                                                                                ^r    <*\   o
                                                                                                                C--    CM   >!•
                                                                                                                                  CM    p    CM
                                                                                                                                        CM


                                                                                                                                        •H    O
                                                               II
                                                               oS
                                                                                                  w.
                                                                                                  O
                                                                                                  m
                                                                                                                                                    I
                                                                          CMCMCM       QQQ      CMCMCM
                                                                          tf\   l/N    ITN       O   O   O      ^O    ^O   ^O
                                                                                                                                        rH   rH     •>*
                                                                                                                                        r-   t>     a
                                                                                                                                                    0
      &                 K
      .1                 ?
                                                                                             *
                                                                                                               €    43

                                                                                                               *fcf
                                                                                                               +> O 3

-------
                                                                 IV-14


D.  SUMMARY AND COMPARISON OF NUTRIENTS, BOD, AND CARBON CONTRIBUTIONS

     For the 50- and 95-percent flow durations, the largest source of

BOD and nutrients is from wastewater discharges in the Washington area.

As summarized below, under low-flow conditions, wastewater discharges

contributed over 55 percent of all four parameters.

                             95$                         5056
                     Low-Flow Condition         Median-Flow Condition
                 Potomac R. Flow = 1200 cfs   Potomac R. Flow = 6470 cfs
                 Total From    Percentage     Total From    Percentage
Parameter        all Sources From Wastewater  all Sources From Wastewater
                  (Ibs/day)       (%)          (Ibs/day)
T. Oxygen Demand   515,800         88           733,000         62

T. Carbon          380,000         55           720,000         29

T. Nitrogen         66,900         90           100,000         60   •

T. Phosphorus       25,000         96            29,300         82

BOD5               161,580         87           242,900         58

Even under median-flow conditions, the contribution of total oxygen

demand, total nitrogen, and total phosphorus is largest from the waste-

water treatment facilities.  At the 5-percent frequency or for a Potomac

flow of 34,600 cfs, only in the case of phosphorus (52$) is the largest

percentage from wastewater discharges (see Table IV-6).

-------
                              8
                              c\
                                      6  CM    ir>

                              e»\  8  8  c\i    vo
                              O
                              f-
                      00   C-   >fN  rH
                                                           v£>  O  VO  ^»
                                                           01  >r  oi  r-
                      C~   CVJ   Ol  i-H    00   <\l  Q"*  0s  CM   r^-  00  tfN  O^  «>
                      rHrHrHiA    UN   *O  Kl  >A  CO   00  CO  lA  ft  CT-
             >>   Q
             0    O
             •o    o

             0)    rH  \O   O
             rH    rH  ^t  Oj
             2  S  oi   ^*  S
                                       rH VO   O  O
                                       r4   ~t   PJ
                                                                   o  o  ^r
                                                                   ^  o  evl
  y>

1
3
S M
00 ^
(
11
1
0

rH
ffl
+J
O
rH
Vl
O
Vt.




4
^s.
m
xS
iH
B\D f
r*\ C
o ^o y





8 § \
>r\ 0s C
->r VD c
rH
""S CT^ CO tf\ Q^ t*"
U OJ O r-t O iH
•X 0 C- UN •* >t





3 8 8 888
J f\ f*N *f\ O O
-^- r^\ CM O O
° ^ rH C-N <^
O 0s ^D t^ ^O CJ^ r*\
-* CM O O CM O O





O CO O CO O HJ
^J rH m O
r-«
Ob.
                                       to   r-
                  ai  vo
             •g    VO   f-
I   §
                                               St- VO   rH
                                               O CO   »H

                                          y~\    OJ O   cvj
8   8
8   8
                 ^   O   O
                  H   r\   O
                      g   §
                 «  g
              .   9  ft
             •S  S  8
             a  s  £
                  m   H   H   t-i  H
                              t^  o
                              •-»  00
                              CV1  ^f
                                                                           O
                                                                           01
                 «O
         g  §  9  -a
                                           £ 3  S  £

                                           •A 1  1  1
                                           « €  S  t5
                                           H H  H  H
         C

         bO
                                                                   H  H
                                                  .33
                                                  •o +»
                                                  JS
                                                                                    C « o
                                                                                    tl


                                                                                    M    OJ

                                                                                    a 3 rn"
                              <^5sl       si'
                                                                                   <~
                                                                                    o
                                                                                      a
                                                                                     «»

-------
                                                                   V-l






                             CHAPTER V



                WATER QUALITY CONDITIONS AND TRENDS



     The water quality problems resulting from discharge of municipal



wastewater into the Potomac Estuary are not new.  The first three



conclusions of a study conducted in 1913 [7], which are as applicable



today as they were then, are listed below:



     1.  "That at no point above Washington is the water of the



Potomac River safe for use as a public water supply without reasonable




treatment.



     2.  "That portions of the main or Georgetown Channel, between



the Chain Bridge and the junction of the main channel with Anacostia



River and Washington Channel, are so heavily polluted that the water




is unsafe for bathing purposes.  The water from this section supplies




the Tidal Basin.



     3.  "That the conditions of that area in Anacostia River in the



neighborhood of the sewage-pumping station and at the junction of the



three channels is bad during hot weather, at times constituting a



nuisance; but that, when the improvements now planned or under con-



struction are completed, these conditions should no longer exist."



     Not only has the water quality problem as stated above persisted,



conditions have deteriorated considerably.

-------
                                                                   V-2




A.  BACTERIAL DENSITIES



     Bacterial densities in the Potomac Estuary have been determined



routinely since 1938.  Total coliform counts in the Potomac at Three



Sisters Island have remained fairly constant for the past 20 years



at about 2,000 MPN/100 ml during the summer months (Figure V-l).  In



contrast, total coliform densities in the estuary have increased to



over 2,000,000 in 1966 and then decreased to less than 7,000 in 1970



near the Blue Plains Sewage Treatment Plant.  The reduction in recent



years can be attributed in part to an increase in overall wastewater



treatment efficiency including chlorination, and to higher river flows.



     During 1969, continuous year-around chlorination of final effluents



was initiated at all major plants.  This appears to be the most signifi-



cant single factor in the reduction of bacterial densities in the estuary



near Washington.  As shown in Figure V-2, there has been a corresponding



reduction in fecal coliform counts under similar flow and temperature



conditions in August 1968 and August 1970.



     The highest fecal coliform densities in 1968 were found between



River Mile 10 and 15 in the vicinity of the major wastewater discharges.



In August 1970, the highest densities were found at River Mile 7 in the



vicinity of Hains Point.  At times, 10 to 20 mgd of untreated sewage is



discharged into the estuary as a result of inadequate sewerage and



treatment plant capacity at Blue Plains.  Urban runoff from the Anacostia



River and Rock Creek basins also add to the fecal coliform problem.

-------
     II*- 001 «3d)
SWS1NV9UO WHOJITOO

-------
                         FECAL  COLIFORM  DENSITIES
                              UPPER  POTOMAC  ESTUARY
   100,000-
   10,000-
cr ,,
8 N i.ooo;

£~
      100-
                                            MEAN OF 10 SAMPLES — AUGUST  19-23. 1968
                                             FLOW = 2.800 cf>
                                             TEMP. = 27.5'C
                                     AUGUST 17, 1970
                                      FLOW = 2300 cf»
                                      TEMP. = 28.0'C
                                                             X  Md. SHORE

                                                             D  MAIN CHANNEL
                                                             o  Vo. SHORE
                               I
                               10
                                          15
                                                    20
                                                                25
                                                                          30
                                                                                     35
                                   RIVER  MILES  FROM CHAIN  BRIDGE
                                                                            FIGURE  V-2

-------
                                                                   V-5





     At the Fort Washington monitoring station, total coliform densities



during the summer months have remained fairly constant except for recent



downtrends (see Figure V-l).  These downtrends can also be attributed



to recent chlorination of treatment plant effluents.

-------
                                                                   V-6






B.  DISSOLVED OXTGEN



     Dissolved oxygen (DO) concentrations in the upper Potomac Estuary



have also been routinely monitored since 1938.  As shown in Figure V-3,



there has been a continuous downward trend in DO in the Potomac Estuary



near and below the wastewater discharges.



     A significant increase in DO occurred in the early 1960's near



the Blue Plains outfall.  However, with the population increase of the



past decade and little or no increase in treatment plant capacities,




DO in the Blue Plains vicinity during the summer months is now approaching



the levels of the late 1950's.



     With increased loadings to existing waste treatment plants and



additional facilities being located farther downstream, the number of



miles affected by wastewater effluents has increased.  As presented in



Figure V-3, the minimum 28-day DO concentrations at Fort Washington



have decreased from approximately 5.0 mg/1 to less than 4.0 mg/1 since



1938.  Currently, about 20 miles of the estuary has a DO concentration of



less than 5.0 mg/1 (the water quality standard for that reach of the



Potomac) during low-flow periods.



     The DO concentration at any given location in the estuary is a



function of many factors including biological activity, freshwater



inflow, temperature, wastewater loadings, and tidal stage.  On four




sampling cruises made during the summer months of 1969, the locations



and readings of the minimum concentration of DO varied as shown in



Figure V-4.  Minimum dissolved oxygen readings of less than 2.0 mg/1



were recorded on all four cruises, even when the freshwater inflow was

-------
                                                                   V-7





as high as 8,890 cfs.  Increases in freshwater inflows caused the point



of minimum DO to move downstream as evidenced when the DO profiles for



June 30 and August 14 are compared.



     Data for the Potomac Estuary at the Woodrow Wilson Bridge (Figures



V-5 and V-6) show the typical annual variation in DO.  During the summer



of 1965, DO concentrations ranged from 0.5 to 3.5 mg/1 with an average



of 2.0 mg/1.  DO during the summer months of 1966 ranged from 0.5 to 3.0




mg/1 with an average of 1.5 mg/1.  For the months of September through



December 1965, the DC concentrations remained depressed as a result of



low-flow conditions.  During December 1965, the DC was approximately



5.5 mg/1 even when the water temperature was less than 10°C0



     The DO concentration for a given time and location can also vary



over the cross-section of the estuary.  In the Piscataway embayment,



DO varied from 4.0 to 12.0 mg/1 during a sampling cruise made on



June 27, 1970.  At the same time, the main channel of the Potomac



Estuary showed a fairly uniform DO (about 4.0 mg/l) as a result of



tidal mixing (see Figure V-7).  The higher DO concentrations in the



embayment were attributed to the photosyr.thetic production by dense



algal growths.  During hours of darkness, the DO dropped to less than



8.0 mg/1 in the embayment while it remained around 4.0 mg/1 in the



main Potomac.

-------
•OOOCO  03A10590

-------
                                                    DO  PROFILES
                                             UPPER POTOMAC ESTUARY
                                                          1969
                                                                 JUNE II, 1969
                                                         /'      FLOW=l800cfs
                                                        x        TEMP. = 26* C
                                                                JUNE 30,1969
                                                                FLOW = 940cfs
                                                                TEMP. = 28 5* C
x   8
Ol

O
Q   6
    0


    10
                                                                JULY 24, 1969
                                                                FLOW = 3200 cfs
                                                                TEMP. = 27* C
	 SURFACE
	 BOTTOM
               W.WILSON  BRIDGE
    AUGUST 14.1969
    FLOW = 8890 cfs
    TEMP.= 27*C
                             10                     20
                            RIVER MILES FROM CHAIN BRIDGE
             30
                                                                                FIGURE  V-4

-------
     UJ
O  £

*z

e  1
Z  d
Ld  £
o
Ld

<3
     ce
     o
     O  in
     O  to
     o:

o  5

>  IS
'I  Ld
°§
     CL
                         S

                        O.)
                                     i.'
                                      i
                                  o
                                             o
                                             -5
                                             §
                                             —
                                             of

                                             <
                                                               o
                                                                      o
                                                                                    o
                                                                                            I
                                                                                           q
                                                                                                     a.
                                                                                                     LJ
                                                                                                     CO
                                                                                                     O
                                                                                                     LJ
                                                                                                     £
                                                                                                     m
                                                                                                     LJ
                                                                                                     u.
                                                                         oa
                                                                                           FIGURE   V-5

-------





o
b:
 . •
:'
g
<
) •.. ;;: ••• •" ' "
CD
S ' ' • . .

z ' '-.
- •'•-.-.
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
O O O OOQOOOOOO
05 w ~ •* CJ O 00 <£)'•* N O'
0.) (I/6-")
3aniVci3dW3i oa
FIGURE   V-6

-------
    fc5
    U
        I,

        a  g

        UJ  CJ
O  <
w  CD
o  u


1
    o
                                                                             -8
                                                                               (O
                          I

                         O
                                      IO
r
•*
to
                                                 Hld3Q
                                                                           FIGURE V-7

-------
                                                                  V-13



C.  SILT AND DEBRIS



     The upper Potomac Estuary has changed drastically during the



past hundred years.  At one time, water covered what is now the



corner of Seventeenth Street and Constitution Avenue.  Potomac Park



and Hains Point did not exist.  Tidewaters covered the present site



of National Airport and Boiling Field.  The Anacostia River was a



broad stream with extensive mud flats.  Many of the tidal flats of



the upper Potomac were formed by sediments and have been transformed



by dredged material into the present Washington area waterfronts.



     The silt in the Potomac Estuary can be attributed to three



sources:



     a.  Above Great Falls, mainly forested;



     b.  Washington metropolitan area, mainly urban;



     c.  Coastal area, mainly rural.



     For the water years 196l through 1968, the average sediment



yield of the upper Potomac above Great Falls was 1.98 billion Ibs/year



(Table V-l).  The highest percentage of the annual contribution occurred



during either February or March with the maximum month values ranging



from 51 percent to 90 percent of the total annual load.



     The Northwest Branch of the Anacostia River near Colesville,



Maryland with a drainage area of 21.1 square miles showed an annual



yield ranging from 1.0 to 1.6 million Ibs/sq mile with an average of



1.34 million Ibs/sq mi/yr (Table V-2).  This is about seven times



greater than that from the upper basin which averages about 0.190



million Ibs/sq mi/yr.

-------
Tl
H
 0)
 S

 0<
 CO
ft
o
CM
O

H
ft
CM
                                            CM
                                            rH
                                                  CM
                                                         TV
                                                            O
                                                            ON
                                                                      TJ   ~
          t>-
             CM
               •
             --t
                       CO
                    VO


                    TV
                           t»
                            •
                           O
                           TV
                                                  TO
          fi
                       fl
                        o
                                     0
                                               A
                                               o
                                               I
                                                                          Q>
cd
0)
fc


-P tJO
cd -O
T3 -H
             CM


             H
                       VO

                       H
                           TV

                           O
                           H
                                 O
                                 MD
                                 ON
                                 TO

                                 *
                                                                
co  cd

-------
                                   Table V-2

                                 SEDIMENT DATA
           Northwest Branch Anacostia River near Colesville, Maryland
                          (Drainage Area = 21.1 sq. mi)
Year                   Total for Year                  Annual Yield
                                                    (1000 Ibs/sq mile)

                                                           1,590

                                                           1,090

                                                           1,540

                                                           1,360

                                                           1,420

                                                           1,000


Average                    28,300                          1,341

1963
1964
1965
1966
1967
1968
(1000 Ibs)
33,600
23,200
32,800
28,800
30,000
21,100

-------
                                                                   V-16


     Applying the Anacostia station average (1.34 million Ibs/sq mi/yr)

to the entire Washington metropolitan area and a yield rate of 0.20

million Ibs/sq mile to the lower coastal area, an estimate of the silt

loading to the entire Potomac River is as follows:
Yield Drainage Area
(1000 Ibs/sq mi/yr)
190
1,340
200
246*
(sq mi)
11,640
714
2r326
14,670
Average
Annual
Loading
(1000 Ibs/yr)
2,200,000
957,000
465.000
3,622,000
Upper Potomac
(above Great Falls)

Washington Area

Lower Coastal Area

Total

^Average Annual Yield

The upper basin is the greatest source of sediments.

     In addition to the obvious silting of navigation channels, sedi-

ments have other relationships to water quality management problems,

some which are favorable and some unfavorable.  During periods of

high flow and suspended sediment load, the Potomac contains corres-

pondingly greater quantities of organic carbon, nitrogen and phosphorus.

The suspended and adsorbed pollutants are deposited as the silt settles,

primarily in the upper 20 miles of the Potomac Estuary.  During high

runoff periods, the upper 10 to 20 miles is chocolate brown in color

and aesthetically objectionable.  Since the high silt loadings usually

occur during the spring months when fish are spawning in the estuary,

the silt may cover freshly laid eggs, thus reducing the effective

spawning area in the upper estuary.

-------
                                                                  V-17






     While silt transports a considerable amount of adsorbed nutrients



during high-river flows, the overall effect is to reduce the nutrient



concentration in the estuary, especially phosphorus.  Sampling before



and after a period of extremely high runoff in March 1967, as reported



by CTSL  [8], confirmed this observation.  Silt also tends to cover



much of the organic matter deposited from wastewater discharges.



This covering generally reduces the availability of nutrients and



oxygen demanding material from bottom deposits.



     It was observed by CTSL on numerous occasions that suspended



sediments contribute to algal control in the upper estuary.  During



the summer months, runoff resulting from heavy rainfall usually causes



high turbidity in the upper estuary which restricts light penetration



in the water and reduces algal growth even though all other environ-



mental conditions may be favorable.



     During the low-flow periods of 1966 and 1970, a reduction in



turbidity in the upper estuary along with other favorable environmental



condtions caused a significant increase in nuisance algal blooms near



and above Woodrow Wilson Bridge [52].  These nuisance blooms can be



expected to become more frequent as the silt control program becomes



more effective unless there is a simultaneous adequate removal of



nutrients from wastewater effluents.



     During periods of high runoff, large quantities of debris enter



the estuary from the upper basin as well as from the metropolitan area.

-------
                                                                  V-18




     Debris from the upper basin is typically trees, brush, leaves, and



miscellaneous trash, and is usually partially decomposed.  Debris from



the metropolitan area not only enters the estuary from local streams



but also from storm sewers and often contains paper, vegetable and



fruit peelings, styrofoam cups, etc.  It appears that better solid-



waste management practices would decrease the amount of local debris



entering the estuary.



     The effect of the increased silt and debris organic loadings on



the oxygen resources of the estuary has not been well defined.  Based



upon DO studies made during a period of heavy precipitation, it appeared



that increased flows and the resulting dilution minimized any immediate



effect on the oxygen budget.  Most of the organic matter carried into the



estuary by silt and debris settles and contributes to the benthic oxygen



demand.  CTSL studies in the Potomac Estuary indicated that oxygen uptake



from benthic deposits was about twice as large in areas with treated



waste sludge deposits than in other areas of the upper estuary (Figure



V-8).  Analysis of sediments for chemical oxygen demand (COD), as pre-



sented in Figure V-9, shows a fairly close relationship between COD



and benthic demand.  From COD and uptake data, it appears that the



effect of sludge deposits and other suspended solids from wastewater



on the oxygen resources is much greater than the effect from the



organic solids in silt and debris.

-------
i
LJ

5
LJ
U

O
        >-  fc
        DC   i
        13
            z

            UJ
                                  IO
                                *«•>
                                                                               . .
-------
LJ


<   I
P   ^
CL   p:

3   a
S
     Z
            o

            in
o
LJ

S
o:
tr

8
o
u
cr



1
2


 I
                 I
                 o
                                                                        1-8
                                                                     oo
                                                   -8


                                                   -SB
 I
O)
                 I
                00
 I
r-
T
(O
 I
't
 i
ro
                                                 (M
                                                                         -S
                                                                         -00
                                                                         -to
                                                                         -
-------
                                                                  V-21



D.  NUTRIENTS AND ALGAL GROWTH



     As discussed previously in this report, the major source of nitrogen



and phosphorus in the upper Potomac Estuary is from the wastewater dis-



charges in the Washington area.  Total phosphorus has increased about



22-fold, from 1,100 Ibs/day in 1913 to 24,000 Ibs/day in 1970, with



total nitrogen loadings increasing from 6,400 to 60,000 Ibs/day.  A



greater increase for phosphorus reflects not only an increase in popu-



lation but also the increased use of detergents.  The current carbon



loadings are about 100,000 Ibs/day, approximately the same as they were



in the mid-19401s.  The decrease in organic carbon in the early 1960's



was a result of the completion of present treatment facilities at Blue




Plains.



1.  Nutrient Concentrations in the Potomac Estuary



     The concentrations and forms of phosphorus and nitrogen in the



Potomac Estuary are a function of wastewater loadings, temperature,



freshwater inflow, and biological activity.  As shown in Figure V-10,



the inorganic phosphorus varied considerably for the six stations



sampled from March 1969 through September 1970.  The concentration



at Mains Point, located at the upper end of the tidal excursion of



the major wastewater discharges, was fairly uniform averaging about



0.3 mg/1.  At Woodrow Wilson Bridge, located below the Blue Plains



wastewater discharge, the inorganic phosphorus increased appreciably



with concentrations over 2.5 mg/1 during periods of low flow such as



those that occurred in July to October 1969 and September 1970.  The

-------
                                        INORGANIC    PHOSPHATE   CONCENTRATION   «
                                                               POTOMAC  ESTUARY
                        HAMS  POMT
                           MCES  BELOW CHAIN  BMDGC » 7.60
                                        JUN     JUC     MJG     SEP.  'OCT  '   NOV.     DCC.  I   JAN.     Ftt.
                        WOODROW  WILSON  BRIDGE
                           MLES  BELOW CHAW  BRIDGE *
                          APB. '   MAY     JUN.     JUL.  '   AUG.  '   SEP.  '  OCt
                                                                               1   -  I   '
                                                                                  MB«4-»I
 1.2-
 LO -
                        INWAN  HEAD
                                        JUN.    JUL   '  AUG.    XP     OCT.     NOU
 07-
= 06-
f 05-
 OJ-
 03-
 02-
 01-
                        SMITH  POINT
                            MLES BELOW CHAIN BRIDGE * 4640
 or-
 06-
!03-
 02-
 Ol-
             FU.     MAM.     AM.    MAY      JUN.
                        301  BRIDGE
                                                             SCR     OCT.     NOV.     DGC.     JtM.
                                                                                        • mo
                                                                                   C.     Jt
                                                                                    B i  I •
                                                                                                             AML    MW      JIM.
                                 MAY     JUN.
                                                      AUG.  '  sa  '  OCT.     NOU  '  occT 1  J«t  '   roT
                                                                                  m0-*-!-*• «7o
 07-
 06-
 oft-
e O*-
- os-
 02-
                         PINEY  PONT
                            MLES BELOW CHAM BROGC a 99.20
                           Am.    MAY     JUN
                                                      AUG.     SCR    OCT.     NOU
                                                                                         JAN.     FEI.

-------
                                                                  V-23





remaining four downstream stations had concentrations progressively



smaller.



     It was observed that much of the phosphorus is deposited into



the upper estuary even during high flows such as those in August 1969



and April 1970.  During periods of high freshwater inflow, the sediment



appears to adsorb more phosphorus than it releases.  This is discussed



in greater detail later.



     The total phosphorus concentration closely parallels that of



inorganic phosphorus.  In the upper reach, the ratio of total phos-



phorus to inorganic phosphorus ranges from 1.1 to 1.5.  The ratio is



higher in the middle reach normally varying from 1.5 to 2.0 with the



lower reach having a range from approximately 2.0 to 2.5.



     The concentration of nitrite (N02) and nitrate (N03) nitrogen at




Hains Point and Woodrow Wilson Bridge varies almost inversely to that of



phosphorus (Figure V-ll).  The N02 + N03 concentration was highest in



July and August 1969 and during the spring months of 1970.  During these



months, both high-flow periods, the phosphorus was lowest (Figure V-10).



The increase of N02 + N03 at Indian Head as compared to Woodrow Wilson



Bridge in May-June 1969, September-November 1969, and July 1970 was a



result of the conversion of ammonia from the wastewater treatment plant



discharges to NO^.  The extremely low concentration of N02 + N03 in the



summer months at Smith Point was caused by uptake by algal cells [52].



During winter months algal utilization is lower [52], thus the concen-



trations of nitrates are high, as in January and April 1970.  At Piney



Point, concentrations of N02 + N03 are usually less  than 0.1 mg/1.

-------
   Li-
   U-
   13-
   12-
+ r«H
£-~07-

    O5-
    O4-
    03-
    02-
MAINS  POINT
   MUS BELOW CHAIN WKXJE •
                                  NITRATE  
-------
                                                                  V-25


     As shown in Figure V-12, the concentration of ammonia nitrogen

is also affected by flow and temperature conditions.  Although large

quantities of ammonia are discharged from wastewater treatment facilities

into the Potomac near Woodrow Wilson Bridge, the ammonia at Indian Head

during the summer months is low because of nitrification.

     During the summer and early fall months, the average ranges of pH,

alkalinity, and free dissolved C02 (measured by titration) for the five

stations in the upper and middle reaches were:

                                                    Free Dissolved
Location              _piL_        Alkalinity       	CO?	
                     (units)     (mg/1 as CaC03         (mg/T)

Chain Bridge        7.5 - 8.0       80-100            2 -  4

W. Wilson Bridge    7,0 - 7.5       90 - 110            8 - 12

Indian Head         7.2-8.0       70-90            6-10

Maryland Point      7.5-8.2       60-85            2-8

Rte. 301 Bridge     7.5-8.0       65-85            7-8

     In the vicinity of the Woodrow Wilson Bridge, there is an increase

in both alkalinity and C02 with a corresponding decrease in pH attri-

buted to wastewater discharges.  There is a decrease in both alkalinity

and C02 with a corresponding increase in pH at the Indian Head and

Maryland Point stations which are due to algal growths.  In the lower

estuary, the alkalinity and C02 increases while pH decreases.  The

algal standing crops are considerably smaller in this reach.

-------
 «^OJ-
* I 07-
   04-
   OS-
   o.*-
   O3-
   02-
   01-
   00-
                                                            AMMONIA  MTROGEN  a
                                                                 POTOMAC  ESTUMtV
                                                                      NW-V7D
                                                                                    N
        WOODROW WILSON BRIDGE
          ML£S BELOW CHAM WUX3E > 12.10
        SMITH POINT
           MILES BELOW CHAIN BRIDGE * 4C.80
n
 0.7-
 OJt-
 05-
=_04-
 03-
 M-
 0.1-
        301 BRIDGE
           ML£S BELOW CHAM BRIDGE * 67.40
              A
^/v^x^
   (U-
   O7-
   (U-
   O5-
                                                                    M"
                                                                    tft I 1 • <
      PMEY POINT
         MLES BELOW OiWN MDGE - M.ZO
                                                                                                                  FIGURE V-12

-------
                                                                  V-27
2.  Mathematical Models for Nutrient Transport



     Mathematical models for predicting the movement and transport



of phosphorus and nitrogen have been developed by CTSL.  A detailed



report of the modeling of nutrient transport is in preparation.



