10160 - Justman Farm Drainage Report - 20241010
Larson & Associates
surveyors, engineers and planners
9027 Pacific Ave. Suite 4
Tacoma, WA 98444
STORM DRAINAGE REPORT
PROPONENT:
C&E DEVELOPMENTS, LLC
P.O. BOX 2983
YELM, WA 98597
CONTACT: ERIC PETERSON
PHONE: (253) 278-0343
PREPARED BY:
Larson & Associates
surveyors, engineers and planners
9027 Pacific Ave. Suite 4
Tacoma, WA 98444
(253) 474-3404
October 10, 2024
Page 1 of 29
STORMWATER SITE PLAN
CHAPTER 1 - PROJECT OVERVIEW ........................................................................................................................... 4
CHAPTER 2 - EXISTING CONDITIONS SUMMARY ...................................................................................................... 4
CHAPTER 3 - OFF-SITE ANALYSIS ........................................................................................................................... 4
CHAPTER 4 - PERMANENT STORMWATER CONTROL PLAN ...................................................................................4-5
SECTION 1 - PRE-DEVELOPED SITE HYDROLOGY ............................................................................................ 4
SECTION 2 - DEVELOPED SITE HYDROLOGY .................................................................................................... 5
SECTION 3 - PERFORMANCE STANDARDS AND GOALS ..................................................................................... 5
SECTION 4 - FLOW CONTROL SYSTEMS ........................................................................................................... 5
CHAPTER 5 - DISCUSSION OF MINIMUM REQUIREMENTS .....................................................................................5-7
CHAPTER 6 - SPECIAL REPORTS AND STUDIES ......................................................................................................... 7
CHAPTER 7 - OTHER PERMITS .................................................................................................................................. 7
CHAPTER 8 - OPERATION AND MAINTENANCE MANUAL ......................................................................................... 7
CHAPTER 9 - BOND QUANTITIES WORKSHEET ........................................................................................................ 7
APPENDICES
APPENDIX "A" ..................................................................................................................................... VICINITY MAP
APPENDIX "B" ........................................................................................................................................... NRCS MAP
APPENDIX "C" .......................................................................................................................................... FEMA MAP
APPENDIX "D" .................................................................................... PRE-DEVELOPED AND DEVELOPED BASIN MAP
APPENDIX "E" ............................................................................................................ STORMWATER CALCULATIONS
Page 2 of 29
I hereby state that this Stormwater Pollution Prevention Plan for JUSTMAN FARM has
been prepared by me or under my supervision and meets the standard of care and expertise
which is usual and customary in this community for professional engineers. I understand
that Washington State and City of Yelm does not and will not assume liability for the
sufficiency, suitability, or performance of drainage facilities prepared by me.
October 10, 2024
Grant J. Middleton, P.E.
Page 3 of 29
CHAPTER 1 – PROJECT OVERVIEW
The proposed JUSTMAN FARM is located in Section 29, Township 17 North, Range 2 East of
the Willamette Meridian in Yelm, Washington. Parcel number is TPN 64303200600, the area of
the lot is 9.37 ac., and address is 16731 State Route 507 SE Yelm, WA 98597. The project
consists of providing a landscaping wall and grading the site. A vicinity map is included in
Appendix “A”.
Stormwater runoff generated from pervious surfaces will be collected and conveyed to an
infiltration pond for infiltration. All created landscaped areas will receive compost amended
topsoil in accordance with BMP T5.13, Chapter V-12, Volume V of the SWMMWW. Due to
converting more than 2.5 acres of native vegetation to pasture, it is necessary to address all
Minimum Requirements for this project.
CHAPTER 2 – EXISTING CONDITION SUMMARY
The project parcel is located on the south side of SR 507 at the eastern edge of the City of Yelm’s
city limits. The property is currently zoned C-2 Heavy Commercial according to the City’s current
Zoning Map. Surrounding properties consist of large tract farms to the south, west and east.
Per USDA Natural Resources Conservation Service (NRCS), on-site soils consist of Spanaway
gravelly sandy loam, 0 to 3 percent. See the NRCS Soils Information Map located in the Appendix
“B” for additional information. Based on our knowledge of the soil characteristics and previous
projects completed in this area, a conservative design infiltration rate of 17 inches per hours can
be used for infiltration facilities for this project.
