HomeMy WebLinkAboutPD 2021-0045; 3880 WESTHAVEN DR; DRAINAGE STUDY; 2022-06-28DRAINAGE STUDY – 3830 WESTHAVEN DRIVE
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DRAINAGE STUDY
3880 WESTHAVEN DR.
APN: 207-053-29
3880 Westhaven Dr.
Carlsbad, CA 92008
Prepared By:
John A. Van Ryn, P.E. RCE 80667 EXP: 3-31-23
Van Ryn Engineering, Inc.
16766 Bernardo Center Dr., Ste 213
San Diego, CA 92128
Prepared for:
Daniel Caldwell
3880 Westhaven Dr.
Carlsbad, CA 92008
June 28th 2022
"~ VAN RVN
DRAINAGE STUDY – 3830 WESTHAVEN DRIVE
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TABLE OF CONTENTS
1. INTRODUCTION ................................................................................................................................... 4
1.1 Project Description ........................................................................................................................ 4
1.2 Existing Conditions ........................................................................................................................ 4
1.3 Proposed Conditions .................................................................................................................... 4
2. METHODOLOGY .................................................................................................................................. 6
2.1 Rational Method............................................................................................................................ 6
2.2 Runoff Coefficient ......................................................................................................................... 6
2.3 Rainfall Intensity ............................................................................................................................ 6
2.4 Tributary Areas .............................................................................................................................. 6
3. CALCULATIONS/RESULTS ................................................................................................................... 7
3.1 Pre & Post Development Peak Flow Comparison ...................................................................... 7
3.2 Storm Water Quality ..................................................................................................................... 8
3.3 Storm Water Volume Calculations .............................................................................................. 9
4. CONCLUSION ....................................................................................................................................... 9
Appendix 1 .......................................................... Existing and Proposed Drainage Exhibits
Appendix 2 .................................... Supplemental Hydrologic Calculations and Documents
DRAINAGE STUDY – 3830 WESTHAVEN DRIVE
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Figure 1 Vicinity Map
VICINITY MAP
CITY OF
PACIFIC
OCEAN
CITY OF ENCINITAS
OF
MARCOS
DRAINAGE STUDY – 3830 WESTHAVEN DRIVE
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1. INTRODUCTION
1.1 Project Description
The project is located on Westhaven Dr approximately 900 feet southeast of Chestnut Ave. located in
the City of Carlsbad. The site exists today as an existing developed lot with a single family detached
house. The project proposes to remodel the existing house and construct an additional dwelling unit,
and art studio onsite. Also proposed are hardscape and landscape improvement typical to residential
redevelopment.
1.2 Existing Conditions
The existing lot is approximately 14,576 sq-ft or 0.33 acres. Currently a residential home with existing
hardscape that includes an asphalt driveway make up approximately 3,147 square feet of impervious
area. The remaining area is made up of landscaping and natural ground cover on moderate to steep
slopes. Storm water sheet flows across the site in a westerly direction until it discharges offsite and
onto Westhaven Drive. Storm water continues in a southerly direction until it reaches the intersection
of Woodvale Drive and Park Drive, where it is collected by a public storm drain inlet and ultimately
conveyed westerly to the Pacific Ocean.
The project site has a hydrologic soil group type B, according to the USDA web soil survey. The
peak storm water run-off for the site was calculated using the rational method equation (Q=CiA). The
precipitation volume of 2.7 inches was used for design consideration according to the San Diego
County 100yr 6hr Isopluvial Map. A 6.9 in/hr intensity was determined from the San Diego County
Hydrology Manual Figure 3-1 assuming the minimum allowable time of concentration of 5 minutes
because the site is relatively small. This resulted in a peak pre-project run-off of Q= 0.89 CFS. A
weighted runoff coefficient of 0.39 based on the existing 22% of impervious area. See section 3 of
this report for detailed calculations.
1.3 Proposed Conditions
The project proposes to remodel the existing residential structure and construct an additional dwelling
unit, and art studio onsite. Additional hardscape improvements included the replacement of roof area,
expansion of the existing asphalt driveway, installation of concrete walkways and masonry retaining
walls, with other improvement construction typical to residential remodels. The project proposes a new
total of 6,682 square feet of impervious area. Similar to the exiting site condition, storm water will be
conveyed in a westerly direction. Drainage will sheet flow, down the existing slope in the rear yard until
it’s captured through a series of area drains and conveyed into a detention basin located near the
southwest corner of the proposed addition to the main residence.
