United States         Office of Water
Environmental Protection     4305               February, 2009
Agency



  &EPA  BASINS Technical Note 11
  Infiltration BMP Tutorial for HSPF

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                               Technical Note 11
                       Infiltration BMP Tutorial for HSPF

                  Yusuf Mohamoud, Rajbir Parmar, and Kurt Wolfe
                                 February, 2009

The infiltration BMP tool allows modelers to select a BMP type, channel shape and
BMP facility dimensions, flow control devices, and infiltration method. Based on the
modeler's selection, the program generates an HSPF-formatted FTABLE. HSPF's Reach
module (RCHRES) is used to represent infiltration BMPs. The specific characteristics of
each BMP are captured by the FTABLE. Unlike storage BMPs (e.g., detention basins)
that store runoff from relatively large areas, infiltration BMPs are source control facilities
that capture runoff from small impervious areas (e.g., parking lots or rooftops).

The HSPF BMP tool presented herein is used to design  and simulate structural BMPs.
Just like storage BMPs, infiltration BMPs use HSPF's reach module (RCHRES). When
designing infiltration BMPs, we recommend the use of Maryland's unified stormwater
sizing criteria. The unified approach has five specific design objectives: meet pollutant
removal goals (WQv), maintain groundwater recharge (Rev), reduce channel erosion
(CPv), prevent overbank flooding, and pass extreme floods.

The HSPF Web-based BMP modeling tool can be as a pretreatment facility or as the
main treatment facility. Pretreatment is used mainly to capture suspended solids before
reaching the treatment facility. The pretreatment volume treats 25% of the water quality
volume (WQv) whereas the main treatment facility treats 50% of the water quality
volume (WQv).  To represent the treatment train in HSPF users should build one
FTABLE for the pretreatment and another separate FTABLE for the treatment facility.
Tool users must ensure that the two FTABLES are linked through the SCHEMATIC-
BLOCK of the User Control Input (UCI) file. Overall, the BMP facility (pretreatment and
main treatment) is intended to treat 75% of the water  quality volume (WQv) generated
from the contributing impervious area.

Representing most infiltration BMPs in HSPF is straightforward. However, to build an
FTABLE for some BMPs, i.e. sand filters, may require several steps. Although  the tool
may  be used in many BMP modeling applications, how accurately one can represent a
particular BMP depends on a user's skill.

There are several important infiltration BMP related topics that are not covered in this
tutorial. For example, this tutorial does not provide discussions on how to delineate small
urban watersheds as well as methods to estimate stormwater runoff rates and volumes
using HSPF and other models. The primary design considerations for any infiltration
BMP are to ensure that the infiltration BMP has the capacity to store the capture volume
and to ensure that the underlying soil can adequately drain the design capture volume
within the permissible drainage time.

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A detailed discussion of HSPF BMP tools will be published as a User's Manual Report.
The manual will cover HSPF BMP modeling capabilities. It will specifically address how
HSPF represents and simulates storage, infiltration, and vegetative BMPs.
The steps to follow when sizing infiltration facilities are:
   1.  Estimate the volume of stormwater runoff that the infiltration facility must store
       and infiltrate. In some cases, the runoff volume is referred to as water quality
       volume (WQv). Modelers can use Schueler's simple method (1987), U. S. Soil
       Conservation Service TR-55 Hydrologic Analysis model (1986), or HSPF
       (Bicknell et al. 2001) to determine the runoff volume generated from an
       impervious area.
   2.  Select the BMP type for the site.
   3.  Estimate storage capacity of the infiltration facility by selecting the appropriate
       BMP dimensions (make sure the facility adequately stores the runoff capture
       volume, as estimated above in Step 1).
   4.  Estimate average infiltration rate of the underlying soil using soil textural classes
       or field measurements (make sure the selected infiltration rate can sufficiently
       drain the storage volume within the allowable drain time).
   5.  Select a flow control device for the infiltration facility. Modelers can select
       underdrain pipes that drain water  particularly for soils with low infiltration
       capacity and/or overflow devices  that safely remove water when the facility fills
       up (e.g., weirs and riser orifices).
   6.  Copy and paste the resulting BMP FTABLE to your HSPF UCI file.
   7.  Run the model to route the pre-development and post-development runoff
       hydrographs through the BMP facility.
A. Infiltration BMPs With Regular Channel Shapes

To become familiar with HSPF infiltration BMP applications, model users should follow
this step-by-step tutorial.