Some of the model's predictions for phosphorus are shown in Figures



V-13 and V-14 and for nitrogen in Figures V-15 and V-l6.



     The effects of temperature on nutrient transport, deposition,



and utilization by the biota were determined by CTSL.  The rates of



phosphorus loss, ammonia utilization, and nitrate algal uptake as a



function of temperature are shown in Figures V-17, V-18, and V-19,



respectively.



     These models, which considered the effects of temperature on



the algal productivity rates, were used to investigate the role of



nutrients in eutrophication.  The models were also used to establish



maximum allowable nutrient loadings by zones as presented later in



this report.

-------
O
cr
o


D
    Ul
            in
            
-------
                                                   in
                                                  _o
H

1 1 1 1 1 1 1 1 1 1 1 1 1
                                                   ID
                                                   "5
                                                   5

                                                  -IT)
                                                  _O
                                                   If)
SV
                                         FIGURE  V-14

-------

LJ rf >o
Z u -.
8^1

z 11
£ o
*» V
« a
ii u
^ a*
O 2
     CO
o 5
g"
1
Tl-
(VI

M
(VJ

O
rvi

op
—

(O
—

•*.
—
i
CM
—

q
—
1
oo
ci
1
IO
o

•*
o
1
M
O

C
c
                       (l/6ul) N39OHJ.IN
                                                     FIGURE V-15

-------
Z
U  ^
O  fe
Z  u

fi  °
o  <



Ld  O
O  Q.
O
tr
         oo
         u>
         o>
(VI
CM
O
                                j: o
                       (M  N

                       n  "
          (M
                  o

                  (M
                          oo
                                                                                            m
                               o
                               9


                               00

                               2
                                                                                                   -S
                                                                                                 to
                                                                                                 UJ
                                                                                                 .j

                                                                                                 5
                                                                                                   _o
                                                                                                   -in
                                  (O
                                                  M
00


O

-------
 . I-

.09-

.08-

.07-


.06-


.05-



.04-




.03-
    .02-
5   .01-

-  .009-
O.

   .008-

   .007-


   .006-


   .005-
   .004-
   .003-
   .002-
    001-
                                   EFFECT OF  TEMPERATURE
                                              ON

                              PHOSPHCJRUS DEPOSITION  RATE

                                        POTOMAC ESTUARY
                      11.000 cf»
                                                                  8800 cf>
                                                           185 cf»
                                               bf ** I   *» tT —T \
                                               r\ p I   fl  I  **'
                                               R72


                                                 0 : 1.084



                                             Kp.20'Cr 0.0225 (BASE •)

                                             (SECOND-ORDER  KINETICS)
                             10
                                        15          20
                                          TEMP. to:c)
                                                              25
                                                                     30          35
                                                                        FIGURE  V-17

-------
 0.4-
 0.3-
 0.2-
^
 O.M
 .09-
 .08-
 .07-
 .06-
 .05-

 .04-

 .03-


 .02-
 .01-
.009-
.008-
.007-
.006-
.005-

.004-

.003-


.002-
.001-
                             EFFECT   OF  TEMPERATURE
                                            ON
                                 NITRIFICATION   RATE
                                   POTOMAC  ESTUARY
                                   NH,
                                             NO2+ NO3
                                                0 = 1.188
                                                KN= 0.068 (BASE «)  a* 20'C
                                                (FIRST ORDER  KINETICS)
                           10
                                          I            I
                                          15          20
                                           TEMPERATURE
                                               CO
 I
25
 I
30
 I
35
                                                                            FIGURE  V-18

-------
 0.2-
 0.1-
 .09-
 .08-

 .07-

 .06-

 .05-


 .04-


 .03-
 .02-
 .01-
.009-
.008-

.007-

.006-

.005-


.004-


.003-
.002H
.001
                          EFFECT   OF  TEMPERATURE
                                       ON

             RATE   OF  NITROGEN   UTILIZATION   BY  ALGAE

                                POTOMAC  ESTUARY
                               NO —*• ALGAL  NITROGEN
             9 = 1-120
             KN2 = 0.034 (BASE •)  at 20*C

             (FIRST  ORDER KINETICS)
                          I
                          10
I
15
 I
20
25
 I
30
 I
35
                                      TEMPERATURE
                                         CO
                                                                      FIGURE  V-19

-------
                                                                   V-35



3.  Ecological ^rends as Related to Nutrient Loadings



     The Potomac tidal system is saline in the lower reach with the



middle reach brackish and the upper reach fresh water.  These dif-



ferences in salinity as well as nutrient enrichment by wastewater



discharges have a pronounced effect on the ecology of the estuary.



Under summer and fall conditions, large populations of blue-green



algae (a pollution tolerant phytoplanlcton), mainly Anacvstis sp.



are prevalent in the freshwater portion of the estuary.  Large



standing crops of this alga occur, especially during periods of



low flow, forming green mats of cells.  The blue-green algae are



apparently not readily grazed by the higher trophic forms and



therefore are often considered a "dead end" of the normal food chain.



     In the saline portion of the Potomac Estuary, the algal popu-



lations are not as dense as in the freshwater portion.  Nevertheless,



at times large populations of marine phytoplankton, primarily the



algae Gvmnodinium sp. and Amnhidinium sp., occur producing massive



growths known as "red tides."



     The effect of the increases in nutrient loadings from wastewater



since 1913 on the dominant plant forms in the upper estuary has been



dramatic (Figure V-20).  Several nutrients and other growth factors



have been implicated as stimulating this, with nitrogen and phos-



phorus showing promise of being the most manageable.



     The historical plant life cycles in the upper Potomac Estuary



can be inferred from several studies.  Gumming [7] surveyed the



estuary in 1913-1914 and noted the absence of plant life near the

-------
                                           O «» NO9HVD  DINV9MO
I   I
01
O

ul
o:
    (E
    IU
1 2
u x

Z &
Ul 3
a

z
tr:
u
t
1
LJ
10
1
t-
D
Z
H
(/)
¥
O
a:
V
4




V—
J«rt
a. ui
O
O
z
0
O
0
o"
IO

o
o
q
o
(M
O
o
o
in
*
N «
0
8
iff
—
0
8
o"
CO
0 N39OM1IN ~lViOl
O
8
o

o
o
o
m"



o




O 0
8
in

                                          d «° SnMOHdSOHd  IVIOI
                                                                                     FIGURE V-20

-------
                                                                  V-37






major waste outfalls with "normal" amounts of rooted aquatic plants on



the flats or shoal areas below the urban area.  No nuisance levels of



rooted aquatic plants or phytoplankton blooms were noted.



     In the 1920"s, an infestation of water chestnut appeared in the



waters of the Chesapeake Bay including the Potomac Estuary.  This



infestation was controlled by mechanical removal [9].



     In September and October 1952, another survey of the reaches



near the metropolitan area made by Bartsch [10] revealed that vege-



tation in the area was virtually nonexistent.  No dense phytoplankton



blooms were reported although the study did not include the downstream



areas where they were subsequently found.



     In August and September 1959, a survey of the area was made by



Stotts and Longwell [11].  Blooms of the nuisance blue-green alga



Anacystis were reported in the Anacostia and Potomac Rivers near



Washington.



     In 1958 a rooted aquatic plant, water milfoil, developed in the



Potomac Estuary and created nuisance conditions.  The growth increased



to major proportions by 1963, especially in the embayments from Indian



Head downstream [12].



     These dense strands of rooted aquatic plants,  which rapidly



invaded the system, dramatically disappeared in 1965 and 1966.   The



decrease was presumably due to a natural virus [13].

-------
                                                                  V-38
     Subsequent and continuing observations by CTSL have confirmed per-



sistent massive summer blooms of the blue-green alga Anacystis in



nuisance concentrations of greater than 50 ug/1 from the metropolitan



area downstream at least as far as Maryland Point [14].   Chlorophyll a



determinations (a gross measure of algal standing crop)  in the upper



reach and in the middle and lower reaches of the Potomac Estuary are



presented in Figures V-21 and V-22 respectively.



     Chlorophyll a at Indian Head and Smith Point for 1965-1966 and



1969-1970, as presented in Figures V-21 and V-22 respectively, indi-




cate that algal populations have not only increased in density but



have become more persistent over the annual cycle.  At both stations,



higher values of chlorophyll were measured during the 1969-1970




sampling cruises.  The occurrence of a spring bloom of diatoms was



observed in 1969 and 1970.  This had not been observed during the



1965-1966 cruises.



     These biological observations over the years appear to indicate



a species succession.  The initial response to a relatively light



overenrichment [9] was the growth of water chestnut which when



removed allowed the increasing nutrient load to be taken up into



the rooted aquatic plant, water milfoil (Myriophvllum snicatum).



The die-off of water milfoil then allowed the nutrients  to be



competitively selected by the blue-green alga Anacystis.  Since



Anacystis is apparently not utilized in the normal food chain, huge



mats and masses accumulate, die off, and decay.

-------
HAMS POMT
   MLES KU3W CHAM BBCG£ s 7.60
CHUOROPHYLL  a

POTOMAC ESTUARY
    UPPER REACH

-------
        SMITH  POINT
            MLES KLOW CHAM  MMI « 4140
  CHLOROPHYLL   a
  POTOMAC  ESTUARY
MDOLE t*  LOWE*  REACH
SI-
                                HAY     JUN
           ni*
         »•«—I—••*>
                                                                                                                   JM.    JUL    MJG.
        301  BRIDGE
           MLES BELOW CHAIN BRIDGE < 67.40
        JAN    FEL
                          APR    MAY     JIM
                                                                OCT    MOV    oec    S*.
                                                                             IBM *-!-* KflO
                                                                                                                                AUG.    SCf
         WNEY  POINT
            MILES BELOW CHAM BRIDGE = M.20
                                       JUN.    JUL
                                                          SCR    OCT     NOW    DEC  |   JAN.
                                                                             IM9 *
           r-p
           »»-!—•«
                                                                                                                            ~>—r^;—>—™—'

-------
                                                                   V-41
      From the above  considerations, it would appear that nuisance
 conditions did not develop  linearly with an increase in nutrients.
 Instead, the increase  in nutrients appeared to favor the growth and
 thus  the domination  by a given species.  As nutrients increased
 further, the species in turn was rapidly replaced by another dominant
 form.  For example,  water chestnut was replaced by water milfoil
 which in turn was replaced by Anacystis.
      Figure V-20 indicates that the massive blue-green algal blooms
 were  associated with large phosphorus and nitrogen loading increases
 in the upper reaches of the Potomac River tidal system.  The massive
 algal blooms have persisted since the early 1960's even though the
 amount of organic carbon from wastewater discharges has been reduced
 by almost 50 percent.
     Laboratory and  controlled field pond studies by Mulligan [15]
 have shown similar results.  Ponds receiving low-nutrient additions
 (phosphorus and nitrogen) contained submerged aquatic weeds.  Con-
 tinuous blooms of algae appeared in the ponds having high nitrogen
 and phosphorus concentrations.  An important observation in Mulligan's
 studies was that when the water quality was returned to its original
 state by reduction of nutrient concentrations, the ecosystem also
 reverted to its previous state.  This observation was also supported
by studies of Edmondson [16] on Lake Washington and Easier on the
Madison, Wisconsin lakes [17].

-------
                                                                  V-42






E.  EFFECTS OF EUTROPHIGATION ON WATER QUALITY



     The effects of nutrient enrichment and the resulting algal growths



are fourfold:  (l) an increase in organic oxygen demanding load,



(2) an increase or decrease in dissolved oxygen caused by algal photo-



synthesis or respiration, (3) the creation of nuisance and aesthetically



objectionable conditions, and (4) the possible toxic effects on other




plants and aquatic life.  Each of the effects is discussed separately



below;



1»  Increase in Organic Oxygen Demanding Load



     Algal cells convert inorganic carbon and nitrogen into organic



compounds and result in an appreciable oxygen demanding load after



their death.  For example, under summer conditions, all of the



60,000 Ibs/day of nitrogen discharged into the estuary from wastewater



treatment facilities is converted into algal cells.  The combined



ultimate oxygen demand of nitrogen and carbon from these cells is



approximately 490,000 Ibs/day.  This load, though dispersed over the



entire upper estuary, is nevertheless greater than the total oxygen



demand by all wastewater discharges into the upper estuary.



     Laboratory studies on rate kinetics of the oxidation of algal cells



at temperatures of 28°C to 30 C indicated that the reaction rates for



the oxygen demanding process vary from 0.16 to 1.25 per day.  The



increase in organic oxygen demanding loads is often concentrated in



the embayments or along the shores as a result of wind action.



These concentrations of decaying algae produce noxious odors.

-------
                                                                  V-43
2.  Algal Oxygen Production and Respiration



     As shown in Figure V-7, the DO concentration in the Piscataway



embayment was 12 mg/1 which was about 4 nig/1 above saturation capacity



at the observed water temperature.  This increase in DO above satura-



tion capacity is due to oxygen produced by algal cells.  The total



oxygen production of a community as a result of the photosynthetic



activity is a function of algal biomass and population composition,



light intensity, and temperature.  In the upper and middle Potomac



Estuary, light penetration is usually limited to the upper 2 to 4



feet of the water column.



     Bacterial and algal respiration occur simultaneously with the



oxygen production process.  Since the upper estuary is well mixed,



this respiration process occurs over the entire water column.  During



the months of June and July 1970, oxygen production and respiration



rate studies were made in the upper and middle Potomac Estuary as



presented in Table Y-3„  A special respiration study was conducted on



July 29, 1970, which indicated that .0010 mg 02/hr/ug of chlorophyll



respiration could te attributed to algae with the remainder due to



bacterial and other oxidation processes.



     With a euphctic zone of 2 feet, an average oxygen production of



.010 mg 02/hr/ug cf chlorophyll for 12 hours/day, an average respiration



of 0001Q mg 02/hr/ug of chlorophyll for 24 hours/day, and an average



chlorophyll concentration of 100 ug/1, the oxygen balance for various



water columns is given in Table V-4.  The data indicate that for a

-------
                  Table V-3
OXYGEN PRODUCTION AND RESPIRATION RATE SURVEY
       Upper and Middle Potomac Estuary
                    1970
Date
6-22
6-23
6-24
6-25
7-20
7-21
7-22
7-27
Water
Temp.
(°c)
26
27
27
27
28
27
26
28
Chlorophyll a
Range
(ug/1)
40-110
70-120
54-110
50- 60
30-100
30-143
30-140
_
Light
Intensity
Range
(foot candles)
250-300
200-300
200-300
200-300
250-400
200-300
100-200
_
Oxygen
Production
mg/hr/ug of
Chlorophyll a
.0073
.0084
.0087
.0121
.0130
.0130
.0146
.0060
Respiration
mg/hr/ug of
Chlorophyll a.
.0023
.0011
.0024
.0033
.0022
.0016
.0017
.0010

-------
                                       Table V-4

                         OXTCEN PRODUCTION-RESPIRATION BALANCES

                                Chlorophyll a = 100 ug/1
             Oxygen Production = .010 mg/hr/ug chlorophyll for 12 hours/day
               Respiration = .0010 mg/hr/ug chlorophyll for 24 hours/day


                               Euphotic Zone of 2.0 feet

                    Increase in Oxygen
                    Averaged over Entire         Decrease in
                    Water Column due to          Oxygen due to
Water Column        Fhotosynthes is	         Respiration              Net
(depth)
4
8
12
16
20
4
8
12
16
20
(mg/l/day)
6.0
3.0
2.0
1.5
1.2
Euphotic Zone
12.0
6.0
4.0
3.0
2.4
2.4
2.4
2.4
2.4
2.4
of 4.0 feet
2.4
2.4
2.4
2.4
2.4
(mg/l/day)
3.6
0.6
-0.4
-0.9
-1.2
+9.6
+3.6
+1.6
+0.6
0.0

-------
                                                                  V-46






water depth greater than 10 feet, respiration would be larger than



production, thus resulting in a negative net balance on the oxygen



resources of the system.



     If the euphotic zone were increased to 4 feet, there would be a



net oxygen production for water columns of 24 feet or less.  Conversely,



if the depth of the euphotic zone were 1 foot, there would be a net



oxygen production for water approximately 6 feet and less in depth.




     The DO budget in the Potomac Estuary is affected by algal pro-



duction and respiration as shown in Figure V-23.  The net result of



oxygen production and demand by algal respiration and decay is a



reduction of the oxygen resources.  This DO depression is approxi-




mately 2.0 mg/1 in the estuary and can be attributed to algal



respiration and decay.  The net oxygen production concept has been



incorporated into the DO budget model for the Potomac Estuary.

-------
                  j;  o
                  8  «
                  oo  r-
                  (VJ  CM
O
         00
     
-------
                                                                  V-48






3.  Unfavorable Physical and Aesthetic Characteristics of Algal Blooms



     When algal blooms become extensive, large mats are formed causing



what appears to be a coating of green paint on the water surface.  In



embayments such as Gunston Cove, Piscataway and Dogue Creeks, these mats



usually concentrate in the vicinity of marinas not only coating the



hulls of boats but also emitting an obnoxious odor when the cells die



and decay.



     Along the Potomac shorelines, rows of algal mats are often formed



by wind action.  These windrows of algae render the shoreline unsuitable




for swimming and recreation.



     In September 1970, after a period of low flows, the algal blooms



became quite prominent in the area of Woodrow Wilson Bridge.  After a



week of temperatures in the 90's Fahrenheit, an algal mat developed in



the Tidal Basin.  The dense growth of algae was physically removed to



minimize the obnoxious odors emanating from the decaying mats.  This



was the first known occurrence of a heavy algal bloom in the Tidal



Basin.

-------
                                                                  V-49





4.  Algal Toxicitv



     It has been postulated that some algal species cause gastric



disturbances in human beings who ingest infested water.  Under cer-



tain conditions, several species of blue-green algae produce toxic



organic compounds that can kill fish, birds, and domestic animals




[21].  Of the 10 such known genera, three (Anabaena, Oscillatoria,



and Anacystis) grow profusely in the upper Potomac Estuary.




     At the present time, the effects of toxins from blue-green algae



on other forms of life in the waters of the Potomac Estuary are not



well established.  In the summer of 1970, the blue crab harvest in



an area of heavy algal blooms was reduced because of undesirable



tastes and odors.  It was also reported that several people became



ill after eating crabs from this area.  Crabbing in the lower Potomac,



where there are no blue-green algal blooms, was not affected.  It is



postulated that the objectionable taste and odor of the crabs was



related to the blue-green algae.



     If the estuary is to be used as a water supply source, the



possibility of the effect of toxins from blue-green algae must be



considered.  The genera currently found in the Potomac have known



species which are toxin producers and as mentioned previously are



also known to affect the taste and odor of seafood.

-------
                                                                  VI-1



                             CHAPTER VI



                    DISSOLVED OXYGEN ENHANCEMENT




A.  STUDY APPROACH



     The concentration of dissolved oxygen in the upper estuary is



a function of environmental conditions, biological population and



activity, and concentration and composition of organic matter in the



system.  A schematic diagram shown in Figure VI-1, originally pre-



sented by Torpey  [18], demonstrates the interrelationships of the



oxidation of carbonaceous and nitrogenous components of organic



matter by bacteria, and photosynthetic activity by phytoplankton,



and dissolved oxygen.



     The three biological systems having the greatest effect on the



DO are the bacteria which oxidize the carbonaceous matter, the bac-



teria which oxidize the nitrogenous matter, and the phytoplankton



which grow as a result of nutrient enrichment.  In the upper Potomac



Estuary, these three biological systems can and do occur simultaneously



in the same area.  The predominance of one or all of the three systems



depends not only on the source of organic matter (wastewater effluents)



but also on such environmental factors as temperature, light penetration,



and freshwater inflow.



     A DO budget has been incorporated into the FWQA Dynamic Quality



Model consisting of the following five linkages:



     (l)  Oxidation of carbonaceous matter,



     (2)  Oxidation of nitrogenous matter (ammonia and organic),

-------
   I
   CO   CO
   Z   2
   O   if
   %   £
   H ui<"
   y cc
< 2
  X
  O
  §
  co
  CO
  5
CD
CC
O
             (JJONfia QNVT)
            noaOHDVB - DIHLN38)
             (a30.VM3J.SVM)
                      QNVT)
                 N39AXO
              QNV1)
       (a3i.VM3.LSVM)
     Noaavo  DINVOWO
            (Dia3HdSOWlV)
            (a31VM31SVM)
            (JJONOH  ONV1)
           Noaavo
                    JLH9H
                      NHS
        (QNnoaoxova -
            (JdONOa QNVT)
             (a31VM31SVM)
                TVI1N3SS3 a3H10
                                                                                          FIGURE  VI-I

-------
                                                                  VI -3
      (3)   Oxygen production and  respiration  of simulated algal

           standing  crops  based upon  nitrate  utilization by the

           cells ,

      (4)   Benthic demand, and

      (5)   Reaeration from the atmosphere.

The model, which is  described in a CTSL report  currently in pre-

paration,  has been  verified for  flow ranges  from 212 to 8800 cfs .

The average  observed and  predicted DO  concentrations for the

periods of September 22,  1968, and August 12-19, 1969, as  shown in

Figures VI -2 and  VI -3 respectively,  demonstrate that the model can

predict DO responses  over a wide range of freshwater inflows.

      The basic coefficients used in  the DO budget model are:

                                 Rate (base e)  Temperature Coeffici-
      Process                    at 20°C        ent 9(^1- ?2Q)
Carbonaceous oxidation             0.170             1.047

Nitrogenous oxidation              0.068             1.188

Algal utilization of nitrogen      0.034             1.120

Reaeration from the atmosphere       *               1.021

The remaining processes in the DO budget are given below:

Algal oxygen production rate = 0.012 mg 02/hr/ug chlorophyll §.

Algal respiration rate = 0.0008 mg 02/hr/ug chlorophyll a

Euphotic zone = 2 feet deep

Respiration depth = full depth of water column

Algal oxygen production period = 12 hours

Algal respiration period = 24 hours

Benthic demand rate = 1.0 gr 02/day sq mi

* The model calculates reaeration as a function of depth and velocity
  using any one of three formulations.

-------
                                o
                                                                   _ o
 I

o>
 I

CO
                      
-------
        (VI
           u
           O
           o
          1
          o


          I
          10
          Ul
      _ o

FIGURE  VI-3

-------
                                                                  VI-6






Details of the effect of these parameters on the DO budget will also



•be given in the CTSL report now in preparation.



     The major area of depressed oxygen during low-flow periods is



from Hains Point to about Gunston Cove.  In this area, the major



source of the oxygen depression is from wastewater effluent.  The



total daily oxygen demanding loads from these discharges are as




follows:



     Carbonaceous = 200,000 Ibs/day



     Nitrogenous = 250,000 Ibs/day



Under these flow conditions, approximately 65,000 Ibs/day of car-



bonaceous and nitrogenous oxygen demand enter the upper estuary from



land runoff.  From the above, it can be concluded that the current



nitrogenous demand has the greatest effect on the oxygen resources



of the estuary with carbonaceous demand being slightly lower.



     However, the rate at which the demand (carbonaceous and nitro-



genous) is exerted varies significantly depending upon temperature.



At a 28°C temperature, the demand rates are equal at 0.34 day (base e);



while at 15°C, the carbonaceous demand rate is 0.18 with the nitro-



genous demand dropping to 0.03.  See Figure V-18 for nitrification rates.



     Simulation runs with the model indicate that while nitrification



continues to occur at temperatures of 15°C or lower, it plays a minor



role in the overall DO budget of the upper Potomac Estuary.

-------
                                                                  VI-7
     For 22 years of record, mean monthly water temperatures in the



upper estuary have been determined as given below:



     January     2.5°C           July          28.1°C



     February    3.3°C           August        27.8OC



     March       7.8QC           September     24.7°C




     April      14.0°C           October       18.400



     May        20.4°C           November      11.5°C




     June       25.9°C           December       4.8°C



Based upon the above tabulation and the study discussed above,  it



appears that nitrification control for DO enhancement is required



only for the months of April through October.  This is developed




further in Chapter XII.

-------
                                                                 VI-8


B.  DO CRITERIA

     Water quality standards for dissolved oxygen have been  adopted

by the States of Maryland and Virginia and by the District of  Columbia.

     For the waters of the Potomac,  the standards are as  given below:

     Jurisdiction                Average DO          Minimum  DO
                                   (mg/1)              lmg/1)

     District of Columbia*       5.0 (Daily)              4.0

     State of Maryland           5.0 (Monthly)           4.0

     State of Virginia           5.0 (Daily)              4.0

* Except between the Rocbambeau Memorial and  Prince Georges  County
  (Maryland) line where the average  is 4.0 and the minimum DO  is 3.0.

     These DO .standards were used as criteria in this study.

-------
                                                                  VII-1





                            CHAPTER VII



             ALGAL GROWTH RESPONSE TO NUTRIENT CONTROL



     Reductions in the standing crop (biomass) of algae in the Potomac



Estuary can be achieved by management, singly or in combinations, of



carbon, nitrogen, and phosphorus content.  The decision as to which



nutrient or nutrients to control may depend upon several factors



especially the four listed below:



     1.  Level of algal reduction required to minimize the effect on



water quality such as DO and recreational water use,



     2.  Maximum nutrient concentration allowable to maintain a maxi-



mum permissible algal standing crop,



     3.  Controllability and mobility of a given nutrient, and



     4.  The overall water quality objectives, such as DO enhancement,



eutrophication reversal, or reduction of potentially toxic matter



including heavy metals.



The four factors listed above were used not only to establish the




nutrient criteria but also to develop the overall wastewater manage-



ment program for the Potomac Estuary.

-------
                                                                  VII-2




A.  EUTRQEHICATION CONTROL OBJECTIVES



     For purposes of water quality management, the upper Potomac



Estuary may be considered eutrophic when undesired standing crops



become the predominant plant life as is now occurring with the nuisance



blue-green alga species.   The major objectives for controlling the blue-



green algal standing crop in the upper estuary are fourfold:



     1.  To reduce the dissolved oxygen (DO) depression caused by res-



piration and the decay of algal growths especially in waters over 10



feet in depth.  At times, DO depressions of more than 3.0 mg/1 below



saturation occur even during daylight hours.



     2.  To minimize the increase of ultimate oxygen demand (UOD)



resulting from the conversion by algal cells of inorganic carbon and



nitrogen from wastewater to oxidizable organic compounds.  Currently,



more UOD is added to the upper Potomac Estuary in the summer months as



a result of algal growth than from wastewater discharges.



     3.  To enhance the aesthetic conditions in the upper estuary.  Large



green mats develop during the months of June through October and create



objectionable odors, clog marinas, cover beaches and shorelines, and in



general reduce the potential of the estuary for recreational purposes



such as fishing1, boating, and water skiing.



     4.  To reduce any potential toxin problem and objectionable taste



and odor problems related to excessive blue-green algal crops if the



upper estuary is to be used as a supplemental \vater supply.