The proposed detention basin is only required to serve the site as a detention facility for the increase in
storm water runoff from the proposed improvements. However, the detention basin has been designed to
also provide some level of storm water treatment. The detention basin has many of the same structural
attribute as a BMP biofiltration basin. The detention basin will be built with 6” of ponding and 6” of
freeboard above surface. The subsurface basin configuration will consist of 18” of engineered soil, 2”
chocker layer, and 10 crushed rock. Also proposed as part of the detention basin is an overflow outlet
structure; an 18”x18” NDS riser will be installed with a 6” perforated PVC subdrain to run the length of
the basin. The outlet structure will have an 2x 3” PVC drain pipes that will outlet the overflow of storm
DRAINAGE STUDY – 3830 WESTHAVEN DRIVE
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water out to Westhaven Drive. The detention basin footprint will be approximately 180 sq. ft. and will be
lined with an impermeable visqueen liner to prevent infiltration into the native soil.
During the 100-year storm event, runoff will follow the pre-development flow path in a westerly direction
and outlet onto Westhaven Drive bypassing the subgrade of the detention facility and be routed directly
through the onsite outlet structure. As in the existing condition, the peak storm water runoff for the site
was calculated using the rational method equation (Q=CiA). The precipitation volume of 2.7 inches
was used for design consideration according to the San Diego County 100yr 6hr Isopluvial Map. A
6.9 in/hr intensity was determined from the San Diego County Hydrology Manual Figure 3-1
assuming the minimum allowable time of concentration of 5 minutes because the site is relatively
small. This resulted in a peak post-project runoff of Q= 1.25 CFS. A weighted runoff coefficient of
0.55 based on the proposed 46% of impervious area. See section 3 of this report for detailed
calculations. Routing of peak post-project flow through the detention basin has been modeled using
AutoCAD Hydrographs. The result peak flow through the basin has been calculated to be 0.77 CFS. See
Appendix 2 of this report.
DRAINAGE STUDY – 3830 WESTHAVEN DRIVE
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2. METHODOLOGY
The proposed project has been analyzed to determine the peak runoff flow for the 100 year, 6 hour rainfall
event using the Rational Method per the San Diego County Hydrology Manual. The Weighted Runoff
Coefficient, C, for the existing and proposed conditions were calculated using Table 3-1 of the same
manual. The rainfall intensity for the existing and proposed drainage areas were calculated using a
minimum Tc of 5 min, and the rainfall intensity equation described in section 3.1.3 of the San Diego County
Hydrology Manual which yields an intensity of 6.9 inches per hour, for both the existing and proposed
conditions.
The proposed LID best management practices have been sized and located such that runoff will be directed
to pervious areas where feasible, and into an onsite storm water detention basin before ultimately
discharging to the downstream curb-and-gutter.
2.1 Rational Method
As mentioned above, runoff from the project site was calculated for the 100-year storm events. Runoff was
calculated using the Rational Method which is given by the following equation:
Q = C x I x A
Where:
Q = Flow rate in cubic feet per second (cfs)
C = Runoff coefficient
I = Rainfall Intensity in inches per hour (in/hr)
A = Drainage basin area in acres, (ac)
Rational Method calculations were performed using the San Diego County Hydrology Manual (Section
3.1)
2.2 Runoff Coefficient
The runoff coefficients for the project were calculated using section 3.1.2 of the San Diego County
Hydrology Manual and using a weighted average runoff coefficient based on the actual and proposed
impervious areas which was calculated to be 0.39 and 0.55, respectively.
2.3 Rainfall Intensity
Rainfall intensity was determined using the Rainfall Intensity section of the San Diego County Hydrology
Manual (Section 3.1.3). Based on a 5 min time of concentration, an intensity of 6.9 inches per hour has
been calculated for both the existing and proposed conditions.
2.4 Tributary Areas
Drainage basins are delineated in the Post-Project Hydrology Exhibit in Appendix 1 and graphically portray
the tributary area for each drainage basin.