Step 1. BMP tool users must select one of the seven BMP types from the pull down menu
(Figure 1). These types have different names, but some have similar characteristics.
There are two general types of infiltration BMPs: those that store water above the soil
surface as a ponding reservoir (e.g., infiltration basins, rain gardens, etc.) and those that
store water in backfilled underground reservoirs (e.g., infiltration trench and dry well,
etc.).  In both types, infiltration rate is controlled by the underlying soil.

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 H A p p [et Viewe r: go v/e pa/ne r I/at he ns/f tdb le/FTdb leA p p let. c lass
  Applet

       Select a BMP type from the menu:

   RECTANGULAR   TRIANGULAR   TRAPEZOIDAL
                Infiltration trench
                Infiltration trench
                Infiltration Basin
               r Rain garden 'Bioreteirtioii
                Vegetated swale
                Dry well
                Wetland
                Sand filter
                                   Infiltration BMP Input Data
  Structure geometry:
  Maximum Depth P):
  Top Width (ft):
  Length P):
6.0
36.0
400.0
  ] This structure contains backfill
                                            Infiltration rate (iii'lir):
                                            Infiltration Depth (in):
                                            Drain time (hr):
                                             8.27
Figure 1. BMP type selection screen.

Step 2. Select a channel shape for the BMP (Figure 2). The tool suggests a default
channel shape for each BMP type, but users can override the suggestion by clicking on
the shape of their choice.
   RECTANGULAR   TRIANGULAR
  Structure geometry:
  Maximum Depth (ft):
  Top Width (ft):
  Side Slope (H:V):
  Length (ft):
  TRAPEZOIDAL i' PARABOLIC  i NATURAL
                                               6.0
                                   IrrflrationB^
6.0
36.0
2.0
4000.0
  1 This structure contains backfill
Infiltration rate (inflir):
 Figure 2. Channel shape selector.

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Step 3. To store the design runoff volume generated from impervious areas, users must
type in channel depth, width, and length for the infiltration BMP (Figure 2). The final
selected channel dimensions must adequately store the design runoff capture volume.
Step 4. After selecting depth, width, and length channel dimensions, tool users need to
 r i        CalculateFTable        ,   ,                       ,            __._,T_
click on                    to calculate depth-area-storage columns of the FTABLE
(Figure 3).  The maximum storage capacity for the FTABLE, as shown below, must
always be greater than or equal to the calculated design runoff capture volume. To match
the design runoff capture volume and the maximum storage capacity of the infiltration
BMP, tool users can change the channel dimensions until the calculated maximum
storage volume becomes equal to or slightly greater than the design runoff capture
volume for the design storm. For trapezoidal channel shapes, make sure that the top width
is not mistakenly input as the bottom width.  Top width for trapezoidal channels is equal
to the sum of the bottom width and two times the product of the side slope ratio and the
maximum depth (TW = bw + 2.Z.D). Tool users can also add a minimum freeboard to the
maximum depth.
                                                           Calculate FTable
   Results   Copy Results
Right click the
depth
o7'o'oi"o 	
0.1 01 0
0.201 0
0.301 0
Fioici
0.501 0
FeoTri
OJoTo 	
"6780i6
'0.901 0
'l .001 0
'l.l 01 0
'1,2010
grid for more options.
(ft) a re a (a: res)
	 0.0276
0.0285
0.0294
0.0303
0.031 2
0.0321
	 57533"^
	 57'534"5
	 676349 	
'[1.0358
'[1.0367
"0.0377
0.0386