According to FEMA Flood Map Service Center Flood Map 53067C0362F, flood Zone X with
established base flood elevation 349.7 – 349.9 feet (NAVD 88) located within floodway of Yelm
Creek located west of the property. Refer to Appendix “C” for additional information.
CHAPTER 3 – OFF-SITE ANALYSIS
Due to the topography of the site, there is no off-site runoff naturally contributed to the project
area.
CHAPTER 4 – PERMANENT STORMWATER CONTROL PLAN
SECTION 1 – PRE-DEVELOPED SITE HYDROLOGY
This parcel used to be a farm with some structures on the site that have been demolished and
removed. For stormwater modeling purposes, the entire project parcel was modeled as “A/B
Forest, Flat using 15-minute time steps on MGSFlood (version 4.62). Pre-developed and
Developed Basin Map is provided in Appendix “D”. Table 1 presents viewer with the historic
land cover for the lot.
LAND COVER AREA
A/B, Forest, Flat 210,693 S.F. (4.837 ac.)
TOTAL: 210,693 S.F. (4.837 ac.)
Table 1: Historic Areas
Page 4 of 29
SECTION 2 – DEVELOPED SITE HYDROLOGY
In the developed condition, the natural drainage pattern remains the same to the maximum extent
possible, with the exception of those areas being infiltrated. Table 2 presents the reviewer with the
developed land cover and areas.
LAND COVER AREA
Cleared Area Conveyed
to Infiltration Pond:
190,483 S.F. (4.373 ac.)
Bypass:
Cleared Area (A/B, Pasture, Flat)
20,210 S.F. (0.464 ac.)
Total: 210,693 S.F. (4.837 ac.)
Table 2: Developed Areas
SECTION 3 – PERFORMANCE STANDARDS AND GOALS
According to Figure I-3.1: Flow Chart for Determining Requirements for New Development per
the 2024 Department of Ecology Stormwater Management Manual for Western Washington, all
minimum requirements apply to the new and replaced hard surfaces and converted vegetation
areas. See Chapter 5 below for additional information regarding the minimum requirements,
which have been addressed.
SECTION 4 – FLOW CONTROL SYSTEM
Onsite flow control will be provided with the construction of an infiltration pond. The infiltration
pond is located in the north portion of the property.
Infiltration Pond – Volume V, Chapter 5, BMP T7.10 of the SWMMWW
The dimensions of the pond were determined using MGS Flood with an infiltration rate of 17
inches per hour; the MGS Flood output is provided in Appendix E. In the predeveloped
condition, the 4.837-acre sub-basin was modeled as “A/B, Pasture, Flat”. In the developed
condition, the pervious areas were modeled as “A/B, Pasture, Flat”. The pond bottom is 190 feet
long by 1 foot wide. The bottom of the pond is at elevation 348.00 and the top of the pond is at
elevation 350.00 which allows for live storage between Elev. 348.50 and Elev. 349.00 with 0.5
feet of sediment storage and 1 foot of freeboard. The water surface elevation equivalent to the
100-year, 24-hour storm event occurs at Elev. 348.55. Interior pond side slopes will be 3H:1V;
the pond bottom and side slopes will be hydroseeded using a seed mixture from Table III-3.2.2,
Stormwater Tract “Log Grow” Seed Mix, Volume III, of the SWMMWW. Emergency overflow
will be accommodated via a 6-foot-wide spillway located on the pond’s north side. The spillway
elevation will be 0.5 foot below the pond top at Elev. 349.50.
CHAPTER 5 – DISCUSSION OF MINIMUM REQUIREMENTS
Minimum Requirement #1: Preparation of Stormwater Site Plan
This report and the associated site development plan set fulfill this requirement.
Minimum Requirement #2: Construction SWPPP
The document titled “Construction SWPPP” fulfills this requirement.
Page 5 of 29
Minimum Requirement #3: Source Control of Pollution
The document titled “Construction SWPPP” in fulfills this requirement.
Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls
As described in Chapters 2 and 3 above, onsite runoff does not appear to drain offsite but rather
infiltrates through the highly permeable native soil. The lack of existing drainage outfalls from
or through the site supports this condition.
