Spreadsheet: 28edd9bb-ba73-4940-8e20-af1b7e7cbb1e
Sheet: 1. WQv and WQf

WATER QUALITY VOLUME AND WATER QUALITY FLOW RATE CALCULATOR
This work sheet calculates the Water Quality Flow Rates or Water Quality Volumes for each drainage management area on your site.
CALCULATOR
Step 1 |  | Total Site Area |  | square feet
Step 2 |  | # of DMAs
Step 3 |  | Step 4 |  | Step 5 |  |  |  | Step 6 |  | Step 7 |  | Step 8 |  |  |  |  |  |  | Step 9 | Step 10
 |  |  | Area Impervious (all in square feet) |  |  |  |  |  | Area Pervious (all in square feet)
Drainage Management Areas |  | Drainage Management Area (square feet) | TOTAL | Standard Roof | Asphalt | Concrete | Brick/Pavers | Other | TOTAL | Permeable Pavementa | Vegetated Roofb | Gravelc | Landscaping | [NAME] | Lawns/grass, sandy soil, slope<2% | Lawns/grass, sandy soil, slope>7% | Lawns/grass, heavy soil, slope<2% | Lawns/grass, heavy soil, slope>7% | Other | Total Area Check
A
B
C
D
E
F
G
H
I |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | Comp | Unit [NAME]
J |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | C' | 24 hr drawdown |  | 48 hr drawdown
 | Total |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | Factor | 0.8 | 0.9 | 0.8 | 0.9
 | Total Area Check |  |  | Impervious Runoff Coefficients |  |  |  |  |  |  |  | Pervious Runoff Coefficients |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.05 | 0.025 | 0.04 | 0.04 | 0.055
 | Number of DMAs Check |  |  | Standard Roof |  |  | 0.85 |  |  |  |  | Permeable Pavement a |  |  |  | NA |  |  |  |  |  |  |  |  |  |  |  |  | 0.1 | 0.06 | 0.075 | 0.075 | 0.105
 |  |  |  | Asphalt |  |  | 0.8 |  |  |  |  | Vegetated Roof b |  |  |  | NA |  |  |  |  |  |  |  |  |  |  |  |  | 0.15 | 0.085 | 0.12 | 0.11 | 0.15
 |  |  |  | Concrete |  |  | 0.9 |  |  |  |  | Gravel c |  |  |  | 0.25 |  |  |  |  |  |  |  |  |  |  |  |  | 0.2 | 0.11 | 0.1525 | 0.1475 | 0.2
 |  |  |  | Brick/Pavers |  |  | 0.75 |  |  |  |  | Landscaping |  |  |  | 0.2 |  |  |  |  |  |  |  |  |  |  |  |  | 0.25 | 0.135 | 0.19 | 0.185 | 0.2525
 |  |  |  | Other |  |  |  | Step 6 |  |  |  | [NAME] |  |  |  | 0.35 |  |  |  |  |  |  |  |  |  |  |  |  | 0.3 | 0.1625 | 0.23 | 0.2275 | 0.305
 |  |  |  |  |  |  |  |  |  |  |  | Lawns/grass, sandy soil, slope<2% |  |  |  | 0.08 |  |  |  |  |  |  |  |  |  |  |  |  | 0.35 | 0.19 | 0.26 | 0.26 | 0.3575
 |  | Step 11 |  |  |  |  |  |  |  |  |  | Lawns/grass, sandy soil, slope>7% |  |  |  | 0.17 |  |  |  |  |  |  |  |  |  |  |  |  | 0.4 | 0.215 | 0.3 | 0.2975 | 0.4075
Drainage Management Area |  | Composite Runoff Coefficient |  |  |  |  |  |  |  |  |  | Lawns/grass, heavy soil, slope<2% |  |  |  | 0.15 |  |  |  |  |  |  |  |  |  |  |  |  | 0.45 | 0.24 | 0.325 | 0.3325 | 0.46
A |  |  |  |  |  |  |  |  |  |  |  | Lawns/grass, heavy soil, slope>7% |  |  |  | 0.3 |  |  |  |  |  |  |  |  |  |  |  |  | 0.5 | 0.27 | 0.375 | 0.37 | 0.51