-------
                                                                 VII-3





     To aid in defining an algal standing crop limit, a subjective



analysis using chlorophyll concentrations was developed incorporating



conditions having possible effects on water quality.  Four major



restraints to desired water uses are offered in this analysis (Table



VII-l) including the required reduction in the chlorophyll standing



crop for each of the parameters.




     The desired maximum limit of 0.5 mg/1 DO below saturation was



selected by CTSL to allow for assimilation of waste discharges and




naturally occurring oxygen demanding pollutants.  To minimise the



effects of increased organic loads and sludge deposits caused by



algal growths, an upper limit of 5.0 mg/1 of total oxygen demand is



proposed.



     Of the four restraints, the most stringent reduction percentage



is for control of growths to prevent nuisance conditions.   From the



above analysis, a 75 to 90 percent reduction in chlorophyll concen-



tration will be required in the Potomac Estuary, or chlorophyll



levels of approximately 25 ug/1.

-------








































H
;
M
M
>

0
rH
r~i
"cd
H






































































co

Eg
^H
CM
M
s
8

>-H
§
S
O
o
d
c5
K-5
<

Er-,
0

CO
M
B
!H

^^

&£}
™>
M
e
K)

CQ
CO

























fi
O
•H
-P
O
S P
t3 O
££
0 ty
ho P
cd -H
-p T3
fl fi
0 cd
0 -p
Pi CO
0
CL, -p
fl
T) 0
0 fH
P. P
•H "
3 0
0*
0 VH
tti 0











tfN
to

U"\
vo












-P
•H
%
h4
'O S
0 3
Pi B
CQ X
si


<^
^

*>fN
*
O


*.
CQ
-P
PS
•r-
S
^
cn
•p
P!
•H
$-i cd
O Pi
-P
>> CQ
-p 0
•H fCj
rH
cd 0
( 	 y i ^

£-f Pi
0 0
-P -P
cc cd
^3
TJ
0
CQ

cd
O

SM
o
•H
CQ
CQ
0
ft

£~5

O
Q




























































q
Q
•H
-P
fi
^
_{_>
fU
CO




B
•H
-P
cd

•H
Qt
CQ
0
PS

•a
§

r*i
cd
o
0
P.











O
to
1
lf\
\Q














•!^
%

O
•
ITV





, — |
^

o


o
-p

ITl
rH



0
CQ
cd

fn
o
P!
M

^_l
0
H
^"s^
tip
S


d
0
ho
r?
o
1 — 1
cd

b
EH

P!
•H

0
CQ
cd
0

o
a
t-i
























































Q
o
m

CD
-P

£3
-H
H
[ID

f^
*H









rc3
cd
O
l_Zj

up
•H
TJ
pj
CO
S
Q











O
0

tf\
/*w













&
H
"ho
jj

U^\
nj








I — 1
^-v^
b£
^



rH
/ V


i
£l
o
o

rH
^5
r^-4

P
0
rH
r£*
O


O
•H
-P
-P
CQ
0


o
O
H
P4
cd
A
-t-z
rt
0
-P
cd
S
hO
0
Pi
cd
S
0
•H
-P
cd
Pi
40
K
0
o
P;
o
o

cdl
rH
rH
£
ft
0
£-J
o
1 — t
'o

«\
CO
g
•H
-p
•H
13
PI
O
O
B
0
0
rH
-Q
0
O
cj
cd
CQ
-H
r$
^

0
T3
P5


*






























































rt
P
rH
0
O

in
0
•P
n

i
•H
-P
0

[L|
0
^>
0

Q)
ho
B

J>

-------
                                                                  VII-5


B.  NUTRIENT REQUIREMENTS TO PREVENT EXCESSIVE STANDING CROPS OF BLUE-
    GREEN ALGAE

     Various investigators studying algal growth requirements have dis-

cussed the concentrations of nitrogen and phosphorus needed to stimulate

algal blooms.  In a recent study of the Occoquan Reservoir, located on a

tributary of the Potomac Estuary, Sa-wyer [19] recommended limits of

inorganic nitrogen and inorganic phosphorus of 0.35 and 0.02 mg/1,

respectively.  This reservoir has blue-green algal blooms under summer

conditions attributed to wastewater effluents discharged into tributaries

flowing into the reservoir.  Mackenthun [20] cites data indicating upper

limits of inorganic nitrogen at 0.3 mg/1 and inorganic phosphorus at

0.01 mg/1 at the start of the growing season to prevent blooms.  FWQA's

Committee on Water Quality Criteria recommends an upper limit of 0.05

mg/1 of total phosphorus for estuarine waters [21].  No recommendations

for inorganic nitrogen were made other than that the ratio of nitrogen

to phosphorus should not be radically changed from that naturally

occurring.

     Pritchard [22], studying the Chesapeake Bay and its tributaries,

suggests that if total phosphorus concentrations in estuarine waters are

less than 0.03 mg/1, biologically healthy conditions will be maintained.

Jaworski e_£. ajl [14], reviewing historical data for the upper Potomac

Estuary, suggest that if the concentration of inorganic phosphorus and

inorganic nitrogen were at 0.1 and 0.3 mgA respectively,  algal blooms

of approximately 50 ug/1 of chlorophyll §. would result. A chlorophyll a

concentration of 50 ug/1 or over was considered indicative of excessive

-------
                                                                 VII-6





algae.  Studies of the James River Estuary, a sister estuary to the



Potomac, by Brehmer and Haltiwanger [23] indicate that nitrogen appears



to be the rate limiting nutrient.



     Recently, the management of carbon in controlling algal blooms



has been suggested by Kuentzel [24] and Lange [25].  Studies by Kerr



et al [26] also suggest that inorganic carbon is apparently directly



responsible for increased algal populations in waters they have



studied.  The Kerr studies indicate that the addition of nitrogen and



phosphorus indirectly increases algal growth by stimulating growth of



large heterotrophic populations.  No concentration criteria for either



nitrogen, phosphorus, or carbon were suggested to prevent excessive



algal blooms.



     In addition to the review of data cited above and other numerous



articles not reported, six considerations were used to develop the



nutrient requirements for the Potomac Estuary.  The six were



     1.  Algal composition analyses,



     2.  Analysis of the nutrient data on an annual cycle and profile



         basis,



     3.  Nutrient bioassay,



     4,  Nutrient and algal mathematical modeling,



     5.  Comparison with an estuary currently not eutrophic, and



     6.  Review of historical nutrient and ecological trends in the



         Potomac Estuary.

-------
                                                                 VII-7
A comprehensive approach to algal growth control was taken to include



all three reaches of the estuary:  the fresh water, the brackish, and



the saline portions.  In a study undertaken by Carpenter, Pritchard,



and Whaley, oxygen concentrations of less than 1.0 mg/1 v/ere found in



the area of the lower reach of the Potomac [27].  Comparable areas of



the Chesapeake Bay, in terms of salinity and vertical stratification,



did not show depletions to less than 1.0 mg/1.  In terms of plankton



counts and chlorophyll, their study indicated that the lower reach of



the Potomac was more eutrophic than comparable waters of the Chesapeake



Bay.

-------
                                                                  VII-8






1.  Algal Composition Analysis



     In a previous chapter, the need to control algal growth was  estab-



lished.  The three major nutrients in blue-green algal cells are  carbon,



nitrogen, and phosphorus.  The chemical composition by weight of



Anacystis, which is the most common algae in the Potomac as  reported by



Lawrence [21], is presented below:



     Carbon          46.46$



     Nitrogen         8. (



     Phosphorus       CM



Elemental analysis of the blue-green algae in the Potomac was made during



the summer months of 1970 [53] and the data on carbon, nitrogen,  and



phosphorus ratios in terms of micrograms of chlorophyll a. and grams of



suspended solids are presented in Table VII-2.  These data indicate that



water with an algal bloom of 100 ug/1 chlorophyll §. contains the  following;




     Parameter       Concentration



     S. Solids       14.2 mg/1



     Carbon           4.5 mg/1



     Nitrogen         1.0 mg/1



     Phosphorus      0.1 mg/1 (0.3 mg/1 as PO^)



     Assuming that all nutrients can be utilized by the algal cells, an



algal bloom with a concentration of 100 ug/1 of chlorophyll a requires  a



minimum of 4.5 mg/1 of carbon, 1.0 mg/1 of nitrogen, and 0.10 mg/1 of



phosphorus (0.30 mg/1 of PO^) in the supporting water.

-------
03
     t=>
     E-i
     CO
     O
     I—I
     EH
    r?
    cd

    -P

    .3
         w LJ-

        -P C>
8£
o
    fH
J  CD
9  &
9  P<

^^
         O rH
                   S'
                       O
                      •H


                   & «0
                   S  O
                   cd  o

                   CO t-1
VO VO
C x-CO i-H rH
.£ p • o o
^ ft CO
CT
cc
1 s
-3 o en ex)
S -N H O O
g 0 .d 0 0
(P " '
EH!
VO OJ
O CO VO VO
.;: • o o
.p S CO • •
^ & pT
S
a g
f^l O O! O
S rH rH O
,5 ^ O O
"" s; o • •
o $
fn CO C1- VO
o cd • OA OA
.;: o co
i§ m !~
Si £ >0
f 0 fH
j: ,0 o o -o-
r* PH H VO VO
^ CO J3 O CD
o o • •
&i up
fa,

t) -p
I I £
O PH
-pi a
O CO £S
PH -r-f -p
*n3 *H
C C fi
O M CO
Ol O O
-p OJ OJ
ITN r-l OJ
rH 1 i-H OJ
O O O

oj -sf vo OA
O O O O
o o o o

CO OA «A
•^3" t OA O
O O O
• » •


V) OO to O!
O O O O

^J" rH
• •

tO --t UA
«A 1 Nf OJ
O O O


-P rH CvJ
O -p co -P iti -p cO
P 1 f~| fY^ ^j f^^ fj pT^
•rl -H >H
t3 O CO O CQ O CQ
fl PH £: PH |3 PH &
>J> T3 t-J T3 rH TJ rH
.^d cO ijgi cO .-^ cO f^
1^ co- — co — ' co —
~-t -vf VO VO
OJ OJ OJ OJ
II 1 1
!> to to to
1 OA 1 I rH
O O

OJ OA OJ OJ OA
SO O O O
o o o o
• • * * •

OJ OA
1 S ! ' B
* •


O OJ O vo O
8rH O O rH
O O O 0
* • • » •

CJ^ r^
: t> i i OA
• «

o o o o o
• • • • *


rH OJ
-P
^rj T^ T^ p
cd cd cd *H
CD 0 0) O
c a s § o
cd cd cd p 
M M I-H PH >
                                                                                                                                                 ^3


                                                                                                                                                 CO
                                                                                                                                                 TJ
                                                                                                                                                 •H


                                                                                                                                                 •H
                                                                                                                                                 13
                                                                                                                                                 PH
                                                                                                                                                 o
                                                                                                                                                 -P
                                                                                                                                                 S
                                                                                                                                                •H
 C    O

 a   *
 CQ    4°
 PJ    rt
CO    
-------
                                                               VII-10






     For the Potomac Estuary, which can be considered a slow-moving



continuous culture system during the summer,  a carbon concentration



equal to or less than 1.1 mg/1,  0.25 mg/1 of nitrogen, and 0.08 mg/1



(0.027 mg/1 as P) of phosphate would be theoretically required to



maintain a 25 ug/1 chlorophyll a level (or one quarter of the nutrient



content in a bloom of 100 ug/l).  These should be considered maximum




concentrations since no recycling is assumed.

-------
                                                               VII-11






 2.  Analysis of Data on an Annual Cycle and Longitudinal Profile Basis



     Using the disappearance of a  specific nutrient both seasonally



 and along longitudinal profiles, insight can be gained as to the possi-



 bility  of this nutrient becoming algal growth rate limiting.  This



 assumes that other environmental factors do not restrict growth.



     Figure V-10 in Chapter V shows that there was over 0.2 mg/1 of



 available phosphorus as PO^ in the critical reaches above Route 301



 Bridge v/here there is substantial algal growth.  From Indian Head to



 Smith Point, the area of pronounced algal growth, there was over 0.4



 mg/1 of inorganic phosphorus in the waters even under maximum bloom



 conditions.  These data indicate that in the upper and middle reaches



 of the Potomac, phosphorus is in excess of 0.30 mg/1 as PO^ and thus



 not rate limiting.  In the lower reach around Piney Point, the inorganic



 phosphorus was often as high as 0.1 mg/1 and thus phosphorus could be



 limiting for this reach.



     When the NH3 and N02 + NO^ concentrations shown in Figures V-11



 and V-12 are reviewed, it is evident that in the later summer months



 practically all of the inorganic nitrogen had disappeared in the reach



between the Smith Point and Route 301 Bridge stations by late July 1969



and by mid-August 1970.  This depletion occurred even though the summers



 of 1969 and 1970 had relatively high flows.   Based upon the disappearance



of inorganic nitrogen, it appears that nitrogen becomes the major factor



 in limiting algal growth in the middle reach of the estuary.

-------
                                                                VII-12


     To determine if carbon was limiting algal growth in the bloom

area of the Potomac, total and organic carbon analyses were made during

September 1970.  (Flows during August and September 1970 were low with

air temperatures reaching 95°F during the last week of September.)

Dense algal blooms extended from Hains Point to Smith Point.  Carbon

concentrations obtained during a sampling cruise on September 20, 1970,

were as follows:

Station                  Organic Carbon       Inorganic Carbon
                             (mg/1)                (mg/D

Hains Point                    7.2                  12.2

Wilson Bridge                 10.5                  15.4

Piscataway                    10.5                   8.6

Indian Head                   10.5                  15.0

Smith Point                    8.5                   7.7

Route 301 Bridge               6.1                   6.1

The above data, which were obtained during the mid-day hours of

September 20, 1970, indicate that there were large quantities of

inorganic carbon available for algal growth.  As reported earlier,

with the free carbon dioxide in the water ranging between 6.0 and

10.0 at the point of maximum growth (Indian Head), it appears that

there is an excess of inorganic carbon available for algal growths.

     A review of nutrient data for the summer of 1965 yielded similar

results.  As can be seen in Figure VII-1, there was complete utilization

of nitrate nitrogen between March and August by biota in the Potomac

-------
                              NUTRIENT -CHLOROPHYLL  PROFILES
                                       POTOMAC ESTUARY
                                     MARCH — AUGUST ,   IB65
^   lOO-i
§}

    SO-
|J
                                                                     AUGUST  10. IM5
                                                                     MARCH 24.IVCS
                               40          6O           80
                                   MILES HLOW CHAIN MI06C
                                                                                   VII-I

-------
                                                                 VII-14






Estuary from River Mile 20 to 60.  The utilization of significant



quantities of inorganic carbon as indicated by alkalinity was also



observed.



     The basic difference between these sets of conditions was that



the freshwater inflow during June and July 1965 was considerably less



than in 1970.  The increase in freshwater inflow in 1970 was enough




to keep the Potomac high in nitrogen until late August and to maintain



a minimum of 5.0 mg/1 of carbon throughout the estuary.



     From the 1965 data, it can be concluded that:  (l) phosphorus is



excessive in the upper and middle reaches of the estuary with very low



concentrations in the lower reach, (2) inorganic nitrogen has the



largest decrease and virtually disappears, with the lower 60 miles of



the estuary almost void of nitrogen in August, (3) the significant



loss of total alkalinity (a measure of inorganic carbon) occurred in



approximately 15-20 miles of the middle portion of the estuary.  How-



ever, there was a residual of about 3.0 to 5.0 mg/1 of inorganic carbon,



and (4) based on the above, it appears that nitrogen in the middle reach



and possibly both nitrogen and phosphorus in the lower reach was con-



trolling the growth of algae.  All three nutrients are in excess in



the upper reach with light penetration being the limiting factor of



grovrth.



     The 1965 data also demonstrated that another source of inorganic



carbon to the Potomac Estuary is recruitment from the Chesapeake Bay.

-------
                                                                 VII-15





This source of inorganic carbon appears to be a very important part of



the entire carbon balance especially in the middle and lower portion



of the estuary.  In this area, which as previously indicated is more



eutrophic than comparable areas of the Chesapeake Bay, the control of



algae may be limited to management of nitrogen and phosphorus.

-------
                                                                 VII-16
3.  Bioassay Studies
     To determine further what nutrients were limiting algal growth in
the Potomac, bioassay tests as developed by Fitzgerald [28] [29: were
employed.  Tests for both phosphorus and nitrogen were conducted in
the Potomac from Plscataway Creek to Route 301 Bridge for the period
June through October 1970.
     Using the rate of ammonia absorption by algal growths, it is
possible to determine if the algal cells have surplus nitrogen or if
they are nitrogen starved.  Tests made during June and early July
indicate that ammonia was either released or absorbed at a low rate
in the range of 10~° mg N/hr/ug chlorophyll a.  The cells had adequate
nitrogen available for growth as was also indicated by the high nitrate
concentration in the water, especially at the upper stations above
Indian Head.
     Bioassay tests for October 13, 1970, as tabulated below, show a
significant increase in ammonia absorption rates between the Piscataway
station and the Smith Point station farther downstream,
                            Table VII-3
                     NITROGEN BIOASSAY SUMMARY
                          Potomac Estuary
                                1970
                    NH3           NOp + N03             Anmonia
Station          .InJ.Yater         lil_i''!§.ter _        Nitrogen Absorbed
                  (r'g/l)           U'g/1)         (rug N/hr/ug chloro)
Piscatawav        .110            2.560               + i,.0 :'. 10 5
Indian Head       .150             .084               + 6.0 x 10~5
Possum Po-Int      .001             .220               + 2.3 x 10~4
Smith Point       .001             .150               + 1.3 x 10"^

-------
                                                                 VII-17





The higher rates of ammonia absorption for Possum and Smith Points and



the low concentration of inorganic nitrogen indicate that this reach



of the Potomac is becoming nitrogen limited.



     Two tests, an extraction and an enzymatic analysis [29], were



used to determine if algal growth was phosphorus limited.  The phos-



phorus extraction bioassay studies indicated very little difference



between amounts of phosphorus released at the upstream and downstream



stations.  Tests for alkaline phosphatase, an enzyme indicator of



phosphorus starved algal cells, were all negative.  These two tests



also confirmed the observation, discussed in the previous section,



that the phosphorus content in the upper and middle estuary was



excessive (over 0.15 mg/1 as P).

-------
                                                                 VII-18


4.  Nutrient and Algal Modeling

     Recognizing the possibility that the Potomac becomes nitrogen

starved in late summer, an attempt was made to surrogately mathe-

matically model algal growth based on the nitrogen cycle.  The model,

similar to that proposed by Thomann et §JL [30] is a feedback system

as shown below:

                                                     Organic Nitrogen
                                                     Expressed as
V/astewater NH3     Kn^ -^   NOj + N03     Kng \       Chlorophyll a
           t
                                                      To the sediments

This system was incorporated into the dynamic estuary model [41] and

was utilized to establish the first-order rates for the feedback system

for summer conditions.  The established rates (base e) are:

Kinetic Reaction               Rates

     Kni                     .30 - .40           (per day)

     Kno                     .07 ~ .09           (per day)

     Kn3                     .01 - .05           (per day)

     Kn^                 (not established)       (per day)

The first two reactions including the rates Kn]_ and Kn2 have been

fairly well verified as reported earlier and as shown in the pre-

dicted profiles of NH3 and N02 + N03 in Figures V-15 and V-16.  The

feedback link appears to play a minor part in the system during the

earlier summer months.

-------
                                                                 VII-19






     Predicted profiles using the surrogate algal model, as shown in




Figures VII--2 and VII-3, matched the observed data quite closely with




respect to location of maximum concentration and general shape of the




profile.  Other model predictions and a complete description of the




model are also currently being prepared by CTSL.




     From these mathematical model runs, it appears that the standing




crop of the blue-green alga can be predicted using the nitrogen cycle.




This further supports the premise that the availability of nitrogen




appears to be controlling the standing crop of algae.




     Using the model and the August 19-23, 1963, data as shown in




Figure VII-2, the reduction of chlorophyll a. concentrations to 25 ug/1




would result In a maximum N02 + N03 concentration of 0.25 mg/1.  For




the September 6-9, 1966, data as shown in Figure VII-3, an upper




limit of 0.38 mg/1 of nitrogen would be required to reduce the chloro-




phyll level to 25.0 ug/1.  From the modeling analysis, it appears that




if the inorganic nitrogen is between 0.2 and 0.4 mg/1 the blooms can




be held below the maximum level of 25 ug/1 of chlorophyll a..

-------
o
O  Z>  <5



o  ft  8
   Old  I
      0>
* I



I1
Q
           i
           o
           in
                        i

                        8
i
o
m
                                                    LJ

                                                    o
                                                    z


                                                    I
                                                    o
                                                  8
                                                    I
                                                 u. O
                         0 -HAHdOHCriHO
                                                 FIGURE  VII -2

-------
o
8
  u
    (O
!§!
O o-
ac
Q
                       8
                      (\/*r1)
                                 I
                                 S
                                           •8
                                             z
                                             $
                                             o
                                           -o
                                          — m
                                          o
                                        FIGURE VII-3

-------
                                                                VII-22






5.  Comparison With a Less-Stressed Estuary



     To investigate further the nutrient requirements for algal growth,



seven sampling cruises of the upper 30 miles of the Rappahannock



Estuary were made in 19VO.  As shown in Table VII-4, the estuary con-



tains relatively high concentrations of both organic and inorganic



carbon with low nitrates and inorganic phosphates.  This is due in part




to an industrial discharge which is low in nitrogen and phosphorus but



high in organic carbon.  The data suggest that if inorganic phosphate



is approximately 0.1 to 0.2 mg/1 and NO? + N03 between 0.1 to 0.3 mg/1,



the standing crop of algae will be minimal with a chlorophyll a. concen-



tration of less than 40.0 ug/1.

-------
                                    Table VII-4
                                    SUMMARY DATA
                             Upper Rappahannock Estuary

Date
^-23
::-30
7 -07
7-13*
7-°l
7-29
3~?8

Inorganic
P as P04
(mg/1)
0.13
0.18
0.10
0.33
0.15
0.22
0.14

N02 + N03
(mg/1)
0.26
0.12
0.11
0.64
0.27
0.39
0.21
1970
Chloro a
(ug/1)
32
34
40
8
70
17
39

Organic
Carbon
(rag/1)
7.3
No Data
No Data
7.8
5.0
9.7
17.9

Inorganic
Carbon
(mg/1)
No Data
No Data
No Data
No Data
5.0
4.8
No Data
* High river discharge

-------
                                                                 VII-24
6•  Review of Historical Nutrient and Ecological Trends in the Potomac
    Estuary
     As reported in Chapter V, there appears to be a definite relation-
ship between the ecological and nutrient enrichment trends in the upper
Potomac (Figure V-20).  Prior to the 1920's, the phosphorus loading was
1,100 Ibs/day or 4 percent of today's loading.  Similarly, the nitrogen
loading was 6,400 Ibs/day or 10 percent of today's wastewater contri-
bution.
     The concentration in the upper estuary under summer conditions for
the period before 1920 was estimated to be 0.12 to 0.20 mg/1 of PO^
with inorganic nitrogen ranging from 0.15 to 0.30 mg/1.  With a reversion
to these concentrations, not only should there be a significant reduction
in the blue-green algal population, but there should also be a general
reversal in the ecological community succession.

-------
                                                                VII-25



C.  CONTROLLABILITY OF VARIOUS NUTRIENTS



     As discussed previously, the three major sources of nutrients in



the upper estuary are 	 (l) wastewater discharges, (2) the upper



basin, and (3) Washington urban and suburban drainage.



     For the 7 months during which algal growths are most prolific



and affected by changes in nutrient contributions, the percentages of



phosphorus, nitrogen, and carbon attributable to wastewater discharges



are listed below:
Month
April
May
June
July
August
September
October
Mean
Monthly
Flow
(cfs)
20,000
14,500
8,700
5,500
6,000
4,700
6,300
Percentage
Phosphorus
60
67
76
83
82
84
81
Currently from Wastewater
Nitrogen
26
36
50
63
61
66
59
Discharges
Carbon
17
20
26
33
31
35
29
From the above tabulations, it can readily be seen that not only can



phosphorus be controlled by removal to the highest degree (percentage



removal) at the wastewater treatment facility, but phosphorus can be



controlled earliest in the growing season.  These two aspects enhance



the feasibility of phosphorus management.



     While 82 to 96 percent of the phosphorus entering the upper estuary



can be controlled by removal at the wastewater treatment facilities



during median to low flows [52],  an additional reduction of phosphorus

-------
                                                                VII-26






concentration occurs during periods of high runoff within the upper



estuary itself.  As reported by Aalto ei §1 [8], large quantities of



phosphorus (over 100,000 Its/day) enter the upper estuary during high-



flow periods at concentrations over 0.5 mg/1 (1.5 mg/1 as PO^) during



the rising portion of the river discharge hydrograph.  However, high



silt concentrations also accompany high flows.  Large amounts of phos-



phorus are sorbed upon the silt particles and removed from the water



system as sedimentation occurs in the upper reach of the estuary.



     Although there was some dilution of high phosphorus concentrations,



the large sediment load reduced the overall phosphorus concentration by



a minimum of 20 percent in the reaches upstream and downstream from the



major wastewater sources [52].  This reduction during periods of high



flow would tend to add to the controllability of phosphorus as tabulated



earlier.  The high percentage from wastewater discharges, especially



during the early months of the algal growing season and the large losses



to the sediments during high-flow periods made phosphorus an ideal



nutrient to manage.



     The tabulation also indicates that over 60 percent of the nitrogen



originates in the wastewater discharges during the critical months of



July through October.  The previous table does not include nitrogen



recruitment from the atmosphere or by either bacterial or algal fixation.



Hutchinson [31] reported that about 5 Ibs/acre/year of nitrogen is



drawn from the atmosphere.  Using this rate for the upper 60 miles of

-------
                                                                VII-?,'


the Potomac Estuary, about 1,600 Ibs/day of nitrogen is obtained front

the atmosphere as compared to over 50,000 Ibs/day from v/astewater dis-

charges.  Thus it can be concluded that nitrogen fixation is a minor

source of nitrogen in the Potomac Estuary.  Extension of recent data

from studies at the University of Wisconsin F53] indicate that approxi-

mately 5,000 Ibs/day of nitrogen could be fixed by blue--green algae in

the upper and middle reaches of the Potomac Estuary.  Nevertheless,

compared to all other sources, the contribution from the atmosphere

including that by nitrogen fixing algae appears to be insignificant.

Thus, during the summer months, algal control by management of nitrogen

appears to be a feasible alternative to phosphorus control.