.
0.0000
	 0.0028"
0.0057
0.0087
0.01 1 8
0.01 50
	 0.01 82
	 0.0216
0.0250
0.0285
0.0322
0.0359
0.0397
                                            volyrne(ac-ft)
                                                              infil1:ration[:fs)
                                                          0.0000              :*
                                                          0.0000              I
                                                          0.0000              !
                                                          o.oooo              I
                                                          o.oooo              i
                                                          o.oooo              1
                                                          o.oooo              i
                                                          o.oooo              I
                                                          o.oooo              i
                                                          o.oooo              1
                                                          o.oooo              i
                                                          o.oooo              I
                                                          o.oooo              IT..
                          Maximum Storage Capacity1:14,405 feef

 Figure 3. Calculated depth-area-storage columns of the FTABLE.

Step 5.  Once channel dimensions that provide the desired maximum storage capacity are
                           I  Show Infiltration calculator  i
selected, users then click on '                          '  (Figure 4) to determine
infiltration rates for the site. Two options are available to estimate infiltration rates for the
BMP facility. The first uses the Maryland method to select an infiltration rate from a
look-up table (MDE, 1984): it employs soil texture classes to estimate  constant
infiltration rate of the underlying soil (Rawls, Brakensiek, and Saxton,  1982).  The
second option uses the Green-Ampt equation to calculate infiltration rate from soil
properties.

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                 Show infiltration calculator
   Show optional control devices
 Figure 4.  Infiltration method and flow control device selector.
Step 6. Infiltration BMPs use 11 soil textural classes (Figure 5). Each class has distinct
soil parameters. Green-Ampt parameter values, such as hydraulic conductivity, suction
head, and moisture content were determined from soil properties by Rawls, Brakensiek,
and Saxton (1982) and Rawls, Brakensiek, and Miller (1983). Tool users need to select
the site's soil type from the pull down menu (See Figure 5).
                 Hide infiltration calculator
   Show optional control devices
                           Select Soil Type; SSand
    Maryland Method (Look-up)
    (ireen and AffiptMeuiod
Sand
Lo.imy "scind
Sand Loam
 oam
Sirty Loam
sandy Clay Loam
Clay Loam
Silty Clay Loam
                                                              Calculate FTable
Figure 5. Soil type selector.
Step 7. Tool users can select the Green-Ampt method by clicking on the
 (*) Green and Ampt Method
                         . (Figure 6). The only option available there is the Green-Ampt
method. When using the Green-Ampt method, tool users must type in initial water
content and depth of the underlying soil (the two blank input areas). Based on the
selected soil texture, the program automatically fills the appropriate Green-Ampt
parameter values for each soil class.

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  Structure geometry:
  Maximum Depth (ft):
  Top Width (ft):
  Length (ft):
J6.0
fitTo
Infiltration BMP Input Data

     i    G This structure contains backfill
                                         Infiltration rate (Mir):
                                         Infiltration Depth (in):
                                         Drain time (lit i:
                                           00
                  Hide infiltration calculator
               Show optional control devices
                           Select Soil Type: ISand
     Maryland Method (Look-up)
     Green and Ampt Method
               Green and Ampt Method j ^
       Residual Water Content
                                Hydraulic Conductivity(cm/ht)
                                    Suction Head (cm)
                                    J4.95       i
                                   Effective Porosity
                                   [cur?	|

                                 Underlaying Soil Depth (ft)
            Porosity
         0.437
                                 Calculate Infiltration Rate
                                                               Calculate FTable
 Applet started.
Figure 6. Green-Ampt parameters.

Step 8. Tool users should test if the calculated infiltration rate adequately drains the
capture runoff volume within the maximum allowable drain time - which, for most
infiltration BMPs, is usually equal to or less than 72 hours. There are several ways of
testing whether the calculated infiltration rate drains the design runoff capture volume
within a specified drain time. With some assumptions, one can use Green-Ampt equation
to calculate drain time (Figure 6). Another option is to run HSPF for several days and
observe when the volume stored in the BMP facility becomes zero.

