UAL  PROTECTION   AGENCY
                                   THE POTOMAC RIVER ESTUARY IN THE
                                    WASHINGTON METROPOLITAN AREA
                                A HISTORY OF ITS WATER QUALITY PROBLEMS
                                         AND THEIR SOLUTION

                                          November 1972

                                         Technical Report 57
                                       Annapolis Field Office
                                            Region III
                                    Environmental Protection Agency
MIDDLE ATLANTIC REGION- !U   6th and Walnut Streets, Philadelphia. Pennsylvania 19106

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THE POTOMAC RIVER ESTUARY IN THE WASHINGTON METROPOLITAN AREA
 A HISTORY OF ITS WATER QUALITY PROBLEMS AND THEIR SOLUTION
         EPA-903/9-74-011
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9                                          Technical  Report  57
|                                             November 1972
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                                              Johan A.  Aalto*
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_                            * Director,  Annapolis Field Office,  Region  III
                                    Environmental Protection Agency
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A               Chapter
                  I   INTRODUCTION
                 II   BASIN DESCRIPTION
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                                               CONTENTS
                          A.   History
                          B.   Geography
                          C.   Water Quality
                  III   FRAMEWORK FOR ANALYSIS
                        A.   Water Quality Investigations
                               1.  Biochemical Oxygen Demand
m                             2.  Other Oxygen Demands
                             3.  Nutrient-Phytoplankton Relationships
                          B.   Mathematical  Modeling Activities
                        C.   Upper Basin Investigations
                   IV   WATER QUALITY CONTROL ACTIVITIES
J                        A.   Governmental  Agencies
                               1.  Potomac  Enforcement Conference
                               2.  District of Columbia Government
I                             3.  Washington Suburban Sanitary Commission
                               4.  Fairfax  County
0                             5.  Other Governmental Agencies
A                        B.   Federal Activities
                          C.   Annapolis Field Office - EPA
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P                                       CONTENTS  (Continued)
t                  V   OTHER WATER QUALITY CONSIDERATIONS
                          A.  Water Quality Parameters
P                              1.  Bacteriological
*                              2.  Heavy Metals
                                3.  Pesticides
I                              4.  Thermal
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                               5.  Sediments
                          B.  Special Problems
                               1.  Water Supply
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                               2.  Discharges to Embayments
                               3.  Noxious Plant Growth
                   VI   GUIDELINES FOR CORRECTIVE ACTION
m                        A.  The Surrogate Model
                        B.  The Water Quality Control Program
                          C.  Future Study Needs
                             1.  Improved AWT Processes
                               2.  Nutrient-Phytoplankton Relationships
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     3.  Embayment Studies
D.  Recapitulation

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                                            CHAPTER  I

                                          INTRODUCTION
9                    The Potomac  River,  more  than  any  other,  is  the  focal  point
m               of the American conscience  in water quality control  and  has  been
                 the subject of extensive study since the  middle  of the nineteenth
               century.
                      While  pollution  problems  have persisted in various areas
                 throughout  the  basin,  the most serious occur in the populated
m               Washington  metropolitan area and provide a classic example of the
                 dilemma,  present  or imminent,  faced by most of the large cities in
               the  country.  These cities have been situated on estuaries with
                 their natural harbors  and fisheries resources but where waste
m               discharges  from cities on free flowing streams readily transport
jm               the  pollution problem downstream, cities like Washington find that
'               the  ebb and flow  of the tides  provide no dependable disposal of the
               liquid wastes during  low river flow periods.
                      To compound  the  problem,  development of water supply resources,
                 and  water power,  flood control and recreational facilities as well,
m               has  resulted in the regulation of river flows to reduce the periodic
                 flushing  actions  of past years that ameliorated to some extent the
                 accumulation of pollutants both in the waters and bottom deposits
                 near  these  large municipalities.
                      This,  then, is the dilemma faced by Washington, D. C., by
                 several other coastal and large inland lake cities and eventually

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                 by all similarly located cities as their population growth ac-


                celerates.  Its resolution requires a multi-faceted approach  in-


                 volving social  and economic, as well  as  scientific disciplines,

                to provide a viable course of action to  preserve both the  cities


                and the natural resources.

                      The author, as Director of the Annapolis  Field Office, U. S.


                Environmental  Protection Agency, has participated in a concentrated,


                 interdisciplinary study of the water quality problems in the  Poto-


 |               mac River metropolitan Washington area for the past seven  years


 m               and offers the  findings of this study as guides, not only  to  the


                 solution to local water quality problems but also to similarly


                situated metropolitan areas.


                      Upon signing the Water Quality Act  of 1965, President Lyndon


                B. Johnson said, "I pledge to you that we are  going to reopen the


                Potomac for swimming by 1975".  Later he stated "The river, rich in


                 history and memory, which flows by our Nation's capital should


                serve as a model of scenic and recreational  values for the entire

                 country".  These pledges can be realized since corrective  action

Qj               schedules adopted by the Potomac Enforcement Conference and sub-


               sequent actions by the agencies involved to  implement construction

                 programs promise completion by 1975.


                     This paper is concerned,primarily,  with identification of


                 the water quality problems, the sources  and  the corrective action


9
required which have for all  practical  purposes  been  completed at

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 w               the  Annapolis  Field  Office.   In a sense though, this work is never
                completed  since  it is  subject to constant verification and refine-
                  ment with  scientific progress.  Progress in improvement of the
 p               aquatic  environment  requires popular acceptance and financial sup-
                port which have  both been  increasingly evident.  It is the obliga-
                tion of  scientists,  engineers and management to provide the most
I                  economical  means of  achieving this goal.
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                                           CHAPTER II
                                        BASIN DESCRIPTION
              A.  History
                    Potomac, Patawomike, Patowomek,  or  in  any of  its  historically
 j             spelled forms is the Algonkin word for  "something  brought"  or more
 _             freely "place to which tribute is brought", singularly appropriate
               for the present day location of our national  capital.
 I                  When explored by Captain John Smith in 1608 the river  abounded
               in fish, the surrounding lands with game and the crude agriculture
 |             of the indigenous Indian tribes had little  impact  on the  environ-
               ment.
                    The upper estuary was  developed  rapidly  as a  shipping center
               from colonial  times.   Alexandria was  then a bustling seaport, ocean-
               going ships  docked  as  far  upstream  as  Bladensburg on the Anacostia
|             and  Georgetown on the  Potomac  River.   The area was intimately involved
             in the history of the  nation,  the westward expansion, the Civil War
               and  the subsequent  reconstruction and  development of a strong central
             government in  Washington which became  increasingly involved  in
               domestic and foreign affairs.