     Also in the above tabulation, the maximum percentage of carbon

from Y/astewater is 35 percent.  Other major sources not included in

this figure are from the atmosphere, bacterial action in -rater, and

bacterial action in the sediments.  The quantity of carbon (002)

exchanged at the air-water interface is a function of the transfer

rates, concentration of C02 in the air, pH of water, and the alkalinity

of the water.  For the Potomac, the maximum potential (Xb transfer from

the atmosphere is approximately 3,500,000,000 Ibs/day*.  This source

from the atmosphere alone ma'kes the possibility of effective carbon

control doubtful at the present time since only about 100,000 Ibs/day

of carbon is discharged in v/astev/ater with over 330,000 Ibs/day from

the upper basin.
  The CO? obtainable from the atmosphere was determined by using a
  transfer rate of 0.6 mg/cm2/min [32]  for an upper estuary surface
  area equal to 2.0 x 109 ft2.

-------
                                                                VII-28






     Another aspect of nutrient management is the transport and/or



deposit of the various nutrients along the longitudinal profile of



the estuary.  Because of the great solubility in water, inorganic



nitrogen and carbon are easily transported through the estuary



especially during high-flow periods in the winter and spring months.



     The large quantities of phosphorus and organic carbon which



originate in wastewater discharges do not move as easily through the



estuary.  Large quantities of phosphorus and organic carbon are lost



to sediments.  Analysis of the sediment confirms the deposit of both



carbon and phosphorus (Figure VII-4).



     A review of the management requirements for the estuarine reaches



was made to determine if management of any single nutrient by waste-



water treatment processes can achieve the water quality standards.



For the lower and middle reaches, because of the large carbon supply



intrusion from the Chesapeake Bay, the management of nitrogen and



phosphorus appears to be a feasible approach.  Management of the



upper estuary is limited primarily to nitrogen and phosphorus control



except during periods of extremely low flow when it is anticipated



that the estuary will be used for a supplementary water supply.  When



the estuary is being so used, there will be little or no freshwater



inflov; thus the amount of inflow from the upper basin, especially



carbon, is insignificant.  Under these conditions, control of all



three nutrients in the wastewater treatment process is feasible.

-------
    80
    60-
 II
Po
    20-
                                    CARBON, TKN  &  PHOSPHORUS  IN SEDIMENTS

                                                   POTOMAC ESTUARY
                                                     AUGUST 18-20. WTO
    5.0-
    4.0-
    30-
 ^?
  z
  c
    IjO-
    1X1-
                10
                         ao
                                  30
                                            40       50        60

                                            MILES BELOW  CHAIN  BRIDGE
                                                                         70
80
          90
                   100
                                                                                                FTGURE VII-4

-------
                                                                VII-30




D.  NUTRIENT CRITERIA




     There are no existing nutrient criteria specified by either the




State of Maryland or the District of Columbia.  To control algal growth,




the State of Virginia has set nutrient objectives for nitrogen and




phosphorus of 1.0 and 0.2 mg/1 respectively in wastewater effluent.




Based upon the methodology reported in the previous section, the




following nutrient criteria were developed in Section VII-B with the




objective of reversal of eutrophication in the freshwater portions of




the Potomac Estuary:




              Parameter               Concentration Range




         Inorganic Nitrogen             0.30 -- 0.5 mg/1




         Total Phosphorus               0.03 - 0.1 nig/1




Since there was over 5.0 mg/1 of inorganic carbon in the estuary, even




under maximum bloom conditions, no criteria for carbon could be estab-




lished at the present time.




     The lower values in these ranges are to be applied to the fresh-




v;ater portion of  Zone  III  and to the embayment portions of the estuary




in whicn the environmental conditions are more favorable toward algal




growth.  The upper ranges of the criteria are more applicable to




Zone I of the Potomac Estuary which has a light-limited euphotic zone




of: usually less than 2 feet.




     Studies of the Potomac Estuary showed a relatively sharp transition




from freshwater to a typical mesohaline environment as indicated by the




rapid increase in salinity.  At the upper end of the 22-mile reach at




Laryland Point, there are primarily freshwater phytoplankton and zoo-




plankton populations.  Above Maryland Point, the salinities are less

-------
                                                                VII-31






than two parts per thousand.  At low flows, marine forms dominate the



lower end of the transition zone at the Route 301 Bridge with salinities



in summer approximating 12 parts per thousand.



     Based on the past 5 years of field studies, it appears that the



growth of massive blue-green algal mats are apparently restricted to the



freshwater portions.  In the mesohaline environment, dinoflagellates




were often encountered in "red tide" proportions.



     These observations lead to tuo points of emphasis in estuarine




water quality management:



     (l)  Fairly discrete biotic provinces may be identified within a



given reach of the estuary, responding differently to a given stress.



     (2)  There is insufficient evidence to date to generalize on



nutrient parameters and hypertrophic conditions in all portions of s



given estuary.



Therefore, at the present time, no specific nutrient criteria have been



established for the mesohaline portion of the Potomac Estuary.



     These criteria, along with a high degree of carbon removal for



enhancement of dissolved oxygen would not only lead to a reversal of



nutrient buildup in the estuary but also creation of an environment



conducive to reversal of the aquatic plant succession that has occurred



in the Potomac.   This reversal has occurred in the lakes surrounding



L'iadison, Wisconsin [17] and Lake Washington [16] when wastewater dis-



charges . ere diverted from the lakes.

-------
                                                                 VII-32





     The criteria shown above give maximum concentrations for both




nitrogen and phosphorus.  Limits for both were incorporated for the




following reasons:




     (l)  Since the flow of the Potomac River is very flashy, neither




phosphorus nor nitrogen can be controlled throughout the estuary at




all times.  To reduce eutrophication in the entire estuary for years




having average or above average flow conditions, phosphorus control




appears to be more feasible.  However, in the middle and upper estuary




during low-flow years, nitrogen control appears to be more effective.




This is because the nitrogen criterion for restricting algal growth




is 10 times that for phosphorus (0.30 versus 0.03 mg/l) while the




nitrogen loading from the wastewater treatment facilities is 2.4 times




that of phosphorus (60,000 versus 2/4,000 Ibs/day).  Considering only the




magnitude of the limiting nutrient concentrations and the magnitude of




the percentage of the wastewater contribution, this results in more than




a fourfold advantage in removing nitrogen over that of phosphorus.




     (2)  Various investigators report that increases in nitrogen and/or




phosphorus can increase heterotrophic activity which in turn stimulates




algal growth, and




     (3)  There is compatibility between wastewater treatment require-




ments for dissolved oxygen enhancement and eutrophication control.




     Compatibility of treatment requirements is probably one of the




most important considerations of the four factors influencing the




selection of wastewater treatment unit processes.  For example, to




maintain the dissolved oxygen standard in the upper estuary under




summer conditions, a high degree of carbonaceous and nitrogenous

-------
                                                                 VII-33






oxygen demand removal is required, whereas the control of algal standing



crops is predicated on phosphorus and nitrogen removal.  To obtain a



high degree of carbonaceous oxygen demand removal, a chemical coagulation



unit process is usually required beyond secondary treatment.  This unit



process will also remove a high percentage of phosphorus.   The removal



of the nitrogenous demand can be satisfied by one of two methods:



(1) by converting the unoxidized nitrogen to nitrates (commonly called



nitrification), or (2) by removal of nitrogen completely.   If a unit



process such as biological nitrification-denitrification is employed,



both the DO and algal requirements for nitrogen can be met.




     Thus v/ith proper selection of wastewater treatment unit processes,



it is feasible not only to enhance the DO by removing the carbonaceous



and nitrogenous UOD but also to reduce nuisance algal growth by removing



nutrients.

-------
                                                                VIII-1

                            CHAPTER VIII

   CONTROL CONSIDERATIONS FOR BACTERIAL DENSITIES, VIRUSES, HEAVY
             METALS, AND OTHER WATER QUALITY PARAMETERS

A.  BACTERIAL DENSITIES

1.  Indicator Organisms

     Four bacterial organisms have been used as indicators of the

sanitary water quality of the Potomac.  These four are:

     (1)  Total coliform,

     (2)  Fecal coliform,

     (3)  Fecal streptococci, and

     (4)  Salmonella.

In a 1969 report entitled "Sanitary Bacteriology of the Upper Potomac

Estuary" by Lear and Jaworski [33], the folloi;7ing conclusions were

reached:

     (l)  High total coliform, fecal coliform, and fecal streptococci

densities were found in the Washington metropolitan area,

     (2)  Fecal coliform/fecal streptococci ratios indicated that most of

the bacterial pollution in the upper estuary vras probably of human origin,

     (3)  A potential health hazard existed in the Washington area in

that salmonella organisms were readily and regularly isolated in waters

of the estuary, and

     (4)  In general, greater incidence of salmonella recovery occurred

in 'vaters having high total and/or fecal coliform densities.

Data collected during 1969 [34]  also reflected the earlier findings

including the salmonella isolations.

-------
                                                                 VIII-2






     As reported earlier, all discharges from wastewater facilities in



the upper estuary were being chlorinated as of September 1969.  This has



dramatically reduced fecal coliform densities near the v/astewater outfalls,



However, overflows from overloaded sanitary and combined sewers still



cause high fecal coliform densities as was shown in Figure V-2.  These



high densities are a result of overflov/s of untreated wastewater



entering the estuary near the confluence with Rock Creelc.



     The complete control of bacterial densities in the upper estuary



cannot be realized until both continuous chlorination of wastev/ater



effluent is maintained and sanitary, combined and storm sewer over-



flov/s are reduced or eliminated.  While the storm sewers increase



bacterial indicator densities in the estuary significantly, the



increased flows tend to reduce their populations by dilution and to



disperse them downstream.  Apparently, the more persistent bacterial



problems result from overflov/s of the combined sevrer system, especially



during the summer recreation period.  This becomes increasingly serious



./hen the estuary is considered as a public water supply source.

-------
                                                                VIII-3


2.  Bacterial Standards

     The bacterial water quality standards for the upper estuary are

as given below:

     Jurisdiction            Total Coliform       Fecal Coliform

     Virginia                2400 MPN/100 ml       200 MPN/100 ml
                             (monthly avg.)       (30-day log mean)

     Maryland                                      240 MPN/100 ml
                                                  (by survey)

     District of Columbia                         1000 MPN/100 nil
                                                  (geometric  mean)

For the shellfish producing area of the Potomac,  a total coliform

density of 70 MPN/100 ml is used by both the States of Maryland and

Virginia.

-------
                                                                 VIII-4



B.  VIRUSES



     The role of water as a vector in the dissemination of viruses is



not well understood.  However, enteric viruses are present in sewage



effluents and can find their ways into public water supplies [35].



     In the Potomac Estuary, the problem of viruses and associated



health hazards has three aspects that must be considered:  (l) the



lower portion of the estuary is a prime shellfish area, (2) the entire



estuary is an ideal recreational use area, and (3) the upper estuary



has been proposed as a public water supply source.  While no epidemio-



logical evidence exists relating waste discharges to the first two



aspects presented, a potential hazard does exist at present and will



probably become greater as the population increases.



     The viral problem will be of major concern if the estuary is to



be used as a water supply source.  Since both wastewater effluents and



overflows from storm, sanitary, and combined sewers contain viruses and



do enter the estuary, the need to determine the threat to public health



remains.



     To evaluate this health hazard, a three-phase investigation is



required to determine:




     (l)  The existing virus population along the longitudinal dimension



of the estuary,



     (2)  The role of v/astewater treatment facilities in removing viral



particles, and



     (3)  The effectiveness of water treatment processes in removing



viruses.

-------
                                                                VIII-5




Studies regarding the viral removal effectiveness of wastewater and


water supply treatment processes have been undertaken by fWQA's


Advanced Waste Treatment Research Laboratory in Cincinnati, Ohio


and by the U. S. Army Corps of Engineers,"respectively.  The RVQA


studies include an  investigation of the erTect of advanced waste


treatment processes on viruses.  While a  complete review is beyond


the scope of this report, virus data on v/astewater as reported by


Berg [35] indicates that AWT units are approximately 90 percent


effective in removing viruses.  An evaluation of virus hazards by


the American Society of Civil Engineers indicated that chlorination


without reaching free chlorine residual will not insure virus free


effluents [36],


     As one aspect of the cooperative study with FWQA on the feasi-


bility of the estuary as a supplemental water supply, the U. S. Army


Corps of Engineers investigated the effectiveness of water supply
                                          *

treatment processes on virus removal.  The study dealt primarily
                                          V

with the effectiveness of chlorination in deactivating various types


of human enteric viruses.


     A joint investigation by FWQA's Chesapeake Technical Support


Laboratory and the Cincinnati Advanced Waste Treatment Research


Laboratory to determine existing viral populations in the estuary was


undertaken.   Preliminary results from the first set of samples taken

-------
                                                                VIII-6




during the low-flow period of September 1970 for the stations presented


below were negative.


Number                        Station Location


  I              Great Falls at Current Water Intake


 II              Below Chain Bridge Near Site of Proposed Intake


III              Near Woodrow Wilson Bridge Below Blue Plains


This study is being continued and will be repeated under various


temperature and flow conditions.


     There are no water quality standards for viruses at present.  Use


of various indicator organisms such as coliforms have been suggested


with the Bacillus subtilis spore [37] very promising as an indicator of


virus disinfection.


     A committee report for the American Water Works Association [38]


summarized their study findings by stating:  "There is no doubt that


water can be treated so that it is always free from infectious micro-


organisms—it will be biologically safe.  Adequate treatment means


clarification (coagulation, sedimentation, and filtration), followed


by effective disinfection."  They further concluded that there is
                                         i»,

considerable room for research, both laboratory and epidemologic, to


determine if there is a problem in virus disease transmission by water.

-------
                                                                 VIII-7


C.  HEAVY METALS


     A cooperative program with the laboratory at the U. S. Naval


Ordnance Station in Indian Head, Maryland, to determine periodically


the heavy metal occurrence in the Potomac Estuary waters and sedi-


ments was initiated during the summer of 1970.  While only small
                                          i

concentrations of zinc and manganese v/ere.detected in the overlying


waters of the estuary, considerable amounts of various heavy metals


"by acid extraction from the sediments were recorded.


     From the sediment analysis (Table VIII-l), it can be seen that


there are significant increases of lead, cobalt, chromium, cadmium,


copper, nickel, zinc, silver, and barium in the upper estuary near


the Woodrow Wilson Bridge.  Since concentrations of metal are


greatest near the sewage outfalls where other components of waste-


water such as phosphorus and carbon are also highly concentrated,


it can be concluded that the heavy metals originate in the waste-


water discharges.  Some accumulations such as cadmium could also be


from urban and suburban runoff.


     The effect of these heavy metal accumulations on the ecology of


the estuary is indeterminate.  Since the lower estuary is a prime


shellfish production area, a study of the possible availability and


effects of the apparently small but continuous discharges of heavy


metals on the water quality and biota should be undertaken.  With


wastewater loadings projected to increase over fourfold and with


increases in the number of  discharge points farther down the estuary,


this heavy metal accumulation could develop into a serious water quality


management problem.

-------
                                                                VIII-8



     Heavy metals in the sediments must also be considered in the



disposal of dredged spoil.  Dredging operations involving deepening



and widening of the channels near Washington, construction of piers



and marinas, etc. disturb the sediments and require disposal of the



dredged spoil.  These activities should also be monitored especially



where there are known high concentrations of potentially toxic metals



in the sediments.

-------
      o
      OJ
      (D

      ra
EH    ^

*!

|p S^
ft
ft


N ft

W %

ft


O ft
ft

O ft
ft

o §
O ft
ft


O ft
ft

& ft






0
H
£-(

u





CM
SO
ON
O
0

-4-
LA
O
O
H
SO
O

%
-<
CO
ON
-4-
01
I-
s
ro
SO
LA

LA
-4-
ON
OJ
H
CO
OO
-4-

LA
ON
3
O
ON
H
OJ
so
ON
ON

o
01
o

IA
ON
ro
oo










V
9
•H

£
-» SO
ON -4-
H
OO b-
-* ON
ro oo
H rH
O CO
CO OO
SO CM
CTs O
rH
rH CO
LA LA
rH H
-4- OJ
H H

(^ -3"
t— CO
CM 01
OO b-
ON ON
CM LA
LA CM
S? S
% $
CO CO

ON UN
o-l -4-
O -4-
OJ OJ
CO ON
OO OO
H -4-
rH 00
-4- eg
t— CO

-4" OO
CO ON
ON ro
OJ ro
CO OO
CO ON
CM 00
rH SO
ON ON
t— ON
rH H
o

d O

£ 8
ON H
-* SO




o
0
H
LA
so
H
so
oo
3
co
t—
rH
CM
OO

ON
oo
r-
oo
t-
"
CM
SO
-4-
0
rH
CM
ON
SO
OJ
ON
ro
O
O
.4-
rH
SO
CO
t—
c-
co
LA
-4-
oo
ON
OO
OJ


d

§8
ON











(U
£
•d


O ON
CO CM
LA LA
-4- OO
CO OO
rH rH
CO CVI
CM
CO OO
Oj co
CO 00
$ 21
CM O
00 01

ON ON
OO CM
t*- OO
ON -4-
ON so
IV- 0
H LA
-4- -4-
ON SO
ro O

CM LA
CM OJ
ON CO
b- ON
-4- H
LA rH
LA OO
-4- t—
so -=t
rH H
OJ ON
CO -4-
OO LA
SO -4-
SO ON
CO SO
ON t—
-4- CM
LA O
ON CO
ON t—
rH rH


a a*

SO CM
CO SO
H ro
LA ro





CD
D

Q

>, V
oj D
§ rj
OS V
o rd

pj Q
SO CO
rH 21
ON b-
ON -4-
O ON
H O
CM SO
CM r-H
so op
CO CO
SO CM
ON S-
SO CM
ro oo

t— oo
ON -4-
CM CM
O ON
° ^
LA O
S S
CM O
8 ON
CO
J- -4-

CO OO
ON ON
rH 00
CM CM
0 0
oj1 %
SO -=f
oo O
LA CO
OO LA
rH rH
SO t—
ON CO
3 S
t- CM
ON ON
LA LA
01 01
& *
LA OO
H H


cj cs

SO ON
LA LA
OO OO





.p
£*
•H
O


1 |

« H
ON OO
LA CO
i-l CM
H t-
H r-l
0 .4-
00 H
00 [-
OO O
H
OO LA
LA SO
CO ^t
CM OI

oo co
t— SO
SO CO
ro ro
SO -4-
® ^
»- OI
* ON
SO so
OO ON
ON -4"
ro ON
r-H
-4- b-
co b-
LA b-
OI OJ
ON CO
ro b-
01 CM
I- O
ON ON
O oo
b- LA
rH OJ
H H
b- so
b- I—
-4- ^t
cS tt
LA rH
OJ 00
O\ LA
CO CO
t— t—
rH H


CJ> d>

fL fi
LA LA
OO CO








+3
C -P
•H a
PH O
01 rg
§f4
gj
SO O
t- o
CM H
so so
rH H
CO ON
rH rH
SO SO
CO SO
CO LA
H rH
CM OI
CO rH
H CM

LA t—
O CM
-4- -4-
ON CO
ON SO
3 rl
oj as
GO CO
3> ^
H

b- CO
01 OJ
O H
SO ON
00 OJ
SO rH
LA O
01 SO
CM O
OO CM
LA H
ON -4-
t— O
ro LA
SO CO
CT\ O
ON ON
CM OJ
b- ON
ON OO
ON ON
rH H


a> en

LA SO
ON sS
LA CM
CO -4^






-p
d
•H
-P O

•rH
O 13

1 I
LA ^*
CO O
rH rH
ro ON
LA b-
rH 0
CO O
H
SO O
CM H
b- 0
CO LA
0 -*
H rH

LA CTs
00 ON
r-H CO
oo O
H O
ON LA
CO rH
H
LA SO
H so
rH CM
CO O
-4- 01
O C^
r? ON

H ON
-4- -4-
CO SO
r-H
ON O
H -4-
OJ
J- CO
SO -4-
SO O
b- rH

ro ON
co ON
LA b-
OO
O ON
ON ON
rH LA
OJ
& $
oo oo
H


a> a

IA ON
CO ON
H b-
ro
9)
CO -H
H K


CO
co
ON
rH





V
^

OH

O
O
to
•H
ft

S3
SO SO
CO H
SO O
00 ON
OO b—
H 0
-4- O
CM H
CO
H -4-
CM -4-
SO OO
rH

^ C^

ON rH
O b~
oo O
co co
b- ON
rH H
CM
CM CO
0 -4-
LA O
S-4-
OI
CO O
-4- -4-
OI

H CO
CO -4-
CO LA
r-H
b- O
LA -4-
OI
SO H
00 -4-
& *-

ON O
LA ON
ON t—
OO
^t 00
CO ON
LA LA
H
O OO
ON ON
ON LA



o> a>

o
CO
ON O
rH








Ij
a -p
•H El
^ 1

S £
                                                                                                                                                                    g«
                                                                                                                                                                    S  5
                                                                                                                                                                    •P   O
                                                                                                                                                                    O   ru
                                                                                                                                                                    d)  +5
                                                                                                                                                                    +3   U)
                                                                                                                                                                    0)  rd
                                                                                                                                                                    •d   fl
                                                                                                                                                                    
-------
                                                                VIII-10



D.  OTHER WATER QUALITY INDICATORS



     Other water quality parameters are temperature, color, odor,  taste,



total dissolved solids, carbon chloroform.extractions, pesticides, and



herbicides.




1.  Thermal



     The most pronounced effect of thermal discharges on elevation of



ambient water temperature can be found in the reach of the Potomac between



Hains Point and Woodrow Wilson Bridge and in the Anacostia River near the



Benning and East Capitol Street Bridges.  Of these two areas, the rise in



the Anacostia is the greatest with a 5-degree rise occurring above the



ambient water temperature, reaching a high of 33°C.



     Since the two areas periodically contain low dissolved oxygen



concentrations, the effect of the elevated temperature is difficult to



assess.  Future thermal control may be required to provide a more



favorable environment for aquatic life and to enhance dissolved oxygen



when the wastewater plants are upgraded and the overflows from combined



sewers are eliminated.



2.  Carbon Chloroform Extraction



     Using carbon chloroform extraction (CCE) as an indicator of



potentially toxic organic materials, it can be seen in Figure VIII-1



that there is a significant increase in the waters between Great Falls




and Memorial Bridge upstream from the combined sewer overflow discharges.



At times, the relative increase is high, approximately 400 ug/1 or 0.4 mg/1,



twice the recommended standard for CCE.

-------
FIGURE  VIII-I

-------
                                                               VIII-12




     If the estuary is to be used for a water supply, a more detailed



analysis of CCE should be undertaken.  A study of the effects of water



supply withdrawals on CCE should also be initiated.



3.  Chlorides and Total Dissolved Solids



     Of the remaining parameters, increases in total dissolved solids



and chlorides are major considerations in the use of the estuary as



a water supply.  The concentrations of total dissolved solids and



chlorides at the proposed intake are functions of concentrations in



the freshwater flow, location of the salt wedge, and total increase



of each parameter resulting from water treatment, domestic use, and



waste treatment.  Water quality simulations for both parameters were



made using the FWQA Dynamic Estuary Mathematical Model.



     To demonstrate the model's capability to simulate changing salinity



conditions in the estuary, a test condition was selected for which suf-



ficient data were available to establish the salinity gradient through



the system at two different points in time.  An historic period (July



through December 1965) was selected for which flow conditions in the



prototype were relatively uniform throughout the period.  The mean



Potomac River flow over Great Falls remained near 1300 cfs with the



mean monthly flows varying between 1018 and 1586 cfs during this period.



     Chloride and salinity data were available to establish the salt



wedge position in the main stem of the Potomac near the start of this



period (July 7-8, 1965) and near the end (December 1-2, 1965).  These



data were utilized to establish visually the "best fit" profiles for



these tv/o points in time as illustrated in Figure VIII-2.

-------
                                                                VIII-13





     The profile for July 7-8, 1965, was specified as the initial



profile in the model.  For the simulation, the network extended to



Piney Point near River Mile 96.  The specified chloride concentration



at the seaward boundary was changed during the simulation in corres-



pondence to the change noted in the prototype during the same period,



i.e., the concentration was increased from 8400 mg/1 to 10930 mg/1 in



small steps (increased 55 mg/1 every 3 days).  A uniform flow of 1300



cfs in the Potomac River was maintained throughout the simulation.



     The chloride profile predicted by the mathematical model after the



147 day simulation period is also illustrated in Figure VIII-2 along



with that measured in the estuary.  The predicted and observed profiles,



which overlap, indicate that the model can accurately simulate the



intrusion of chloride from the Chesapeake Bay.



     The simulation was completed utilizing a dispersion coefficient



ranging from approximately 0.5 square miles per day (175 square feet



per second) in the upper 55 miles of the estuary, 5.0 square miles



per day (1600 ft2/sec) in the next 15 miles, and 12.5 mi2/day (4000



ft^/sec) in the lower 26 miles of the estuary.  These coefficients are



of the order of magnitude suggested by Harleman [49]  for the freshwater



and salinity incursion zones, respectively, of estuary.   These coeffici-



ents were utilized for the chloride and TDS simulations  presented later



in this report.

-------
                  CHLORIDE  CONCENTRATION
                           POTOMAC  ESTUARY
'2
O
UJ
* >
"Z
o
o
Id
o
3
X
u
    11000
    10000
    9000
    3000
    7000
     6000
5000
•4000
     3000
    2000
     1000
               LEGEND
        •   CBI DATA. JULY 7-8.1965
        x   D.C. DATA. JULY 7-8. 1965
        a   CBI DATA. DEC. 1-2.1965
        o   CTSL DATA. DEC. 1-2,1965
      	 PROTOTYPE
      	 MODEL
               DEC. 1-2. 1965 PROFILE
             10
                                             INITIAL PROFILE  JULY 7-8. 1965
                                                   (ALSO MODEL)
                    30   40    50    60    70
                      MILES BELOW  CHAIN BRIDGE
80
90
100
                                                        FIGURE  VIII-2

-------
                                                               VIII-15






4.  Pesticides and Herbicides



     Samples taken from six points in the Potomac Estuary were analyzed



for 12 hydrocarbon pesticides in August 1969.  None of these compounds



were found at detectable concentrations in the samples nor in a 24-hour



composite sample taken from the Blue Plains Sewage Treatment Plant



effluent [341.  Since there is considerable agricultural use of pesti-



cides and herbicides within the Potomac River Basin at certain times



of the year, further EPA surveys to include those seasons of use are



indicated as well as a data search of investigations by other agencies.

-------
                                                                  IX-1




                              CHAPTER  IX




                POPULATION AND WASTEWATER PROJECTIONS



A.   POPULATION  PROJECTIONS



      To  facilitate the  determination  of wastewater loading rates and




water supply requirements for the entire Washington metropolitan area,



population projections  were developed for 13 service areas.  Deline-



ation of watersheds within each service area is presented in Table




IX-1.