DRAINAGE STUDY – 3830 WESTHAVEN DRIVE
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3. CALCULATIONS/RESULTS
3.1 Pre & Post-Development Peak Flow Comparison
3.1.1 Pre-Development Peak Flow
P100yr,6hr = 2.6
C= 3,147 sf * 0.9 + 11,429 sf *.25 = 0.39
14,576 sf
Tc=5 min.
i=7.44*P6*D-0.645 D = 5 min., for minimum time of concentration
i=7.44*2.6*5-0.645 = 6.9 in/hr
Q=C*i*A = 0.39 * 6.9 in/hr * 0.33 ac = 0.89 cfs
3.1.2 Post-Development Peak Flow
Cn = 6,682 sf * 0.9 + 7,894 sf *.25 = 0.55
14,576 sf
Tc=5 min.
i=7.44*P6*D-0.645 D = 5 min, for minimum time of concentration
i=7.44*2.6*5-0.645 = 6.9 in/hr
Q=C*i*A = 0.55 * 6.9 in/hr * 0.33 ac = 1.25 cfs
Below are a series of tables which summarize the calculations provided
SITE IMPERVIOUS AREA COMPOSITION
TOTAL
IMPERVIOUS
AREA
(SQ-FT)
TOTAL
PERVIOUS
AREA
(SQ-FT)
TOTAL
PROJECT
AREA
(SQ-FT)
%
IMPERVIOUS
SURFACES
WEIGHTED
RUNOFF
COEFFICIENT
“C”
Existing 3,147 11,429 14,576 22% 0.39
Proposed 6,682 7,894 14,576 46% 0.55
Table 1. Runoff Coefficient “C” Comparison
The table above shows the difference in the weighted runoff coefficient, “C”, between the existing and
proposed condition. Calculations of the weighted runoff coefficients are based on Table 3-1 of the San
Diego County Hydrology Manual and underlying hydrologic soil group B.
DRAINAGE STUDY – 3830 WESTHAVEN DRIVE
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EXISTING DRAINAGE FLOWS
DRAINAGE
AREA
DRAINAGE
AREA
(SQ-FT)
WEIGHTED
RUNOFF
COEFFICIENT
(C)
Q100
(CFS)
I100
(IN/HR)
BASIN A 14,576 0.39 0.89 6.9
Table 2. Existing Condition Peak Drainage Flow Rates
Table 2 above lists the peak flow rates for the project site in the existing condition for the respective rainfall
events.
PROPOSED DRAINAGE FLOWS
DRAINAGE
AREA
DRAINAGE
AREA
(SQ-FT)
RUNOFF
COEFFICIENT
(C)
Q100
(CFS)
I100
(IN/HR)
BASIN A 14,576 0.55 1.25 6.9
Table 3. Proposed Condition Peak Drainage Flow Rates
Table 3 above lists the peak flow rates for the project site for the proposed condition for the respective
rainfall events.
PEAK FLOW COMPARISON
CONDITION
DRAINAGE
AREA
(SQ-FT)
Q100
(CFS)
V100
(CU-FT)
Existing 14,576 0.89 1,215
Proposed 14,576 1.25 1,713
Table 4. Proposed Condition Peak Drainage Flow Rates
Table 4 above shows a comparison between the peak flow rates and precipitation volume for the proposed
condition and the existing condition.
3.2 Storm Water Quality
Although site storm water quality requirements are not applicable for this project, runoff will be routed
toward an onsite detention basin that will also provide some storm water treatment. Specifically, the
detention basin will be constructed with an 18” thick layer of engineered soil, 2” thick chocker layer of 3/8”
pea gravel, and 10” thick layer of 3/4" clean crushed rock. The project is considered a “Standard”
Development project in terms of storm water requirement therefore, the design capture volume (DCV) is
not required to be treated in a permanent storm water treatment facility before leaving the site.
DRAINAGE STUDY – 3830 WESTHAVEN DRIVE
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3.3 Storm Water Volume Calculations
*This section is for reference only. The detention basin has not been designed to capture the
entire increase in storm water volume. Storm water routing through the detention basin has been
modeled using AutoCAD Hydrographs. See Appendix 2 for model outputs.
