HomeMy WebLinkAbout6034; Palomar Airport Road at Melrose Drive Improvements; South Melrose Dr N of Palomar Airport Road; 2012-07-02
TECHNICAL MEMORANDUM:
SWMM Modeling for
Hydromodification Compliance of:
SOUTH MELROSE DRIVE NORTH OF
PALOMAR AIRPORT ROAD
Prepared for:
City of Carlsbad
July 2, 2012
Tory R. Walker, R.C.E. 45005
President
122 Civic Center Drive, Suite 206, Vista, CA 92084 Ph: 760.414.9212 Fx: 760.414.9277 www.Trwengineering.Com
TECHNICAL MEMORANDUM
TO: Mr. Brandon Miles
City of Carlsbad
FROM: Tory Walker, PE, CFM, LEED GA
Luis Parra, PhD, PE, CPSWQ, ToR, D.WRE.
DATE: July 2, 2012
RE: Summary of SWMM Modeling for Hydromodification Compliance for the Expansion of
South Melrose Drive North of Palomar Airport Rd in Carlsbad, CA.
INTRODUCTION
This memorandum summarizes the approach used to model the proposed Expansion of South Melrose
Drive North of Palomar Airport Rd in Carlsbad using the Environmental Protection Agency (EPA) Storm
Water Management Model 5.0 (SWMM). SWMM models were prepared for the pre and post
developed conditions at the site in order to determine if the proposed detention facility has sufficient
volume to meet the current Hydromodification Management Plan (HMP) requirements from the San
Diego Regional Water Quality Control Board (SDRWQCB).
SWMM MODEL DEVELOPMENT
Two (2) SWMM models were prepared for this study, one for existing conditions and the second for the
proposed condition. SWMM was used since we have found it to be more comparable to San Diego area
watersheds than the more widely used San Diego Hydrology Model (SDHM). For both SWMM models,
flow duration curves were prepared to determine if the proposed bioretention footprints were sufficient
to meet the current HMP requirements.
The inputs required to develop SWMM models include rainfall, watershed characteristics, and BMP
configurations. The Oceanside Gage from the Project Clean Water website was used for this study, since
it is the most representative of the project site precipitation among the three gages used for modeling
the characteristics of the county by the approved calculator (Lindbergh, Wohlford and Oceanside).
Evaporation for the site was modeled using average monthly values from the county hourly dataset.
The site was modeled with hydrologic soil group D soils as determined from both the San Diego County
Hydrology Manual soil map and the USGS Survey web-based Soil Survey Map. Other SWMM inputs for
the subareas are discussed in the appendices to this document, where the selection of the parameters is
explained in detail.
HMP MODELING
Storm water runoff from the developed project site is routed through one (1) HMP basin located near
the northern limit of the expansion of Melrose Drive. Flow from the proposed road expansion, the
adjacent existing road and the existing adjacent park are intercepted by a proposed F-type inlet,
South Melrose Drive SWMM Memo
7/2/2012
2 236-05
draining to a forty-five (45) foot long 60-inch RCP. The 60-inch RCP provides the required detention
volume to mitigate the approximate 10% increase in impermeable surface area, discharging mitigated
flows to the existing storm drain system within Melrose Drive.
Flow will exit the basin via multiple orifices built into the side of the 60-inch RCP basin outlet structure.
A single 1 5/8-inch (2.074 sq.in.) orifice will be located at the flowline of the RCP with an additional 1
5/8-inch (2.074 sq.in.) orifice 1.5 feet above the RCP flowline invert. A tertiary 4-inch (12.57 sq.in.)
orifice will be located at an elevation of 2.5 feet above the RCP flowline to assist in dewatering the
facility and mimic the existing condition Flow Duration Curve (FDC). A 3-foot spillway weir will be
located 4.7 feet above the RCP flowline; once flows exceed 4.7 feet in the RCP basin, runoff will spill
over the top of the weir and drop to the basin outlet pipe.
It is assumed that flows up to but not exceeding the 10-year event will be intercepted by the proposed
inlet structure. Water quality requirements will be addressed via a curbside bioretention facility
upstream of the HMP detention facility. It is assumed all water quality requirements for the project will
be met by this bioretention Best Management Practice (BMP) and will not be discussed within this
document. For further information in regards to storm water quality requirements for the project,
please refer to the site specific Water Quality Technical Report (WQTR).
FLOW DURATION CURVE COMPARISON
The Flow Duration Curve (FDC) for the site was compared at the Point of Compliance (POC-1) by
exporting the half-hourly runoff time series results from SWMM to a spreadsheet. FDC was compared
between 10% of the existing condition Q2 up to the existing condition Q10. The Q2 and Q10 were
determined using a partial duration statistical analysis of the runoff time series in an Excel spreadsheet
using the Cunnane plotting position method (which is the preferred plotting methodology in the HMP
Permit). As the SWMM Model includes a statistical analysis based on the Weibull Plotting Position
Method, the Weibull Method was also used within the spreadsheet to ensure that the results were
similar to those obtained by the SWMM Model.
Due to the limited volume provided within the HMP facility and the fact that the 1 hour interval
reporting does not provide the desired accuracy in this project, analysis was required to be undertaken
on a shorter interval period to ensure that routing could be calculated within the basin and stage-
discharge relationships. The SWMM model was configured to provide a reporting calculation in 30
minute intervals, with analysis performed at 5 minute intervals for the entire 57 years of precipitation
on record. Precipitation is still hourly, but as the model is now reporting every 30 minutes, the model
will assign the same intensity to the two consecutive 30-minute intervals.
In terms of FDC calculation the range between 10% of Q2 and Q10 was divided into 100 equal time
intervals; the number of half-hours that each flow rate was exceeded was counted from the 30-min
series. Additionally, the intermediate peaks with a return period “i” were obtained (Qi with i=3 to 9).
For the purpose of the plot, the values were presented as percentage of time exceeded for each flow
rate.
FDC comparison at POC-1 is illustrated in Figure 1 in both normal and logarithmic scale. POC-1
corresponds with the point located downstream of the junction of the discharges of the HMP basin and
the portion of the existing park and Melrose Avenue that do not drain to the basin. Attachment 7
provides a detailed drainage exhibit for the post-developed condition.
South Melrose Drive SWMM Memo
7/2/2012
3 236-05
As can be seen in Figure 1, the FDC for the proposed condition with the HMP basins is within 110% of
the curve for the existing condition in both peak flows and durations. The additional runoff volume
generated from developing the site will be released to the downstream storm drain at a flow rate below
the 10% Q2 lower threshold. Additionally, the project will also not increase peak flow rates between the
Q2 and the Q10, as shown in the graphic and also in the attached table.
SUMMARY
This study has demonstrated that the proposed HMP basin provided at the expansion of Melrose Drive
is sufficient to meet the current HMP criteria if the bioretention cross-section areas and volumes
recommended within this technical memorandum are incorporated within the proposed project site.
KEY ASSUMPTIONS
1. D Soils are representative of the existing condition site.
ATTACHMENTS
1. Q2 to Q10 Comparison Table
2. FDC Plots (log and natural “x” scale) and Flow Duration Table.
3. List of the “n” largest Peaks: Pre-Development and Post-Development Conditions
4. Elevation vs. Area Curves and Elevations vs. Discharge Curves to be used in SWMM
5. Pre & Post Development Maps, Project Plan and Bioretention section sketches
6. SWMM Input Data in Input Format (Existing and Proposed Models)
7. SWMM Screens and Explanation of Significant Variables
8. Drying Time of the basin
9. USGS Soil Map for justification of Soil Type D Conditions
10. Summary files from the SWMM Model
South Melrose Drive SWMM Memo
7/2/2012
4 236-05
Figure 1a and 1b. Flow Duration Curve Comparison (logarithmic and normal “x” scale)
South Melrose Drive SWMM Memo
7/2/2012
5 236-05
ATTACHMENT 1.