B |  |  |  |  |  |  |  |  |  |  |  | Other |  |  |  |  | Step 9 |  |  |  |  |  |  |  |  |  |  |  | 0.55 | 0.3 | 0.42 | 0.4075 | 0.5605
C |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.6 | 0.325 | 0.4525 | 0.44 | 0.615
D |  |  |  |  |  |  | Chose Jurisdiction for WQv [NAME] |  |  |  |  |  |  |  |  |  | Step 12 |  |  |  |  |  |  |  |  |  |  |  | 0.65 | 0.35 | 0.495 | 0.48 | 0.665
E |  |  |  |  |  |  | 1. | Port of San Francisco jurisdiction: 48 hour, 80% capture. Enter "1" in Step 12. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.7 | 0.38 | 0.53 | 0.515 | 0.72
F |  |  |  |  |  |  | 2. | SFPUC jurisdiction: 0.75 inch rainfall depth. Enter "2" in Step 12. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.75 | 0.41 | 0.565 | 0.5525 | 0.77
G |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.8 | 0.43 | 0.605 | 0.59 | 0.82
H |  |  |  |  |  |  | WQf [NAME] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.85 | 0.465 | 0.645 | 0.625 | 0.87
I |  |  |  |  |  |  | Design Rainfall Intensity (in/hr) |  |  |  |  |  |  |  |  | 0.2 |  |  |  |  |  |  |  |  |  |  |  |  | 0.9 | 0.49 | 0.685 | 0.66 | 0.92
J |  |  |  |  |  |  | Note: For both the Port of San Francisco and the SFPUC, the WQf performance measure is based on a 0.2 in/hr rainfall intensity. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.95 | 0.515 | 0.72 | 0.695 | 0.97
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 | 0.54 | 0.755 | 0.735 | 1.025
 |  | Step 13 |  |  | Step 14 |  |  |  | Step 15
Drainage Management Area |  | Water Quality Flow Rate |  |  | Water Quality Volume |  |  |  | DMA | Area | Drainage area constraints table
 |  | [NAME]/sec |  |  | [NAME] |  |  |  |  | acres | BMP |  |  | min | [NAME] | BMP |  |  | min | [NAME]
A |  |  |  |  |  |  |  |  | A |  | Detention pond |  |  | 5 ac* |  | Bioretention |  |  |  | 1 ac **
B |  |  |  |  |  |  |  |  | B |  | Wet pond |  |  | 5 ac |  | Media filter |  |  |  | 5 ac
C |  |  |  |  |  |  |  |  | C |  | Dry well |  |  |  | 0.25 ac | Water quality inlet |  |  |  | 1 ac
D |  |  |  |  |  |  |  |  | D |  | Infiltration basin |  |  |  | 10 ac | Vegetated rock filter |  |  | no contraints
E |  |  |  |  |  |  |  |  | E |  | Infiltration trench |  |  |  | 5 ac | Permeable pavement |  |  | no contraints
F |  |  |  |  |  |  |  |  | F |  | Vegetated swale |  |  |  | 5 ac | Swirl separator |  |  | no contraints
G |  |  |  |  |  |  |  |  | G |  | Vegetated buffer strip |  |  |  | 2(Astrip) | Drain insert |  |  | no contraints
H |  |  |  |  |  |  |  |  | H |  | Constructed wetland |  |  | 5 ac |  | Vegetated roof |  |  | no contraints
I |  |  |  |  |  |  |  |  | I |  | Detention vault |  |  |  | 10 ac | [NAME] harvesting |  |  | no contraints
J |  |  |  |  |  |  |  |  | J |  | * Or minimum orifice diameter of 1 inch |  |  |  |  | ** Multiple cells can be used to treat larger areas
INSTRUCTIONS
Step
1 | Enter the total square footage of your site. Areas are entered in units of square feet. Note: 1 acre = 43,560 square feet.