3.3.1 Pre-Development Volume
Vol=C*P6*A
Vol=0.39*2.6 in*0.33 ac*3630 = 1,215 cu-ft
3.3.2 Post-Development Volume
Vol=C*P6*A
Vol=0.55*2.6 in*0.33 ac*3630 = 1,713 cu-ft
∆ Vol = Post-Development Volume – Pre-Developement Volume
∆ Vol = 1,713 cu-ft – 1,215 cu-ft = 498 cu-ft
4. CONCLUSION
As discussed previously, storm water will be routed toward an onsite detention basin that has been designed
to have similar characteristics as a BMP biofiltration basin. The basin will capture and detain storm water
produced by the new onsite improvement; the basin will also rout storm water adequately without
infiltrating into the native soil. The onsite storm water routing and detention design will produce a peak
post-project runoff of 0.77 CFS, which is reduced from the 0.89 CFS produced in the pre-project condition.
Therefore, the project will not negatively affect downstream facilities. Additionally, the project does not
negatively impact adjacent properties. It is my professional opinion that the storm drain systems as
proposed in this report and on the precise grading plans herein is adequate to intercept, contain and convey
Q100 and will not create negative impacts to the existing drainage system.
DRAINAGE STUDY – 3830 WESTHAVEN DRIVE
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APPENDIX 1
EXISTING & PROPOSED
DRAINAGE EXHIBITS
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DRAINAGE STUDY – 3830 WESTHAVEN DRIVE
11 | P a g e
APPENDIX 2
SUPPLIMENTAL HYDROLOGIC
CALCULATIONS AND DOCUMENTS
Hydrologic Soil Group—San Diego County Area, California
Natural Resources
Conservation Service
Web Soil SurveyNational Cooperative Soil Survey 9/10/2021Page 1 of 436689873668994366900136690083669015366902236690293668987366899436690013669008366901536690223669029469891469898469905469912469919469926469933469940469947469954469961
469891 469898 469905 469912 469919 469926 469933 469940 469947 469954 469961
33° 9' 34'' N 117° 19' 22'' W33° 9' 34'' N117° 19' 19'' W33° 9' 33'' N
117° 19' 22'' W33° 9' 33'' N
117° 19' 19'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 11N WGS84
0 15 30 60 90Feet
0 4 9 18 27Meters
Map Scale: 1:334 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
USDA =
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at 1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map measurements.
Source of Map: Natural Resources Conservation ServiceWeb Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as of the version date(s) listed below.
Soil Survey Area: San Diego County Area, CaliforniaSurvey Area Data: Version 15, May 27, 2020
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jan 24, 2020—Feb
12, 2020
The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident.
Hydrologic Soil Group—San Diego County Area, California
Natural Resources
Conservation Service
Web Soil SurveyNational Cooperative Soil Survey 9/10/2021Page 2 of 4USDA =
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Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
MlC Marina loamy coarse sand, 2 to 9 percent slopes
B 0.0 10.8%
MlE Marina loamy coarse sand, 9 to 30 percent slopes
B 0.4 89.2%
Totals for Area of Interest 0.4 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes.