For soils with low infiltration rates, tool users can place an underground pipe to drain
water stored in the BMP facility within the allowable drain time. The tool user can select
the control device option and select an underdrain orifice. The options presented  herein
are used if users have no field measured infiltration data. If field-measured infiltration
rate data is are available, tool users can select the Maryland method and then type in the
measured infiltration rate over the Maryland value in the textbox (Figure 6). Make sure
that the units are in inches per hour.  As shown in the fourth column of Figure 7,

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calculated infiltration rates are converted into volumetric rates (cfs) by multiplying
infiltration rate by the surface area (bottom and non-vertical side areas) of the infiltration
BMP.
                  Show infiltration calculator
                        Show optional control devices
   Results   Copy Results
  Right click the grid for more options.
  0.0010
  0.1010
  0.2010
  0.3010
  0.4010
  0.5010
  0.6010
  0.7010
  0.3010
  0.9010
  1.0010
  1.1 01 0
  1.2010
         depth (ft)
      a re a (acres)
volume(ac-ft)
03306               0.0003
03306               0.0334
0.3306               I0.0664
'03306               0.0995
10.3306               (0.1326
03306               0.1656
0.3306               J0.1987
10.3306               JO.231 7
03306               0.2648
0.3306               0.2979
'03306               0.3309
10.3306               (0.3640
'0.3306               0.3970

      Maximum Storage Capacity1: 86,414 feet"1
                                                                 Calculate FTable
     infiltration (cfs')
0 0986
0.0986
0 0986
0.0986
0 0986
0.0986
0 0986
0.0986
0 0986
0.0986
0 0986
0.0986
0.0986
 Figure 1'. An FTABLE with an infiltration outflow.
Step 9. To generate an FTABLE with a control device, tool users must select one or more

                                         Show optional control devices
flow control devices by clicking on
Figure 1'.
                                                   as shown in

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      CONTROL STRUCTURES (optional)
VnolchWeir
Vertex Angle (deg):
Weir Invert (ft):
Sharp Crested Weir (Cipoletti)
Weir Crest Width (ft):
Weir Invert (ft):
Broad Crested Weir
Weir Crest Width (ft):
Weir Invert (ft):
Rectangular Weir
Weir Crest Width (ft):
Weir Invert (ft):
Underdrain Orifice
Orifice Diameter (ft):
Orifice Height (ft):
 Riser Orifice
Orifice Diameter (ft):
Weir Invert (ft):
30
5

'30
5
30
5
30
,5
5
2
js 	
\2
Figure 8. Input table for flow control devices (weirs and orifices).

Step 10. As an example, we selected a Riser Orifice as shown in Figure 8. Tool users
need to type in the orifice diameter and riser invert height to calculate an FTABLE with a
riser flow control and then click on
                                    Calculate FTable
(Figure 9). Note that infiltration
BMPs show infiltration in the outflow column of the FTABLE, whereas storage BMPs
show outflow in the same column. The flow control devices used for the infiltration
BMPs are similar to those used for the storage BMPs except that their sizes are smaller
than those used for the storage BMPs.
   Results   Copy Results
 i Right click the grid for more options.
i: depth(ft)
0.300000
HO. 400000
HO. 500000
HO. 600000
JO. 700000
i 0.800000
0.900000
jh.oooooo
h. 100000
Hi .200000 	
I h .306000 	
1.400000
'1.500000
I area(acres)
0.330579
0.330579
JO. 330579
|0. 330579
|0. 330579
JO. 330579
JO. 330579
JO. 330579
0.330579
	 0.330579
JO. 330579
"o. 330579
0.330579
{ volume (a oft)
0.099174
{0.132231
{0.165289
0.198347
0.231405
0.264463
0.297521
0.330579
0.363636
JO. 396694
0.429752
'0.462810
'0.495868
| shpc
lo.o
lo.o
0.0
lo.o
jo.o
Jo.o
jo.o
jo.o
3.1942
9.0346
.16.5976
25.5537
35.7124
                                                                         infiltration(cfs)
                                                                      {2.7567
                                                                      J2.7567
                                                                      {2.7567
                                                                      12.7567
                                                                      J2.7567
                                                                      {2.7567
                                                                      {2.7567
                                                                      {2.7567
                                                                      2 7567
                                                                      ,2.7567
                                                                      .2.7567
                                                                      2.7567
                                                                      ,2.7567
Figure 9.  FTABLE with a control device column.