               B.   Geography
                  The historic source of the Potomac River is the Fairfax Stone
_             at the headwaters of the North Branch  in the rugged, forested Al-
^             legheny Mountains of the Appalachian  chain at the Maryland-West
A             Virginia border.  The  river flows first northeasterly, then  south-

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                                                                           II-2
*            easterly through several geophysical provinces some 400 miles to
            the Chesapeake Bay.
                   Above Washington, the river drains the Piedmont Plateau and,
(|            traversing the Fall Line,becomes tidal at the city  where it is
.            several hundred feet wide, draining the Coastal Plain and extending
*            114 miles to the Bay where it becomes six miles wide.
                 Though the average depth of the estuary is 18 feet, the upper
              reaches have become silted through poor land use practices so that
|            regular dredging is required to maintain the 24 foot channel upstream
            to Washington.
'                 During low river flow periods in the summer, the upper estuary
            waters are fresh for approximately 30 miles downstream from Chain
              Bridge to above Indian Head, then brackish to the Potomac Bridge
J            except during high river flows, then more or less saline to the
m            mouth depending upon river flows.  (Figure II-l)
                   Tidal ranges in the Washington area average 2.9 feet with an
I            approximate 4.5 mile excursion.
                   The Potomac River, draining 14,670 square miles, may be classi-
>|            fied as a "flashy" stream with an average annual flow of 11,340 cfs
              and recorded extremes of 484,000 and 800 cfs.
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              C.  Water Quality
*                 It was recorded that President Adams swam in the Potomac in
            the late 1790's, but by the 1860's the canals leading to the river
              often emitted such objectionable sewage odors that President Lincoln
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CHAIN BRIDGE

    N
                                                     CHESAPEAKE
                                                        BAY
           POTOMAC  RIVER TIDAL SYSTEM

                           1971
FIGURE  II -1

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               was forced to leave the White House at night.  Following the gener-
              ally accepted practice of that time, the first sewers constructed
               in 1870 carried sanitary wastes to the river.
                   With the rapid population growth in Washington following the
 m             Civil War, river conditions became so bad that under President
               Harrison a system was devised to convey all sewage into the Potomac
              downstream from the city.  By 1920 the need for sewage treatment
               was recognized but it was not until 1938 that a plant providing
              primary or settling type sewage treatment only was completed.
                   As the population continued to increase to over the 2.5 mil-
               lion mark currently in the area, some secondary or biological
 I             treatment was operating in 1958.  While the efficiency of treat-
 .              ment by conventional methods has since been increased, the continued
 W             population growth has overloaded the sewerage facilities and un-
              til the additional capacity under construction is completed, water
               quality in the area will continue to deteriorate unless use,
              occupancy or other restrictive measures are taken.
                    Pollution in the upper river basin, while significant, is
 B             largely local and has only a minor role in polluting the estuary.

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                                                                            III-l

                                           CHAPTER III
                                     FRAMEWORK FOR ANALYSIS



               A.  Water Quality Investigations

                  1.  Biochemical Oxygen Demand

                         The Annapolis Field Office (AFO) from the time of its

 |             establishment in 1965, first as the Chesapeake Field Station and

 f             later as the Chesapeake Technical Support Laboratory under success-

               ively the Federal Water Pollution Control Administration, the

              Federal Water Quality Administration and presently the U. S. En-

               vironmental Protection Agency, has expended a major effort on the

 I             Potomac River in general and the estuary in particular.

                   With the continuing degradation of water quality, AFO in-

               vestigated the Potomac Estuary first in 1966 as part of the Presi-


              dential Task Force - Project Potomac and later for the reconvened

               Potomac Washington Metropolitan Area Enforcement Conference.  The

              original session of the Conference in 1957-1958 had set an 80 per-

              cent five-day biochemical  oxygen demand (BOD) removal  as a minimum

               average performance standard for area sewage treatment plants (STP).

              A survey by AFO in 1966, using moving averages for dissolved oxygen

               (DO) data to cancel  the effects of tidal excursion, showed that
               the major DO depression occurred immediately downstream from the

             major municipal  discharge (Figures III  1  and 2)  and  was considerably

               below the minimum average DO standard of  5 milligrams  per liter  (mg/1)

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                    POTOMAC   RIVER  ESTUARY
                  WASTEWATER  TREATMENT PLANTS
                     ANNAPOLIS FIELD  OFFICE  EPA
                                   1971




N


\ PENTAGON
ARLINGTON
ALEXANDRIA
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                                                  RIVER MILES FROM CHAIN BRIDGE - 0
                               WASHINGTON D.C.
                                            ISTRICT OF COLUMBIA (309mgd)

                                            W.W. Br.
                                                 RIVER MILES FROM CHAIN BRIDGE - IS
                                                               NDREWS A.F.B.
                                               ISCATAWAY OOmgd)
                                              MARYLAND
                                   ZONE JT
                                                RIVER MILES  FROM CHAIN BRIDGE -' 30
                                     EXISTING WASTEWATER  TREATMENT  PLANTS
                                     (PROJECTED FULL DEVELOPMENT CAPACITY)
                                     EXISTING PLANTS TO BE ABANDONED
                   ZONE JZI
                                                RIVER MILES FROM CHAIN BRIDGE - 45
     VIRGINIA           WESTGATE  Q


         LITTLE  HUNTING CREEK

     DOGUE CREEK
      FORT BELVOIR
LOWEP POTOMAC
                                                               FIGURE HI-I

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       POTOMAC   RIVER   ESTUARY

BOD5  CONTRIBUTIONS FROM SEWAGE TREATMENT PLANTS

       ANNAPOLIS  FIELD  OFFICE  EPA

                    1956

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                   It soon became evident that the 80 percent BOD removal  re-
H            quirement agreed upon at the Conference would no longer be ade-
              quate to meet the adopted DO standards and when reconvening  of
m            the Conference was proposed, AFO began a detailed investigation of
            the sources of oxygen-demandtng wastes.  The first of several
              waste inventories, the latest of which was in 1969 [2], established
            the significant waste sources.  A study of the estuary [3] com-
              pleted in 1965 showed not only that a BOD removal nearer 95  percent
|            was currently required but that oxygen demands far greater than
            that measured by 5-day BOD were exerted in the estuary.