      Population data for the  Virginia and Maryland portions of the



Washington metropolitan area  along with the District of Columbia are



shown in Figure IX-2 for the  three benchmarks investigated.  Summarized



below are the total population projections for the Washington metro-



politan  area:



                Year               Population



                1969               2,800,000



                1980               4,000,000



                2000               6,700,000



                2020               9,300,000



     Population projections for the benchmark years of 1980 and 2000



were  furnished by the Metropolitan Washington Council of Governments



(COG).   Control populations for these benchmarks were based on the



"low-estimate"  figures prepared for COG by Hammer, Green, Siler



Associates [39].  Distribution by individual service areas was essen-



tially determined from 1960-1968 population trends with consideration

-------
 o
•g
•a
 o

I
      I     I
              cd

      I    I
                          o
                          iH


                          g
                                    •a     «
                                     0)    -H
                                            O
                                           o
                                            o
                                           -H
                                            t.
      *
                              *
                                                            0    •o     o    -a
                                                           3131
                                                            &    &     &    &
                                                                               Jf
 I        I
 o,        P,
+>     o>           
 o
t-»
 (4

 m
•H
Q
                                                  1
                                                                        I

o
s
          MM>>MI-11-(M
          M    (H    M           >    W     M    M
                 M                        >     M    M

-------
                                                                  IX-3





given to land use potential and other attenuating factors.  A similar



methodology was employed by JWQA-'s Middle Atlantic Region economists



to develop population estimates for the year 2020 benchmark except that



the control figure was derived from a long-term relationship of national,



regional, and metropolitan area population trends.

-------
FIGURE  IX-1

-------
 10-
                         POPULATION  PROJECTIONS


                       WASHINGTON METROPOLITAN  AREA
        o
        ci
  9-
  8-
  7-
10


O
2



i-
O
Q.

O
  4-
  3-
  2-
  I-
          1968
                         1980
                                        2000
2020
                              BENCHMARK
                                                                 FIGURE  IX -2

-------
                                                                  IX-6






B.  WATER SUPPLY REQUIREMENTS



     Data pertaining to current water supply demands and per capita



usage were obtained from the major water suppliers in the metropolitan



area and served as a baseline for the water supply projections shown



in Table IX-2.  The total projected average yearly water requirements



for the three benchmarks are presented as follows:



                Year               Projected Usage



                1969,                   370 mgd



                1980                   556 mgd



                2000                  1009 mgd



                2020                  1568 mgd



V/ater supply requirements for shorter demand periods are delineated




in Table IX-3.



     The per capita water use was assumed to increase through the year



2020 at a rate of one gpcd/year.  Allowing for the maximum dependable



yield of other existing sources of water such as Occoquan and Goose



Creeks, it appears that all of the District of Columbia's water supply



and a major portion of the water supply for the metropolitan area within



Virginia and Maryland must be provided by a combination of the Potomac



River and the upper Potomac Estuary.  Of the total projected 2020 demand,



these latter sources are expected to supply approximately 1/400 mgd or



90 percent.  The Patuxent River currently supplies 42 mgd to the



Washington metropolitan area but will be unable to serve this area in



the future due to projected needs within the Patuxent Basin [40].

-------
&i
3!
0)
bp
3
I|S
0)
99
•H «o^
«J T?
S «> &
O| M +»•— .
OJ| 0) 01
PH *
g
•H 13
t^
CO
&.
0)
bo
oT
o) -o

H *-->
a
*
0)
•H m^_^
a) *5
QIC d a
Oj t) bo
cdl o> 01
&< >
I,
•p g
"3 oi
gl CO
PH
c
ni^
•g MM
&H 4^ ^— •*
«J
*
0)
5Sf
•H a
Ql «| trl
«lo ^ 5,
aj o bo
0) $^^
g^
+> f>
«H M
g.CO
01
a bo
•P 01
iH 03
3^?
v S
0) «"^

OS -ttt
vp o
^ CO
iH rH C3'-N
^ -p ^ *S>
+J O 4) B
to *
•H -a
II
P,


8
rt



O
OJ


§
irT

c\T cvT

8 8
O^ "^
ON CO
rH rH





0 0
H r-*

§o
o
**D
-*P Nf
5 5

8 8
r-l r-l


8 8
r-I to"
1-1

§ §
80
o
i—( TO
r-l
I 1

8
5







§
•s
*r\

oT

8



rH







0
,
^
^o
^0

8
•0
ir\








g
><•
OJ
8





8
o
r--

§
8
cu
1

-------
                             Table IX-3
                    VARIOUS WATER SUPPLY DEMANDS
                   Washington Metropolitan Area

     Duration            1980         2000         2020
                         (mgd)        (mgd)        (mgd)

Maximum Day              1,001        1,816        2,822

Maximum Five Day           950        1,730        2,680

Maximum Month              723        1,312        2,038

Maximum Two Months         712        1,292        2,007

Maximum Three Months       695        l,26l        1,960

Maximum Six Months         634        1,150        1,788

Yearly Average             556        1,009        1,568

-------
                                                                  IX-9
C.  WASTEWATER LOADINGS



     Utilizing the population projections discussed previously and the



current waste flows and loading rates for each existing treatment



facility as shown in Table IX-4, future wastewater trends were developed



for the 13 service areas comprising the Washington metropolitan area.



These data are presented in Tables IX-5, IX-6, and IX-7 for 1980, 2000,



and 2020 respectively.  It can be seen from these tables that the BOD,



nitrogen and phosphorus loadings before treatment are projected to



increase drastically.  The table below summarizes these loading condi-



tions :



                                      Before Treatment
1969        325



1980        473



2000        861



2020       1342



     Wastewater flows were adjusted upward to reflect the additional



per capita water usage.  Consumptive losses were maintained at approxi-



mately 14 percent.  In the case of Federal installations, waste flow



was computed by assuming a per capita contribution of 100 gpd.  The



per capita BOD load was also increased slightly in accordance with



historical loading trends while current per capita nitrogen and phos-



phorus loadings were held constant for each of the benchmark years.
BOD*;
(ibs/day)
483,500
823,500
1,463,500
2,195,000
TKN as N
(Ibs/day)
63,500
95,600
155,700
215,600
T. P as P
(Ibs/day)
27,300
43,100
70,300
97,400

-------


























>
a. o o
a-H^a
NJ-CQ
IH Q ,0
OJ ft rH
OH f-l-^
4) >j
-p co a
co a TJ
h •>!" CQ

Pi rX rH
0 & —
•P *-*
•r- 1 TJ t>J
& 8 •§
W
0) S rH
0^ CH • 	 *
T) '"^
"£ -8
n*^

S £-,_
a
P T>'->
PI o a
a 1-3 T3
o ^\
rW CT,S
OJ O rH
0, CQ^--
1 ^5
H O tO
S d
a *
•p 5
•H H
O 4) P.
-p HO
M CO ~~^r
oj a
OH s=
C
5
•H T3
•P 0)
a >
t3 OJ
& w
o
OH
11
CO
4) OT?
IH v5

<




>>
4?
•rl
rH
•H
O
rS


§
o


S
rH





OJ

O



O
^




o
OJ
o


8
rH
OJ




8




§
VO
O~
rH




0
8
rH








C
Pent ago

to
o


in

^p




o^
1^
0



8
to
Nf



-sf
rH
O


8
c*C




?




g
o
p-
OJ



o
o-
rH







g
1

O
o


«N
VO





in
0
0



0
•*




o
OJ
o


0
p-
c^




to




8
C'N
to
rH




VD
rH
OJ




O

«
Q
1
d
r.
IH
to

O
8
o


o






o
8
0



o





8
o


OJ





8
"



S
ITS
O





S
0




o
+9

a
1
a
z

8
o


0

^
VO



m
8
o



g
^
vo



o
OJ
0


8
£>
c^\
^



00




g
o
0
m
rH


§
rH

OJ


a
•H
_o
rH
O
o
fc
•p
Distric

rH
8
o


o

vo"




-^-
0
0



§
"\
>»•



o
OJ
o


g
CO




OJ




0
o
s
r-H



8
<-N
(TN
OJ







a
•H
rl
Alexand

p-OtOrHO(»\O(Hr-l
CJOjrHOJoJrAcvxajoj
OOOOOOOOC5
ooooooooo


O^ O *n rH iH C^\ O P* O*^ 1

C*S rH




inoto-^tOQvr^ooj
O O O f~^ O c~l O O O
ooooooooo



OOOCVTvOtfNU^iO
NtlTiOrHrHCViVO-^^O 1
rH VO I> ^ rH O
t^N rH



SrH T\OJM3MDOOO
ooooooooo


QOQ^OOCOQO
OOOOrHVD ** O O
U^O^OJrHi-COOrHiTx
rH VO rH ^ ->T rH r^v
rH



r*\vo QQQOOJr^c^
0s O O O O <*\ OJ VO c\l 1




go|S$oogg
-stOOJCovOoOvO -*4"
~^~ ir\ co if\ o c*\ co
OJ lA OJ OJ rH
rH



OOOvOc^OHOO
HmOOOr^OJOOJ
rH

1
M 0

§O M g
ft Q rH OJ O
H ^J- Ti O 93 -P
4) -p H • • O
-p ••aboooocH
a OOP!? z z
BB Z Z tO -H 4> rl
P -p p M In 4)
CO EQCL) •CbO'rf'rts
CO^^EjbjSpOOOO
^ g<;HflC8,HlHP-Prl
•HCO'^'O^-H-Hrlt-.-H
a -H q s a a ,« p p a
C(X.H

o to c«>
8 8 8
o o o*


O O w^v






OJ fX O>
a 8 8
o o o



O O OJ
C*N rH





VO O C*\
O rH O
d o o'


m in OJ
in in
rH (•*>





888




§* *
o o
in vo
oj" c^C




O O vn
0 0 0


g
•H
•P
0
•p
to
c a IH IH M
3 OJ M rH
£ G 4) 41 OJ
o a -p •*> -p
vH iH -H *H
rH -O tO CO (O
? M
S

8
o


tfx






o
OJ
o



OJ





o
OJ
o


OJ





8




rH






8
o







HH
41
p
•H
CO
o




o^"
in


OJ
         IW
         OJ
         +>
        
-------
8rH
+» if
+* tH J3
s •i
3 <->

S-S'S
^9
tSBi
!S1
f H j!
S £

S^T;
P< O 40
*a1
0) H rH
0t v_x
3 &
(0 iA t3
2 S oT

C rH
5 C
tit
•AM
rl O .O
0) O r-l
PL, £Q % 	 *•
g
* t5
3" ^o
a +> elf
< J'"'
58
3 «lL
rl 0-55
££
•H TJ

CO t*
S.«
CU








+»
iH
rH
C

S 3
to" to"



8 8
0 0

P- O
tA VQ


IA v\
OJ oj
O O
0 0


So
OJ
O f*>



OJ OJ
OJ OJ
0 O




S S
>r\ \o
OJ C\J

O O
rH rl


O CO
•Nt H
c*\ to
rH rH
OJ OJ







. ,
- g
0 0
03 tf
i i
+? -B
o o
PL. 0,
rl rl
II
rH
to"



8
0

9
lf\


§
o


H
rH
rH
"A


OJ
OJ
O




to
>A
OJ

o
rH


to
IA
OJ










3
*
O
O
§
rH



C*-

o

5



i
o


OJ
r^N
OJ



OJ
OJ
O




«
rH


8


8
VO
O
rH









•
^
§
Sf
I
§
,_!
™


8
o

E;
rH


tr\
a
o


*TN
rH
*rT
P'N
rH

8J
o




£\
^


o
rH


«>
OJ
^
rH
VO






3

4)
rH
rH
01
Anacoeti
o
VO


O
8
o

o
-*


§
o


g
VO
IA



o
OJ
o




o
to
OJ
OJ

8


g
o
to
OJ
CM









$
5
Arlingtc
»
to
OJ

m
8
O

>r\
OJ


§
o


o
OJ
^

rH

OJ
OJ
0




o
o
rt

O


to
rH
to
j_
SI






CO
*H
rQ
i
s
o
District
5
»r\



8
o

to
to
r->


§
O


vS
rH
^



81
o




H
O
OJ

0


8

IA*
rH









s2
'A
Alexandi
S
»r\



8
o

to
6
-*


§
o


s
CD
IA



OJ
OJ
o




^
^


o
rH


8
r-l
f*\
H

£

a
41

i
H
rH
=S
i
Cameron
o
r\
in


O
8
0

o
p-
^


o
8
o


o
r>
Vr
OJ



rH
O




OJ
OJ
OJ

8


g
O
rH
rH









2
fr
Piacatai
to
S?
_^.
"


8
0

to
R
S


§
0


>A
OJ
r\



OJ
OJ
o




VO
VO


o
rH


rx
O^
f*\

•K
O
1
J
^
rH


WN
8
o

fe



§
o


s
EN
t^-



SI
o




UN
to
f\


0
rH


cu
<^v
O
lA
r-i









3
a
0
i
5
^.


v\
8
o

g
o"
rH


§
O


r-N
VD
Q



OJ
OJ
o




OJ
r\
in


o
rH


vS
y
rH
rH









a
^
1
o
iH
ft




8
O

tfN



§
o


R
C*N
OJ



OJ
OJ
0




8
rH


0


to
to
IA
0
rH





•
O
Q
•S

&
i
R




8
o

o



o
0
o


0





o
0




o
rH
o


8


g
o
rH






Sj
0
0
S
3
rH
CO
S3
O r^ *^ ^f ^0
a OJ rH 3 J..




53 81 o a 8
o o o o o

8 'rH ri S g



O ^D O O O
rH H OJ ^ >T»
tj O tj O O
o o o o o


o o \o o o
»Tv rH rH OJ C"-
,-T rH tT\



E> -vf CO O O
rH ^ rH (T\ OJ
0 O O O O




Q O t O O
O- rH O C^ >t
O O O O C\J


8 8 8 S ft


§8888
O o r** oj o^
a- I-H] -^ co
rH

g
•H
a

to
g
O rH 01
rH >»• -H
• • O O
O 0 u Z Z
2 2 1 * "
§ 1 1 1 1
1 1 III
S04 03 iT\
f*\




8 8 S S
O* O C3 CJ

VO OJ r^ OJ
r*N rH



OJ (*N t*\ O
rH Q C*N Q
O O O Si
O O O O


§O r> OJ
Q
rH ^t




«O r*\ O
rH O OJ
0 O O O




O O 'rH
O O O


8888
rH rH H rH


§o o o
O O rH
O rH
r»*\ -^~




c

•H
«
to
o -o
II M a a &
IS 5 5 5 5
rH -O tO tO tO tO
1"
                                                                                                                                                g

-------
                             i-l   O  O
                             CJ>   r^  c«"\
                             Ov   CU  T\
                                                         C-   TV ir\ cu
                                                         oj   in -*vb
                                                                 D to
                                                            to
                                                            fc
                                          VD    to  O
to
s

9
$ TJ^N
>   ir\   «"\  u"\  C"*    r\   >r\    ir\  o   *r\  *f\ u~\ u"\    tf\OO(*\    OOO

JS-JjS   3883    8888    888  888    8888    8  8  8

           o'   o'  o'  o*    o'  o*  o'   o'    o*  o*   o*  o'o'o'    o'   o'  o°  o'    o'  o'  o"

     •
                                                                                                                  §00   <*\  O
                                                                                                                  O   to  O
                                                                                                                  O   O   Q* CL
i! Cf ?5
S

s s§
oJ H

o|
CM|
^

g m oooo oooo
to! H-d

•o -^
> r^\OO-^ OJO>^\O
•P a»C\jQi>'«tQOCo^p^-
0 tf\ ^ O O C*- tfN O O^ ~*^ O^
H o at CT^CO^DOJ r^r^ojr^
+3 ^ Q ON \^ ;^~ r^\ CD O "^
G H H OJ OJ
& — *

3'°'-
P*0o >4--vt^t^l; >J-C\J->tNt
JT ^5 T3 OJCMOJCM OJCMCMCM
if\m OOOO* OOOO
h Q jo
£§Ci


§
0) rH
bDfe^"^ ^OC^^O UNtOrHO^
J) +» S" t-v rH rH rH VO C-- O* O*
> a) — VN O -J- CM CA \O CM
<* 01 rH rH
0 O O OOO



C'N O >f r^ to to
o vo ^o to oj oj
CO "^ "^ V\ rH C^
1A VD to rH rH CM
rH OJ



~^ O^ "^ ^ *^ ~^"
CM rH OJ OJ OJ OJ
OOOOOO





r> O CM O rH TV
r-l 0 Q  O O
•* TV i-H rH CM t-
rH rH C^



*>* TV C^. -^ CO O O
CM O rH rH rH (^ OJ
OOOO OOO





if\ O O O C; O O
OOOO O O CM

                                                                                                               «•
                                                                                                              «  S  8   8
                                                                                                               oooo
                                                                                                               O  O  rH
                                                                                                               p\  <*  O

                                                                                                               d  o  o
                         8
                                                 OOO  OOO
                                                         rH   rH rH rH
                                                                         O  Q  O   Q   Q
                                                                         CT1  O  O   O   O
                                                                        8888
                Q
                O
                         O    rH
                         rH    t-
                               0*
                                       of
H  O

CM  r-v
»
                                                                                           8
                                                             O)
                                                             rH
                                                                                 8
 8
            £
                 2   3
                 5  J<
                 •P  «i
                               3


                               if
                 £  S  §    S
                     O  M    m
                 I*
                 O<  Q
                                   s-
                                    t<
                                   <
,        I
*        3
          f   s   o  s;._.

          II
I!        f   *F
 m   m    6   a   6  -p
•H   rH    S   -H   5  ffl
Q   <;   o   a,   J  a
                                    •   o
                                   >£  °
                                       VI
                                    •   o

-------
    t>  cd  ci  ^  S   o*» w  jf\
    jf  o  o  c*\  "-O   ^o *-*  w


i fi •   Q  ^  r**>       r\ O*-  ff*
; H 3   «  •>}•  H       •*     cvi
                                            £  «
                                              O
                                                                R  8
«
ft.
   -
  O
  C
             8p"\  r°*\ r*4   r*\  P**\ P**\  f*\   p"^  P*\  f\ f*\ c*\ f\   (*\ p*^  oj   cy   Q  oj  w        w  O  to  o
             O  O O   O  O O  O   O  O  O O O O   O O  O   O   O  O  O        O  O  O  ^

          0*0*0*0'   oooo   d  o  o o o o   d o*  CD*   CD*   odd        d  d  d  d
  SET"!    c-  Rj  «s
  B\     «  •   •>
                 CvJ^t   OOC^-Q    cuir\r^c\ic^Ch
                         to^tf^o^    i-<  *\  to  N to H
                                                                              to  tf>
                                                                              vi>  ^f
                                                                              S  o^
             l*\  to       O  ^O  rH  VN    f^
          i-l  <»\          c^     CM
                                                             ir\OOvo   OOO
          a  a  a  s   a  a  a  a   a  s  a  aaa.   a  8  a   a   a  ar s
                                                                                                 f*\  C*\
                                                                                                 O  C\
                                                                                                 O  O
          OOOO   OOOO    OOO  OOO   OOOO   OOO        OOOO
"O  ""^
•   >>
•g   ?

• jS^
COB
4*03,2
                                                        *^  NjOO
                                                                OOO   \Q  O
                                                                «\f*\«*   OI>A

                                                                    *   "
          r\  «\  ej  ev    O vo  cv   i-    •>
               -
                                              »
                                                                8  5? 4   38 8
          oooo   oooo   o  o  o  o o o   oooo   ooo
                                                                                             «  S  8  8
                                                                                             oooo
                                »T\rH   C-^OCVJ
   13  S  »  Z
                                                             WNOOO   ^OO        OOi-l
                                                             H'f-ICT>i-l   Ot^^*        (»\>»O

                                                             £>O*O'CDOO**-OC\J   tOHOr^Ot^   C*-OOO   P*
         tO  00
         to  t\I
               cj  S
p^  O  *f* ^O   "^  **"^
p"\  (M  v\ r^   to  to
C\J  C«i  tO OJ   OJ  "*
                                               *r\  o* ¥\ p«-
                                               3  *"*
                                                                                                    8  S
                                        jS
                                         0>
                                                                            i
               s.,-
                         I".
                         «   c"
                         •rt   O
                                               lg
                «;     >    a
               "  3   o  SS
                                                                                       S
                                                                                       CO
                                        =8
                 I!   1
                                    "O
                                    c

                         o  ^  *  S
                         +>  +»
                         8  i
                             iH  f)  O    £  to
                                                    g
                                                    *
                                       f,   ia  ^  5H
                                       0)   O   f>
                                                      8£
                   ts  -8
                   5  -
II

I  ^
i  5
&  &

3§
                                         ra
                                            IX,
                                                  -H tn O

                                                  ^S
                                       co

                                       e>*
                1
2  £

1?
«i

    I
 il
*s  2
•g-s  «
 J» t-l
S
                                                                                             M  M  M  t>
                                                                                                 M  M  M
                                                                                                 »  5  5
                                                                                                 -H  -H  -H
                                                                                                 U3  
-------
                                                                    X-l




                             CHAPTER X




                     WATER QUALITY SIMULATIONS




A.  WATER QUALITY SIMULATION MODELS




     Water quality simulations for this report were made using the




FWQA Dynamic Estuary Model (DEM) and DECS III.  The DEM, which was




used to evaluate allowable wastewater loadings and chloride intrusion




as discussed subsequently in this chapter, is a real-time system




incorporating a hydraulic component that describes tidal movement and




a quality component that considers the basic transport mechanisms of




advection and dispersion as well as the pertinent sources and sinks




of each constituent.  The ability to utilize a two-dimensional network




of interconnecting junctions and channels makes it possible to include




the embayments directly in the flow network.  A detailed description




of the model is available from FWQA [41].  DECS III is based on a




time-dependent tidal average solution of the basic mass balance




equations as originally developed by Thomann [541.  This model was




used to investigate seasonal variations in the nitrogen and phosphorus




distributions of the upper Potomac Estuary.




     A study investigating the relative merits of the FWQA Dynamic




PJstuary Model versus the tidal average approach has been made by




CTSL and a report of this investigation is currently in preparation.




     A schematic diagram of the Potomac Estuary used in the Dynamic




Estuary Model is given in Figure X-l.   The location nodes for the




existing discharges and proposed locations for future discharges

-------
                                                                   X-2
are also shown in this figure.  A similar segmentation of the main



Potomac was also used for DECS III.



     In simulating the various water quality constitutents,  a water



flow system as shown in Figure X-2 was incorporated into the Dynamic



Estuary Model.  This feature was necessary to simulate conservative



constituents such as chlorides and total dissolved solids.

-------
                    CHAIN WtlOOC
                                                       WASTEWATER  PLANT  NODES
                                                       NODE      PLANT
                                                        78        MUMGTON
                                                       i2»        ILUC PLAINS
                                                        2        UWtR POTOMAC
                                                                 PISCATAWAY
                                                                 PENTAGON
                                                                 LOWEM  POTOMAC
                                                                 ANACOSTIA


                                                                 MATTMOMAN
                                                                 PORT TOBACCO
LOWEH MACHOOOC  Ci
                                  MANVS RIVEH
                CHtSAPEAKf  KAV
                                                SCHEMATIC  OF  POTOMAC   ESTUARY
                                                       FOR  FWQA   DYNAMIC   MODEL

-------
*   §
     7,
0
H

Ul
                                                                                                  FIGURE  X-2

-------
                                                                   X-5
B.  ALTERNATIVE WASTEWATER TREATMENT SYSTEMS
     As shown  in  Figures X-3, X-4, and X-5, three basic alternative
wastewater treatment systems were investigated.  A fourth system,
similar to Alternative III except for a facility on Rock Creek, was
also investigated; however, the population projections indicated
that the expanded Blue Plains, Upper Potomac, and Anacostia plants
could readily  serve the Rock Creek area and this alternative was
subsequently omitted.  Alternative discharge locations for two of the
above schemes  were considered in the mathematical model simulation
and are presented in Figures X-6 and X-7.
     Alternative  I consisted of nine wastewater treatment plants in
the upper Potomac Estuary.  The projected waste flows for each of
these facilities  are shown in the following table:
                            Table X-l
           WASTEWATER FACILITIES AND PROJECTED FLOWS
                         Alternative I
Facility

Pentagon
Arlington
?lue Plains
Alexandria
Piscataway
Lower Potomac
Occoquan
Mattawoman
Port Tobacco
* Proposed capacity = 309 mgd
.980
mgd)
I
23
285*
-38
24
50
45
5
0
2000
(mgd)
1
37
473
61
49
103
121
9
6
2020
(mgd)
1
45
702
83
79
170
235
13
11

-------
     WASTEWATER  TREATMENT  SYSTEMS
            UPPER POTOMAC ESTUARY
                 ALTERNATIVE  I
OCCOQUAN
                                         OF COLUMBIA
                                       (etUE PLAINS)
                                                 FIGURE X - 3

-------
WASTEWATER  TREATMENT  SYSTEMS
       UPPER POTOMAC ESTUARY
            ALTERNATIVE  Tt
                               ^'DISTRICT OF COLUMBIA
                                  (BLUE PLAINS)
                                            FIGURE X-4

-------
     WASTEWATER  TREATMENT  SYSTEMS
            UPPER POTOMAC ESTUARY
                 ALTERNATIVE  HI
                         UPPER POTOMAC     \

                             WASHINGTON
OCCOQUAN
                                                FIGURE X-5

-------
     WASTEWATER  TREATMENT SYSTEMS

            UPPER POTOMAC ESTUARY
                 ALTERNATIVE 31
                                         OF COLUMMA
                                      (BLUE PLAINS)
OCCOQUAN
                                                FIGURE X-e

-------
     WASTEWATER TREATMENT  SYSTEMS
            UPPER POTOMAC ESTUARY
                ALTERNATIVE  3C
                                      OAWAY
OCCOQUAN
                                              FIGURE X-7

-------
                                                                  X-ll





     Under Alternative I, the District of Columbia's Blue Plains



 facility will also serve the upper Potomac area within Virginia and



 Maryland, the Anacostia Valley, and the Rock Creek Basin.  In this



 alternative, it is assumed that the expansion at Blue Plains is not



 restricted.  In all three alternatives, Alexandria's facility will



 also serve the Cameron Run and Belle Haven areas, Piscataway will



 serve Andrews Air Force Base, and the Lower Potomac plant will



 serve Fort Belvoir.  The existing Fairfax Dogue and Little Hunting



 Creek plants are to be abandoned and the waste transported to the



 Lower Potomac facility.



     Alternative II was identical to Alternative I except that a



 wastewater plant was assumed on the Anacostia River.  This facility



 will only serve the Anacostia Valley.  It was also assumed that the



 Blue Plains treatment plant would be expanded to accomodate the



 remainder of the flow.  The facilities and wastewater flows associ-



 ated with Alternative II are shown in Table X-2.