Minimum Requirement #5: On-Site Stormwater Management
According to Figure I-3.3: Flow Chart for Determining MR #5 Requirements per the 2024
Department of Ecology Stormwater Management Manual for Western Washington, the project
developer needs to choose to meet the LID Performance Standard or for each surface, consider
the BMPs in the order listed in List #2 for that type of surface. The project chose to meet LID
Performance Standard.
• Lawn and Landscaped Areas
Lawn and Landscaped Areas shall follow the BMP T5.13: Post-Construction Soil Quality
and Depth.
• Roofs
No structures are proposed for this project.
• Other Hard Surfaces
No other hard surfaces are proposed for this project.
MGS Flood calculations show that the project meets the LID requirements. Refer to Appendix
“E”.
Minimum Requirement #6: Runoff Treatment
No pollution generating impervious surfaces are proposed. Runoff treatment is not required.
Minimum Requirement #7: Flow Control
I-3.4.7 MR7: Flow Control of the Manual contains the following thresholds when determining if
flow control is required for a project. For each threshold, a response in bold lettering provides the
reviewer with the applicability of that particular threshold as it relates to this project.
• TDAs that have a total of 10,000 square feet or more of effective impervious surfaces.
The project proposes no hard surfaces; therefore, this threshold is not triggered.
• TDAs that convert ¾ acres or more of native vegetation, pasture, scrub/shrub, or
unmaintained non-native vegetation to lawn or landscape, or convert 2.5 acres or more of
native vegetation to pasture, and from which there is a surface discharge in a natural or
manmade conveyance system from the TDA. The project proposes to convert 4.837
acres of native vegetation to pasture, which is more than 2.5 acres threshold;
therefore, flow control is required for this project. MGS Flood calculations show
that the project meets the Flood Control requirements. Refer to Appendix “E”.
Page 6 of 29
• TDAs that through a combination of effective hard surfaces and converted vegetation
areas cause a 0.15 cubic feet per second (cfs) or greater increase in the 100-year flow
frequency as estimated using an approved continuous simulation model and 15-minute
time steps. The 100-year pre-developed run-off is 0.02654 cfs. The 100-year
developed run-off is 0.01232 cfs. This results in a decrease of 0.01422 cfs, which is
less than the 0.15 cfs increase threshold. The calculations are presented within
Appendix “E” of this report.
Minimum Requirement #8: Wetland Protection
All proposed surfaces are outside of the wetland buffer. This project proposes full
infiltration; therefore, no additional wetland protection is required.
Minimum Requirement #9: Operation and Maintenance
The accompanying Operation and Maintenance Manual fulfills this requirement.
CHAPTER 6 – SPECIAL REPORT AND STUDIES
• No reports or studies has been completed.
CHAPTER 7 – OTHER PERMITS
• No other permits are required.
CHAPTER 8 – OPERATION AND MAINTENANCE MANUAL
A completed Operation and Maintenance Manual accompanies this report.
CHAPTER 9 – BOND QUANTITIES WORKSHEET
• No Bond Quantities Worksheets are required.
End of Report
Page 7 of 29
APPENDIX “A”
VICINITY MAP
Page 8 of 29
Page 9 of 29
APPENDIX “B”
NRCS MAP
Page 10 of 29
Soil Map—Thurston County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/7/2024
Page 1 of 3
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Map Scale: 1:1,090 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
Page 11 of 29
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Page 12 of 29
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
110 Spanaway gravelly sandy
loam, 0 to 3 percent slopes
4.8 100.0%
Totals for Area of Interest 4.8 100.0%
Soil Map—Thurston County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/7/2024
Page 3 of 3
Page 13 of 29
Thurston County Area, Washington
110—Spanaway gravelly sandy loam, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: 2ndb6
Elevation: 330 to 1,310 feet
Mean annual precipitation: 35 to 65 inches
Mean annual air temperature: 50 degrees F