                   2.  Other Oxygen Demands
                      Specifically, there were two sources of the demand on
            dissolved oxygen not previously considered, the first, a nitro-
              genous demand by ammonia and organic nitrogen in the discharges,
J            as measured by total Kjeldahl nitrogen (TKN), and the second,  a
            secondary carbonaceous and nitrogenous oxygen demand from the  excessive
            algae whose growth had been stimulated by nutrients, primarily nitrogen
            and phosphorus, in the treated waste discharges.  Figure II 1-3
              shows the relative demands as measured in the estuary from the
P            above sources.

                 3.  Nutri ent-Phy topi ankton Rel ati onshi ps
                        Since nutrient concentrations were not enforceable
I            water quality parameters though the relationships between  both

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|            nitrogen and phosphorus and the standing crop of algae (as measured
_            by chlorophyll  a_)  had been established (Figures III-4 & 5), it became
              necessary to determine a relationship between nutrients in their role
I            of stimulating  algal  growth and excessive standing crops of algae in
              depressing dissolved  oxygen levels by respiration and decay.   These
|            relationships were reported [3] and became the basis for fixing the
_            maximum allowable  loadings of BOD and the nutrients nitrogen  (N) and
"            phosphorus (P), that  could be discharged into the estuary and still
I            maintain the adopted  water quality standards.
                   The investigations (Figures III-4 & 5) showed the direct relation-
|            ships existing  between the algal standing crop (as measured by chlorophyll
            aj and nitrogen and phosphorus.  jtMs interesting to observe that_whj'1e
              no emphasis was placed on a specific responsible nutrient at  that early
I            date, the algal standing crop was found to be directly projDortionaJLto
              the nitrogen concentrations while the response rate changed abj^upjtly_
|            for phosphorus  concentrations exceeding approximately 0.5 milligrams
m            per liter (0.5  mg/1)  qrjparts per million.  At that time a phosphorus
              concentration of 0.1  mg/1 had been selected as the maximum to prevent
            excessive algal growth in the estuary based upon field observations.
            B.  Mathematical Modeling Activities
                   Mathematical  methods of evaluating the effects of waste  loadings
            had been in use for several decades but were readily applicable to
              free flowing streams.  The problems of dilution and dispersion by tidal
            excursion in estuaries such as the Potomac required application of more

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                                                                           III-9

             sophisticated mathematical modeling techniques.  These were adapted
I           by AFO to fix maximum allowable loading limits for BOD, nitrogen (N)
             and phosphorus  (P) in 15 mile zones of the estuary beginning at Chain
           Bridge and proceeding downstream.  The zonal length was selected since
           it approximated the segments of similar quality and conveniently placed
             the major waste discharges near the center of each zone.  This concept
           allowed the technical allocation of maximum loads for each zone without
             the need to make management decisions on individual load allocation by
           discharge or geographical subdivision, a political responsibility more
           properly assumed under an interstate compact or by the conferees.  In
             order to apply  the mathematical model, however, it was necessary to assume
I           future loadings which were based upon population projections and projected
             waste discharge locations arrived at after consultation with the various
8           involved agencies.  In addition, it was assumed that all discharges
           were to be made to the main channel to assure maximum dispersion and
             dilution of the discharges and that a uniform treatment policy would be
I           adopted within  each zone.
                  The first  application of the model, previously verified by dye and
           salinity studies, provided maximum loadings to Zone I of BOD = 16500 Ibs/day,
           N = 8000 Ibs/day and P = 740 Ibs/day, which incidentally represented a 96
             percent removal of BOD and P for existing treatment plant loadings and were
           adopted by the  Potomac Enforcement Conference as discussed later.

I           C.  Upper Basin Investigations
                  At the third session of the Conference investigation of upstream
|           pollution contributions to the Conference (estuarlne) area was recommended

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              for investigation.  AFO prepared a report (4) which gave the results
             of the physical, chemical, biological and bacteriological studies in
              the upper basin and their effects on water quality in the estuary.  The
             pertinent findings were that:
                       1.  No thermal problems existed.
                        2.  High acidity from mine drainage in over 40 miles of the
                  North Branch was a local problem only.  The measurable effects
                   did not extend beyond another 10 miles downstream.
                       3.  Pesticides were a sporadic minor local problem and
                  required additional surveillance.
                        4.  Low dissolved oxygen levels on certain reaches of tributaries
 I                 including the North Branch but did not occur in the main river.
                        5.  BOD concentrations discharging to the estuary were low,
                  ranging from 2 to 4 mg/1 .
                       6.  Nutrient concentrations were high in localized reaches
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                   of tributaries.
                         7.   Only local  bacterial  problems exfsted^with complete
                    recovery only short distances  downstream.