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B. Transferring Calculated FTABLES to HSPF's UCI File

Step 11. Now that the program has generated an FTABLE with the desired channel
dimensions, flow control, and infiltration rate, the next step is to transfer the FTABLE to
the HSPF UCI file and to ensure that its format is compatible with the UCI file format.
To transfer the FTABLE to a UCI file, point the mouse anywhere on the output grid
table, right click, and then select "Copy to UCI file" (see Figure 10).

                                                              Calculate FTable
  Results  Copy Results
 Riyht click the grid for more options.
        depth(ft)              area(acres)             volume(ac-ft)             riserorf(cfs)
  0.40               1.25                 0.47                 0.0                 [-
  0.50               '1.29                 '"                 0.0                 
 .......... 0.6Q [[[ il2 ............................. Copy To Spreadsheet                  -^ [[[ ;
  0.70               1.36      Copy To UCI File      '               0.0                 i
  0.80               '1.40                                    ,0.0                 j
  O.go               '] 43      Java Applet Window                     'g.g                 !
  1.00               '1.47                 1.29                 0.0                 :
  1.10               ;l.51                 1.44                 J10                 k,

Figure 10. FTABLE transfer to HSPF UCI file.

Step 12. After clicking on "Copy to UCI FILE," the program generates an FTABLE that
is compatible with the HSPF UCI format (Figure 1 1). To copy the FTABLE to a UCI file,
select the entire FTABLE (left mouse click and drag), then press CTRL+C to export the
file to a UCI file. For UCI file related guidance, refer to the section on UCI File
modifications (Step 18).

                                                              Calculate FTable
  Results   Copy Results
Select the contents of the text area below and press Ctrl+C to copy.
...... '         """
FTABLE _ID*
rows cols
61 4
depth area
0.00 1.1
0.1 1.14
0.2 1.18
0.3 1.21
0.4 1.25
tr*
volume riserorf
0.00 0.00
0.11 0.00
0.23 0.00
0.35 0.00
0.47 0.00|
Figure 1 1 . Exporting FTABLE to HSPF UCI file.

C. Infiltration BMPs That Use Natural Channels (e.g., wetlands)

Presently, BASINS/WinHSPF use either of two automated methods to generate
FTABLES for a reach cross-section. These are the default and the alternate FTABLE
methods. These automated FTABLE generation methods are intended for use in areas

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                                                                                  10
The natural channel option employs channel cross-section data that is similar to those
obtained using the U.S. Army Corps of Engineers' HEC-RAS model. Just like HEC-
RAS, when entering (x, y) data, x values must always increase from the left overbank to
the right overbank (Figure 12). Although the natural channel program is capable of
generating FTABLES for many irregular channel shapes, it may not work for some
channel cross-sections. For example, it does not work for divided channels or for
channels with fewer than six data points. In such cases, users may increase the number of
data points by interpolation, or choose one of the regular channel shapes (e.g.,
trapezoidal) to approximate the natural channel.
RECTANGULAR
TRIANGULAR
TRAPEZOIDAL
PARABOLIC
                                                           NATURAL
                                                                    ,y8 High Point (Right)
Figure 12. Schematic diagram of a natural channel cross-section.