     Table X-3 shows wastewater facility data corresponding to



 Alternative III which assumes another plant built in 1980 to serve



 the upper Potomac area.  In Alternative III,  the maximum size of Blue



 Plains is limited to 309 mgd.  The Anacostia facility would serve the



Anacostia Valley and the remainder of the flow shown as  transported



 to Blue Plains in the first two alternatives  would be conveyed to the



 upper Potomac plant.

-------
                             Table X-2

             WASTEWATER FACILITIES AND PROJECTED FLOWS
                           Alternative II
Facility
Pentagon

Arlington

Anacostia

Blue Plains

Alexandria

Pis cataway

Lower Potomac

Gccoquan

Mattaworaan

Port Tobacco

* Proposed capacity = 309 mgd
1980
(mgd)
1
23
0
285*
38
24
50
45
5
0
2000
(mgd)
1
37
126
347
61
49
103
121
10
• 6
2020
(mgd)
1
45
185
518
83
79
170
235
13
11

-------
                             Table X-3
             WASTEWATER FACILITIES AND PROJECTED FLOWS
                          Alternative III
Facility


Pentagon

Upper Potomac

Anacostia

Arlington

Blue Plains

Alexandria

Piscatav/ay

Lower Potomac

Occoquan

Mattawoman

Port Tobacco

* Proposed capacity =309 mgd
1980
(ngd)
1
0
0
23
285*
38
24
50
45
5
0
2000
(rogd)
1
38
126
37
309
61
49
103
121
10
6
2020
(mgd)
1
209
185
45
309
83
79
170
235
13
11

-------
                                                                  x-u






     Alternative III is similar to the proposals in the "Memorandum



of Understanding" with reference to the Washington metropolitan



regional water pollution control plan as presented at a special



session of the Potomac River Washington Metropolitan Area Enforcement



Conference on October 13, 1970.  In this memorandum, a maximum capacity



of 309 mgd for the Blue Plains facility was proposed.  It also required



the appropriate parties to provide another regional plant or plants to



accomodate the projected increases in wastewater volumes.



     While there can be numerous variations of Alternative III in



respect to flow distribution, the basic layout concept is fundamental.



Alternative V, presented later in this report, is one variation with



discharge points to the main Potomac.



     Alternative IV, which is identical with Alternative I for waste-



water treatment plant location, differs in that the effluents from



the upper six plants are conveyed downstream as far as Occoquan Bay.



This plan was investigated to determine the effects of discharges



lower in the estuary on its use as a water supply source (Figure X-6).



     Alternative V was developed to investigate the effects of dis-



charging the effluents directly into the main Potomac instead of the



embayments.  This alternative, which is identical to Alternative III



in facility locations has the Anacostia, Arlington, Alexandria,



Piscataway, Lov/er Potomac, Occoquan, and Port Tobacco facilities



discharging into the Potomac main channel.  The Blue Plains, Upper



Potomac, and Mattawoman facilities either do or were assumed to dis-



charge into the main channel.

-------
                                                                   X-15






     The estuary water supply intake was assumed to be one-half mile



below Chain Bridge.  In Figure X-l, the schematic diagram for the



model, the water supply intake is at Node 11/4.



     When the current wastewater collection and treatment facilities,



projected populations, "Memorandum of Understanding," and water supply



needs are reviewed, it can readily be observed that:



     (1)  Shortly after 1980, the Dulles Interceptor with its current



capacity of 64 mgd will be overloaded.



     (2)  To provide for future wastewater collection and treatment



services in the upper Potomac, either the Dulles Interceptor should



be significantly enlarged or wastewater treatment facilities con-



structed in this region.



     (3)  If the Dulles Interceptor is enlarged, wastewater treatment



capacity must be increased at either Blue Plains, Anacostia Valley,



and Pis cata-.vay or a combination of all three.



     (4)  With the current capacity limitation of 309 mgd at Blue



Plains, it appears that treatment facilities will be needed not only



in the upper Potomac but also in the Anacostia Valley.



     (5)  Large wastewater volumes will be generated in the lower



counties of Virginia, mainly in the Occoquan and Pohick watersheds.



     The above five observations indicate that consideration in



selection of wastewater management programs should not only include



treatment facilities but also collection systems.  This is discussed in



greater detail later in this report when the water supply aspects are



presented.

-------
                                                                   X-16

C.  WASTEWATER MANAGEMENT ZONES AND STREAMFLOW CRITERIA

     To facilitate determination of wastewater management requirements,

the upper and middle estuary were initially divided into three 15-mile

zones with similar physical characteristics beginning at Chain Bridge.

This allowed greater flexibility in developing control needs.

     River mile distances for the three upper zones, from both the

Chesapeake Bay and Chain Bridge, are given in Table X-4.  The  zonal

concept was adopted by the Conferees at the Potomac Enforcement

Conference Progress Meeting on Fay 8, 1969.

     More recent studies have suggested that Zone I be divided into

three subzones as shown in Figure X-8.  The three subzones are

described as follows:

Subzone                         Description

  I-a       Potomac Estuary from Chain Bridge to Hains Point,
            a distance of 7.6 miles

  I-b       Anacostia tidal river from Bladensburg, Maryland to the
            confluence with the Potomac, a distance of 9.0 miles

  I-c       Potomac Estuary from Hains Point to Broad Creek, a
            distance of 7.4 miles

Discharges to embayments are also considered in this report.

     Using the zonal concept, a total maximum loading for a specific

pollutant is given for each zone.  Allocation of pound loading for each

discharge can be obtained by prorating the total zonal poundage using

various bases such as population, drainage areas, and geographical

subdivisions.

-------
   o

        4)
        > N
               ofl
               CO
               <

0)
1-1
,0
0)
   Q

   2
t    P

          §1^
          tsi  rt o
                          „
             •H
              f-<
             m -o

              «3
5?
•gl

o  3
•»* ^
  a.
•o
«"a
a «

s^
•H al

-------
                                               RIVER MILES  FROM CHAIN  BRIDGE = 0
                        PENTAGON
               SUBZONE la
                      ARLINGTON
            SUBZONE Xb  ZONE
N^ "^      /
DISTRICT OF/COLUMBA
                     ALEXANO
                        WESTGATE
                                       SUBZONE I e
                                         *       RIVER MILES  FROM  CHAM  BRIDGE = IS
             LITTLE  HUNTNG  Cr-
                                                             ANDREWS A.FB.
   FORT BELVOIR
LOWER POTOMAC
                              P1SCATAWAY Cr.
                                                                ZONE   II
                                                RIVIH MIUES FROM  CHAIN  BRIDGE = 30
                  WASTEWATER  DISCHARGE  ZONES
                       in  UPPER POTOMAC ESTUARY
                       ZONE  III
                                                RIVER  MILES FROM  CHAIN BRDGE = 45
                                                         FIGURE X-8

-------
                                                                  X-19





     The 7-day-low-flow into the Potomac Estuary, with a recurrence



interval of once-in-10-years, is 95-4 cfs before water supply diversion.



Since the need for water supply is projected to utilize all of the



river flow during critical flow conditions by 1980, a design flow of



300 cfs was used in determining wastewater loadings.  This minimum



flow serves to maintain an ecological balance in critical stream



segments during low-flow periods as well as preserve the aesthetic



appearance of this historic area.  Where applicable, effects of flow



changes including withdrawal from the estuary for water supply are



also presented.

-------
                                                                   X-20

D.  ULTIMATE OXYGEN DEMAND

     The interrelationship between ultimate oxygen demand* (UOD) and

dissolved oxygen (DO) in the Potomac Estuary was determined using a

verified mathematical model.  Studies included investigations of

alternative wastewater treatment schemes, UOD loading rates, and net

flows into the estuary for the three benchmark years.  Maximum allowable

UOD loadings in pounds per day, based upon compliance with existing DO

stream standards were established for each of the zones including the

embayments.

     In developing the allowable UOD loadings, the reaction kinetics,

as given in Chapter VI, were used, including the following DO criteria:

     Parameter                    Value

     Water temperature           29.0°C

     DO standard (average)        5.0 mg/1

     DO saturation at 29°C        7.7 mg/1

     Background DO deficit        0.7 mg/1

     Allowable deficit            2.0 mg/1

     Included in the 0.7 mg/1 DO deficit for background are the effects

of algal growth and benthic demand.  In using this deficit, it was

assumed that the algal populations were under control and that the

benthic demand resulting from wastewater sludge deposits had been

substantially reduced from existing conditions.  The UOD loadings were

based upon maintaining 5.0 mg/1 of DO averaged over the tidal cycle.
* The ultimate oxygen demand represents the sum of unoxidized carbon
  and nitrogen

-------
                           Table X-5
                UOD LOADINGS FOR POTOMAC ESTUARY
               Based Upon Maintaining 5.0 mg/1 DO
   Freshwater Inflow = 300 cfs (after water supply diversion)
                    Water temperature = 29°C

     Zone                      Allowable UOD
                                 (Its/day)

      I-a                           4,000

      I-b                           3,000*

      I-c                          75,000

     II                           190,000

    III                           380,000
The loading increases with increase in waste flow (See text for
more details).

-------
                                                                   X-22






     Subzone I-c currently receives waste-water effluents fron the Blue



Plains Sewage Treatment Plant which serves the District of Columbia



and surrounding portions of Maryland and Virginia, and from sewage



treatment plants in Arlington, Alexandria, and Fairfax County,



Virginia.  As shown in Table X-5, a maximum UOD loading of approxi-



mately 75,000 Ibs/day may be discharged into Subzone I-c regardless




of the alternative investigated.



     The effect of eliminating effluent aeration as a treatment process



was determined for Subzone I-c.  If a dissolved oxygen concentration of



2.0 mg/1 instead of 6.0 mg/1 in the wastewater is assumed, the allowable



UOD loading in Subzone I-c would be about 60,000 Ibs/day, or a reduction



of 20 percent.



     Two other subzones within Zone I, Subzone I-a of the Potomac Estuary



in the vicinity of Chain Bridge and Subzone I-b of the Anacostia tidal



river, were evaluated separately for Alternatives II and III because



their waste assimilative capacities are quite limited.  The allowable



QOD loading for Subzone I-a based upon a freshwater flow of 200 to 300



cfs is 4000 Ibs/day.  The lack of adequate transport under low-flow



conditions, and more important, the limited reaeration capability due



to the considerable depth of water in this area greatly reduce the




maximum allowable UOD loadings in the Potomac near Chain Bridge.  CTSL



mathematical modeling studies have shown that the allowable UOD load




to this portion of the estuary increases substantially with increasing



water supply flow withdrawals.  This relationship, which is due to

-------
                                                                  X-23


the direct removal of UOD before it is exerted in the receiving water,

is shown below:

     Net Flow
     into the
     Estuary*                  Allowable UOD
      (cfs)                      (Ibs/day)

      + 250                         -4000

      - 500                         6000

      -1250                        12000

      -2000                        18000

     The allowable UOD loadings in Subzone I-b, which is the upper

Anacostia tidal river (Alternative II), are given for the three

waste flow conditions as follows:

     Wastewater
        Flow                   Allowable UOD
        (mgd)                    (Ibs/day)

          68                        3000

         126                        6000

         185                        9000

     Again the absence of adequate transport and dilution restricts

the waste assimilative capacity of the Anacostia tidal river.  The

increase in the allowable UOD shown above can be attributed to the

progressive increase in wastewater discharges which greatly exceeds

the natural inflow to the Anacostia tidal system in importance.  In

effect,  the proposed wastewater discharge would substantially
  Negative net flows represent water supply withdrawal from the estuary
  assuming that all freshwater inflow from the upper basin, except for
  a base flow of 200 mgd, has already been diverted.

-------
                                                                  X-24






increase the downstream advective movement and the assimilative capacity



of the Anacostia -River._




     Zone II of the Potomac Estuary currently receives effluents from



the Piscataway and Lower Potomac wastewater treatment facilities via



the Piscataway Creek and Gunston Cove embayments.  By 1980, a third



facility serving Mattawoman Creek basin in Charles County will also



discharge into Zone II near Indian Head.  Two basic schemes were



investigated to determine UOD loadings in this zone.  One scheme



(Alternative V) assumes that all effluents discharge directly into



the Potomac main channel whereas the other (Alternative I) assumes



that the Piscataway Creek and Gunston Cove embayments continue to



receive treated effluents from their respective wastewater plants.



     According to Table X-5, the maximum UOD which can be discharged



into Zone II and still permit the DO standard of 5.0 mg/1 to be



realized is 190,000 Ibs/day.  It should be noted that prior to



determination of this allowable load, the residual or carryover



effects of Zone I and Zone III loadings upon Zone II were determined



and included.



     If Piscataway Creek and Gunston Cove receive the wastev/ater efflu-



ents projected in Alternative I, the maximum allowable UOD loadings




will be reduced considerably when compared to Zone II loadings.  The

-------
                                                                   X-25
relative inability of these embayments to assimilate organic waste-



water is reflected in the data shown below:



         UOD LOADINGS FOR PISCATAVIIAY CREEK AND GUNSTON COVE
Piscata

Flow
(mgd)
24
49
79
wav Creek
Maximum
UOD Load
(Ibs/day)
10,000
10,000
12,000
Guns ton Cove
Maximum
Flow UOD Load
(mgd) (Ibs/day)
50 7,000
103 11,000
170 16,000
     Since the physical characteristics for each embayment vary widely,



it must be emphasized that separate determinations of loadings will be




required for embayments other than those given above.



     Because of the stringent loading requirements associated with



discharges to embayments, it would appear advisable to discharge



wastewater effluents directly to the Potomac (as in Alternative V) and



utilize the additional dilution and transport capability it affords.



     There are at present no significant wastewater discharges within



Zone III of the Potomac Estuary; however, a treatment facility to serve



the Occoquan watershed in Virginia has been proposed for construction



by 1980.  Moreover, it was assumed that a facility at Port Tobacco,



Maryland, would also be in existence prior to the year 2000.  With



Zone II receiving its allowable UOD load (190,000 Ibs/day) and deducting



the necessary carryover effects, the allowable UOD loading for Zone III



was estimated at 380,000 Ibs/day (Table X-5).

-------
                                                                  X-26
E.  PHOSPHORUS




     Simulation of phosphorus discharges in the Potomac Estuary was



made using the mathematical model with second-order reaction kinetics



previously described.  Included in the model was a phosphorus deposition



rate of 0.05 mg/day at a temperature of 29°C.  The allowable phosphorus



loadings in pounds per day were determined based on maintaining an average



of 0.067 mg/1 of phosphorus (P) within Zones I and II and 0.03 mg/1 (P)



within Zone III and all embayments.  All effluents were assumed to be of



the same concentration.  While various freshwater inflow rates (before



water supply diversions) between 300 cfs and 1800 cfs were investigated,



their effect on the allowable phosphorus loadings appeared to be quite



small.



     The allowable phosphorus loading for Subzone I-c of the Potomac



Estuary is 900 Ibs/day as shown in Table X-6.  It should be noted



that this loading remains about the same for each alternative investi-



gated.



     When Alternative III was considered, the limited waste assimilative



capacity of the Potomac Estuary in Subzone I-a near Chain Bridge became



evident.  For a freshwater flow of 300 cfs, the allowable phosphorus




loading to this area was determined to be 200 Ibs/day.  If water supply



withdrawals are assumed, a certain portion of the phosphorus will be



removed directly, thereby increasing the allowable load from wastev/ater

-------
                             Table X-6

              PHOSPHORUS LOADINGS FOR POTOMAC ESTUARY
     Freshwater Inflow = 300 cfs (after water supply diversion)

       Zone                Allowable Phosphorus
                               (Ibs/day

         I-a                        200

         I-b                         85*

         I-c                        900

        II                         1500

       III                         2000
* The loading in this zone is sensitive to wastewater flow as
  described in the text of this report.

-------
                                                                  X-28

effluents.  The relationship of allowable phosphorus load to rate of

withdrawal is presented in the following table:

     Net Flow Into             Allowable Phos-
        Estuary                phorus Loadings
          (cfs)                   (Ibs/day)

          + 300                      200

          - 500                      300

          -1250                      400

          -2000                      500

     For Alternative II, which includes a discharge into the Anacostia

River, simulation runs indicate that the minimum transport and dilution

greatly restricts the allowable phosphorus load that may be discharged

into the Anacostia tidal system.  As in the case of UOD, the phosphorus

loadings into Subzone I-b are also a function of wastev/ater as follows:

     Wastewater                Allowable Phos-
        Flow                   phorus Loadings
        (mgd)                     (Ibs/day)

          68                          85

         126                         135

         185                         180

     As shown in Table X-6, the allowable phosphorus loading into

Zone II of the Potomac is 1500 Ibs/day.  The appropriate carryover

effects from both Zones I and III were incorporated into the phos-

phorus analysis for Zone II.

-------
                                                                   X-29


     When wastewater effluents are discharged into the embayments of

Zone II, there is a much larger increase in phosphorus concentration

for a given phosphorus loading.  As an example, assuming 1980 waste-

water flow data and a 1000 cfs inflow, if the effluent contains 10 mg/1

of phosphorus, the result in the Piscataway embayment would be as

follows:

                       Increase in Phosphorus    Increase in Phosphorus
Discharge Location     Upper_End of Emba.vment    Lower End of Embayment
                               (mg/1)                    (mg/1)

Into Embayment                   3.93                      1.22

Into Main Potomac                0.78                      0.92

     A similar tabulation for Gunston Cove, again assuming 1980 con-

ditions , follows:

                       Increase in Phosphorus    Increase in Phosphorus
Discharge Location     Upper.End of Embayment    Lower End of Embayment
                               (mg/1)                    (rag/1)

Into iJmbayment                   8.62                      O.ol

Into Main Potoraac                0.49                      0.62

The above tabulations clearly show that concentrations in the upper

end of the embayments can be drastically reduced by diverting discharges

to the main Potomac.  However, they also show that the phosphorus concen-

trations in the lower end of the embayments are considerably less affected,

This can be attributed to the tidal exchange between the main Potomac and

the erabayments.

-------
                                                                  X-30
     If discharges projected in Alternative I are made to the upper

end of the Piscataway Creek and Gunston Cove embayments, the maximum

allowable phosphorus loadings are as follows:

                 PHOSPHORUS LOADINGS TO EMBAmENTS

     Piscataway Creek                         Gunston Cove

                 Maximum                                   Maximum
How        Phosphorus Load               Flow        Phosphorus Load
(mgd)          (Ibs/day)                  (mgd)          (Ibs/day)

  24               35                       50               35

  49               50                      103               60

  79               65                      170              140

     The loadings given apply to these embayments only.  A separate

determination will be required for other embayments because of different

physical configuration.  The effect of the main Potomac on the embayments

was previously demonstrated by Jaworski and Johnson in a preliminary study

of the Piscataway embayment [-42].

     It can be concluded that there is a significant advantage in dis-

charging wastewater effluents into the main channel (Zone II) from the

standpoint of phosphorus buildup.  Moreover, it appears that with the

lack of transport in the embayments, the allowable phosphorus concen-

tration in discharges to the embayments begins to approach the developed

criteria.

     In order to realize the phosphorus criterion for Zone III of the

Potomac Estuary (0'.03 mg/1), the maximum phosphorus loading from

-------
                                                                  X-31






wastewater effluents within this zone was determined to be 2,000 Ibs/day



as shovrn in Table X-6.



     Using phosphorus as a tracer, simulation runs were made to determine



ho.v quickly any component in the >,rastewater discharge could reach the



proposed estuary water intake.  Table X-? shors that in the extreme case



investigated, about 4 days vraxild elapse before detection there.  For the




projected year 2020, wastewater diseharces and a river flow of 1800 cfc,



the time would be increased to o days.

-------
                             Table X-7

      INTRUSION TIMES FOR PHOSPHORUS INTO ESTUARY WATER INTAKE
                      Wastewater Alternative I
Year
1980
1980
1980
2000
2000
2000
2020
2020
2020
Net
Inflow
+1250
+ 250
- 500
+ 500
- 500
-1000
- 500
-1500
-2000
Days Required to Detect
in Phos -chorus at Water
— *
— *
10
.-_•*
9
5
8
5
4
an Increase
Intake









* With a positive net inflow, there was no measurable intrusion into
  the intake.

-------
                                                                  X-33



F.  NITROGEN



     Inorganic nitrogen was simulated using a mathematical model which



had already been verified based upon observed data.  For purposes of



developing zonal loadings, the total inorganic nitrogen was assumed



to behave conservatively.  Since nitrogen appears to be limiting the



rate of algal growth in Zones II and III, more stringent criteria



were adopted for those areas.  The upper nitrogen concentration limits



used for Zones I, II, and III were 0.5, 0.4, and 0.3 mg/1 respectively



at a temperature of 29°C.  V/ith these levels of inorganic nitrogen,



some algal growth will occur but nuisance conditions should be pre-



vented.  The net estuary inflow, water supply withdrawal rates,



population benchmarks, and alternative vrastewater treatment schemes



incorporated in the analysis of nitrogen were identical to those used



for determining phosphorus loadings.



     The allowable nitrogen loading for Subzone I-c of the Potomac



Estuary is 3,400 Ibs/day (Table X-8).  For Alternative III and a



freshwater inflow of 300 cfs, Subzone I-a can receive and adequately



assimilate 1,000 Ibs/day of nitrogen from wastewater effluents.  If



nitrogen is removed from this portion of the estuary via water supply



withdrawals, the allowable nitrogen loadings will,  of course,  increase



in a manner similar to that shown previously for UOD and phosphorus.

-------
                           Table X-8

             NITROGEN LOADINGS FOR POTOMAC ESTUARY
   Freshwater Inflow = 300 cfs (after water supply diversion)


      Zone                        Allowable Nitrogen
                                      (Ibs/day)

        I-a                              1000

        I-b                               300*

        I-c                              3400

       II                                5800

      III                                9000
* The loading in this zone is sensitive to waste flow as  des-
  cribed in the text of this report.

-------
                                                                  X-35


     Allowable nitrogen loadings for Subzone I-b, which is the upper

Anacostia tidal river, are also a function of wastewater flow and are

as follows:

     Flow,,             Allowable Nitrogen
     (mgd)                (Ibs/day)

       68                    300

      126                    550

      185                    800

     With all major wastewater effluents discharging to the main

channel, Zone II of the Potomac Estuary can receive 5800 Ibs/day of

inorganic nitrogen (Table X-8) and still maintain the criterion of

0.4 mg/1.  As shown in Table X-8, the allowable nitrogen loading for

Zone III of the Potomac is 9000 Ibs/day.

     The importance of nitrogen as a potential rate-limiting nutrient

within Zone II must be considered when evaluating the loading require-

ments for embayments such as Piscataway Creek and Gunston Cove.  As in

the case of phosphorus, the lack of movement from the head end of the

embayments necessitates reducing the nitrogen concentration in waste-

water effluents to a level approaching the established criteria.

-------
                                                                  X-36
     For discharges made to the upper end of the embayments for



Alternative I, the maximum allowable nitrogen loadings are:






                  NITROGEN LOADINGS TO EMBABffiNTS



    Piscatawav                                Gunston Cove
Flow
(mgd)
24
49
79
Maximum
Nitroeen Load
(Ibs/day)
120
170
270
Flow
(mgd)
50
103
170
Maximum
Nitrosen Load
(Ibs/day)
130
270
460
     Independent determinations of nitrogen loadings must be made



for other embayments because of varying hydrography and tidal



characteristics.  In view of this stringent allowable loading, a



definite advantage is evident in discharging into the main channel.

-------
                                                                   X-37




G.  CHLORIDE AND TOTAL DISSOLVED SOLIDS SIMULATIONS



1.  Estuary Water _Supply Withdrawal




     In March 1969, Hetling  [43] investigated the possible use  of  the




upper Potomac Estuary as a water supply source, primarily from  the




chloride intrusion aspect.  From this study, it was concluded that




(l) under most critical summer-flow conditions on record (1930'-193l)




and the year 2010 demand, the estuary could be used for potable water




supply purposes, and (2) if the wastewater is discharged out of the




basin, such as to the Chesapeake Bay, the water supply potential of




the estuary is reduced considerably.  In light of the large projected




wastewater volumes in the lower counties of Virginia along the  upper




Potomac, a review of the possible intrusion of chlorides and total




dissolved solids into the estuary water intake was undertaken.




     Data in Figure X-9  indicate that the chloride intrusion from




Chesapeake Bay varies appreciably.  This variation is rrainly a  func-




tion of freshwater inflow rate and duration.  The November 19J\-




profile shows the farthest upstream intrusion as a result of prolonged




low flows of less than V'OO efs from July through Uover/oer.  -^I'L/JO1:;-^




the drought conditions in September 19fco were more severe \ J.hV  "leys




of approximately 220 cfs, the duration 'ras shorter and 'i;nce 'Lhc




intrusion was not as great.

-------
FIGURE  X-9

-------
                                                                  X-39


     Using four historic low-flow conditions, the rate of intrusion was

calculated as follows:

     Flows                 Upstream Movement
     (cfs)                    (miles/day)

     5000                         0.00

     1100                         0.07

      580                         0.21

      214                         0.71

The above tabulation clearly shows the effect of freshwater inflov.' on

the rate of the chloride intrusion from the Chesapeake Bay.

     The intrusion of chlorides and total dissolved solids was simu-

lated using the RVQA Dynamic Estuary Quality Model.  For Alternatives I

and IV, the simulations were made assuming the following freshwater

inflows and water supply withdrawals:

Year 1980

Year 2000

Year 2020

Freshwater
Inflow at
Great Falls
(cfs)
1870
1120
3'/0
1750
1000
250
1900
1150
400
Water Supply
Withdrawal
(cfs)
870
870
870
1500
1500
1500
2400
2400
2400
Net Flow Into
the Estuary*
(cfs)
+1000
+ 250
- 500
+ 250
- 500
-1250
- 500
-1250
-2000
* Negative net flow represents withdrawal from estuary for water supply

-------
                                                                  X-40
     Two sets of initial conditions were used for each simulation:

(l) an initial chloride wedge position as observed on September 13,  1966,

and (2) a less severe condition using July 7-8,  1965, observations.   The

upper end of the chloride wedges under these two conditions is shown in

Figure X-9.

     To obtain the initial conditions for total  dissolved solids (TDS),

a relationship between TDS and chlorides was established from existing

data as follows:

     IDS (mg/1) =1.69 Chlorides (mg/l) + 300

Boundary and loading conditions used in the simulations are itemized

below:



Chesapeake Bay chloride concentration

Chesapeake Bay TDS concentration

Freshwater inflow chloride concentration

Freshwater inflow TDS concentration

Wastewater TDS concentration*

Water use chloride increment

Water use TDS increment (Run l)

Water use TDS increment (Run 2)

Currently the average concentration of chlorides and TDS in the waste-

water effluents are about 40 and 300 mg/1, respectively.  The above

40 and 240 increments for TDS are well within the range of accepted

concentrations in the effluent of 200 to 400 mg/1.  In this study,
1966 Wedge
11000 mg/1
18000 mg/1
30 mg/1
160 mg/1
300 mg/1
25 mg/1
40 mg/1
240 mg/1
1965 Wedge
9000 mg/1
14000 mg/1
15 mg/1
160 mg/1
300 mg/1
25 mg/1
40 mg/1
240 mg/1
* The total TDS increase from water intake to wastewater discharge is
  currently about 140 mg/1

-------
                                                                  X-41


maximum upper limits for municipal water supply of 250 and 500 mg/1 of

chlorides and TDS respectively in the blended mix of estuary water and

freshwater inflow were used as recommended by the U. S. Public Health

Service  [44],

     With the concentration of TDS in both the estuary and the wastewater

effluent higher than for chlorides, the restricting limitation on the use

of the estuary is TDS.  This finding is also supported by Hydroscience

[45J in their preliminary report on the feasibility of the Potomac Estuary

as a supplemental v/ater supply source.