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                                         CHAPTER IV
                              WATER QUALITY CONTROL ACTIVITIES

            A.  Governmental Agencies
                   The upper Potomac Estuary is geographically in the states of
I            Maryland and Virginia and in the District of Columbia (Figure III-l).
              The situation is further complicated by the historical fixing of the
I            Maryland state boundary, and consequently that of the District of
            Columbia as well, along the Virginia shoreline.  Since discharges
              from all three jurisdictions were the causes of the water quality
I            degradation, an interstate cooperative activity was essential for
              corrective action.
                 1 .  Potomac Enforcement Conference
                      Since there was no appropriate authoritative interstate agency
              in existence, it was mutually agreed that a Conference on Pollution of
I            Interstate Waters of the Potomac River in the Washington Metropolitan
              Area could be called by the U. S. Department of Health, Education and
            Welfare under provisions of Section 8 of the Federal  Water Pollution
            Control Act, Public Law 660, 84th Congress.
                        The Conference was initially in two sessions in 1957 and 1958 and
I            resulted in a remedial  action program requiring a minimum wastewater
              treatment to achieve 80 percent BOD removal, disinfection when required
            and control of stormwater overflows by 1966.
                      By 1969 water quality conditions had become progressively worse
              and the recommended actions had not been implemented according to the
              agreed schedule.  Moreover, AFO studies [3] had clearly established the
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|            present inadequacy of the  proposed  actions.
_                 It was  agreed by the  conferees that  a  third  session  of  the Potomac
*            Enforcement  Conference be  held  to review  the existing  situation and
            progress made  to date.  Since the initial sessions, the Federal Water
              Pollution Control  Act of 1965 had been  passed  resulting in the adoption
I            of water quality standards for  all  interstate  waters.
m                 The third session on  May 8, 1969 recommended the  loading limits
*            developed by AFO,  expanded by fixing specific  load limits at existing
            treatment plants in Zone 1 representing 96  percent BOD removal, 96
              percent phosphorus removal and  85 percent nitrogen removal.  Construction
|            schedules to achieve these levels of treatment at all  wastewater  treatment
_            plants in Zones I  and II by 1977 were also  recommended.   Of  the several
              other recommendations four are  deserving  of special  note, the first,
I            that the effect of upstream discharges  on the  estuary  be  evaluated, the
              second, that public progress meetings be  held  every six months to review
I            the status of  compliance with the several recommendations, the third,  that
            continuous disinfection of all  treated  sewage  effluents be practiced and
              the fourth,  that a joint study  of the entire Potomac River basin  be made
8            to determine the controls  required  to protect  the river and  the estuary.
                   At the  reconvened third session on October 13,  1970  a "Memorandum
|            of Understanding"  among the jurisdictions involved;  Maryland, Virginia,
            and the District of Columbia was submitted  and adopted.   Essentially,
              it limited the capacity of the  Blue Plains  facility to 309 mgd because
            of inadequate  space for further expansion primarily  to serve areas outside
              the District of Columbia.   These areas  would be served at a  new regional
            plant to be  located at a site selected  by the  Washington  Suburban Sanitary

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I            Commission (WSSC).  The load limitations at Blue Plains applied to
            Virginia areas as well, which retained as in the case of Maryland, basic
              load limits as provided in the original Blue Plains agreement.
I                 The progress meeting of December 8-9, 1970 in response to  dis-
              satisfaction with the 1977 completion schedule, moved up the agreed
I            completion date to 1974.  While this accelerated schedule posed many
              construction and financing problems, this too was agreed upon.
                   2.  District of Columbia Government
                      The Conference thus placed the primary burden of corrective
              action on the District, understandably so, since the loading was greater
I            and degree of treatment lower than that of other major discharges.  The
            District is less able to fund expansion of facilities since it  is dependent
              upon Congressional action for financing major projects.  Considerable
            progress was made in (1) reduction of bacterial pollution by institution
              of full-time adequate chlorination (2) raising the BOD removal  efficiency
I            by addition of flocculants and (3) reduction of raw and combined sewer
            overflows by provision of more adequate sewerage capacity.  Construction
              is under way to increase the capacity at the Blue Plains treatment plant.
            When the first stage of increasing primary treatment capacity to 309 mgd
              is completed, most incoming  sewage will  receive at least some treatment.
                 3.  Washington Suburban Sanitary Commission
                      This agency has the responsibility of providing water and waste
              services to Montgomery and Prince George's Counties in Maryland immediately
            adjacent to the District of Columbia.  Most of the sanitary sewage is
              treated at Blue Plains at present but in accordance with the Conference
            agreement, other treatment plant location sites must be agreed  upon.  An

I

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                                                                            IV-4

              STP at Piscataway provides a higher degree of treatment to about
             8 mgd of sewage from southern Prince George's County and the facility
              is presently being expanded to a 30 mgd capacity.   Further expansion to
 B            90 mgd in the same area is under study.  Since Piscataway discharges to
             an embayment of the Potomac Estuary, advanced waste treatment (AWT)  for
              the removal  of nutrients will ultimately be required for the present
 I            facility as  determined in an AFO study [5].  The expanded facility will
              require AWT  and discharge to the main channel of the Potomac.
                       In the meantime the Piscataway plant has  been upgraded in
             efficiency by the addition of two lagoons or polishing ponds after
              secondary treatment and disinfection before discharge into the embayment.
             BOD removal  regularly exceeds 95 percent and a substantial degree of
              phosphorus removal is sporadically achieved.  Considering that the primary
             source of nutrients and organic loading to the embayment is the Potomac
             River, operating efficiency at this plant shows progress well ahead  of
              other facilities in the area [5].
 J                      There are present plans for at least another sewage treatment
 _            plant for Montgomery County to take care of sanitary waste discharges from
             the area west of the District.  This has been tentatively determined to be
             the answer to the building moratorium required because of inadequate existing
              sewerage and the long delay before such sewerage could be constructed,
 J            even if economically feasible.  No investigation of such location had been
 _            made previously because (1) the AFO mathematical model was applicable
             to the estuary only, (2) a policy of no treated waste discharges upstream
             of the water supply intake had been in effect for several  years and, (3)
              no maximum capacity had previously been set at Blue Plains.
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                 4.  Fairfax County
                      Upgrading performance of the sewage treatment plants discharging
              directly to the Potomac: Westgate, Dogue and Little Hunting Creek had
|            been accomplished partly by the use of flocculants in the existing
_            plants.
                      The new Lower Potomac STP (Gunston Cove) will ultimately be
            expanded to eliminate these three plants and part of the Fairfax
              County sewerage load will be treated at Alexandria.
J                 5.  Other Governmental Agencies
                      The City of Alexandria will expand their STP facility not only
            to serve the expanding population but parts of Fairfax County by agreement
            as well .
                        Arlington County will expand their facility.
|            B.  Federal Activities
                 There are several Federal activities providing their own waste treat-
              ment facilities which will be phased out as soon as other treatment plants
            can provide adequate capacity (Figure III-l).
                   The Pentagon will be served by Arlington, Fort Belvoir by the Lower
|            Potomac STP and Andrews Air Force Base by the Piscataway STP.
M                 At present two Federal activities, the Naval Ordnance Station at
              Indian Head and the Marine Corps Schools at Quantico provide their own
            adequate secondary treatment but are outside the Conference Area.
              C.  Annapolis Field Office - EPA
I                 Since the activities (Chapter III) which, had provided the technical
            basis for the administrative actions just outlined, AFO has continued
              more detailed investigations to refine the previous allowable load figures.
 I