Step 13. To use the natural channel FTABLE option, prepare cross-sectional data (x,y)
data in comma-delimited text format (CSV) by using a text editor such as Notepad. The
user must first populate the left-hand side of the input grid with channel length and other
input parameters that vary with BMP type.  To import (x, y) data, point the mouse at the
input grid table and then right click to get "import from CSV file" (Figure 13). Also,
users have the option to type data in the input table.
                   Infiltration IMP Input Data
 Structure parrotry.
 Length (ft):
 Height Increment (ft):
j This structure contains backfill
                          Infiltration rate (Mr):
                          Infiltration Depth (in);
                         ;(=  Distance torn Let.. Y= Height torn Thalw.
                                 Import from Spreadsheet
                                 Import from
                                 Clear Table
                                 Undo Clear Table
Figure 13. Natural input grid table.

Step 14. An empty Java Applet Window (Figure 14)will appear. Go to the input data file
containing the (x, y) data (just a notepad not shown here), select all the (x, y) data, then
copy it.

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                                                                                11
   Jmpflrrt Dj*tn From CSV Filfe
  ten your CSV file. It should have a range of two numbers separated by commas.
 ;opy the range of numbers and paste (Ctrl+V) it into the text area below.
 Tick 'Import Data' to place the data into the grid.
                               Import Data
I Java Applet Window
Figure 14. Data import screen.

Step 15. An example data file is shown in Figure 15. Go back to the empty Java Applet
Window and hit CTRL+V to paste the data into the empty Applet Window shown in
Figure 14.

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                                                                               12
  pen your CSV file. It should have a range of two numbers separated by commas.
  opy the range of numbers and paste (Ctrl W) ft into the text area below.
  HckTimpojtJDaite^	
  ,6	
  ,5
  ,4
  ,3
  2,2
  6,1
  8,0
  1,1
  4,2
  7,3
  0,4
  3,5
  6,6
                              Import Data
  lava Applet Window
Figure 15. A Java Applet Window showing imported (x, y) data.
STEP 16. To transfer the pasted data into the natural channel grid, hit "Import Data" (see
the lower side of Figure 15). Make sure that the data is entered into the grid as shown in
Figure 16.
Infiltration BMP Input Data
Structure geometry:
Length (ft): flOO
Height Increment (ft): flT
D This structure contains b

Infiltration rate (Mir):
Infiltration Depth (in):
Drain time (hr):
X= Distant efiom Left. ,.v= Hei|M|m[[ha^
0 !6 |*|
ackfill 3 5 S
,6 4 i i
9 3 ||
12 2 ||
15 1
^18 0 ||
21 1 I I
24 2 	 hi
Figure 16. A natural channel showing imported cross-section data points.
                                              Calculate FTable
STEP 17. Generate an FTABLE by clicking on  I	'. Figure 17 shows an
FTABLE for a natural channel. The default height increment is one foot for the natural
channel. To refine the resolution of the FTABLE, set the height increment to any number

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                                                                                   13
from 0 to 1. The generated FTABLE can be exported to a UCI following instructions
given in Section B (transferring the calculated FTABLE to HSPF's UCI File).
  Results  Copy Results
 Right click the grid for more options.
                       a re a (acres)
 0.000000
 0.100000
 0.200000
 0.300000
 0.400000
 0.500000
 0.600000
 0.700000
 0.800000
 0.900000'
 i.'ooo'ooo'
 V.I 00000 '
 1,200000'
 0.000000
 0.005510
 0.011019
 0.016529
 0.022039
 a02754B'
 0.033058
"0.038567'
"0'.044077 '
'01149587'
 0.055096
"0.060606'
'n',066116"
     volume(ac-ft)
 0.000000
 ao'i'275	
 0.001102	
 11002479	
"0.004408	
"H006887	
"0.009917	
"O.0l'3499	
' 0^017631	
"H022314	
"0.027548	
"0.033333	
jl ,039669	
                                     shpcstdwr(cfs)
                                Maximum Storage Capacity: 42,600 feet3
Figure 17. FTABLE generated for a natural channel.