Frost-free period: 150 to 200 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Spanaway and similar soils:100 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Spanaway
Setting
Landform:Terraces, outwash plains
Parent material:Volcanic ash over gravelly outwash
Typical profile
H1 - 0 to 15 inches: gravelly sandy loam
H2 - 15 to 20 inches: very gravelly loam
H3 - 20 to 60 inches: extremely gravelly sand
Properties and qualities
Slope:0 to 3 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Somewhat excessively drained
Capacity of the most limiting layer to transmit water (Ksat):High
(1.98 to 5.95 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Available water supply, 0 to 60 inches: Low (about 3.8 inches)
Interpretive groups
Land capability classification (irrigated): 3s
Land capability classification (nonirrigated): 3s
Hydrologic Soil Group: A
Ecological site: R002XA006WA - Puget Lowlands Prairie
Forage suitability group: Droughty Soils (G002XS401WA)
Other vegetative classification: Droughty Soils (G002XS401WA)
Map Unit Description: Spanaway gravelly sandy loam, 0 to 3 percent slopes---Thurston County
Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/7/2024
Page 1 of 2
Page 14 of 29
Hydric soil rating: No
Data Source Information
Soil Survey Area: Thurston County Area, Washington
Survey Area Data: Version 18, Aug 27, 2024
Map Unit Description: Spanaway gravelly sandy loam, 0 to 3 percent slopes---Thurston County
Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/7/2024
Page 2 of 2
Page 15 of 29
APPENDIX “C”
FEMA MAP
Page 16 of 29
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Page 17 of 29
APPENDIX “D”
PRE-DEVELOPED AND DEVELOPED BASIN MAP
Page 18 of 29
P
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Page 19 of 29
APPENDIX “E”
STORMWATER CALCULATIONS
Page 20 of 29
STORMWATER CALCULATIONS
JUSTMAN FARM (J# 10160)
PREDEVELOPED
POSTDEVELOPED
Page 21 of 29
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.62
Program License Number: 200810005
Project Simulation Performed on: 10/10/2024 9:48 AM
Report Generation Date: 10/10/2024 9:48 AM
—————————————————————————————————
Input File Name: 10160 - Justman Farm.fld
Project Name: 10160 - Justman Farm
Analysis Title: Storm Design
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Full Period of Record Available used for Routing
Climatic Region Number: 16
Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961044 Puget East 44 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : Ecology Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 4.837 4.837
Area of Links that Include Precip/Evap (acres) 0.000 0.000
Total (acres) 4.837 4.837
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : LOT ----------
-------Area (Acres) --------
A/B, Forest, Flat 4.837
----------------------------------------------
Page 22 of 29
Subbasin Total 4.837
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 2
---------- Subbasin : LOT ----------
-------Area (Acres) --------
A/B, Pasture, Flat 4.373
----------------------------------------------
Subbasin Total 4.373
---------- Subbasin : BYPASS ----------
-------Area (Acres) --------
A/B, Pasture, Flat 0.464
----------------------------------------------
Subbasin Total 0.464
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: POC
Link Type: Copy
Downstream Link: None
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 2
------------------------------------------
Link Name: POC
Link Type: Copy
Downstream Link: None
------------------------------------------
Link Name: POND
Link Type: Structure
Downstream Link Name: POC
Prismatic Pond Option Used
Pond Floor Elevation (ft) : 348.50
Riser Crest Elevation (ft) : 349.00
Max Pond Elevation (ft) : 350.00
Storage Depth (ft) : 0.50
Pond Bottom Length (ft) : 190.0
Page 23 of 29
Pond Bottom Width (ft) : 1.0
Pond Side Slopes (ft/ft) : Z1= 3.00 Z2= 3.00 Z3= 3.00 Z4= 3.00
Bottom Area (sq-ft) : 190.
Area at Riser Crest El (sq-ft) : 772.
(acres) : 0.018
Volume at Riser Crest (cu-ft) : 240.
(ac-ft) : 0.006
Area at Max Elevation (sq-ft) : 1990.
(acres) : 0.046
Vol at Max Elevation (cu-ft) : 1,614.