Hydrologic Soil Group—San Diego County Area, California
Natural Resources
Conservation Service
Web Soil SurveyNational Cooperative Soil Survey 9/10/2021Page 3 of 4USDA =
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—San Diego County Area, California
Natural Resources
Conservation Service
Web Soil SurveyNational Cooperative Soil Survey 9/10/2021Page 4 of 4~
SITE IL__·-----_--_I
San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 6 of 26 Table 3-1 RUNOFF COEFFICIENTS FOR URBAN AREAS Land Use Runoff Coefficient “C” Soil TypeNRCS Elements County Elements % IMPER. A B C D Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.200.250.300.35Low Density Residential (LDR) Residential, 1.0 DU/A or less 10 0.27 0.32 0.36 0.41 Low Density Residential (LDR) Residential, 2.0 DU/A or less 20 0.34 0.38 0.42 0.46 Low Density Residential (LDR) Residential, 2.9 DU/A or less 25 0.38 0.41 0.45 0.49 Medium Density Residential (MDR) Residential, 4.3 DU/A or less 30 0.41 0.45 0.48 0.52 Medium Density Residential (MDR) Residential, 7.3 DU/A or less 40 0.48 0.51 0.54 0.57 Medium Density Residential (MDR) Residential, 10.9 DU/A or less 45 0.52 0.54 0.57 0.60 Medium Density Residential (MDR) Residential, 14.5 DU/A or less 50 0.55 0.58 0.60 0.63 High Density Residential (HDR) Residential, 24.0 DU/A or less 65 0.66 0.67 0.69 0.71 High Density Residential (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77 0.78 0.79 Commercial/Industrial (N. Com) Neighborhood Commercial 80 0.76 0.77 0.78 0.79 Commercial/Industrial (G. Com) General Commercial 85 0.80 0.80 0.81 0.82 Commercial/Industrial (O.P. Com) Office Professional/Commercial 90 0.83 0.84 0.84 0.85 Commercial/Industrial (Limited I.) Limited Industrial 90 0.83 0.84 0.84 0.85 Commercial/Industrial (General I.) General Industrial 95 0.87 0.87 0.87 0.87 *The values associated with 0% impervious may be used for direct calculation of the runoff coefficient as described in Section 3.1.2 (representing the pervious runoff coefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given that the area will remain natural forever (e.g., the area is located in Cleveland National Forest). DU/A = dwelling units per acre NRCS = National Resources Conservation Service 3-6
San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 7 of 26
3.1.3 Rainfall Intensity
The rainfall intensity (I) is the rainfall in inches per hour (in/hr) for a duration equal to the Tc
for a selected storm frequency. Once a particular storm frequency has been selected for
design and a Tc calculated for the drainage area, the rainfall intensity can be determined from
the Intensity-Duration Design Chart (Figure 3-1). The 6-hour storm rainfall amount (P6) and
the 24-hour storm rainfall amount (P24) for the selected storm frequency are also needed for
calculation of I. P6 and P24 can be read from the isopluvial maps provided in Appendix B.
An Intensity-Duration Design Chart applicable to all areas within San Diego County is
provided as Figure 3-1. Figure 3-2 provides an example of use of the Intensity-Duration
Design Chart. Intensity can also be calculated using the following equation:
I = 7.44 P6 D-0.645
Where: P6 = adjusted 6-hour storm rainfall amount (see discussion below)
D = duration in minutes (use Tc)
Note: This equation applies only to the 6-hour storm rainfall amount (i.e., P6 cannot be
changed to P24 to calculate a 24-hour intensity using this equation).
The Intensity-Duration Design Chart and the equation are for the 6-hour storm rainfall
amount. In general, P6 for the selected frequency should be between 45% and 65% of P24 for
the selected frequency. If P6 is not within 45% to 65% of P24, P6 should be increased or
decreased as necessary to meet this criteria. The isopluvial lines are based on precipitation
gauge data. At the time that the isopluvial lines were created, the majority of precipitation
gauges in San Diego County were read daily, and these readings yielded 24-hour
precipitation data. Some 6-hour data were available from the few recording gauges
distributed throughout the County at that time; however, some 6-hour data were extrapolated.
Therefore, the 24-hour precipitation data for San Diego County are considered to be more
reliable.