     Summaries of the results of the TDS simulations for the initial con-

ditions of July 7-8, 1965, and September 13, 1966, are given in Tables X-9

and X-10.  Based on data summarized in these two tables as well as from

other simulations runs, it can be concluded that:

     1.  Even with no water supply withdrawals from the estuary, chloride

and TDS intrusion will occur farther upstream in the Potomac Estuary as a

result of the larger percentages of total wastewater volumes discharged

farther downstream and projected increases in consumptive loss.  Currently,

less than 20 mgd is discharged into saline waters.  By 2020, approximately

31 percent of the wastewater or over 400 mgd will be discharged into the

saltwater wedge.  The consumptive loss, which is water supply withdrawal

minus wastewater discharge,  is projected to increase as shown below:

              Yegr               Consumptive Loss
                                      (mgd)
              1966*                     44

              1980                      83

              2000                     148

              2020                     226

* During the month of August in which the flow into the estuary was  538 cfs,
  the consumptive loss was about 13.5 percent

-------
                                                                   X-42





This increased downstream discharge, coupled with the above increased



consumptive loss will reduce the net seaward flow in the upper estuary



even without any water supply withdrawal.



     2.  The number of days that the estuary can be used for v/ater supply



depends Fa inly on (a) duration and magnitude of drought conditions,



(b) location of wastewater treatment facility discharges, and (c) position



of the salt wedge before low-flow conditions begin.



     3.  The effect of the incremental increase in TDS in the waste-water



on the concentration at Chain Bridge is not significant for the upper or



lov/er -..-edge positions for Alternative IV.  The number of days that the



estuary could be used for a water supply did not vary if 40 or 240 mg/1



was used.  The major effect on the concentration was the intrusion from



the Chesapeake Bay which is controlled by freshwater inflow and wastewater



discharge locations (Table X~9),.



     For the upper wedge position, as given in Table X-10, the effect of



the concentration of IDS in the effluent is more significant especially



for Alternative I and the year 2020.  The tiuie was reduced by 24 days



when the TDS increment was increased from 40 to 240 mg/1.



     4.  V.'ith the salt wedge in the upper position as of September 13,



1966, using the TBS criterion of 500 r.ig/1 in the blended water,



Alternative I, and with less than 400 cfs coming over Great Falls before

-------
                                                                  X-43
water supply withdrawal, the estuary could be used for water supply

for the following periods:

     Year              40 me/1 Increment        240 me/1 Increment
                         (days of use)             (days of use)

     1980                   > 166                     > 166

     2000                      90                        35

     2020                      45                        15

This reduction In usage between 1980 and 2020 is primarily the result

of increased incursion due to reduced net seaward flow and increased
                                                             t 166                     > 166

     2000                     140                        45

     2020                      95                        20

The above reduction with time again reflects the increasing downstream

discharges and the increasing consumptive losses.

     5.  Assuming about 1800 cfs freshwater inflow and the September

13, 1966, initial wedge location, the estuary can be used as a water

supply source for over 166 days (the upper limit of the simulation

period) for both chlorides  and TDS for all three population benchmark

years 1980, 2000, and 2020.

-------
                                                                  X-44


     6.  The number of days that the estuary can be used as  a  water

supply for the year 2020 beginning with the September 13, 1966,  wedge

location as a function of freshwater flow is given below:

                  MAXIMUM MYS OF USE OF ESTUARY

Freshwater Inflow       Alternative I         Alternative IV
     Before          Water Use Increment   Water Use Increment
Water Supply              of TDS	        of TDS
Withdrawal
(cfs)
400
1100
1800
40 mg/1
( days )
45
>166
>l66
240 mg/1
( days )
15
42
>166
40 mg/1
( days )
18
>166
>166
240 mg/1
(days)
18
41
>166
     7.  Since the projected water supply needs for the year 2020

cannot be met by either the upper basin with seven reservoirs or the

estuary alone, both sources will be needed to supply the water needs

fcr the Washington metropolitan area.

     8.  It is necessary to coordinate both the water supply and

vrastewater treatment requirements for planning in the Washington area

since use of the estuary for water supply purposes is dependent on the

location and distribution of wastewater discharges.

-------
                                      Table X-9
                          TIME, IN DAYS, TO REACH INDICATED
                       CONCENTRATION OF TOTAL DISSOLVED SOLIDS
                                      IN ESTUARY
                     AT PROPOSED WATER INTAKE NEAR CHAIN BRIDGE
                      (Initial Conditions as of July 7-8, 1965)
1980

Freshwater Flow*
Alt. I
Alt. IV
1000 cfs
Water Use Increment 40 mg/1
TDS ( 500) mg/1
TDS (1000) mg/1
TDS (1500) mg/1
>166
>166
>166
Water Use Increment 240 mg/1
TDS ( 500) mg/1
TDS (1000) mg/1
TDS (1500) mg/1
Freshwater Flow
>166
>166
>166
250
Water Use Increment 40 mg/1
TDS ( 500) mg/1
TDS (1000) mg/1
TDS (1500) mg/1
>166
>166
>166
Water Use Increment 240 mg/1
TDS (500) mg/1
TDS (1000) mg/1
TDS (1500) mg/1
freshwater Flow
>166
>166
>166
-500
of TDS
>166
>166
>166
of TDS
>166
>l66
>166
cfs
of TDS
>166
>166
>166
of TDS
>166
>166
>166
cfs
2000
Alt. I
250

>166
>166
>166

>166
>166
>166
-500

>166
>166
>166

>166
>166
>166
-1250
Alt. IV
cfs

>166
>166
>166

>166
>166
>166
cfs

124
>166
>166

123
>166
>166
cfs
Ait. :


>l66
>166
>166

>166
>l66
>166


>166
>166
>166

32
>166
>166

2020
I Alt. IV
-500 cfs

132
>166
>166

162
>166
>l66
-1250 cfs

63
100
126

60
97
122
-2000 cfs
V.'ster Use Increment 40 mg/1 of TDS

IDS ( 500) mg/1    >l66         118
1JO

-------
                                     Table X-10

                         TIME, IN BAYS, TO REACH INDICATED
                      CONCENTRATION OF TOTAL DISSOLVED SOLIDS
                                     IN ESTUARY
                    AT PROPOSED WATER INTAKE NEAR CHAIN BRIDGE
                    (Initial Conditions as of September 13, 1966)
                        1280.
                                               2000
                                                    2020
                 Alt. I
                             Alt.  IV
                      Alt. I
           Alt. IV
                                                               Alt. I
           Alt. IV
Freshwater Flow*
                        1000 cfs
                             250 cfs
                             -500 cfs
Water Use Increment 40 mg/1 of TDS

TDS ( 500) mg/1    >l66        >l66
TDS (1000) mg/1    >166        >166
TDS (1500) mg/1    >l66        >l66

ti'ater Use Increment 240 mg/1 of TDS

IDS ( 500) mg/1    >166        >166
TDS (1000) mg/1    >166        >166
LD3 (1500) mg/1    >l66        >l66
                                         >166
                                         >l66
                                         >l66
                                         >166
                                         >l66
                                         >166
                                                    >166
                                                    >166
                                                    >166
                                                    >166
                                                    >166
                                                    >166
                                              >166
                                              >166
                                              >16'6
                                              > 166
                                              >l66
                                              >166
                                    132
                                   >166
                                   >156
                                    162
                                   > 166
                                   >l66
Freshwater Flow
                         250 cfs
                            -500 cfs
                            -1250 cfs
V/ater Use Increment 40 mg/l of TDS

TDS ( 500) mg/1
IDS (1000) mg/1
IDS (1500) mg/1

Water Use Increment 240 rcg/1 of TDS

      >00) mg/1    >166        >166
                  >166        >166
                              >166
>166
>l66
>166
>166
>l66
>166
>166
>l66
>l66
124
>166
>166
>166
>166
>166
TIS (1000) mg/1
TJS (1500) mg/1
>166
>166
>166
>166
>166
                                                      123
                                                     >l66
                                                     > 166
   32
> 166
>166
                                                                              63
                                                                             100
                                                                             126
 60
 97
122

-------
                     Tci.'blc> X- -10

      fj':\l'A}} It VdYS, TO K/.AOK  li'DIOAT^D
   oo/:CtvOj'uAv;KK>; o/ TOivu, jxf^oLY.jn) CO/.TIXJ
 AT i'i?avo3;-:D vAyxi; IKTAKM KJ-:/J{ cMitf }irax;^;
(initial Cloaca tu OIL.-; as  of fkrptc.rfjcr .13,  1966)



.(.' .C'O-
T f- . I
l-iS
TD3
T.>3
0'D:i
',/li^t
T.D3
T.JX3
TC-3
"103
Frcs
,L /i C-' J?
?E£5
T.Bo
T.DS
TIo
Jnev
'.i.' u3
TD3
T.03
TTo
i-re.
Tr.cr
TiO

T.t/V>
T.u.
Til,::,-
TiX;

'•.-.•;•',
1 .1 - *



hv ' l->.r
-::-.;.-. ;.er
\ x* /
(1003)
(1500)
(2000)
:-r,. ":!•.; or
( 500)
(1000)
(1500)
(2000)
h^ator
e-i-^nt
( 500)
(HO DO)
(.1500)
(2000)
e.r.oat '
( 503)
(-'030)
(1500)
(2000)
":.;; ',--.-r

(' 500)
')':(-r'^J(
} ' ^ A \
v-;o,-o)
: ,• ' •"• i
( V03)
( ' , ')-;}
t i %
v '-''',' ';


Alt .
}'U.OW
Incrccmer'a;
xi 66
X166
>l66
XL66
Increraerrb
X166
Xi.66
xi 66
X166
Flo-.-r
^0 rng/1
>166
>166
X166
xv66
•>];.Q m:r/l
Xi.66
X166
Xi.66
Xi.66
i'.l o-.f
-0 r.-Vl
v_->/
Xi.66
X166
X166
X166
-)',n - ^-/i
83
Xi66
xi 66
Xi 66
3980

I Alt. p
1030 cTs
hO it.-/.!
X166
X166
>166
Xi 66.
2'iO j.^-./.l.
Xi 66 '
X166
xi.66
X166
250 el's

Xi.66
X166
Xi.66
Xi.66

Xi 66
Xi 66
X166
Xi 66
-500 c,7.

Y'.
-i 06
3.29
l':-5

yl;
1 06
129
t';>


jTi-l L'


Xi 66
X165
X166
Xi.66

XL66
>165
Xi 66
Xi.66


>166
X166
X166
Xi.66

5Y
Xi.66
Xi 66
Xi.66


Y8
132
165
Xi.66
,
26
.'i 03
.1 ': 0
>:i 66
2.000

I Alt. N
250 cis

X166
>i66
>l65
>166

>166
X166
Xi 66
Xi 66
-500 ci's

YO
110
:i35
15Y

YO
110
135

-.3250 cr«

•28^
j'5
58
YO

28
V;
58
YO


Alt .


xi.66
X166
Xi 66
Xi 66

XL66
>166
X166
Xi.66


X166
XL66
X166
XI 66

28
Xi 66
Xi.66
X166


39
Y8
100
122

-15
60
83
103
2020

1 Alt J//
-500 cfs

Y-L
115
150
- X166

Y-i
a 15

Xi.66
-1250 cl-s

28
),y
61
Y8

28

60
Y6
-2500 el's

2-';

39


-'Y

-,'s
;_c)

-------

-------
                                    Table X-10
                        TIME, IN DAYS, TO REACH INDICATED
                     CONCENTRATION OF TOTAL DISSOLVED SOLIDS
                                    IN ESTUARY
                   AT PROPOSED WATER INTAKE NEAR CHAIN BRIDGE
                  (Initial Conditions as of September 13, 1966)
1980
Alt. I Alt. IV
Freshwater Flow* 1000 cfs
Water Use Increment 40 mg/1 of TDS
77JS ( 500) mg/1 >166 >l66
7D3 (1000) mg/1 >166 >166
126 (1500) mg/1 >166 >166
Vi'ater Use Increment 240 mg/1 of TDS
IDS ( 500) mg/1 >l66 >l66
IDS (1000) mg/1 >l66 >166
ID3 (1500) mg/1 >l66 >l66
Freshwater Flow 250 cfs
i'/ater Use Increment 40 mg/1 of TDS
TDS ( 500) mg/1 >l66 >l66
IDS (1000) mg/1 >166 >166
TDS (1500) mg/1 >l66 >l66
\/ate," U?e Increment 240 mg/1 of TDS
irs ( 500) mg/1 >l66 >l66
776 (1000) mg/1 >166 >l66
"X (1500'; mg/l >166 >166
'.resb.water Flow -500 cfs
Y/>ter Use Increment 40 mg/1 of TDS
::,;' i 500) mg/1 >166 118
I~£ (1000) mg/1 >166 >166
7.TS (1500) mg/1 >l66 >l66
','/at,er Ifee Increment 240 mg/1 of TDS
TDt> ( 500) mg/1 83 11?
IuS (1000) mg/1 >l66 160
70S (1500) mg/1 >166 >166
2000
Alt. I
250

>166
>166
>166

>166
>166
>166
-500

>166
>166
>l66

>166
>l66
>166
-1250

130
>166
>166

126
147
>166
Alt. IV
cfs

>166
>166
>166

>l66
>166
>166
cfs

124
>166
>166

123
>l66
>l66
cfs

58
S8
107

57
87
106
2020
Alt. I Alt. IV


>166
>166
>l66

>166
>166
>166


>166
>166
>166

32
> 166
> 166


o/.
130
159

15
130
159
-500 cfs

132
>166
>166

162
> 166
>l66
-1250 cfs

63
100
126

60
97
122
-2000 cfs

43
68
00

43
•^ ; o
36
Inflow to estuary after water supply withdra\val

-------
                                   Table  X-9
                        TIME,  IN DAYS, TO  REACH  INDICATED
                     CONCENTRATION  OF TOTAL DISSOLVED SOLIDS
                                   IN ESTUARY
                   AT PROPOSED WATER  INTAKE NEAR CHAIN BRIDGE
                    (Initial Conditions  as of July 7-8, 1965)
1980

Freshwater Flow*
Alt. I
1000
Water Use Increment 40 mg/1
TDS ( 500) mg/1
TDS (1000) mg/1
TDS (1500) mg/1
>166
>166
>166
Water Use Increment 240 mg/1
TDS ( 500) mg/1
TDS (1000) mg/1
TDS (1500) mg/1
Freshwater Flow
>166
>166
>166
250
Water Use Increment 40 mg/1
TDS ( 500) mg/1
TDS (1000) mg/1
TDS (1500) mg/1
>166
>166
>166
Water Use Increment 240 mg/1
TDS ( 500) mg/1
TDS (1000) mg/1
TDS (1500) mg/1
freshwater Flow
>166
>166
>166
-500
"tfster Use Increment 40 mg/1
TDS ( 500) mg/1
TDS (1000) mg/1
TD3 (1500) mg/1
>l66
>166
>l66
Water Use Increment 240 mg/1
IDS ( 500) mg/1
TDS (1000) mg/1
TDS (1500) mg/1
83
>l66
>166
Alt. IV
cfs
of TDS
>l66
>166
>166
of TDS
>166
>166
>166
cfs
of TDS
>166
>166
>166
of TDS
>166
>166
>166
cfs
of TDS
118
>166
>166
of TDS
117
160
>166
2000
Alt. I
250

>166
>166
>166

>166
>166
>166
-500

>166
>166
>166

>166
>166
>166
-1250

130
>166
>166

126
147
>166
Alt. IV
cfs

>166
>166
>166

>166
>166
>166
cfs

124
>166
>166

123
>166
>166
cfs

58
88
107

57
87
106
2020
Alt. I Alt. IV


>166
>166
>166

>166
>166
>166


>166
>166
>166

32
>166
>166


84
130
159

15
130
159
-500 cfs

132
> 166
>166

162
>166
>166
-1250 cfs

63
100
126

60
97
122
-2000 cfs

43
68
86

43
68
86
Inflow to estuary after water supply withdrawal

-------
                                                                  X-47


2.  Direct Reuse of Treated Wastewater

     In the system where treated wastewater is discharged into the fresh-

water estuary, intrusion of salt from Chesapeake Bay is one of the major

restrictions if the upper estuary is to be used as a potable water supply.

The direct reuse system (that is, going directly from the advanced waste-

water treatment facility to the water supply facility) removes this

restriction.

     Using the water requirements for the year 2020 and conditions as

defined in the previous section, simulations were made with the direct

reuse system to determine the rate of buildup of both chlorides and TDS.

The results of these simulations for various flow conditions are presented

below:

                             	Equilibrium Concentrations	
V/ater from    Water from     Chlorides max.  40 mg/1 of     240 mg/1 of
Upper Basin   Direct Reuse   Concentration   TDS Increase   TGB Increase
(cfs)
400
1150
1900
(cfs)
2000
1250
500
(mg/1)
140
42
22
(mg/1)
360
203
171
(mg/1)
1360
421
233
The equilibrium concentrations or maximum concentrations to which the

system would build up with partial direct recycling usually were

reached in less than 20 days except for the first flow condition (400 cfs

from Great Falls) in which 40 days were required.

-------
                                                                  X-48





     The above tabulation indicates that direct reuse is a feasible



solution to the future water supply needs of the Washington metro-



politan area with respect to TE6 and chlorides.  The only restriction



is that with over 80 percent of the water supply from renovated waste-



water, the maximum combined buildup in TDS from both the water supply



and wastewater treatment facilities has to be less than 65 mg/1.  For



a flow of 670 cfs (the s even-day-lo?/~f low with a recurrence interval



of once-in-50-years) or with approximately 70 percent of the water



supply from renovated wastewater, the maximum TDS buildup would have



to be restricted to 1-40 mg/1.  As reported earlier, this is the current



buildup in the entire water use system.



     Based on data obtained from the AIT pilot plant operation at



Blue Plains [46], the TES, excluding the bicarbonate system, is not



anticipated to increase and in fact may decrease,,  Since the bicarbonate



concentration can be controlled by proper selection of unit processes



of the AWT treatment facilities, the 140 mg/1 increment can readily be



maintained.



     The direct reuse concept has the following advantages:



     (l)  Effects of intrusion from the Chesapeake Bay are eliminated,



     (2)  Need for the protection of the upper estuary from accidental



spills, urban runoff, storm and combined sewer overflows with respect



to water supply is eliminated,



     (3)  Restriction on the location of wastewater facilities with



respect to water supply needs is eliminated,

-------
                                                                  X-49






      (4)  With proper planning, the need for massive wastewater



collection and water distribution systems can be reduced.  For example,



both  facilities can be located in the upper Potomac area with reuse



being instituted whenever needed.  During high-flow periods, the



effluent may be discharged into the Chesapeake and Ohio Canal and



conveyed past the downstream water intake.



      (5)  The need for the proposed upstream impoundments for water



supply in the Washington area would be eliminated.



     The major disadvantages are:



      (l)  Ammonia nitrogen conversion or removal will be required at



temperatures approaching 5°C.  Technology for this requirement is not



fully developed at the present time.



      (2)  With the potential buildup of TDS, unit process will have



to be carefully selected.



      (3)  A high degree of operation efficiency, including "fail safe"



concepts, must be maintained at both the wastewater and the water




supply facilities.



     The direct reuse concept has great potential.  However, there are



many aspects which need to be investigated.   These concepts could also



be readily applied to small areas such as the Occoquan watershed, a



sub-basin of the Potomac below Washington, and the Patuxent River Basin,



a watershed bet?/een Baltimore and Washington.

-------

-------
                                                                  XI-1



                             CHAPTER XI



             WASTEWATER TREATMENT  FACILITIES AND COSTS




A.  TREATMENT  CONSIDERATIONS



     To meet the  carbon (UOD), nitrogen, and phosphorus requirements




previously specified, a high degree of wastewater treatment will be




required for Zone I.  Based upon the performance of the FWQA. pilot




plant at Blue  Plains, Bishop [46]  indicates that the following removal




rates can be anticipated from April to November (winter operation




reliability has not been demonstrated):




     Parameter            After Treatment,            % Removal




     BOD5                     <2.0                     >99




     Nitrogen  as N              1.0 - 2.0                 90 - 95




     Phosphorus as P          < 0.1                     > 99




To achieve the above removals, the following unit process sequence




could be selected:




     (l)  Primary settling and activated sludge,




     (2)  Biological nitrification,




     (3)  Biological denitrification,



     (4)  Lime treatment,




     (5)  Dual media filtration,




     (6)  Effluent breakpoint chlorination, and




     (7)  Effluent aeration.




     The above unit processes can produce an effluent which will meet




the removal requirements for phosphorus and ultimate oxygen demand.




However, with respect to nitrogen removal for algal control, it appears

-------
                                                                   XI-2






that the requirement cannot be readily met.  Since over 99 percent of



phosphorus can be removed, it appears that with a combination having a



high percentage of carbon removal and 90 percent nitrogen removal, such



as the preceeding seven unit processes can provide, both the DO enhance-



ment and algal control will be realized.  At present,  the need for



activated carbon adsorption has not been adequately demonstrated.



     An important aspect of wastewater treatment will  be the additional



effluent aeration required, especially in Zone I, or for large dis-



charges into small embayments.  For example, a discharge of 185 mgd



into the Anacostia River will be over 35 times greater than the



freshwater inflow during low-flow periods.  Hence, to  maintain a DO



level of 5.0 mg/1, the discharge will have to have at  least 5.0 mg/1



of DO.  The unit process for this effluent quality is  included in all



costs presented in this report.



     Additional removal of inorganic nitrogen and carbon could be



provided by activated carbon.  The activated carbon beds become media



for bacterial growths which convert some of the organic nitrogen to



ammonia.  The ammonia can then be removed by additional chlorination.



Since the continued effectiveness of this additional nitrogen removal



process is not well established, the effectiveness or  the need for



carbon adsorption as an additional wastewater unit process has not at



present been established.  Its utility appears to be more predicated on



the use of the estuary as a water supply than for wastewater treatment.

-------
                                                                   XI-3






B.  WASTEWATER TREATMENT COSTS



     Cost estimates for conventional secondary treatment and six



advanced waste treatment (AWT) processes were developed for 15 present



and planned facilities.  The AWT processes considered include lime



clarification with dual media filtration (for phosphorus removal and



for additional carbon  removal), carbon adsorption, biological nitrifi-



cation and denitrification (for removal of ammonia and nitrate nitrogen



respectively), and effluent aeration (to increase the DO from 1.0 to



6.0 rag/1).  Capital costs and operation and maintenance (0 & M) costs



for each process were  obtained chiefly from the Bechtel Corporation's



report [47] on AWT at  Blue Plains and cost data prepared by Smith and



McMichael [4.8].  Where necessary, these costs were adjusted to reflect



mid-1970 engineering indexes.



     Cost data for specific years were determined by a computer systems



program which incorporated equations describing the dollar per unit



discharge relationship.  One of the cost curves used is shown in



Figure XI-1.  Basic assumptions and alternative amortization and plant



operat i on s chemes included:



     (l)  Expenditures for new construction required in 1970, 1980, and



2000 are based upon design for conditions 10 or 20 years hence.



     (2)  In the case of existing treatment plants, construction of AWT



units would begin in 1970 with 0 & M cost accruing from that time.



Other plants were assumed to be constructed in 1980.

-------
                        •"1V£> OOOI/» - J.SOO   XN3WJLV3MJ.

                                   8                             o

        J
         I


        1
                                           - J.SOO  TVXIdVO
    O

HGURE Xl-l

-------
                                                                  XI-5





      (3)  If a new AWT plant is to be constructed in 1970, a 15-percent



replacement of this plant would be necessary by 1980 in addition to



required expansion.  For the year 2000 construction, it was assumed that



the entire original plant built in 1970 and 30 percent of the plant



built in 1980 would be replaced.



      (4)  If a new AWT plant is to be constructed in 1980, 30-percent



replacement would be provided for the year 2000 along with expansion to



meet  2020 needs.



      (5)  With the exception of Arlington, conventional treatment units



at the existing plants were considered to be new in 1970.  The current



capacity at Piscataway was assumed to be 30 mgd since construction of



additional facilities is well under way.



      (6)  0 & M costs for AWT units were based on 6-month and 12-month



operating periods and the average projected waste flows for the specific



time  frame.



      (7)  The amortization of capital costs was assumed over a 20-year



period with an interest rate of 5-1/8 percent.



     Table XI-1 presents a summary of the treatment cost data for the



upper Potomac Estuary through the year 2020.



     Using Alternative III, the total present worth cost of wastewater



treatment expenditures from 1970 to 2020 was determined to be $1,340



million (Table XI-l).  If activated carbon is added, the cost will



increase to $1,700 million.  The annual cost basis  for an average

-------
                                                                   XI-6






population of six million people reduces to approximately $11 per person



per year.  With the activated carbon units, the cost increases to




$14 per person per year.



     Capital cost expenditures and 0 & M costs are presented by unit



process for-the three periods (1) 1970-1980, (2) 1980-2000,  and



(3) 2000-2020 in Table XI-2.  As can be seen in the table,  the largest



capital costs of the total initial cost of $2,272 million are $737 million



for secondary and $463 million for activated carbon unit process, with



the 0 & M cost being largest for the lime clarification and  activated



carbon processes.



     With nitrification and denitrification required for only 7 months



out of 12, an annual 0 & M savings of $3 million from 1970-1980,



$4 million from 1980-2000, and $6 million from 2000-2020 can be realized.



Continued studies will be required to further define the temporal removal



requirements for nitrogen.