Q2 to Q10 Comparison Table
Return Period Existing Condition (cfs) Mitigated Condition (cfs) Reduction, Exist -
Mitigated (cfs)
2-year 0.989 0.997 -0.008
3-year 1.106 1.093 0.013
4-year 1.188 1.168 0.020
5-year 1.227 1.204 0.023
6-year 1.272 1.250 0.022
7-year 1.305 1.278 0.027
8-year 1.354 1.324 0.030
9-year 1.454 1.434 0.020
10-year 1.621 1.625 -0.004
ATTACHMENT 2
FLOW DURATION CURVE ANALYSIS
1) Flow duration curve shall not exceed the existing conditions by more than 10%, neither in
peak flow nor duration.
The figure on the following page illustrates that the flow duration curve in post-development
conditions after the proposed BMP is below the existing flow duration curve. The flow duration
curve table following the curve shows that if the interval 0.10Q2 – Q10 is divided in 100 sub-
intervals, then a) the post development divided by pre-development durations are never larger
than 110% (the permit allows up to 110%); and b) there are no more than 10 intervals in the
range 101%-110% which would imply an excess over 10% of the length of the curve (the permit
allows less than 10% of excesses measured as 101-110%).
Consequently, the design passes the hydromodification test.
It is important to note that the flow duration curve can be expressed in the “x” axis as
percentage of time, hours per year, total number of hours, or any other similar time variable. As
those variables only differ by a multiplying constant, their plot in logarithmic scale is going to
look exactly the same, and compliance can be observed regardless of the variable selected.
However, in order to satisfy the City of Carlsbad HMP example, % of time exceeded is the
variable of choice in the flow duration curve. The selection of a logarithmic scale in lieu of the
normal scale is preferred, as differences between the pre-development and post-development
curves can be seen more clearly in the entire range of analysis. Both graphics are presented just
to prove the difference.
In terms of the “y” axis, the peak flow value is the variable of choice. As an additional analysis
performed by TRWE, not only the range of analysis is clearly depicted (10% of Q2 to Q10) but
also all intermediate flows are shown (30% of Q2, 50% of Q2, Q2, Q3, Q4, Q5, Q6, Q7, Q8 and Q9) in
order to demonstrate compliance at any range Qx – Qx+1. It must be pointed out that one of the
limitations of both the SWMM and SDHM models is that the intermediate analysis is not
performed (to obtain Qi from i = 2 to 10). TRWE performed the analysis using the Cunnane
Plotting position Method (the preferred method in the HMP permit) from the “n” largest
independent peak flows obtained from the continuous time series.
The largest “n” peak flows are attached in this appendix, as well as the values of Qi with a
return period “i”, from i=2 to 10. The Qi values are also added into the flow-duration plot.
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
0.001 0.01 0.1Q (cfs)Percentage of time exceeded (%)
Melrose Flow Duration Curve
Existing
Proposed
Qx
-0.10
0.10
0.30
0.50
0.70
0.90
1.10
1.30
1.50
1.70
0 0.05 0.1 0.15 0.2 0.25 0.3Q (cfs)Percentage of time exceeded (%)
Melrose Flow Duration Curve
Existing
Proposed
Qx
Flow Duration Curve Data for South Melrose, Carslbad CA
Q2 =0.99 cfs Fraction 10 %
Q10 =1.62 cfs
Step =0.0154 cfs
Count =499678 hours
57.00 years
Pass or
Q (cfs)Hours > Q % time Hours>Q % time Post/Pre Fail?
1 0.099 1976 3.95E-01 2175 4.35E-01 110%Pass
2 0.114 1727 3.46E-01 1741 3.48E-01 101%Pass
3 0.130 1504 3.01E-01 1481 2.96E-01 98%Pass
4 0.145 1318 2.64E-01 1296 2.59E-01 98%Pass
5 0.160 1142 2.28E-01 1151 2.30E-01 101%Pass
6 0.176 1061 2.12E-01 1009 2.02E-01 95%Pass
7 0.191 943 1.89E-01 871 1.74E-01 92%Pass
8 0.207 807 1.62E-01 769 1.54E-01 95%Pass
9 0.222 742 1.48E-01 676 1.35E-01 91%Pass
10 0.237 659 1.32E-01 578 1.16E-01 88%Pass
11 0.253 611 1.22E-01 494 9.88E-02 81%Pass
12 0.268 564 1.13E-01 439 8.78E-02 78%Pass
13 0.283 509 1.02E-01 402 8.05E-02 79%Pass
14 0.299 458 9.17E-02 367 7.33E-02 80%Pass
15 0.314 405 8.10E-02 348 6.96E-02 86%Pass
16 0.330 362 7.24E-02 314 6.27E-02 87%Pass
17 0.345 334 6.67E-02 284 5.68E-02 85%Pass
18 0.360 313 6.26E-02 267 5.33E-02 85%Pass
19 0.376 295 5.89E-02 258 5.15E-02 87%Pass
20 0.391 274 5.48E-02 247 4.93E-02 90%Pass
21 0.406 255 5.09E-02 233 4.65E-02 91%Pass
22 0.422 237 4.73E-02 218 4.36E-02 92%Pass
23 0.437 221 4.41E-02 209 4.17E-02 95%Pass
24 0.453 206 4.12E-02 204 4.07E-02 99%Pass
25 0.468 190 3.80E-02 192 3.84E-02 101%Pass
26 0.483 171 3.41E-02 176 3.51E-02 103%Pass
27 0.499 158 3.15E-02 158 3.15E-02 100%Pass
28 0.514 144 2.87E-02 144 2.88E-02 100%Pass
29 0.529 134 2.68E-02 135 2.70E-02 101%Pass
30 0.545 127 2.53E-02 127 2.54E-02 100%Pass
31 0.560 121 2.41E-02 120 2.39E-02 99%Pass
32 0.576 114 2.27E-02 114 2.28E-02 100%Pass
33 0.591 110 2.19E-02 108 2.16E-02 99%Pass
34 0.606 103 2.06E-02 103 2.05E-02 100%Pass
35 0.622 94 1.88E-02 96 1.91E-02 102%Pass
36 0.637 87 1.74E-02 88 1.76E-02 101%Pass
Underground Detention Optimized
Interval
Existing Condition
Pass or
Q (cfs)Hours > Q % time Hours>Q % time Post/Pre Fail?