3-7
RATIONAL METHOD HYDROGRAPH PROGRAMCOPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY RUN DATE 3/3/2022 HYDROGRAPH FILE NAME Text1TIME OF CONCENTRATION 5 MIN.6 HOUR RAINFALL 2.6 INCHESBASIN AREA 0.33 ACRESRUNOFF COEFFICIENT 0.55 PEAK DISCHARGE 1.25 CFS TIME (MIN) = 0 DISCHARGE (CFS) = 0 TIME (MIN) = 5 DISCHARGE (CFS) = 0 TIME (MIN) = 10 DISCHARGE (CFS) = 0 TIME (MIN) = 15 DISCHARGE (CFS) = 0 TIME (MIN) = 20 DISCHARGE (CFS) = 0 TIME (MIN) = 25 DISCHARGE (CFS) = 0 TIME (MIN) = 30 DISCHARGE (CFS) = 0 TIME (MIN) = 35 DISCHARGE (CFS) = 0 TIME (MIN) = 40 DISCHARGE (CFS) = 0 TIME (MIN) = 45 DISCHARGE (CFS) = 0 TIME (MIN) = 50 DISCHARGE (CFS) = 0 TIME (MIN) = 55 DISCHARGE (CFS) = 0 TIME (MIN) = 60 DISCHARGE (CFS) = 0 TIME (MIN) = 65 DISCHARGE (CFS) = 0 TIME (MIN) = 70 DISCHARGE (CFS) = 0 TIME (MIN) = 75 DISCHARGE (CFS) = 0 TIME (MIN) = 80 DISCHARGE (CFS) = 0 TIME (MIN) = 85 DISCHARGE (CFS) = 0 TIME (MIN) = 90 DISCHARGE (CFS) = 0 TIME (MIN) = 95 DISCHARGE (CFS) = 0 TIME (MIN) = 100 DISCHARGE (CFS) = 0 TIME (MIN) = 105 DISCHARGE (CFS) = 0 TIME (MIN) = 110 DISCHARGE (CFS) = 0 TIME (MIN) = 115 DISCHARGE (CFS) = 0 TIME (MIN) = 120 DISCHARGE (CFS) = 0 TIME (MIN) = 125 DISCHARGE (CFS) = 0 TIME (MIN) = 130 DISCHARGE (CFS) = 0 TIME (MIN) = 135 DISCHARGE (CFS) = 0 TIME (MIN) = 140 DISCHARGE (CFS) = 0 TIME (MIN) = 145 DISCHARGE (CFS) = 0 TIME (MIN) = 150 DISCHARGE (CFS) = 0.1 TIME (MIN) = 155 DISCHARGE (CFS) = 0.1 TIME (MIN) = 160 DISCHARGE (CFS) = 0.1 TIME (MIN) = 165 DISCHARGE (CFS) = 0.1 TIME (MIN) = 170 DISCHARGE (CFS) = 0.1 TIME (MIN) = 175 DISCHARGE (CFS) = 0.1 TIME (MIN) = 180 DISCHARGE (CFS) = 0.1 TIME (MIN) = 185 DISCHARGE (CFS) = 0.1 TIME (MIN) = 190 DISCHARGE (CFS) = 0.1 TIME (MIN) = 195 DISCHARGE (CFS) = 0.1 TIME (MIN) = 200 DISCHARGE (CFS) = 0.1 TIME (MIN) = 205 DISCHARGE (CFS) = 0.1 TIME (MIN) = 210 DISCHARGE (CFS) = 0.1 TIME (MIN) = 215 DISCHARGE (CFS) = 0.1 TIME (MIN) = 220 DISCHARGE (CFS) = 0.1 TIME (MIN) = 225 DISCHARGE (CFS) = 0.1 TIME (MIN) = 230 DISCHARGE (CFS) = 0.2 TIME (MIN) = 235 DISCHARGE (CFS) = 0.2 TIME (MIN) = 240 DISCHARGE (CFS) = 0.3 TIME (MIN) = 245 DISCHARGE (CFS) = 1.25 TIME (MIN) = 250 DISCHARGE (CFS) = 0.2 TIME (MIN) = 255 DISCHARGE (CFS) = 0.1 TIME (MIN) = 260 DISCHARGE (CFS) = 0.1 TIME (MIN) = 265 DISCHARGE (CFS) = 0.1 TIME (MIN) = 270 DISCHARGE (CFS) = 0.1 TIME (MIN) = 275 DISCHARGE (CFS) = 0.1 TIME (MIN) = 280 DISCHARGE (CFS) = 0.1 TIME (MIN) = 285 DISCHARGE (CFS) = 0.1 TIME (MIN) = 290 DISCHARGE (CFS) = 0.1 TIME (MIN) = 295 DISCHARGE (CFS) = 0 TIME (MIN) = 300 DISCHARGE (CFS) = 0 TIME (MIN) = 305 DISCHARGE (CFS) = 0 TIME (MIN) = 310 DISCHARGE (CFS) = 0 TIME (MIN) = 315 DISCHARGE (CFS) = 0 TIME (MIN) = 320 DISCHARGE (CFS) = 0 TIME (MIN) = 325 DISCHARGE (CFS) = 0 TIME (MIN) = 330 DISCHARGE (CFS) = 0 TIME (MIN) = 335 DISCHARGE (CFS) = 0 TIME (MIN) = 340 DISCHARGE (CFS) = 0 TIME (MIN) = 345 DISCHARGE (CFS) = 0 TIME (MIN) = 350 DISCHARGE (CFS) = 0 TIME (MIN) = 355 DISCHARGE (CFS) = 0 TIME (MIN) = 360 DISCHARGE (CFS) = 0 TIME (MIN) = 365 DISCHARGE (CFS) = 0
Hydrograph Return Period Recap
2
Hyd. Hydrograph Inflow Peak Outflow (cfs)Hydrograph