D. HSPF USER CONTROL INPUT (UCI)  FILE MODIFICATIONS
FOR BMP MODELING

STEP 18. To place the generated FTABLE in a UCI file, users must have an HSPF
project with existing FTABLES. It is wise to save a backup copy of the UCI file before
making any modifications. Select the UCI file to change in the HSPF project,  open it with
a text editor, identify the FTABLE to change, then paste the calculated FTABLE (copied
from the Web-tool) above or below the existing FTABLE. Give the new FTABLE the
same ID as the FTABLE being replaced. Make sure to delete or comment out the existing
FTABLE.
*** TRAPEZOIDAL ***
FTABLE JD***
rows cols ***
61 5
depth
0.00
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1

area
1.1
1.14
1.18
1.21
1.25
1.29
1.32
1.36
1.4
1.43
1.47

volume
0.00
0.11
0.23
0.35
0.47
0.6
0.73
0.86
1
1.14
1.29

outflowl
0.00
1.24
3.92
7.71
12.48
18.17
24.73
32.13
40.33
49.34
59.13

riserorf ***
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00

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                                                                           14
Figure 18. An FTABLE generated for a trapezoidal channel.

STEP 19. Set the appropriate number of exits in the GEN-INFO block of the RCHRES
section of the RCHRES module (Figure 19). Note that only Reach 8 has multiple exits in
this example. Also set the Print Flags (not shown here) to 2.0 for the RCFIRES section to
allow the model to generate an output for each time step. This is important for testing and
evaluation.
GEN-INFO
*** Name
*** RCHRES
Nexits Unit Systems Printer
t-series Engl Metr LKFG
*** X - X
3
4
5
6
7
8
9
CIRCULAR
CIRCULAR
CIRCULAR
CIRCULAR
CIRCULAR
NATURAL
CIRCULAR
PIPE
PIPE
PIPE
PIPE
PIPE

PIPE
in out
1
1
1
1
1
5
1
1 1
1 1
1 1
1 1
1 1
1 1
1 1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Figure 19. HSPF input table with a bolded multiple exit reach.

STEP 20. Select the exits that have control devices in HYDR-PARMl and type those
whose exit numbers are to be routed downstream. Users can select specific flow control
exits by placing the exit numbers (4, 5, 6, 7, and 8) in the UCI file (Figure 20). Placing
zero in a HYDR-PARMl column allows HSPF to ignore the flow from that particular
exit of the FTABLE.

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                                                                          15
HYDR-PARM1
*** Flags
***RCHRES
for each
3
4
5
6
7
8
9

for HYDR
VC Al A2

FGFGFG
0 1 1
0
0
0
0
0
0
1 1
1 1
1 1
1 1
1 1
1 1

FG
1
1
1
1
1
1
1
section
A3 ODFVFGfor



possible exit ***
40000
4
4
4
4
4
4
000
000
000
000
567
000
0
0
0
0
8
0
each * * * ODGTFG for each FUNCT


possible exit
00000
000
000
000
000
000
000
0 0
0 0
0 0
0 0
0 0
0 0


possible
333
3 3
3 3
3 3
3 3
3 3
3 3
3
3
3
3
3
3

exit
3 3
3 3
3 3
3 3
3 3
3 3
3 3
END HYDR-PARM1
Figure 20. HSPF input table with a bolded multiple exit reach.

STEP 21. If more than one control device is used, one must modify the MASS-LINK
block to allow volume-dependent outflows from multiple exits to be routed downstream
(see bolded row of Figure 20).
  MASS-LINK    5
 <-Volume-> <-Grp> <-Member-><~Mult~>   <-Target vols> <-Grp> <-Member-> * * *
        x x<-factor->            x x * * *
 * * * Reach Transfer of FLOW * * *
 RCHRES  ROFLOW                     RCHRES    INFLOW
 RCHRES  8OFLOW                     RCHRES     INFLOW  (multiple exit reach)
  END MASS-LINK  5
Figure 21. A MASS-LINK Block with outflows from multiple exits.
STEP 22. Convert generated FTABLE channel length to miles and place it in the "LEN"
Column 1 of HYDR-PARM2. To convert feet to miles, multiply feet by 0.000189394
and substitute that number for the one in the existing FTABLE. Make sure to choose the
correct FTABLE ID Number.
HYDR-PARM2
*** RCHRES FTBW FTBU
1 0. 1
END HYDR-PARM2

LEN
(miles)
2.8


DELTH
(ft)
22


STCOR
(ft)
3.2


KS DB50
(in)
0.5 0.01

Figure 22. HSPF input table showing reach length parameter in bold.