Underground Detention Optimized
Interval
Existing Condition
37 0.652 80 1.60E-02 80 1.60E-02 100%Pass
38 0.668 73 1.45E-02 73 1.46E-02 101%Pass
39 0.683 68 1.36E-02 65 1.30E-02 96%Pass
40 0.699 66 1.32E-02 63 1.25E-02 95%Pass
41 0.714 62 1.23E-02 62 1.23E-02 100%Pass
42 0.729 60 1.19E-02 60 1.19E-02 100%Pass
43 0.745 58 1.15E-02 57 1.14E-02 99%Pass
44 0.760 56 1.11E-02 54 1.07E-02 96%Pass
45 0.775 54 1.07E-02 52 1.04E-02 97%Pass
46 0.791 50 9.91E-03 49 9.81E-03 99%Pass
47 0.806 47 9.31E-03 46 9.21E-03 99%Pass
48 0.822 44 8.71E-03 42 8.41E-03 97%Pass
49 0.837 41 8.21E-03 39 7.81E-03 95%Pass
50 0.852 39 7.81E-03 38 7.50E-03 96%Pass
51 0.868 37 7.40E-03 35 7.00E-03 95%Pass
52 0.883 36 7.20E-03 35 6.90E-03 96%Pass
53 0.898 35 7.00E-03 33 6.50E-03 93%Pass
54 0.914 33 6.60E-03 31 6.10E-03 92%Pass
55 0.929 33 6.60E-03 30 5.90E-03 89%Pass
56 0.945 32 6.40E-03 29 5.80E-03 91%Pass
57 0.960 30 6.00E-03 27 5.40E-03 90%Pass
58 0.975 29 5.70E-03 26 5.20E-03 91%Pass
59 0.991 27 5.30E-03 25 4.90E-03 92%Pass
60 1.006 26 5.10E-03 24 4.70E-03 92%Pass
61 1.021 24 4.80E-03 22 4.30E-03 90%Pass
62 1.037 22 4.30E-03 20 4.00E-03 93%Pass
63 1.052 21 4.10E-03 19 3.80E-03 93%Pass
64 1.068 20 4.00E-03 19 3.70E-03 93%Pass
65 1.083 19 3.80E-03 18 3.50E-03 92%Pass
66 1.098 19 3.80E-03 17 3.40E-03 89%Pass
67 1.114 18 3.60E-03 17 3.30E-03 92%Pass
68 1.129 18 3.50E-03 16 3.20E-03 91%Pass
69 1.144 16 3.20E-03 16 3.20E-03 100%Pass
70 1.160 16 3.20E-03 15 3.00E-03 94%Pass
71 1.175 16 3.10E-03 13 2.60E-03 84%Pass
72 1.191 14 2.70E-03 12 2.40E-03 89%Pass
73 1.206 13 2.60E-03 11 2.20E-03 85%Pass
74 1.221 12 2.30E-03 10 1.90E-03 83%Pass
75 1.237 10 2.00E-03 9 1.70E-03 85%Pass
76 1.252 9 1.70E-03 8 1.60E-03 94%Pass
77 1.267 9 1.70E-03 8 1.50E-03 88%Pass
78 1.283 8 1.60E-03 7 1.40E-03 88%Pass
79 1.298 8 1.50E-03 7 1.40E-03 93%Pass
80 1.314 8 1.50E-03 7 1.30E-03 87%Pass
81 1.329 7 1.40E-03 7 1.30E-03 93%Pass
Pass or
Q (cfs)Hours > Q % time Hours>Q % time Post/Pre Fail?
Underground Detention Optimized
Interval
Existing Condition
82 1.344 7 1.30E-03 6 1.20E-03 92%Pass
83 1.360 6 1.20E-03 6 1.20E-03 100%Pass
84 1.375 6 1.20E-03 6 1.20E-03 100%Pass
85 1.390 6 1.20E-03 6 1.20E-03 100%Pass
86 1.406 6 1.10E-03 6 1.20E-03 109%Pass
87 1.421 6 1.10E-03 6 1.10E-03 100%Pass
88 1.437 6 1.10E-03 6 1.10E-03 100%Pass
89 1.452 6 1.10E-03 6 1.10E-03 100%Pass
90 1.467 6 1.10E-03 6 1.10E-03 100%Pass
91 1.483 6 1.10E-03 6 1.10E-03 100%Pass
92 1.498 6 1.10E-03 6 1.10E-03 100%Pass
93 1.514 6 1.10E-03 6 1.10E-03 100%Pass
94 1.529 6 1.10E-03 6 1.10E-03 100%Pass
95 1.544 6 1.10E-03 6 1.10E-03 100%Pass
96 1.560 6 1.10E-03 6 1.10E-03 100%Pass
97 1.575 6 1.10E-03 6 1.10E-03 100%Pass
98 1.590 6 1.10E-03 6 1.10E-03 100%Pass
99 1.606 6 1.10E-03 6 1.10E-03 100%Pass
100 1.621 6 1.10E-03 6 1.10E-03 100%Pass
Peak Flows calculated with Cunnane Plotting Position
Return Period
Pre-dev. Q Post-Dev. Q Reduction
10 1.621 1.625 -0.004
9 1.454 1.434 0.020
8 1.354 1.324 0.030
7 1.305 1.278 0.027
6 1.272 1.250 0.022
5 1.227 1.204 0.023
4 1.188 1.168 0.020
3 1.106 1.093 0.013
2 0.989 0.997 -0.008
ATTACHMENT 3
List of the “n” Largest Peaks: Pre & Post-Developed Conditions
List of Peak events and Determination of P2 and P10 (Post-Development)
T Cunnane Weibull Period of Return
10 1.625 1.678 Peaks Date Posit Weibull Cunnane
9 1.434 1.523 0.781 1/13/1957 57 1.02 1.01
8 1.324 1.348 0.787 12/24/1971 56 1.04 1.03
7 1.278 1.284 0.789 2/13/1992 55 1.05 1.05
6 1.250 1.256 0.796 4/1/1958 54 1.07 1.07
5 1.204 1.207 0.805 2/2/1960 53 1.09 1.09
4 1.168 1.170 0.808 2/14/1980 52 1.12 1.11
3 1.093 1.095 0.814 10/29/2000 51 1.14 1.13
2 0.997 0.997 0.819 11/29/1985 50 1.16 1.15
0.826 10/20/2004 49 1.18 1.18
0.835 3/1/1983 48 1.21 1.20
Note:0.837 2/13/1954 47 1.23 1.23
Cunnane is the preferred 0.838 1/16/1972 46 1.26 1.25
method by the HMP permit.0.848 2/3/1998 45 1.29 1.28
0.851 2/18/1980 44 1.32 1.31
0.858 2/26/2004 43 1.35 1.34
0.864 1/22/1967 42 1.38 1.38
0.865 12/25/1983 41 1.41 1.41
0.879 1/11/1980 40 1.45 1.44
0.899 2/18/2005 39 1.49 1.48
0.9 1/13/1997 38 1.53 1.52
0.903 1/25/1969 37 1.57 1.56
0.919 11/30/2007 36 1.61 1.61
0.942 1/16/1993 35 1.66 1.65
0.951 2/23/2005 34 1.71 1.70
0.953 3/5/1995 33 1.76 1.75
0.968 3/2/1980 32 1.81 1.81
0.973 3/11/1995 31 1.87 1.87
0.976 11/22/1996 30 1.93 1.93
0.997 12/5/1966 29 2.00 2.00
0.997 2/10/1978 28 2.07 2.07
1.001 1/9/2005 27 2.15 2.15
1.013 1/15/1978 26 2.23 2.23
1.013 1/16/1978 25 2.32 2.33
1.023 2/15/1986 24 2.42 2.42
1.035 1/20/1962 23 2.52 2.53
1.049 12/30/1991 22 2.64 2.65
1.07 2/20/1980 21 2.76 2.78
1.085 8/17/1977 20 2.90 2.92
1.101 9/23/1986 19 3.05 3.08
1.138 3/8/1968 18 3.22 3.25
1.154 1/6/1979 17 3.41 3.45
1.162 2/22/2008 16 3.63 3.67
1.165 2/23/1998 15 3.87 3.92
1.176 10/27/2004 14 4.14 4.21
1.18 11/22/1965 13 4.46 4.54
1.202 3/17/1982 12 4.83 4.93
1.215 1/16/1952 11 5.27 5.40
1.249 1/29/1980 10 5.80 5.96
1.27 2/4/1958 9 6.44 6.65