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                                                                            IV-6
I
              With advances  in the  state  of the  art  in  mathematical modeling,  a dynamic
            model  was  developed and  verified providing  a  surprisingly  close
            confirmation of the loadings  previously determined.   It was  realized  that
              because of the approximate  three week  residence  time  of discharge
I            components in  the estuary under low  flow  conditions,  that  five day  BOD
              figures did not accurately  reflect the organic carbon nor  nitrogenous
            oxygen demands.  These were now combined  in an ultimate oxygen demand
            (UOD)  factor which was achieved by use of the classical relationship:
                        UOD  = 1.45  BOD +  4.57 TKN
I            where  TKN  (total Kjeldahl nitrogen)  represents the  unoxidized  nitrogen,
_.            organic nitrogen and  ammonia  [6].
"                 Extensive field  studies  by AFO  on nutrient-phytoplankton  relation-
            ships  gave more precise  allowable  nutrient  loadings to control the  algal
              standing crop.  These figures now  vary by zones,  being  lower downstream.
I            where  turbidities are lower because  of settlement and dilution.  This
_            has  posed  a dilemma in water  quality control  in  the upper  estuary,  a  brown
            (turbid) water versus a  green (algal)  one.  Control of both  is possible
I            but  cost considerations  may defer  such a  solution until more urgent water
              quality problems are  resolved.
|                 The previous maximum figures  for  nutrients  (N  =  0.3 mg/1, p =  0.1 mg/1)
            become [6]j
"                      Zone I              N -  0.5               P = 0.067
                           II             N =  0.4               P = 0.03
                             III            N =  0.3               P = 0.03
                 As a  result of these AFO investigations  loading  figures developed  from
            the  1969 report [3] were reconciled  with  those of the 1971 report  [6],  pre-

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 *                                                                           IV-7
 I

              pared  for  Zone  I  and  submitted  to  the  Conference progress meeting in
              November 1971 as  follows:
                   1971                                    1969 (page  III-ll)
               UOD  =  75000  Ibs/day              BOD  =  16500  X  1.45 =  24000  Ibs/day
                                              TKN  =   8000  X  4.57 =  36500  Ibs/day
                                               UOD  (equivalent)   =  60500  Ibs/day
 I             N.   =   3400  Ibs/day                N  =                 8000  Ibs/day
              P    =   900  Ibs/day                P  =                   740  Ibs/day
                   Except  for the nitrogen  loadings  the  agreement is  reasonably close
 I             with distinct benefits  resulting from  the  more recent figures,  (1)
 f             phosphorus and  ultimate oxygen  demand  controls are much more feasible
               that nitrogen control and  (2) there  is  a choice between degrees of BOD
 A             and  TKN control to arrive  at  a  net UOD  figure.  This  "trade-off" lends
               a  substantial flexibility  in  selection  of  a  treatment process.
 I                 The lower  nitrogen loading  figures are  a  result  of better  under-
 _             standing of  the relationship  between nitrogen  availability  and  phytoplankton
              growth  and not  to its role  in the  DO budget.   In addition,  a strict
H             comparison cannot be  made  between  the  1969 and 1971 N figures since the
               former  is  unoxidized  and thus includes  organic N while  the  latter is
g             inorganic  only.   The  figures  are probably  much more nearly  in agreement.
              Practical  nitrogen control  methods on  a large  scale are yet to  be
I
I
demonstrated so that the drastically reduced loading figure makes
the solution less formidable.

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I

I                                          CHAPTER V

I                             OTHER  WATER  QUALITY CONSIDERATIONS

            A.   Water  Quality Parameters
                   1.  Bacteriological
p                      Probably the  most important parameter from the point of view
M            of  beneficial  public  use  is bacteriological  - the continuing  incidence
              of  high  coliform bacterial populations which indicate the probable
M            presence of  pathogens.  The sources are  known in  (1) inadequately treated
              sewage overflows, (2) urban runoff and  (3) discharge from boats.
                      Since  1969, all  treated waste  discharges from sewage treat-
            ment plants  in the area have  been continously disinfected and this
              source has been  virtually eliminated.  Upstream treatment plant dis-
            charges  are  not  a problem because of inability of the pathogens to
              survive  the  time of travel to the estuary.
I                      The  primary coliform bacterial sources are the overflows of
            raw sewage from  inadequate sewerage and  from combined sewers  after
              storms.  The former are the result of excessive population  growth with
            corrective actions obvious, zoning and restriction of building permits
              pending  construction of adequate sewerage and treatment facilities.  A
            continuing program of sewer separation and additional interceptor capacity
            will  ultimately  eliminate the combined sewer overflow sources.
                        Urban  runoff  has always provided a significant coliform source
            especially during the first few minutes  of heavy rainfall.  The indicated
^            solutions  are  (1) a high  standard of urban sanitation,  (2)  storage of at
P            least the  early  runoff  for later treatment in the system when flows sub-

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                                                                           V-2
             side or  (3) installation of screening and disinfection equipment at all
storm water outfalls.
          The effects  of sanitary waste discharges  from pleasure  boats
have been investigated by AFO.   The contribution  was  found  to  be  insig-
nificant in comparison with land based pollution  sources.   Only when
              large congregations of boats occurred as during a regatta could any
I            coliforms be measured and then only in areas of low background pollution.
              This potential pollution source cannot be neglected however, since
              proposed regulation by requiring onboard sanitation devices in a few years
*            would be effective at about the time when effective shore pollution control
              should be realized and boat sources then become more significant.
                2.  Heavy Metals
                       Certain metals, notably mercury, lead, chromium and cadmium,
9            are toxic to marine life in small concentrations especially in warm
A            weather, during spawning periods and to shellfish which, being filter
              feeders, readily concentrate the metal to potentially toxic levels.
                     There is relatively little industry in the area to provide
              major metals sources.and their discharges are invariably to municipal
            sewerage systems.  Periodic analyses of discharges by AFO have failed to
            show heavy metals content above minimum detectable limits.  Samples of
              bottom sediments in the vicinity of outfalls, however, show varying
            heavy metals content.  These were determined by hot acid extraction and
              would not normally be taken up by the overlying water [6].
        .        3.  Pesticides
                     Infrequent AFO sampling has shown no significant incidence of
              pesticides in the estuary [6].  It is known, however, that pesticides
I            have been found on occasion upstream.  The sources could be industrial