2 | Divide your entire site into discrete drainage management areas (DMAs) and enter the number of DMAs. A DMA is a portion of your site that drains to a common location.
3 | Name each DMA and enter one name per row in the cells adjacent to "A", "B", "C", etc.
4 | Enter the square footage of each DMA.
5 | Identify the different impervious land surfaces for each DMA and enter their square footage. If a permeable pavement area (i.e., pervious concrete, porous asphalt, or permeable paver) will receive run-on from adjacent surfaces, then the entire paved area (including the area planned for permeable pavement) should be entered as an impervious surface. The required size of the permeable pavement facility can then be calculated using the permeable pavement sizer.
6 | Use the "other" column for impervious land surfaces not described. Enter the square footage of the "other surface" in the table.  Below, in the Impervious Runoff Coefficients Table, enter a runoff coefficient, C, for the "other" impervious surface.
7 | Identify any existing permeable pavement or vegetated roofs on your site that are designed according to SDG requirements and do not receive runoff from adjacent surfaces. Enter their areas. See "Notes" section (a and b) at bottom of worksheet for additional description of permeable pavement and vegetated roofs.
8 | Identify additional pervious land surfaces for each DMA and enter their areas. See "Notes" section (c) at bottom of worksheet for a description of whether to categorize gravel as permeable pavement or pervious area.
9 | Use the "other" column, column T, for pervious land surfaces not described. Enter the square footage of the "other surface" in the table.  Below, in the Pervious Runoff Coefficients Table, enter a runoff coefficient, C, for the "other" pervious surface .
10 | Check column U is "okay". If not, adjust areas accordingly.
11 | Composite runoff coefficients for each DMA are calculated and displayed here.
12 | Choose jurisdication for performance measure. Projects in the Port of SF jurisdiction should select "1". Projects in SFPUC jurisdiction should select "2".
13 | The Water Quality Flow Rate (WQf) for each DMA is calculated here. The WQf is the required flowrate to be managed by flow-based BMPs such that the water quality performance measure requirements are met.
14 | The Water Quality Volume (WQv) for each DMA is calculated here. The WQv is the required volume to be managed by volume-based BMPs such that the water quality performance measure requirements are met.
15 | Use DMA areas and drainage area constraints table to determine which BMPs are possible for which DMAs.
NEXT STEPS
 | Use the BMP sizing calculators to help you size and design each treatment control measure.
 | For flow-based measures, the treatment control measure must be sized such that it accommodates the Water Quality Flow Rate for each DMA.
 | For volume-based measures, the treatment control measure must be sized such that it accommodates the Water Quality Volume for each DMA.
NOTES
a | Permeable pavement includes permeable pavers, porous asphalt, and pervious concrete designed according to SDG requirements.  If runoff from adjacent impervious surfaces is draining to the permeable pavement, then the total paved area (including the area planned for permeable pavement) should be entered as impervious area in Step 5.  The portion of this total paved area that must be converted to permeable pavement to meet the SDG treatment requirements can then be calculated using the Permeable Pavement calculator.
b | Vegetated roofs should be designed in accordance with the SDG to capture the WQv from the roof DMA.
c | Gravel surfaces can be considered a permeable pavement system if designed in accordance with the storage layer requirements outlined in the permeable pavement sizer and fact sheet. The gravel should be an open graded crushed washed AASHTO No. 8 stone or larger.  The system should be designed to completely capture the WQv and either infiltrate it or detain it over a 48 hour period.
DEFINITIONS
 | Water Quality Volume Equation: | WQv = C x A x d/12
 | Water Quality Flow Equation: | WQf = C x i x A/43560
 | Where: | WQf = water quality flow (cubic feet per second)
 |  | WQv = water quality volume (cubic feet)
 |  | C = runoff coefficient
 |  | i = design rainfall intensity (in/hr) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | Last updated: 11/23/10
 |  | A = drainage area (square feet)
 |  | d = design depth of rainfall (inches)