1.291 3/1/1978 8 7.25 7.53
1.37 1/4/1978 7 8.29 8.67
1.666 2/25/2003 6 9.67 10.21
1.734 2/25/1969 5 11.60 12.43
1.802 1/15/1979 4 14.50 15.89
1.884 10/1/1983 3 19.33 22.00
1.913 1/4/1995 2 29.00 35.75
2.065 4/14/2003 1 58.00 95.33
List of Peak events and Determination of P2 and P10 (Pre-Development)
T Cunnane Weibull Period of Return
10 1.621 1.667 Peaks Date Posit Weibull Cunnane
9 1.454 1.532 0.776 2/6/1969 57 1.02 1.01
8 1.354 1.377 0.777 1/26/2001 56 1.04 1.03
7 1.305 1.313 0.781 12/25/1968 55 1.05 1.05
6 1.272 1.278 0.784 12/24/1983 54 1.07 1.07
5 1.227 1.231 0.788 4/27/1960 53 1.09 1.09
4 1.188 1.191 0.798 2/14/1998 52 1.12 1.11
3 1.106 1.113 0.803 2/8/1993 51 1.14 1.13
2 0.989 0.989 0.803 3/1/1991 50 1.16 1.15
0.813 8/17/1977 49 1.18 1.18
0.825 2/12/1992 48 1.21 1.20
Note:0.829 3/19/1981 47 1.23 1.23
Cunnane is the preferred 0.833 3/15/1986 46 1.26 1.25
method by the HMP permit.0.845 1/16/1972 45 1.29 1.28
0.845 2/15/1986 44 1.32 1.31
0.85 3/11/1995 43 1.35 1.34
0.854 1/29/1980 42 1.38 1.38
0.858 1/18/1993 41 1.41 1.41
0.862 1/16/1978 40 1.45 1.44
0.889 12/2/1961 39 1.49 1.48
0.899 3/17/1963 38 1.53 1.52
0.902 2/17/1998 37 1.57 1.56
0.903 12/22/1982 36 1.61 1.61
0.905 2/4/1994 35 1.66 1.65
0.955 4/28/2005 34 1.71 1.70
0.96 2/23/1998 33 1.76 1.75
0.96 2/27/1991 32 1.81 1.81
0.979 10/20/2004 31 1.87 1.87
0.98 2/16/1980 30 1.93 1.93
0.989 2/27/1983 29 2.00 2.00
1.005 11/22/1965 28 2.07 2.07
1.009 1/29/1983 27 2.15 2.15
1.02 12/30/1991 26 2.23 2.23
1.022 2/3/1998 25 2.32 2.33
1.026 2/10/1978 24 2.42 2.42
1.028 11/15/1952 23 2.52 2.53
1.047 2/18/1993 22 2.64 2.65
1.072 12/19/1970 21 2.76 2.78
1.082 11/11/1985 20 2.90 2.92
1.129 3/2/1980 19 3.05 3.08
1.139 4/1/1958 18 3.22 3.25
1.181 1/16/1952 17 3.41 3.45
1.181 3/1/1978 16 3.63 3.67
1.184 3/17/1982 15 3.87 3.92
1.199 2/20/1980 14 4.14 4.21
1.217 1/14/1993 13 4.46 4.54
1.224 2/18/2005 12 4.83 4.93
1.243 10/29/2000 11 5.27 5.40
1.271 10/27/2004 10 5.80 5.96
1.294 2/25/1969 9 6.44 6.65
1.322 2/4/1958 8 7.25 7.53
1.398 2/25/2003 7 8.29 8.67
1.657 1/4/1995 6 9.67 10.21
1.717 1/15/1979 5 11.60 12.43
1.724 9/23/1986 4 14.50 15.89
1.866 10/1/1983 3 19.33 22.00
1.888 1/4/1978 2 29.00 35.75
2.049 4/14/2003 1 58.00 95.33
ATTACHMENT 4
AREA VS ELEVATION
The area vs. elevation curve in the model is calculated in Excel and imported into the model at a
0.05 ft interval range. As the storage volume for the HMP detention facility is comprised of a
forty-five (45) foot length of 60-inch RCP, the area vs elevation reaches a maximum value at an
elevation equal to the radius of the pipe; because the storage volume is in a pipe, the
incremental volume reduces to zero as the top elevation of the pipe is reached.
DISCHARGE VS ELEVATION
The total discharge peak flow is imported from an Excel spreadsheet that calculates the
discharge vs. elevation of the multiple outlet system.
Flow will exit the basin via multiple orifices built into the side of the 60-inch RCP basin outlet
structure. A single 1 5/8-inch (2.074 sq.in.) orifice will be located at the flowline of the RCP with
an additional 1 5/8-inch (2.074 sq.in.) orifice 1.5 feet above the RCP flowline invert. A tertiary
4-inch (12.57 sq.in.) orifice will be located at an elevation of 2.5 feet above the RCP flowline to
assist in dewatering the facility and mimic the existing condition Flow Duration Curve (FDC). A
3-foot spillway weir will be located 4.7 feet above the RCP flowline; once flows exceed 4.7 feet
in the RCP basin, runoff will spill over the top of the weir and drop to the basin outlet pipe.The
discharge vs elevation curve has been calculated with the level zero set at the invert elevation
of the lower orifice.
The orifices have been selected to maximize their size while still restricting flows to conform
with the required 10% of the Q2 event flow as mandated in the Final Hydromodification
Management Plan by Brown & Caldwell, dated March 2011. While TRWE acknowledges that
these orifices are small, to increase the size of these outlets would impact the basin’s ability to
restrict flows beneath the HMP thresholds, thus preventing the BMP from conformance with
HMP requirements.
It is important to notice that the use of SDHM would suggest an orifice of 1-inch or less. The
use of SWMM has allowed an increase of 260% in the lower orifice size (area). This increase in
orifice size significantly reduces the risk, or frequency, of clogging, reducing maintenance
concerns.
In order to further reduce the risk of blockage of the orifices, a debris screen will be fitted to
the base invert of the orifices located within the detention basins. Regular maintenance of the
riser and orifices must be performed to ensure potential blockages are minimized. A detail of
the orifice and riser structure is provided in Attachment 5 of this memorandum.
The stage-storage and stage-discharge calculations have been provided on the following pages.