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 I                                                                        V-3

              as well as agricultural  and a precautionary monitoring program is
             suggested.
                   4.  Thermal
 I                      Heated  water discharges from electric power plants occur in
 >            several areas upstream and downstream as well  as in the metropolitan
              area itself [6].   The thermal effects contribute directly to low DO by
             lowering the saturation with higher temperatures and stimulating algal
              growth rates.  Adverse effects upstream may result with increases in
 I            power generation  and a present downstream discharge is the cause of an
             unacceptably high temperature rise in Quantico Creek.  A potential problem
              discharge exists  in the Anacostia River but any adverse biological
 I            consequences are  effectively masked by existing gross pollution.
                   5.  Sediments
 V                      A severe sediment problem has its sources throughout the basin
             and though sediments are transported to the estuary during the relatively
              few high flow periods of the year, they cause  serious silting of navigation
             channels as we'll  as excessive turbidity in the upper estuary for most of
              the year.  The metropolitan area sedimentation rate is seven times that
            from the upper basin and yields over 1.3 million Ibs/sq. mi./yr. [6].
                      The adverse effects include the obvious cost of dredging for
              navigation, the covering of fish spawning beds and the obvious aesthetic
            objections in the national  capital area.
                        There are beneficial effects as well.  The previously mentioned
            light interference to retard algal growth-is an example.  Another benefit
            is the reduction  of some 40 percent in phosphorus concentration by
              adsorption to silt particles most of which becomes unavailable for uptake
I

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                                                                           V-4

              either by burial  or transport  seaward  during  flood  periods  [6 &  7].
            B.   Special  Problems
                   1.   Water Supply
I                      In 1966 and again  in 1969  flow  of Potomac water so approached
_            water supply use  that emergency plans  were required.   The Potomac River
            is  the primary potable water source  for the metropolitan area and
            implementation of long term  plans  for  increasing  this  resource by upstream
              storage in multi-purpose  reservoirs  has been  delayed by environmental
|            objections.
                      An AFO  investigation [6] confirmed  a  previous study that  use
            of  water from the estuary could provide not only  an emergency source
            but also provide  an adequate supply  of potable  water almost to the  year
              2000.   Beyond that year upstream storage  would  be required  in any case.
J            Without being involved in what is  essentially a political decision, AFO
_            investigated the  effects  of  water  withdrawals from  the estuary on salinity
*            buildup through reuse as  well  as movement upstream  of  the salt wedge
8            with various rates of withdrawal for a 7-day--10 year low flow.   This
              water could be used on short notice  whereas the lead time for construction
|            of  a storage reservoir is approximately ten years after the project is
.            approved and funded.
                        It was  found that  any substantial increases  in waste discharge
I            quantities downstream from Zone I  would rapidly preclude any contemplated
              use of estuarine  waters for  water  supply  purposes by accelerating movement
|            of  salinity to the intake.   This would also be  the  case where substantial
_            wastewater quantities are diverted out of the basin for treatment or
              disposal.
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I

9                 2.   Discharges to Embayments
                      The AFO mathematical  model  was developed and loadings  determined
              for discharges to the main channel  only.  Most existing treatment plants
I            discharge to embayments of the  Potomac,  the Blue Plains plant being  the
              notable  exception.  Special  model studies were made for Piscataway Creek
            and Gunston Cove (Lower Potomac STP)  and allowable maximum loadings
            established [6].  The Piscataway STP  cannot exceed a 15 mgd discharge  into
              the embayment without contravening  adopted water quality standards unless
            an unusually high degree of AWT is  provided.
m                      Since it is anticipated that Fairfax County treatment  plants
            at Westgate, Dogue and Little Hunting Creek will be taken out of service
            and the  sewage treated at the Lower Potomac STP, no further loading
              figures  are needed.  Recently,  however,  it has appeared that for political
            or economic reasons the Arlington and Alexandria STP's propose to continue
_            discharges to embayments instead of to the main channel.  These  locations
            will  require independent determinations  of allowable load limits and the
            inevitably high degrees of AWT.
                   3.   Noxious Plant Growth
I                      An interesting serendipitous corollary to the nutrient-
_            phytoplankton investigations by AFO was  the historical aquatic plant
I
m            succession in the Potomac Estuary recorded by various observers  (Fig.  V-l).
            It appears that as nutrient concentrations increased, there was  an increase
              in nuisance plant infestations  starting  with  rooted aquatic plants in  the
Q            1920's gradually being displaced by drifting  microscopic plants
            (phytoplankton), first the green algae and finally the blue-green algae
*            (Anacystis).
I

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                                                                                         FIGURE  V- 1