No. type hyd(s)Description
(origin)1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr
1 Manual ------ ------- ------- ------- ------- ------- ------- ------- 1.250 Westhaven 100-yr Post
2 Reservoir 1 ------- ------- ------- ------- ------- ------- ------- 0.767 Detention Basin
Proj. file: 2138-Detention.gpw Monday, 05 / 23 / 2022
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hydrograph Summary Report
3
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft)(ft)(cuft)
1 Manual 1.250 5 245 1,365 ------ ------------ Westhaven 100-yr Post
2 Reservoir 0.767 5 245 1,249 1 264.30 215 Detention Basin
2138-Detention.gpw Return Period: 100 Year Monday, 05 / 23 / 2022
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Monday, 05 / 23 / 2022
Hyd. No. 1
Westhaven 100-yr Post
Hydrograph type = Manual Peak discharge = 1.250 cfs
Storm frequency = 100 yrs Time to peak = 245 min
Time interval = 5 min Hyd. volume = 1,365 cuft
4
0 50 100 150 200 250 300
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
Q (cfs)
Time (min)
Westhaven 100-yr Post
Hyd. No. 1 -- 100 Year
Hyd No. 1
-
\
) \
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Monday, 05 / 23 / 2022
Hyd. No. 2
Detention Basin
Hydrograph type = Reservoir Peak discharge = 0.767 cfs
Storm frequency = 100 yrs Time to peak = 245 min
Time interval = 5 min Hyd. volume = 1,249 cuft
Inflow hyd. No. = 1 - Westhaven 100-yr Post Max. Elevation = 264.30 ft
Reservoir name = Detention Basin Max. Storage = 215 cuft
Storage Indication method used.
5
0 50 100 150 200 250 300
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
Q (cfs)
Time (min)
Detention Basin
Hyd. No. 2 -- 100 Year
Hyd No. 2 Hyd No. 1 Total storage used = 215 cuft
-
' --
) 11 1/ Iii" ~
111111111
Pond Report 6
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Monday, 05 / 23 / 2022
Pond No. 2 - Detention Basin
Pond Data
Pond storage is based on user-defined values.
Stage / Storage Table
Stage (ft)Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft)
0.00 263.50 n/a 0 0
0.17 263.67 n/a 33 33
0.34 263.84 n/a 39 72
0.50 264.00 n/a 44 116
0.66 264.16 n/a 51 166
0.82 264.32 n/a 57 224
1.00 264.50 n/a 64 288
Culvert / Orifice Structures Weir Structures
[A] [B] [C] [PrfRsr][A] [B] [C] [D]
Rise (in)= 3.00 Inactive 0.00 0.00
Span (in)= 3.00 0.00 0.00 0.00
No. Barrels = 2 0 0 0
Invert El. (ft)= 261.25 0.00 0.00 0.00
Length (ft)= 36.40 0.00 0.00 0.00
Slope (%)= 14.90 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff.= 0.60 0.60 0.60 0.60
Multi-Stage = n/a No No No
Crest Len (ft)= 4.50 Inactive Inactive Inactive
Crest El. (ft)= 264.00 0.00 0.00 0.00
Weir Coeff.= 3.33 3.33 3.33 3.33
Weir Type = 1 --- --- ---
Multi-Stage = Yes No No No
Exfil.(in/hr)= 0.000 (by Wet area)
TW Elev. (ft)= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
0.00 0.08 0.16 0.24 0.32 0.40 0.48 0.56 0.64 0.72 0.80
Stage (ft)
0.00 263.50
0.10 263.60
0.20 263.70
0.30 263.80
0.40 263.90
0.50 264.00
0.60 264.10
0.70 264.20
0.80 264.30
0.90 264.40
1.00 264.50
Elev (ft)
Discharge (cfs)
Stage / Discharge
Total Q
t
_J
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