Outlet structure for Discharge of HMP Basin - South Melrose, Carlsbad
Discharge vs Elevation Table
Low orifice:1.625 "Lower weir:
Number:1 Invert:4.70 ft
Cg-low:0.61 B 3.00 ft
Middle orifice:4 "
number of orif:1 Emergency weir:
Cg-middle:0.61 Invert:0.00 ft
invert elev:2.50 ft B:0 ft
h H/D-low H/D-mid Qlow-orif Qlow-weir Qtot-low Qmid-orif Qmid-weir Qtot-med Qweir Qemerg Qtot-low-2nd Q-Total
(ft)--(cfs)(cfs)(cfs)(cfs)(cfs)(cfs)(cfs)(cfs)(cfs)(cfs)
0 0 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
0.05 0.369231 0.000 0.000 0.003 0.003 0.000 0.000 0.000 0.000 0.000 0.000 0.003
0.1 0.738462 0.000 0.013 0.010 0.010 0.000 0.000 0.000 0.000 0.000 0.000 0.010
0.15 1.107692 0.000 0.020 0.021 0.020 0.000 0.000 0.000 0.000 0.000 0.000 0.020
0.2 1.476923 0.000 0.026 0.031 0.026 0.000 0.000 0.000 0.000 0.000 0.000 0.026
0.25 1.846154 0.000 0.030 0.040 0.030 0.000 0.000 0.000 0.000 0.000 0.000 0.030
0.3 2.215385 0.000 0.034 0.045 0.034 0.000 0.000 0.000 0.000 0.000 0.000 0.034
0.35 2.584615 0.000 0.037 0.047 0.037 0.000 0.000 0.000 0.000 0.000 0.000 0.037
0.4 2.953846 0.000 0.041 0.048 0.041 0.000 0.000 0.000 0.000 0.000 0.000 0.041
0.45 3.323077 0.000 0.044 0.050 0.044 0.000 0.000 0.000 0.000 0.000 0.000 0.044
0.5 3.692308 0.000 0.046 0.059 0.046 0.000 0.000 0.000 0.000 0.000 0.000 0.046
0.55 4.061538 0.000 0.049 0.086 0.049 0.000 0.000 0.000 0.000 0.000 0.000 0.049
0.6 4.430769 0.000 0.051 0.141 0.051 0.000 0.000 0.000 0.000 0.000 0.000 0.051
0.65 4.8 0.000 0.054 0.241 0.054 0.000 0.000 0.000 0.000 0.000 0.000 0.054
0.7 5.169231 0.000 0.056 0.407 0.056 0.000 0.000 0.000 0.000 0.000 0.000 0.056
0.75 5.538462 0.000 0.058 0.663 0.058 0.000 0.000 0.000 0.000 0.000 0.000 0.058
0.8 5.907692 0.000 0.060 1.040 0.060 0.000 0.000 0.000 0.000 0.000 0.000 0.060
0.85 6.276923 0.000 0.062 1.574 0.062 0.000 0.000 0.000 0.000 0.000 0.000 0.062
0.9 6.646154 0.000 0.064 2.306 0.064 0.000 0.000 0.000 0.000 0.000 0.000 0.064
0.95 7.015385 0.000 0.066 3.285 0.066 0.000 0.000 0.000 0.000 0.000 0.000 0.066
1 7.384615 0.000 0.068 4.567 0.068 0.000 0.000 0.000 0.000 0.000 0.000 0.068
1.05 7.753846 0.000 0.070 6.214 0.070 0.000 0.000 0.000 0.000 0.000 0.000 0.070
1.1 8.123077 0.000 0.072 8.297 0.072 0.000 0.000 0.000 0.000 0.000 0.000 0.072
1.15 8.492308 0.000 0.073 10.895 0.073 0.000 0.000 0.000 0.000 0.000 0.000 0.073
1.2 8.861538 0.000 0.075 14.095 0.075 0.000 0.000 0.000 0.000 0.000 0.000 0.075
1.25 9.230769 0.000 0.077 17.994 0.077 0.000 0.000 0.000 0.000 0.000 0.000 0.077
1.3 9.6 0.000 0.078 22.698 0.078 0.000 0.000 0.000 0.000 0.000 0.000 0.078
1.35 9.969231 0.000 0.080 28.324 0.080 0.000 0.000 0.000 0.000 0.000 0.000 0.080
1.4 10.33846 0.000 0.081 34.999 0.081 0.000 0.000 0.000 0.000 0.000 0.000 0.081
1.45 10.70769 0.000 0.083 42.860 0.083 0.000 0.000 0.000 0.000 0.000 0.000 0.083
1.5 11.07692 0.000 0.084 52.057 0.084 0.000 0.000 0.000 0.000 0.000 0.000 0.084
1.55 11.44615 0.000 0.086 62.752 0.086 0.000 0.000 0.000 0.000 0.000 0.003 0.089
1.6 11.81538 0.000 0.087 75.116 0.087 0.000 0.000 0.000 0.000 0.000 0.010 0.098
1.65 12.18462 0.000 0.089 89.338 0.089 0.000 0.000 0.000 0.000 0.000 0.020 0.109
1.7 12.55385 0.000 0.090 105.614 0.090 0.000 0.000 0.000 0.000 0.000 0.026 0.116
1.75 12.92308 0.000 0.091 124.160 0.091 0.000 0.000 0.000 0.000 0.000 0.030 0.122
1.8 13.29231 0.000 0.093 145.201 0.093 0.000 0.000 0.000 0.000 0.000 0.034 0.127
1.85 13.66154 0.000 0.094 168.979 0.094 0.000 0.000 0.000 0.000 0.000 0.037 0.132
1.9 14.03077 0.000 0.095 195.751 0.095 0.000 0.000 0.000 0.000 0.000 0.041 0.136
1.95 14.4 0.000 0.097 225.787 0.097 0.000 0.000 0.000 0.000 0.000 0.044 0.140
2 14.76923 0.000 0.098 259.377 0.098 0.000 0.000 0.000 0.000 0.000 0.046 0.144
2.05 15.13846 0.000 0.099 296.824 0.099 0.000 0.000 0.000 0.000 0.000 0.049 0.148
2.1 15.50769 0.000 0.101 338.448 0.101 0.000 0.000 0.000 0.000 0.000 0.051 0.152
2.15 15.87692 0.000 0.102 384.587 0.102 0.000 0.000 0.000 0.000 0.000 0.054 0.156
2.2 16.24615 0.000 0.103 435.597 0.103 0.000 0.000 0.000 0.000 0.000 0.056 0.159
2.25 16.61538 0.000 0.104 491.851 0.104 0.000 0.000 0.000 0.000 0.000 0.058 0.162
2.3 16.98462 0.000 0.105 553.742 0.105 0.000 0.000 0.000 0.000 0.000 0.060 0.166
2.35 17.35385 0.000 0.107 621.680 0.107 0.000 0.000 0.000 0.000 0.000 0.062 0.169
2.4 17.72308 0.000 0.108 696.096 0.108 0.000 0.000 0.000 0.000 0.000 0.064 0.172
2.45 18.09231 0.000 0.109 777.439 0.109 0.000 0.000 0.000 0.000 0.000 0.066 0.175
2.5 18.46154 0.000 0.110 866.181 0.110 0.000 0.000 0.000 0.000 0.000 0.068 0.178
2.55 18.83077 0.150 0.111 962.813 0.111 0.000 0.005 0.005 0.000 0.000 0.070 0.186
2.6 19.2 0.300 0.112 1067.847 0.112 0.000 0.019 0.019 0.000 0.000 0.072 0.202
2.65 19.56923 0.450 0.113 1181.817 0.113 0.000 0.040 0.040 0.000 0.000 0.073 0.227
2.7 19.93846 0.600 0.114 1305.279 0.114 0.078 0.069 0.069 0.000 0.000 0.075 0.258
2.75 20.30769 0.750 0.115 1438.812 0.115 0.123 0.103 0.103 0.000 0.000 0.077 0.295
2.8 20.67692 0.900 0.117 1583.018 0.117 0.156 0.140 0.140 0.000 0.000 0.078 0.335
2.85 21.04615 1.050 0.118 1738.521 0.118 0.183 0.180 0.180 0.000 0.000 0.080 0.378