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                                                                              16
STEP 23. Save the UCI file and run the project with HSPFLite. If no errors are
generated, users can import the project into WinHSPF if they wish to run HSPF this way.
E. BMP Modeling Limitations and Assumptions

The current BMP tool does not support FTABLES for multiple layers. The maximum
number of layers represented by a single FTABLE are two: an upper layer with ponded
reservoir and a lower layer with a backfilled soil (underground reservoir). In cases where
tool users need to use multiple layers, we recommend using separate FTABLES for
 different layers and then linking the FTABLES. Flow from one layer to another can be
linked using the Schematic and the Mass-Link Blocks  of the HSPF model. Methods to
estimate infiltration rates for layered soils may also be added to a later release.

Infiltration BMPs are not suitable for sites with low infiltration capacity, high water table
or in areas where the bedrock is too close to the ground surface.

   Some assumption made when developing the tool include:

   1)  The infiltration BMPs use Darcy' s law, but we assume that the hydraulic gradient
       is equal to one. Note that setting the hydraulic gradient equal to one ignores soil
       water pressure and depth of ponding. For infiltration BMPs that store water within
       a back-filled soil, the volume of the FTABLE is reduced by multiplying the
       calculated channel volume by the soil porosity  (see the top right side of Figure 6).
       We assume an instant surface ponding and we ignore infiltration during rainfall
       events because the BMP filling time is much shorter than the draining time.

   2)  We assume that infiltration rate occurs on the wetted surface area of the
       surrounding soil. We therefore use surface area to calculate volumetric infiltration
       rate, but we do not consider infiltration into vertical sidewalls, i.e. rectangular
       sides. Ignoring infiltration into vertical sidewalls makes the infiltration rate
       calculation more conservative.

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                                                                             17
REFERENCES

Bicknell, B.R., J.C. Imhoff, J.L. Kittle Jr., T.H. Jobes and A.S. Donigian Jr.,
Hydrological Simulation Program-FORTRAN. User's Manual for Release 12, U.S. EPA
Ecosystem Research Division, Athens, Georgia/U.S. Geological Survey, Office of
Surface Water, Reston, Virginia, USA (2001).

Maryland Department of Environemt, Sediment and Stormwater Administration,
Standard and Specifications for infiltration practices, February,  1984.

Rawls, W.J., Brakensiek, D.L., Miller N. 1983. Green-Ampt infiltration parameters from
soil data. Journal of Hydraulic Engineering Vol. 109:62-70.

Rawls, W. J., D. L. Brakensiek and K. E. Saxton. 1982. Estimation of soil water
properties. Trans. Amer. Soc. of Agric. Engin. 25(5): 1316 1320, 1328..

Schueler, T.R.  1987. Controlling Urban Runoff: A Practical Manual for Planning and
Designing Urban BMPs. Metropolitan Washington Council of Governments,
Washington, DC.

Soil Conservation Service (SCS), Urban Hydrology for Small Watersheds., Tech. Release
55, Washington, DC. 1986. Available online at http://www.wcc.nrcs.usda.gov/water
/qualitv/common/tr5 5/tr5 5 .pdf
                                 CONTACT US

If you have questions or would like to report bugs or make suggestions regarding the
web-tool, please contact Yusuf Mohamoud at mohamoud.yusuf@epa.gov. Users may
also contact the authors through the BASINS Listserver, making sure that the subject line
is "HSPF Web-tools".
                                 DISCLAIMER

Although this Web-tool has been reviewed by its developers, no warranty, expressed or
implied, is made to the accuracy and functioning of the tools and related program
material nor shall the fact of its distribution constitute any such warranty and no
responsibility is assumed by the USEPA in connection therewith.

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