(ac-ft) : 0.037
Constant Infiltration Option Used
Infiltration Rate (in/hr): 17.00
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 12.00
Common Length (ft) : 0.000
Riser Crest Elevation : 349.00 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 1
********** Subbasin: LOT **********
Flood Frequency Data (cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 3.751E-03
5-Year 3.869E-03
10-Year 3.897E-03
25-Year 1.464E-02
50-Year 1.831E-02
100-Year 2.654E-02
200-Year 3.986E-02
500-Year 5.763E-02
********** Link: POC ********** Link Inflow
Frequency Stats
Flood Frequency Data (cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 3.751E-03
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5-Year 3.869E-03
10-Year 3.897E-03
25-Year 1.464E-02
50-Year 1.831E-02
100-Year 2.654E-02
200-Year 3.986E-02
500-Year 5.763E-02
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 2
Number of Links: 2
********** Subbasin: LOT **********
Flood Frequency Data (cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 3.450E-03
5-Year 3.873E-03
10-Year 1.680E-02
25-Year 4.280E-02
50-Year 9.287E-02
100-Year 0.116
200-Year 0.143
500-Year 0.178
********** Subbasin: BYPASS **********
Flood Frequency Data (cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 3.661E-04
5-Year 4.110E-04
10-Year 1.783E-03
25-Year 4.542E-03
50-Year 9.855E-03
100-Year 1.231E-02
200-Year 1.513E-02
500-Year 1.887E-02
********** Link: POC ********** Link Inflow
Frequency Stats
Flood Frequency Data (cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 3.661E-04
5-Year 4.110E-04
10-Year 1.783E-03
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25-Year 4.542E-03
50-Year 9.855E-03
100-Year 1.232E-02
200-Year 1.513E-02
500-Year 1.887E-02
********** Link: POND ********** Link Inflow
Frequency Stats
Flood Frequency Data (cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 3.450E-03
5-Year 3.873E-03
10-Year 1.680E-02
25-Year 4.280E-02
50-Year 9.287E-02
100-Year 0.116
200-Year 0.143
500-Year 0.178
********** Link: POND ********** Link Outflow 1
Frequency Stats
Flood Frequency Data (cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 4.191E-09
5-Year 4.641E-09
10-Year 2.001E-08
25-Year 5.007E-08
50-Year 1.534E-07
100-Year 5.346E-07
200-Year 8.454E-07
500-Year 1.252E-06
********** Link: POND ********** Link WSEL
Stats
WSEL Frequency Data(ft)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) WSEL Peak (ft)
======================================
1.05-Year 348.500
1.11-Year 348.500
1.25-Year 348.500
2.00-Year 348.500
3.33-Year 348.500
5-Year 348.501
10-Year 348.502
25-Year 348.505
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50-Year 348.515
100-Year 348.554
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: LOT 1513.208
Link: POC 0.000
_____________________________________
Total: 1513.208
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: LOT 1488.033
Subbasin: BYPASS 157.889
Link: POC 0.000
Link: POND 1.721
_____________________________________
Total: 1647.643
Total Predevelopment Recharge is Less than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 9.577 ac-ft/year, Post Developed: 10.428 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 1
********** Link: POC **********
2-Year Discharge Rate : 0.004 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.00 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.00 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 1.38
Inflow Volume Including PPT-Evap (ac-ft): 1.38
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 1.38
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
Page 27 of 29
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 2
********** Link: POC **********
2-Year Discharge Rate : 0.000 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.00 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.00 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 0.18
Inflow Volume Including PPT-Evap (ac-ft): 0.18
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 0.18
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
********** Link: POND **********
Basic Wet Pond Volume (91% Exceedance): 37. cu-ft
Computed Large Wet Pond Volume, 1.5*Basic Volume: 56. cu-ft
2-Year Discharge Rate : 0.000 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.00 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.00 cfs
Time to Infiltrate 91% Treatment Volume, (Hours): 0.13
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 1.72
Inflow Volume Including PPT-Evap (ac-ft): 1.72
Total Runoff Infiltrated (ac-ft): 1.72, 100.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 0.00
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 100.00%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Link: POC
Scenario Postdeveloped Compliance Link: POC
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Page 28 of 29
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 3.751E-03 2-Year 3.661E-04
5-Year 3.869E-03 5-Year 4.110E-04
10-Year 3.897E-03 10-Year 1.783E-03
25-Year 1.464E-02 25-Year 4.542E-03
50-Year 1.831E-02 50-Year 9.855E-03
100-Year 2.654E-02 100-Year 1.232E-02
200-Year 3.986E-02 200-Year 1.513E-02
500-Year 5.763E-02 500-Year 1.887E-02
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** Flow Duration Performance ****
Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -98.8% PASS
Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -87.0% PASS
Maximum Excursion from Q2 to Q50 (Must be less than 10%): -47.6% PASS
Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -97.2% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -97.2% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
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