2.9 21.41538 1.200 0.119 1905.971 0.119 0.206 0.221 0.206 0.000 0.000 0.081 0.406
2.95 21.78462 1.350 0.120 2086.040 0.120 0.227 0.261 0.227 0.000 0.000 0.083 0.430
3 22.15385 1.500 0.121 2279.427 0.121 0.247 0.300 0.247 0.000 0.000 0.084 0.452
3.05 22.52308 1.650 0.122 2486.854 0.122 0.264 0.335 0.264 0.000 0.000 0.086 0.472
3.1 22.89231 1.800 0.123 2709.070 0.123 0.281 0.367 0.281 0.000 0.000 0.087 0.491
3.15 23.26154 1.950 0.124 2946.851 0.124 0.297 0.393 0.297 0.000 0.000 0.089 0.509
3.2 23.63077 2.100 0.125 3200.997 0.125 0.312 0.415 0.312 0.000 0.000 0.090 0.527
3.25 24 2.250 0.126 3472.336 0.126 0.326 0.431 0.326 0.000 0.000 0.091 0.543
3.3 24.36923 2.400 0.127 3761.724 0.127 0.340 0.441 0.340 0.000 0.000 0.093 0.560
3.35 24.73846 2.550 0.128 4070.046 0.128 0.353 0.448 0.353 0.000 0.000 0.094 0.575
3.4 25.10769 2.700 0.129 4398.211 0.129 0.366 0.450 0.366 0.000 0.000 0.095 0.590
3.45 25.47692 2.850 0.130 4747.162 0.130 0.378 0.451 0.378 0.000 0.000 0.097 0.604
3.5 25.84615 3.000 0.131 5117.868 0.131 0.390 0.453 0.390 0.000 0.000 0.098 0.619
3.55 26.21538 3.150 0.132 5511.328 0.132 0.401 0.458 0.401 0.000 0.000 0.099 0.632
3.6 26.58462 3.300 0.133 5928.572 0.133 0.413 0.469 0.413 0.000 0.000 0.101 0.646
3.65 26.95385 3.450 0.133 6370.659 0.133 0.424 0.492 0.424 0.000 0.000 0.102 0.659
3.7 27.32308 3.600 0.134 6838.681 0.134 0.434 0.530 0.434 0.000 0.000 0.103 0.672
3.75 27.69231 3.750 0.135 7333.760 0.135 0.445 0.591 0.445 0.000 0.000 0.104 0.684
3.8 28.06154 3.900 0.136 7857.051 0.136 0.455 0.679 0.455 0.000 0.000 0.105 0.696
3.85 28.43077 4.050 0.137 8409.739 0.137 0.465 0.803 0.465 0.000 0.000 0.107 0.708
3.9 28.8 4.200 0.138 8993.044 0.138 0.474 0.972 0.474 0.000 0.000 0.108 0.720
3.95 29.16923 4.350 0.139 9608.219 0.139 0.484 1.194 0.484 0.000 0.000 0.109 0.732
4 29.53846 4.500 0.140 10256.550 0.140 0.493 1.480 0.493 0.000 0.000 0.110 0.743
4.05 29.90769 4.650 0.141 10939.356 0.141 0.502 1.842 0.502 0.000 0.000 0.111 0.754
4.1 30.27692 4.800 0.142 11657.993 0.142 0.511 2.292 0.511 0.000 0.000 0.112 0.765
4.15 30.64615 4.950 0.142 12413.850 0.142 0.520 2.844 0.520 0.000 0.000 0.113 0.776
4.2 31.01538 5.100 0.143 13208.353 0.143 0.529 3.514 0.529 0.000 0.000 0.114 0.787
4.25 31.38462 5.250 0.144 14042.962 0.144 0.538 4.317 0.538 0.000 0.000 0.115 0.797
4.3 31.75385 5.400 0.145 14919.174 0.145 0.546 5.271 0.546 0.000 0.000 0.117 0.808
4.35 32.12308 5.550 0.146 15838.525 0.146 0.554 6.395 0.554 0.000 0.000 0.118 0.818
4.4 32.49231 5.700 0.147 16802.584 0.147 0.562 7.710 0.562 0.000 0.000 0.119 0.828
4.45 32.86154 5.850 0.148 17812.961 0.148 0.570 9.237 0.570 0.000 0.000 0.120 0.838
4.5 33.23077 6.000 0.148 18871.303 0.148 0.578 11.000 0.578 0.000 0.000 0.121 0.848
4.55 33.6 6.150 0.149 19979.295 0.149 0.586 13.024 0.586 0.000 0.000 0.122 0.857
4.6 33.96923 6.300 0.150 21138.661 0.150 0.594 15.335 0.594 0.000 0.000 0.123 0.867
4.65 34.33846 6.450 0.151 22351.167 0.151 0.602 17.961 0.602 0.000 0.000 0.124 0.876
4.7 34.70769 6.600 0.152 23618.615 0.152 0.609 20.933 0.609 0.000 0.000 0.125 0.886
4.75 35.07692 6.750 0.153 24942.849 0.153 0.617 24.281 0.617 0.104 0.000 0.126 0.999
4.8 35.44615 6.900 0.153 26325.754 0.153 0.624 28.040 0.624 0.294 0.000 0.127 1.198
4.85 35.81538 7.050 0.154 27769.257 0.154 0.631 32.244 0.631 0.540 0.000 0.128 1.453
4.9 36.18462 7.200 0.155 29275.325 0.155 0.638 36.930 0.638 0.832 0.000 0.129 1.754
4.95 36.55385 7.350 0.156 30845.968 0.156 0.646 42.138 0.646 1.163 0.000 0.130 2.093
5 36.92308 7.500 0.157 32483.238 0.157 0.653 47.908 0.653 1.528 0.000 0.131 2.468
STAGE-STORAGE
Pipe Diam (In) =60
Length (ft) =45
Elev Cross-Sectional Area
(ft^2)Width (ft)Surface Area (ft^2)Volume (ft^3)Cumulative Volume (ft^3)
0 0 0 0 0 0
0.5 1.02 3 135 45.9 45.9
1 1.77 4 180 79.65 125.55
1.5 2.16 4.58 206.1 97.2 222.75
2 2.38 4.9 220.5 107.1 329.85
2.5 2.48 5 225 111.6 441.45
3 2.48 4.9 220.5 111.6 553.05
3.5 2.38 4.58 206.1 107.1 660.15
4 2.16 4 180 97.2 757.35
4.5 1.77 3 135 79.65 837
5 1.02 0 0 45.9 882.9
ATTACHMENT 5
Pre & Post-Developed Maps, Project Plan and Detention
Section Sketches
ATTACHMENT 6
SWMM Input Data in Input Format (Existing & Proposed Models)
Pre_Dev_Evap
[TITLE]
[OPTIONS]
FLOW_UNITS CFS
INFILTRATION GREEN_AMPT
FLOW_ROUTING KINWAVE
START_DATE 10/01/1951
START_TIME 00:00:00
REPORT_START_DATE 10/01/1951
REPORT_START_TIME 00:00:00
END_DATE 09/30/2008
END_TIME 22:00:00
SWEEP_START 01/01
SWEEP_END 12/31
DRY_DAYS 0
REPORT_STEP 00:30:00
WET_STEP 00:05:00
DRY_STEP 02:00:00
ROUTING_STEP 0:01:00
ALLOW_PONDING NO
INERTIAL_DAMPING PARTIAL
VARIABLE_STEP 0.75
LENGTHENING_STEP 0
MIN_SURFAREA 0
NORMAL_FLOW_LIMITED BOTH
SKIP_STEADY_STATE NO
FORCE_MAIN_EQUATION H-W
LINK_OFFSETS DEPTH
MIN_SLOPE 0
[EVAPORATION]
;;Type Parameters
;;---------- ----------
MONTHLY 0.041 0.076 0.118 0.192 0.237 0.318 0.308 0.286 0.217
0.14 0.067 0.041
DRY_ONLY NO
[RAINGAGES]
;; Rain Time Snow Data
;;Name Type Intrvl Catch Source
;;-------------- --------- ------ ------ ----------
Oceanside INTENSITY 1:00 1.0 TIMESERIES Oceanside
[SUBCATCHMENTS]
;; Total Pcnt.