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I
                                                                           V-7
                      Each historical  stage provided  a  balanced  ecological  system
              where the nutrients stimulated the  plant  growth  that was  naturally
I
              controlled either by nutrient limits  or  grazing  by  aquatic  animals,  the
              phytoplankton by the zooplankton,  the zooplankton by  successively  higher
              trophic levels with return of  the  nutrients  by their  waste  discharges,
              death and decay.   The blue-green algae,  however, assume  toxic  forms
              and proliferate rapidly when no  longer grazed by the  zooplankton accelerating
|            the demand on dissolved oxygen,  in effect creating  an unbalanced
_            ecological system and an odorous,  unsightly  mass as well  [6].
*                      It has been demonstrated that  reduction in  nutrients will  reverse
I            this biological succession  notably in the cases  of  Lake  Washington in
              Seattle and the Thames River in  London.
|                      Considerable controversy has arisen regarding  which  of the major
_            constituents of algae should be  controlled to inhibit growth.  AFO has
              proceeded on the basis of controlling all  three:  carbon, nitrogen and
I            phosphorus where possible.   Since  the approximate composition  of algae
              is in the ratio of 100:16:1  of C,  N and  P respectively,  it  would appear
|            that the order of importance is  the same.  Controllability, however, is a
m            major factor [6].
                        In the Potomac, carbon exists  in large amounts in the bicarbonate
            form as well as in the organic form associated with treated sanitary
              waste discharges.   The latter can  be  fairly  well controlled in the treat-
1            ment process but substantial  reduction of the large bicarbonate quantities
            from the upper basin could  not be  achieved without  treating the entire
              flow.  In addition, carbon  can be  fixed  by algae from the carbon dioxide
I
I
              in the air with  even  higher  rates  of  fixation when  carbon  starved

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*                                                                          V-8

*                      Nitrogen control is a problem because large scale application
            of laboratory and pilot plant methods have yet to be demonstrated as
              economically feasible.  Nitrogen also can be fixed from the air by
I            algae especially when nitrogen starved but the rate appears to be negligible
^            compared with the promising removal methods.  Nitrogen probably is the
            algal growth rate-limiting nutrient in the upper estuary according to
fl            AFO data.  These showed carbon and phosphorus levels adequately high
              during periods of heavy algal bloom whereas the inorganic nitrogen had
|            almost disappeared, a certain indication that it had been taken up in algal
            growth.  An approximate evaluation of the growth limiting potential of
              N and P may be made by comparing Figures III-4 and III-5.  The nutrient-
I            phytoplankton (as measured by chlorophyll a) relationships are clearly
              shown but the rate of increase in chlorophyll a^ drops noticeably in the case
|            of P* concentrations over 0.5 mg/1.  Nitrogen plays a minor role in the
M            dissolved oxygen budget at low temperature so that removal is not required
              whenever water temperatures are below 15 degrees Centigrade, or
8            approximately six months of the year for the Potomac [6].
                        Phosphorus is the most readily controllable of the nutrients.
I            Well-tried, economical processes not only remove 95 percent and better
            but most of them make possible an additional 5 percent removal of carbon
              as well.  Moreover, phosphorus starved algae cannot find it in the
            atmosphere.
                        The conclusion to control both nitrogen and phosphorus is based
            upon the findings by AFO as given above.

              * P is approximately one third of P0 values or 0.17 mg/1
I

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I

"                                         CHAPTER VI

                              GUIDELINES FOR CORRECTIVE ACTION

            A.  The Surrogate Model
M                 Here then is the upper Potomac River estuary the Washington
              Metropolitan area which has provided a model for a corrective action
I            program for other coastal cities.  The methodology developed here can
              be applied equally well to cities on the large inland lakes.
I                 Some cities are fortunately located near enough to extend their
m            treated waste discharges well offshore but most are on major estuaries
              that provided them with the natural  harbors  about which  they grew,
            with present or prospective pollution problems as populations continue
              to grow.  Except for serious industrial waste discharge, the Potomac
8            Estuary has them all and has already reached a critical  stage.  The
            conditions which now exist are:
                        1.  Little or no freshwater flow to the estuary to provide
I            seaward transport of treated wastes during low flow seasons.
                        2.  Inadequacy of conventional wastewater treatment methods
I            to control oxygen demanding loads resulting in dissolved oxygen
            depression below adopted concentrations.
                        3.  Stimulation of excessive algal growths resulting in
            unsightly and noxious masses further depressing oxygen levels.
                        4.  Waste discharges primarily from point source discharges
            of treated municipal effluents with relatively minor agricultural or
            forested  non-point-source  discharges.
                        5.  Urban or suburban tributary area to provide pollution
I

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*                                                                         VI-2





*           from street washing or urban storm runoff.  This may include combined



           sewer overflows that are characteristic of older cities.



                       6.  Rapid present and future population growth not already



           controlled by zoning or other regulatory measures.



                     7.  Where applicable, a gradual transition from a freshwater



           to a marine environment with accompanying biological considerations



I           such as  fish spawning areas, shellfish habitat, aquatic plant growth and



             related  recreational use.



I           B.  The  Hater Quality Control Program



                Using the program developed for the upper Potomac Estuary as a



             guide the suggested sequence of investigations could be as follows:



I                     1.  Identify the problem areas, usually the city and its



             urban area but often including industrial areas.



|                     2.  Locate sources of pollutants; municipal, industrial and



tm           agricultural.  Determine qualitatively and quantitatively those para-



             meters affecting water quality both point, and non-point sources.



                     3.  Evaluate the relative contributions of conservative and



             non-conservative parameters as functions of flow, distance from problem



I           areas and temperature.  Generally, the critical conditions occur during



           high-temperature, low-flow periods but for some parameters, seasonal



             population concentrations, agriculture and its incidental food processing



           and certain industrial operations may require special investigation at



             certain  times of the year.



I                     4.  Determine the maximum loading of each critical parameter



           at its source to realize the maximum total loading in the problem area.



             This is  not a technical consideration alone since political or manage-
I

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                                                                           VI-3
I

             ment  decisions  are  required.   In the case of the Potomac Estuary the
           zone  loading concept was used  with the apportionment of loadings
             deferred  to the Conference.  For the purpose of estimating future
|           effects of population growth,  certain assumptions were made and made
M           definite  conditions for the  individual discharge loadings.  They were:
                   a.   Uniform treatment at  all facilities within each zone.
                 b.   Populations served  were in their natural  drainage basins
             with  no interbasin  transfers.
|                 c.   Population projections used were acceptable.
                 d.   The seven-day ten-year low flow was used as the critical flow.
                   e.   Location of major sanitary discharges were substantially as
I           indicated in the report (Figure III-l).
                       5.  Develop an area  plan for the most feasible distribution
I           of  treatment units.  Design  should be such that each construction stage
           be  compatible with  a 50 year plan and meet water quality standards.
                       6.  Eliminate all  raw sewage overflows by separation of storm
           and sewage systems  where existing arid provide adequate capacity in the
             sewerage  system.
                     7.  Initiate measures to reduce pollution by urban runoff by
             screening and disinfection or  storage for later treatment when flows
             subside.
I                     8.  Upgrade treatment methods for industrial wastes and reduce
             quantities by process improvements,whether discharged directly or into a
m           municipal system>to meet adopted water quality standards and Federal laws,