-------
                             Table XI-1

                  TOTAL WASTEWATER TREATMENT COST
                            1970-2020
                          Alternative III
Unit Process
Primary -s e condary
Biological nitrification
Biological denitrification
Lime clarification
Dual media filtration
Effluent Aeration
Chlorination
Subtotal
Activated Carbon
TRY*
($ x 106)
457
2/47
133
370
101
10
22
1,340
360
TAAC**
($ x 106)
13.5
13.8
9.4
20.6
5.7
0.6
1.2
$64.8
20.1
Total                           1,700                $84.9
*  Total present worth cost includes proposed secondary treatment
   expansion cost for Blue Plains

** Total average annual cost including operation and maintenance
   cost based on 12 months of operation

-------
                                      Table XI-2

                             INITIAL CAPITAL CONSTRUCTION
                                         AND
                            OPERATION AND MAINTENANCE COSTS
                   1970-1980, 1980-2000, and 2000-2020 Time Periods
Unit Process
Primary-secondary

Biological nitrification

Biological denitrification

Lime clarification

Dual media filtration

Chlorinat ion

Effluent aeration


Subtotal

Activated carbon


Total
1970-1980
Capital Qtfoer
($x!06) ($x!03)
236.11
70.64
62.11
69.31
27.22
0.37
2.91
468.67
101.96
4H1.48
3968.66
427.29
8661.66
889.15
761.59
226.61
19176.44
5931.92
1980-2000
Capital Other
($xltf>) ($x!03)
129.71
84.53
71.84
81.96
35.02
2.00
4.35
409.49
118.38
7413.07
7097.46
759.32
15573.46
3064.69
1328.37
407.73
35644.10
10535.54
2000-2020
Capital Other
($x!06) ($x!03)
371.11
167.63
148.24
166.12
66.09
3.55
6.90
929.64
243.40
11512.23
11044.23
1197.80
24560.32
4510.30
2165.03
739.27
55729.18
16643.79
570.63  25108.36    527.87   46179.64   1173.04   72372.9?'

-------
                                                                  XI -9
     The tabulation below is a reduction of the initial capital and

operation and maintenance costs to a per capita basis:

          Item               1970-1980      1980-gQOO        2000-2020

Average Population           3,350,000      5,350,000        8,000,000

Total Initial Capital
Cost/Tijue Period          $570,000,000   $528,000,000   $1,173,000,000

Capital Cost/Person/Year       $17.0           $4.9             $7.3

0 & M CostAear            $25,100,000    $46,200,000      $72,400,000

0 & M Cost/Person/Year          $7.5           $8.6             $9.1

Total Cost/Person/Year         $24.5          $13.5            $16.4

The above summary, which does include replacement cost, indicates that

the cost of waste-water treatment in the upper Potomac Estuary is about

$13 to $24/per person/per year.  This expenditure, which includes the

cost of the activated carbon process, will renovate the water to the

chemical and microbiological qualities meeting drinking water standards,

-------

-------
                                                                 XII-1




                            CHAPTER XII



          IMPLEMENTATION TO ACHIEVE WATER QUALITY STANDARDS



A.  SEASONAL WASTE TREATMENT REQUIREMENTS



1.  Ultimate Oxygen Demand



     The maximum allowable UOD loadings presented in Chapter X for



the three upper zones of the Potomac Estuary apply under warm



temperature conditions.  The effects of nitrogenous oxygen demanding



substances on the dissolved oxygen budget were determined to be quite



significant when water temperatures exceed 15°C.  At the present time,



approximately 250,000 Ibs/day of nitrogenous oxygen demand is dis-



charged in wastewater effluents as compared to about 200,000 Ibs/day



of carbonaceous demand.  Therefore, during very warm periods when



nitrification rates are high, the nitrogenous component of UOD exerts



a greater effect on the dissolved oxygen resources than the carbona-



ceous material.  In order to comply with the allowable UOD loadings



shown previously, it is necessary to reduce drastically both the



nitrogen and carbon levels at the wastewater treatment plants whenever



temperatures exceed 15°C.



     During cold weather periods when the ambient water temperature



is less than 15°C, the effects of nitrification on the dissolved



oxygen budget become negligible as reported in Chapter VI.  Therefore,



the need for removal or oxidation of ammonia in wastewater discharges



is not required during these periods.

-------
                                                                 XII-2






     To prevent the accumulation of sludge deposits in the vicinity of



sewage treatment outfalls during cooler weather and to maintain high



DO levels under ice cover, a high degree of removal of suspended solids



and carbonaceous oxygen demanding material must be continued.  Suspended



solids concentrations in the effluent should not exceed 15 mg/1, and a



minimum of 90 percent of the carbonaceous oxygen demand should be removed



on a year-around basis.  Currently, about 72 percent of the UOD load before



wastewater treatment is carbonaceous and the remaining 28 percent nitroge-



nous.  Based upon this proportion of carbonaceous and nitrogenous



components in raw sewage, the requirement for carbonaceous removal would



translate to 70-percent UOD removal.



     Since the quantity of dilution flows in the upper end of the tidal



embayments is greatly limited, continuous aeration of major wastewater



effluents discharged to these areas will be required.



2.  Phosphorus



     Of the various nutrients that have been associated with the eutro-



phication problem in the upper and middle reaches of the Potomac Estuary,



phosphorus has been found to be most controllable, not only on a seasonal



basis but on an annual basis as well.  As presented in Chapter VII,



approximately 60 to 96 percent of the total phosphorus load to the



Potomac Estuary can be controlled depending upon the existing flow



conditions.  An additional reduction in the uncontrollable phosphorus



load from the upper basin occurs in the upper estuary as a result of

-------
                                                                   XII-3






phosphorus being sorbed upon silt particles accompanying high flows,



which is then removed by sedimentation.



     The phosphorus criteria required to prevent nuisance algal blooms



from occurring, as developed in Chapter VII, varied from 0.03 to 0.1 mg/1.



These criteria are approximately an order of magnitude lower than the



corresponding criteria for nitrogen.  Because of these stringent criteria,



particularly in the lower zones of the estuary, and the possibility of



recycling previously deposited phosphorus from the bottom muds (this con-



tribution has not been quantitatively defined), year-around phosphorus



removal at the wastewater treatment facilities in the upper estuary will



be necessary.



     The mathematical model used to predict the annual distribution of



phosphorus in the critical algal growing areas was verified based upon



extensive phosphorus data collected from February 1969 to September 1970.



The close agreement between observed and predicted phosphorus profiles



during this period for the Potomac Estuary at Indian Head is shown in



Figure XII-1.  Also shown in Figure XII-1 are the predicted annual



phosphorus profiles resulting from year-around removal in the upper



estuary, assuming (l) no control and (2) 50-percent control of the



phosphorus load originating in the upper Potomac River Basin.  It can



be concluded after an examination of Figure XII-1 that both phosphorus



removal on a year-around basis in the estuary and partial control of



the incoming load will be required if the recommended phosphorus



criteria are to be achieved.

-------
_J  ^
==  UJ
u.  i


0  2
O H-
TT *O

£ u

  i O
                    ui
                    (0

                    §
                    I    I    I    I    I    I    I    I     I    I    I    I

                    to^<\iai«o*
                    evi«vi<\i«si  —   —   —   —   —   bdd
                                                                                     o:
                                                                                     u
                                                                                     a
                                                                                     a
                                                                                     0.0


                                                                                     i£
                                                                                                                       at
                                                                                                                       UI
                                                                                                                       o
                                                                                                                       UI
                                                                                                                       Q
                                                                                                                       o
                                                                                                                       o
                                                                                                                       3
                        «
                        «
                                                                                                                       o
                                                                                                                       UJ
«  
-------
                                                                  XII-5





     In order to realize a 50-percent reduction in the current phosphorus



load from the upper Potomac River, the wastewater contribution of 6100



Ibs/day must be reduced to 700 Ibs/day.



3.  Nitrogen



     As presented earlier in this chapter, the necessity for nitrogen



control in wastewater discharges to enhance the dissolved oxygen in




the Potomac Estuary is restricted to that time of year when water



temperatures exceed 15°C.  When evaluating inorganic nitrogen treat-



ment requirements for the prevention of excessive algal blooms,



controllability becomes a significant factor.



     Mathematical model studies were used to investigate the effects



of seasonal and continuous nitrogen removal at the wastewater



facilities in the upper Potomac Estuary.  Figure XII-2 shows the



predicted annual nitrogen profiles for the Potomac Estuary at Indian



Head, using the verified mathematical model, assuming (l) no nitrogen



removal, (2) nitrogen removal during periods with temperatures above



15°C (April-November), and (3) year-around nitrogen removal.  These



profiles show that the recommended nitrogen criteria can be obtained



during the critical growing periods with either seasonal or continuous



nitrogen removal.  Though it would be desirable to continuously main-



tain nitrogen concentrations at or below these criteria,  the high flows



from the upper basin during the winter and spring months  contribute



high nitrogen loadings which increase the nitrogen concentrations above



acceptable levels regardless of treatment practices  (Figure XII-2).

-------
LJ
Q-
UJ    <
O    5
O    z
tr    -
      o:
<

Q
      ul
      UJ

      U
      <


      I
      O
      Q.
                             r
                             q
i    r
                                                    I   T   I   I
                                 (M
i    I
                                                                                     ^
                                                                                     ^
                                                                                         o>
                                                                                         IO
                                                                                         01
                                            r
                                        •*   <\J  O
                                        6   6  6
                                                                          FIGURE  XII-2

-------
                                                                  XII-7
     The controllable nitrogen from the waste-water treatment sources



in the Washington metropolitan area is currently limited to about



60 percent of the total contribution from all sources.  If nitrogen



loadings increase as projected, the controllable amounts will also



increase.  Thus it appears that while nitrogen removal for algal



control could be limited to periods when water temperatures in the



estuary exceed 15°C, there may be a need for continuous control by



the year 2000.

-------
                                                                 XII-8




B.  LOCATION OF WASTEWATER DISCHARGES



1.  Wastewater Assimilation Versus Salinity Intrusion



     Projected wastewater loadings are highest in Zone I,  with allow-



able UOD, nitrogen, and phosphorus loadings the lowest of  all three



zones.  The concentration of wastewater discharges in Zone I will



require much higher removal rates there than will be necessary in



Zones II and III.



     When the high degree of wastewater treatment is considered,  it



would appear to be advantageous to discharge effluents farther down-



stream in the estuary.  The assimilation and transport capacity in



Zone II is about four times that of Zone I.  However, when the estuary



is considered as a water supply source, no major effluent  discharges



from the Washington metropolitan area should occur below the middle of



Zone II (or below Gunston Cove).  This downstream discharge limit is



required to keep the salt wedge from moving upstream and causing



chloride and TDS intrusion at the water intake.



     If direct water reuse is eventually adopted, greater  use of



the assimilative and transport capacity of the estuary can be realized.



Moreover, the farther down the estuary residual nutrient loads are



discharged, the less favorable conditions will be for blue-green



algae because of higher salinity.

-------
                                                                  XII-9

2.  Wastewater Discharges to ^he Embaymen.ts

     All present treated waste effluents except that from Blue Plains

discharge into the tidal portion of various embayments.  As presented

in the previous chapter, a high degree of UOD, nitrogen, and phosphorus

removal will be required if the present embayment discharge practice

is continued.

     Based upon detailed analyses, including dye studies, of the

Anacostia, Piscataway, and Gunston Cove tidal embayments, it appears

that major discharges into the upper portion of small tidal embayments

should have a maximum concentration of UOD, phosphorus, and nitrogen

of 10, 0.2, and 1.0 mg/1, respectively.  Effluents from these facilities

will require renovation to approach ultimate wastewater renovation*

(UWR) levels.  Unless UWR is provided, effluents from Alexandria,

Arlington, Piscataway, and the Lower Potomac facilities should be

discharged into the main channel of the Potomac Estuary.

     A detailed investigation is essential for each embayment to

determine which option provides the lesser cost, an outfall to the

main channel of the river or UWR.  Future studies should also include

consideration of effluent dispersion devices to minimize local effects.
  Ultimate wastewater renovation can be defined as renovation of the
  wastewater to such a degree that it can be discharged into the
  receiving stream in unlimited quantities without restriction of the
  designated water resource use due to the lack of needed assimilative
  or transport capability of the stream.  This implies that the quality
  of the effluent from a UWR plant conforms to the stream standards  of
  the receiving waters.

-------
                                                                 XII-10






C.  FLOW REGULATION FOR WATER SUPPLY AND WATER QUALITY CONTROL



     In the original plan for reservoir development in the upper Potomac



River Basin, the U. S. Army Corps of Engineers recommended 16 impound-



ments including the large Seneca Dam [1].  These 16 reservoirs would



regulate the flow of the Potomac at Washington to maintain an approxi-



mate 4600 cfs minimum and would provide the maximum daily water supply



needs of the basin up to the year 2020.  When the Seneca Reservoir is



excluded, the remaining 15 impoundments would increase the dependable



low flow to approximately 3600 cfs.  This would be an adequate flow to



meet the maximum monthly water supply demand for the Washington



metropolitan area up to the year 2020.



     In the original Corps of Engineers' plan, approximately $210



million or 42 percent of the $500 million construction cost was charged



to water quality control.  Of this $210 million water quality control



construction cost, approximately $130 million was required to maintain



Potomac Estuary water quality [I].



     Davis  [50], in his study of the water quality management problems



of the Potomac Estuary, suggested that  mechanical reoxygenation and



low-flow augmentation provided the least costly solution to maintain



a specific dissolved oxygen (DO) level.  Although the costs for



individual wastewater processes as presented by Davis have increased



substantially, later investigations have indicated that algal control



and nitrification requirements are presently the two most important



considerations in water quality management for the upper estuary.

-------
                                                                 XII-11






Nevertheless, the Davis studies demonstrate that DO standards could be



maintained with a high degree of wastewater treatment at lower cost



and with greater dependability than by flow regulation alone.



     As summarized by Reinhardt [51], a program of water resource



management must be flexible in order to make use of modern technological



developments to meet current wastewater treatment requirements.  The



requirements developed in this study reflect not only a need for high



carbonaceous BOD removals but also for nutrient removals to control



algal growth.  Low-flow augmentation for nutrient control will not be



effective since the total nutrient loading in pounds per day entering



the estuary is the primary factor to be considered in algal control.



This insensitivity to flow is especially pronounced in the middle



reach where the volume of the estuary is large, advective movement



slight, and algal growing conditions ideal.



     The maximum waste loadings and treatment costs presented in



Chapters X and XI will not be greatly affected by flow regulation



considerations, even with construction of either 15 or 16 reservoirs.



It appears that the major advantage of flow regulation is for water



supply purposes and not for water quality management.

-------

-------
                          ACKNOWLEDGEMENTS


     The assistance and cooperation of various governmental and

institutional agencies greatly facilitated the collection and

evaluation of the data presented in this report.  While every

agency contacted provided valuable assistance, the cooperation of

the following merit special recognition:

     Maryland Department of Water Resources

     Maryland State Department of Health

     Virginia State Water Control Board

     Virginia Department of Conservation and Economic Development

     District of Columbia, Department of Environmental Health

     District of Columbia, Department of Sanitary Engineering

     County of Fairfax, Virginia

     City of Alexandria, Virginia

     County of Arlington,  Virginia

     Washington Suburban Sanitary Commission

     Andrews Air Force Base

     Department of the Army, Fort Belvoir

     Washington Aqueduct and North Atlantic Division, U.  S.  Army
       Corps of Engineers

     U. S.  Geological Survey, Department of the Interior

     Metropolitan Washington Council of Governments

     Interstate Commission on the Potomac River Basin

-------
     The assistance and guidance given by Dr. George P.  Fitzgerald,



Research Associate, University of Wisconsin, a special consultant to



the Chesapeake Technical Support Laboratory is sincerely appreciated.



The suggestions of the Potomac Enforcement Conference Technical



Advisory Committee were also helpful in formulating this study.



     The authors also wish to acknowledge the assistance of all staff



members of the Chesapeake Technical Support Laboratory,  especially



Mary F. Tornanio who helped in preparing this report, and the following:



     Johan A. Aalto, Chief, Chesapeake Technical Support Laboratory



     Donald W. Lear, Jr., Chief, Ecology Section, CTSL



     James W. Marks, Chief, Laboratory Section, CTSL



     Orterio Villa, Jr., Chief Chemist, CTSL



     Margaret S. Mason, Typist



     Margaret B. Munro, Typist



     Richard Burkett, Draftsman



     Gerard R. Donovan, Jr., Draftsman



     Frederick A. Webb, Draftsman

-------
                                REFERENCES


 1.  U. S. Army Corps of Engineers, "Potomac River Basin Report,"
     Vol. 1 - Vol. VIII, North Atlantic Division,  Baltimore District,
     February 1963.

 2.  FrisMe, C. M. and D. E. Ritchie, "Sport Fishing Survey of the Lower
     Potomac Estuary, 1959-1961," Chesapeake Science. Vol. 4, No. 4,
     December 1963.

 3.  U. S. Department of the Interior, "The Potomac - A Model Estuary,"
     Bureau of Outdoor Recreation, July 1970.

 4.  U. S. Department of the Interior, "Maryland and Virginia Landings
     Annual Summary," Bureau of Commercial Fisheries, Fish and Wildlife
     Service, 1969.

 5.  Jaworski, N. A., "Nutrients in the Upper Potomac River Basin," CTSL,
     MAR, FWPCA, U. S. Department of the Interior,  August 1969.

 6.  Private communication with Roy Weston Consulting Engineering Firm
     currently investigating the storm and combined sewer contribution
     under contract to FJVQA..

 7.  U.S. Public Health Service, "Investigation of the Pollution and
     Sanitary Conditions of the Potomac Watershed," Hygienic Laboratory
     Bulletin No. 104, Treasury Department, February 1915.

 8.  Aalto, J. A., N. A. Jaworski, and Donald W. Lear, Jr.,  "Current
     Water Quality Conditions and Investigations in the Upper Potomac
     River Tidal System," CTSL, MAR, FWQA, U. S. Department  of the Interior,
     Technical Report No. 41, May 1970.

 9.  Livemore, D. F. and W. E. Wanderlich, "Mechanical Removal  of Organic
     Production from Waterways," Eutrophication:  Causes, Consequences.
     Correctives. National Academy of Sciences,  1969.

10.  Bartsch, A. F., "Bottom and Plankton Conditions in the  Potomac River
     in the Washington Metropolitan Area," Appendix A, A report  on water
     pollution in the Washington metropolitan area,  Interstate Commission
     on the Potomac River Basin, 1954.

11.  Stotts, V. D. and J. R. Longwell, "Potomac  River Biological Investi-
     gation 1959," Supplement to technical appendix to Part  VII  of the
     report on the Potomac River Basin studies,  U.  S. Department of Health,
     Education and Welfare,  1962.

-------
12.  Elser, H. J., "Status of Aquatic Week Problems  in Tidewater Maryland,"
     Spring 1965, Maryland Department of Chesapeake  Bay Affairs, 8 pp mimeo,
     1965.

13.  Bayley, S., H. Rabin, and C,.  H.  Southwick,  "Recent Decline in the
     Distribution and Abundance of Eurasian Watermilfoil  in Chesapeake Bay,"
     Chesapeake Science,  Vol. 9, No.  3,  1968.

14.  Jaworski, N. A., D.  W, Lear,  Jr., and J. A. Aalto, "A Technical Assessment
     of Current Water Quality Conditions and Factors Affecting Water Quality
     in the Upper Potomac Estuary," CTSL, FWPCA, MAR,  U.  S. Department of the
     Interior, March 1969.

15.  Mulligan, H. T., "Effects of  Nutrient Enrichment  on  Aquatic Weeds and
     Algae," The Relationship of Agriculture to Soil and  Water Pollution
     Conference Proceedings, Cornell University, January  1970.

16.  Edmondson, W. T., "The Response of  Lake Washington to Large Changes  in
     its Nutrient Income," International Botanical Congress.  1969.

17.  Hasler, A. D., "Culture Eutrophication is Reversible," Bioscience.
     Vol. 19, No. 5, May 1969.

18.  Torpey, W. N., "Efforts of Reducing the Pollution of Thames Estuary,"
     Water and Sewage Works. July  1968.

19.  Sawyer, C. N., "1969 Occoquan Reservoir Study," Metcalf and Eddy, Inc.
     for Commonwealth of Virginia  Water  Control Board, April 1970.

20.  Mackenthun, K. M., "Nitrogen  and Phosphorus in  Water," U. S. Public
     Health Service, Department of Health, Education and  Welfare, 1965.

21.  Federal Water Pollution Control Administration, "Water Quality Criteria,"
     Report of the National Technical Advisory Committee  to the Secretary of
     the Interior, April 1, 1968.

22,  Pritchard, Donald W., "Dispersion and Flushing  of Pollutants in Estuaries,"
     Journal of the Hydraulics Division. ASCE. Vol.  95, No. HY1, January  1969.

23.  Brehmer, M0 L. and Samuel 0.  Haltiwanger, "A  Biological and Chemical Study
     of the Tidal James River," Virginia Institute of  Marine Science,
     Gloucester Point, Virginia, November 15, 1966.

24.  Kuentzel, L. E0, "Bacteria, COg and Algal Blooms," Journal Water Pollution
     Control Federation.  21, 1737-1749,  1969.

25„  Lange, W., "Effect of Carbohydrates on Symbolic Growth of Planktonic Blue-
     Green Algae with Bacteria," Nature  215, 1277-1278, 1967.

-------
26.  Kerr, Pat C., Dorris F. Paris, and D. L. Bruckway,  "The Interrelation
     of Carbon and Phosphorus in Regulating Heterotrophic and Autotrophic
     Populations in Aquatic Ecosystems," Southeast Water Laboratory,  FtfQA,
     U. S. Department of the Interior, 1970.

27.  Carpenter, J. H., D. W. Pritchard, and R. C.  Whaley, "Observation of
     Eutrophication and Nutrient Cycles in Some Coastal  Plain Estuaries,"
     Eutrophication:  Causest Consequences, and Correctives. National
     Academy of Sciences, 1969.

28.  Fitzgerald, George P., "Detection of Limiting on Surplus Nitrogen in
     Algae and Aquatic Weeds," Journal of Phycology.  Vol. 2, No.  1,  1966.

29.  Fitzgerald, George P. and Thomas C. Nelson, "Extractive and  Enzymatic
     Analyses for Limiting on Surplus Phosphorus in Algae,"  Journal  of
     Phycology. Vol. 2, No. 1, 1966.

30.  Thomann, R. V., Donald J. O'Connor, and Dominic  M.  DiTorro,  "Modeling
     of the Nitrogen and Algal Cycles in Estuaries,"  presented at the
     Fifth International Water Pollution Research Conference, San Francisco,
     California, July 1970.

31.  Hutchinson, G. E., A Treatise on Limnology. Vol. 1,  John Wiley & Sons,
     Inc., New York, 1957.

32.  Riley, J. P. and Skirrow, G., Chemical Oceanography. Vol. 1, Academic
     Press, London and New York, 1965.

33.  Lear, D. W., Jr. and N. A. Jaworski, "Sanitary Bacteriology  of the
     Upper Potomac Estuary," CTSL, MAR, FWPCA, U.  S.  Department of the
     Interior, Technical Report No. 6, March 1969.

34.  Jaworski, J. A., "Water Quality and Wastewater Loadings, Upper Potomac
     Estuary, Spring 1969," CTSL,  MAR, FWPCA, U. S. Department of the
     Interior, Technical Report No. 27, November 1969.

35.  Berg, Gerald, "An Integrated Approach to the Problem of Viruses  in
     Water," Proceedings of the National Specialty Conference of  Disinfection,
     University of Massachusetts,  July 1970.

36.  Committee on Environmental Quality Management,"  Engineering  Evaluation
     of Virus Hazard in Water," Journal of Sanitary Engineering Division.
     ASCE. Vol. 96, No. SA1, February 1970.

37.  Toenniessen, G. H. and J. Donald Johnson, "Heat  Schocked Bacillus
     Subtilis Spores as an Indication of Virus Disinfection," Journal of
     the American Water Works Association. Vol 62, No. 9, September 1970.

38.  Committee Report, "Viruses In Water," Journal of the American Water
     Works Association. Vol. 6l, No. 10, October 1969.

-------
39.  Metropolitan Washington Council of Governments, "Population Estimates
     and Forecasts, Selected Jurisdictions, Washington Metropolitan Area,"
     1969.

40.  Chesapeake Technical Support Laboratory, "The Patuxent River,  Water
     Quality Management Technical Evaluation," MAE, FWPCA,  U. S. Department
     of the Interior, September 1969.

41.  Feigner, K. and Howard S. Harris, Documentation Report, FWQA. Dynamic
     Estuary Model, FWQA, U. S. Department of the Interior, July 1970.

42.  Jaworski, N. A. and James H. Johnson, Jr., "Potomac-Piscataway Dye
     Releases and Wastewater Assimilation Studies," CTSL, MAR, FWQA.,
     U. S. Department of the Interior, December 1969.

43.  Hetling, Leo J., "Simulation of Chloride Concentration in the  Potomac
     Estuary," CB-nSRBP Technical Paper No. 12, MAR, FWPCA,  U. S. Department
     of the Interior, March 1968.

44.  U. S. Public Health Service, "Drinking Water Standards," Revised 1962,
     U. S. Department of Health, Education and Welfare, 1962.

4^.  Hydroscience, Inc., "The Feasibility of the Potomac Estuary as a
     Supplemental Water Supply Source," prepared for N.E.W.S. Water Supply
     Study, North Atlantic Division, U. S. Army Corps of Engineers, March
     1970.

46.  Private communication with D. Fred Bishop, FWQA, Blue  Plains Advanced
     Wastewater Treatment Pilot Plant, Washington, D. C., March 1970.

47.  Bechtel Corporation, "Preliminary Cost Estimates for a Blue Plains
     Advanced Waste Treatment Plant," prepared for FWQA, U. S. Department
     of the Interior, July 1970.

48.  Smith, Robert and Walter F. McMichael, "Cost and Performance Estimates
     for Tertiary Wastewater Treatment Processes," Taft Center, FWQA, U. S.
     Department of the Interior, Cincinnati, Ohio, June 1969.

49.  Harleman, D. R. F., "One-Dimensional Mathematical Models in State of
     the Art of Estuary Models," Contract to FWQA by Tracer, Inc. (In
     preparation).

50.  Davis, Robert K., "The Range of Choice in Water Management, A  Study of
     Dissolved Oxygen in the Potomac Estuary," Johns Hopkins Press, Baltimore,
     Maryland, 1968.

51.  Reinhardt, H. R., "The Potomac River Basin, A Case Study of Environmental
     Problems Impeding Effective Water Resource Management," To be  presented
     at the Economic Commission for Europe, Czechoslovakia, May 2-18, 1971.

-------
52.  Jaworski, N. A.,  Donald V/.  Lear,  Jr.,  Orterio Villa,  Jr.,  "Nutrient
     Management in the Potomac Estuary,"  Presented at  the  American Society
     of Limnology Symposium on Nutrients  and Eutrophication, Michigan
     State University, East Lansing, Michigan,  February 1971  (CTSL, MAR,
     WQO,  Environmental Protection Agency,  Technical Report No.  45).

53.  University of Wisconsin, Private  Communication  with George  P.  Fitzgerald,
     January 19, 1971.

54.  Thomann, Rooert V., "Mathematical Model for Dissolved Oxygen,  Journal of
     the Sanitary Engineering Division. ASCE. Vol. 89,  No. SA5,  October 1963.

-------

-------