Pcnt. Curb Snow
;;Name Raingage Outlet Area Imperv Width
Slope Length Pack
;;-------------- ---------------- ---------------- -------- -------- --------
-------- -------- --------
1 Oceanside PC-1 1.75 56.2 133.8
5 0
[SUBAREAS]
;;Subcatchment N-Imperv N-Perv S-Imperv S-Perv PctZero
RouteTo PctRouted
;;-------------- ---------- ---------- ---------- ---------- ----------
---------- ----------
1 0.012 0.15 0.02 0.1 25 OUTLET
[INFILTRATION]
;;Subcatchment Suction HydCon IMDmax
;;-------------- ---------- ---------- ----------
1 9 0.01875 0.3
[OUTFALLS]
Page 1
Pre_Dev_Evap
;; Invert Outfall Stage/Table Tide
;;Name Elev. Type Time Series Gate
;;-------------- ---------- ---------- ---------------- ----
PC-1 0 FREE NO
[TIMESERIES]
;;Name Date Time Value
;;-------------- ---------- ---------- ----------
Oceanside FILE "OsideRain.prn"
[REPORT]
INPUT NO
CONTROLS NO
SUBCATCHMENTS ALL
NODES ALL
LINKS ALL
[TAGS]
[MAP]
DIMENSIONS 0.000 0.000 10000.000 10000.000
Units None
[COORDINATES]
;;Node X-Coord Y-Coord
;;-------------- ------------------ ------------------
PC-1 4932.584 4370.787
[VERTICES]
;;Link X-Coord Y-Coord
;;-------------- ------------------ ------------------
[Polygons]
;;Subcatchment X-Coord Y-Coord
;;-------------- ------------------ ------------------
1 4966.292 6573.034
[SYMBOLS]
;;Gage X-Coord Y-Coord
;;-------------- ------------------ ------------------
Oceanside 7112.360 6752.809
Page 2
Post_Dev_Final
[TITLE]
[OPTIONS]
FLOW_UNITS CFS
INFILTRATION GREEN_AMPT
FLOW_ROUTING KINWAVE
START_DATE 10/17/1948
START_TIME 08:00:00
REPORT_START_DATE 10/17/1948
REPORT_START_TIME 08:00:00
END_DATE 09/30/2005
END_TIME 23:00:00
SWEEP_START 01/01
SWEEP_END 12/31
DRY_DAYS 0
REPORT_STEP 01:00:00
WET_STEP 00:15:00
DRY_STEP 04:00:00
ROUTING_STEP 0:01:00
ALLOW_PONDING NO
INERTIAL_DAMPING PARTIAL
VARIABLE_STEP 0.75
LENGTHENING_STEP 0
MIN_SURFAREA 0
NORMAL_FLOW_LIMITED BOTH
SKIP_STEADY_STATE NO
FORCE_MAIN_EQUATION H-W
LINK_OFFSETS DEPTH
MIN_SLOPE 0
[EVAPORATION]
;;Type Parameters
;;---------- ----------
CONSTANT 0.0
DRY_ONLY NO
[RAINGAGES]
;; Rain Time Snow Data
;;Name Type Intrvl Catch Source
;;-------------- --------- ------ ------ ----------
Oceanside INTENSITY 1:00 1.0 TIMESERIES Oceanside
[SUBCATCHMENTS]
;; Total Pcnt.
Pcnt. Curb Snow
;;Name Raingage Outlet Area Imperv Width
Slope Length Pack
;;-------------- ---------------- ---------------- -------- -------- --------
-------- -------- --------
BASIN_BYPASS Oceanside PC-1 0.55 53.6 219
5 0
DEV_A Oceanside BASIN 1.2 71 113.5
5 0
[SUBAREAS]
;;Subcatchment N-Imperv N-Perv S-Imperv S-Perv PctZero
RouteTo PctRouted
;;-------------- ---------- ---------- ---------- ---------- ----------
---------- ----------
BASIN_BYPASS 0.012 0.15 0.02 0.1 25 OUTLET
DEV_A 0.012 0.15 0.02 0.1 25 OUTLET
[INFILTRATION]
;;Subcatchment Suction HydCon IMDmax
;;-------------- ---------- ---------- ----------
Page 1
Post_Dev_Final
BASIN_BYPASS 9 0.01875 0.3
DEV_A 9 0.01875 0.3
[LID_CONTROLS]
;; Type/Layer Parameters
;;-------------- ---------- ----------
BIO_R BC
BIO_R SURFACE 0.0 0.0 0.1 1.0 5
BIO_R SOIL 24 0.5 0.2 0.1 0.5
10.0 3.5
BIO_R STORAGE 12 0.75 10 0
BIO_R DRAIN 0 0.5 0 6
[LID_USAGE]
;;Subcatchment LID Process Number Area Width InitSatur
FromImprv ToPerv Report File
;;-------------- ---------------- ------- ---------- ---------- ----------
---------- ---------- -----------
[OUTFALLS]
;; Invert Outfall Stage/Table Tide
;;Name Elev. Type Time Series Gate
;;-------------- ---------- ---------- ---------------- ----
PC-1 0 FREE NO
[STORAGE]
;; Invert Max. Init. Storage Curve
Ponded Evap.
;;Name Elev. Depth Depth Curve Params
Area Frac. Infiltration Parameters
;;-------------- -------- -------- -------- ---------- -------- --------
-------- -------- -------- -----------------------
BASIN 0 5 0 TABULAR Basin
0 0
[OUTLETS]
;; Inlet Outlet Outflow Outlet
Qcoeff/ Flap
;;Name Node Node Height Type
QTable Qexpon Gate
;;-------------- ---------------- ---------------- ---------- ---------------
---------------- ---------- ----
3 BASIN PC-1 0 TABULAR/DEPTH
ORIFICE NO
[CURVES]
;;Name Type X-Value Y-Value
;;-------------- ---------- ---------- ----------
ORIFICE Rating 0 0.000
ORIFICE 0.05 0.003
ORIFICE 0.1 0.012
ORIFICE 0.15 0.023
ORIFICE 0.2 0.033
ORIFICE 0.25 0.039
ORIFICE 0.3 0.044
ORIFICE 0.35 0.049
ORIFICE 0.4 0.053
ORIFICE 0.45 0.057
ORIFICE 0.5 0.061
ORIFICE 0.55 0.064
ORIFICE 0.6 0.068
ORIFICE 0.65 0.071
ORIFICE 0.7 0.074
ORIFICE 0.75 0.077
ORIFICE 0.8 0.080
ORIFICE 0.85 0.082
Page 2
Post_Dev_Final
ORIFICE 0.9 0.085
ORIFICE 0.95 0.088
ORIFICE 1 0.090
ORIFICE 1.05 0.093
ORIFICE 1.1 0.095
ORIFICE 1.15 0.097
ORIFICE 1.2 0.099
ORIFICE 1.25 0.102
ORIFICE 1.3 0.104
ORIFICE 1.35 0.106
ORIFICE 1.4 0.108
ORIFICE 1.45 0.110
ORIFICE 1.5 0.112
ORIFICE 1.55 0.117
ORIFICE 1.6 0.127
ORIFICE 1.65 0.141
ORIFICE 1.7 0.152
ORIFICE 1.75 0.160
ORIFICE 1.8 0.167
ORIFICE 1.85 0.174
ORIFICE 1.9 0.180
ORIFICE 1.95 0.186
ORIFICE 2 0.191
ORIFICE 2.05 0.196
ORIFICE 2.1 0.201
ORIFICE 2.15 0.206
ORIFICE 2.2 0.211
ORIFICE 2.25 0.215
ORIFICE 2.3 0.220
ORIFICE 2.35 0.224
ORIFICE 2.4 0.228
ORIFICE 2.45 0.232
ORIFICE 2.5 0.236
ORIFICE 2.55 0.253
ORIFICE 2.6 0.293
ORIFICE 2.65 0.347
ORIFICE 2.7 0.397
ORIFICE 2.75 0.429
ORIFICE 2.8 0.457
ORIFICE 2.85 0.483
ORIFICE 2.9 0.506
ORIFICE 2.95 0.528
ORIFICE 3 0.548
ORIFICE 3.05 0.568
ORIFICE 3.1 0.586
ORIFICE 3.15 0.604
ORIFICE 3.2 0.621
ORIFICE 3.25 0.637
ORIFICE 3.3 0.653
ORIFICE 3.35 0.669
ORIFICE 3.4 0.684
ORIFICE 3.45 0.698
ORIFICE 3.5 0.713
ORIFICE 3.55 0.727
ORIFICE 3.6 0.740
ORIFICE 3.65 0.754
ORIFICE 3.7 0.767
ORIFICE 3.75 0.780
ORIFICE 3.8 0.792
ORIFICE 3.85 0.805
ORIFICE 3.9 0.817
ORIFICE 3.95 0.829