I

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                                                                           VI-4

              C.   Future  Study Needs
                 1.   Improved Advanced Waste Treatment Processes
                       Conventional waste treatment methods, physical solids
I            separation  (primary), biological actions  (secondary) and disinfection of
            the  discharge  is presently the minimum treatment required for municipal
              wastewater.  Where  this degree of treatment is inadequate to achieve
I            approved  water quality standards in the receiving water as in the case
              of the  upper Potomac River estuary, advanced waste treatment is required.
I            This  has  generally  included modular facilities to remove additional
            carbon, nitrogen and phosphorus.  Continuing studies to develop economical
              new  processes  are required especially in  the case of nitrogen where
I            large scale adaptions of  laboratory processes have not yet been applied.
                   2.   Nutrient-Phytoplankton Relationships
I                     a.   Algal Productivity
                          The  use of algal standing  crop as a factor in evaluating
              the  effects of excessive  nutrients has been practical in determination
            of allowable loading limits because it is readily measurable as the
              chlorophyll a^  parameter.  This has been applicable in the case of the
            Potomac because the upper estuary is fairly well mixed.  Even so there is
            some  question  of the relative effect of heavy algal mats inhibiting
              photosynthetic activity to an extent where the effect of nutrient
I            stimulation is not  fully  realized.
                            A more accurate relationship may be made using algal
            productivity rates  for specific nutrient  concentrations if a practical
            methodology can be  developed.

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                                                                           VI-5


I
|                      b.  Marine Phytoplankton
_                           While AFO investigations to date have been in freshwater
              quality problem areas of the Potomac Estuary and in Chesapeake Bay,
I            freshwater algae do  thrive  in  more saline waters of the transition zone
              between the fresh and salt waters.  While freshwater algae do persist
|            in this transition zone there has been a noticeable increase in marine
              species in recent years.  The "red tides" (gymnodinium) have been found
              in quantities not only in the lower Potomac Estuary but during 1971 in
              the Chesapeake Bay north to the Bay Bridge for the first time.  It appears
              that a nutrient-marine phytoplankton relationship exists in saline as
|            well as in freshwaters and this should be quantitatively established.
im            The threat of depressed dissolved oxygen loads may exist in areas where
              population centers exist on saline estuarine waters.  Probably a greater
            potential danger is in the species shift to a toxic dinoflagellate such
              as that which poisoned the shellfish off the New England coast late in 1972.
|                 3.  Embayment Studies
                      It seems obvious from investigations of discharge locations
              in the Potomac Estuary that however desirable discharges to the main
            channels of bays and estuaries may be for dispersion and dilution, major
              discharges will be continued at the heads of embayments for economic
I            or political reasons.  Because they are generally shallower, have lower
            transport rates and offer less mixing, separate mathematical model studies
              are required in each case since hydrographic characteristics are rarely
I            similar.  The greater photosynthetic action and lower transport rates
              increase nutrient efficiency in algal productivity and the degree of AWT
|
              above that for discharges to main estuary channels.   Here again is an
I

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                                                                            VI-6

I            economic "trade-off" between the cost of a long outfall  against  that
            of the higher degree of AWT required.
              D.  Recapitulation
                 The Potomac River upper estuary is  an appropriate surrogate model
              to be used as a guide in corrective water quality  action programs,present
              or future, for similarly situated coastal  cities.   It  offers,  in  fact,
            an unparalleled study situation  because  (1)  as  the site  of  the national
              capital  it has received the higher priority as  a demonstration project
            for water quality control,  (2)  the combination  of  high population-low
              flow characteristics offer  a prototype solution without  the complexities
            of industrial or agricultural waste discharges  which  are better  resolved
            separately and (3) as the federal  center it can demand the  maximum  share
              of federal  funds.
I                 Upon signing the Water Quality Act  of 1965, President  Johnson  said,
              "I pledge to you that we are going to reopen the Potomac for  swimming
I            by 1975".
                   The technical requirements  have been determined  as  outlined in this
              paper.
I                 A suitable interstate  institutional  vehicle,  the Potomac Enforcement
              Conference,  has succeeded in bringing all  involved state agencies to
            agreement on treatment requirements and  construction  schedule.
                 Construction is presently  in  progress.
                   The pledge can be fulfilled subject only to provision  of adequate
I            funds for construction.
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                             REFERENCES
1.  Aalto, J.  A.,  "The Potomac  Estuary,  Statistics  and Projections",
    Proceedings 1968-1, Interstate  Commission  on  the Potomac River
    Basin.

2.  Aalto, J.  A.  and Jaworski,  N. A.,  "Wastewater Inventory, Upper
    Potomac River Basin",  Chesapeake  Field  Station, FWPCA, October
    1969.

3.  Jaworski,  N.  A., Lear, D. W., 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,
    Chesapeake Technical Support Laboratory, FWPCA, March 1969.

4.  Aalto, J.  A.,  Clark, L.  J., Jaworski, N. A.,  "Upper  Potomac
    River  Basin Water Quality Assessment",  Technical Report No. 17,
    Chesapeake Technical Support Laboratory, FWPCA, November 1969.

5.  Aalto, J.  A.,  Jaworski,  N.  A.,  "A  Water  Quality Study of the
    Piscataway Creek Watershed", Chesapeake  Field Station, FWPCA,
    August 1968.

6.  Jaworski,  N.  A., Clark,  L.  J.,  and Feigner,  K.  D., "A Water
    Resource-Water Supply  Study of  the Potomac Estuary", Technical
    Report No. 35, Water Quality Office, EPA,  April 1971.

7.  Aalto, J.  A.,  Jaworski,  N.  A.,  and Lear, D.  W., "Current Water
    Quality Conditions and Investigations in the  Upper Potomac River
    Tidal  System", Technical  Report No.  41,  Chesapeake Technical
    Support Laboratory, FWQA, May 1970.

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