ORIFICE 4 0.840
ORIFICE 4.05 0.852
ORIFICE 4.1 0.863
ORIFICE 4.15 0.875
ORIFICE 4.2 0.886
Page 3
Post_Dev_Final
ORIFICE 4.25 0.897
ORIFICE 4.3 0.907
ORIFICE 4.35 0.918
ORIFICE 4.4 0.929
ORIFICE 4.45 0.939
ORIFICE 4.5 0.949
ORIFICE 4.55 0.959
ORIFICE 4.6 0.969
ORIFICE 4.65 0.979
ORIFICE 4.7 0.989
ORIFICE 4.75 1.103
ORIFICE 4.8 1.303
ORIFICE 4.85 1.558
ORIFICE 4.9 1.859
ORIFICE 4.95 2.199
ORIFICE 5 2.574
Basin Storage 0 0.00
Basin 0.1 112.00
Basin 0.2 156.77
Basin 0.3 189.99
Basin 0.4 217.03
Basin 0.5 240.00
Basin 0.6 259.97
Basin 0.7 277.59
Basin 0.8 293.28
Basin 0.9 307.35
Basin 1 320.00
Basin 1.1 331.40
Basin 1.2 341.67
Basin 1.3 350.91
Basin 1.4 359.20
Basin 1.5 366.61
Basin 1.6 373.18
Basin 1.7 378.97
Basin 1.8 384.00
Basin 1.9 388.31
Basin 2 391.92
Basin 2.1 394.85
Basin 2.2 397.11
Basin 2.3 398.72
Basin 2.4 399.68
Basin 2.5 400.00
Basin 2.6 399.68
Basin 2.7 398.72
Basin 2.8 397.11
Basin 2.9 394.85
Basin 3 391.92
Basin 3.1 388.31
Basin 3.2 384.00
Basin 3.3 378.97
Basin 3.4 373.18
Basin 3.5 366.61
Basin 3.6 359.20
Basin 3.7 350.91
Basin 3.8 341.67
Basin 3.9 331.40
Basin 4 320.00
Basin 4.1 307.35
Basin 4.2 293.28
Basin 4.3 277.59
Basin 4.4 259.97
Basin 4.5 240.00
Basin 4.6 217.03
Basin 4.7 189.99
Basin 4.8 156.77
Basin 4.9 112.00
Page 4
Post_Dev_Final
Basin 5 0.00
[TIMESERIES]
;;Name Date Time Value
;;-------------- ---------- ---------- ----------
Oceanside FILE "OsideRain.prn"
[REPORT]
INPUT NO
CONTROLS NO
SUBCATCHMENTS ALL
NODES ALL
LINKS ALL
[TAGS]
[MAP]
DIMENSIONS 0.000 0.000 10000.000 10000.000
Units None
[COORDINATES]
;;Node X-Coord Y-Coord
;;-------------- ------------------ ------------------
PC-1 4932.584 4370.787
BASIN 2766.191 6805.708
[VERTICES]
;;Link X-Coord Y-Coord
;;-------------- ------------------ ------------------
[Polygons]
;;Subcatchment X-Coord Y-Coord
;;-------------- ------------------ ------------------
BASIN_BYPASS 5898.876 6022.472
DEV_A 1764.045 8146.067
[SYMBOLS]
;;Gage X-Coord Y-Coord
;;-------------- ------------------ ------------------
Oceanside 7112.360 6752.809
Page 5
ATTACHMENT 7
EPA SWMM FIGURES AND EXPLANATIONS
Attached, the reader can see the screens associated with the EPA-SWMM Model in both pre-
development and post-development conditions. Each portion, i.e., sub-catchments, outfalls,
storage units, weir as a discharge, and outfalls (point of compliance), are also shown.
Variables for modeling are associated with typical recommended values by the EPA-SWMM
model, typical values found in technical literature (such as Maidment’s Handbook of
Hydrology). Recommended values for the SWMM model have been attained from the interim
Orange County criteria established for their SWMM calibration. Currently, no recommended
values have been established by the San Diego County HMP Permit for the SWMM Model.
Soil characteristics of the existing soils were determined from the USGS sources.
Some values incorporated within the SWMM model have been determined from the
professional experience of TRWE using conservative assumptions that have a tendency to
increase the size of the needed BMP and also generate a long-term runoff as a percentage of
rainfall similar to those measured in gage stations in Southern California by the USGS.
PRE-DEVELOPED CONDITION
POST-DEVELOPED CONDITION
EXPLANATION OF SELECTED VARIABLES
Sub-Catchment DEV_A represents the areas draining to the HMP detention basin, Sub-Catchment
BASIN_BYPASS represents the areas downstream of the facility that confluence at the point of
compliance (PC-1).
Parameters for the pre- and post-developed models include soil type D in accordance with the San Diego
County Hydrology Manual and the USGS Soil Survey Map (attached at the end of this appendix). Suction
head, conductivity and initial deficit corresponds to average values expected for soils type D, according
to sources consulted, professional experience, and approximate values obtained by the interim Orange
County modeling approach.
TRWE selected infiltration values, such that the percentage of total precipitation that becomes runoff, is
realistic for soil type D and slightly smaller than measured values for Southern California watersheds.
Selection of a Kinematic Approach: As the continuous model is based on hourly rainfall, and the time of
concentration for the pre-development and post-development conditions is significantly smaller than 60
minutes, precise routing of the flows through the impervious surfaces, the underdrain pipe system, and
the discharge pipe was considered unnecessary. The truncation error of the precipitation into hourly
steps is much more significant than the precise routing in a system where the time of concentration is
much smaller than 1 hour.
Note: The complete storage and rating curves and the respective explanation is shown at the end of this
appendix. A variable area vs. elevation storage curve was used for the final model, and a discharge that is a
function of the outlet structure in the surface was used also.
ATTACHMENT 8
Drying Time of the HMP Facility
Per the HMS dewatering model the basin is dry in less than 2 hours, thus complying with RWQCB
requirements for basin dewatering as the basin is dry within a 96 hour period.
ATTACHMENT 9
USGS Soil Map for Justification of Soil Type D Conditions
Melrose DrPalomar Airport Rd Melrose DrAtC
AtE
477030
477030
477060
477060
477090
477090
477120
477120
477150
477150
477180
477180
477210
477210
477240
4772403665760 3665760366579036657903665820366582036658503665850366588036658803665910366591036659403665940366597036659703666000366600036660303666030366606036660600 100 200 30050
Feet
0 20 40 6010
Meters
33° 7' 58''117° 14' 38''33° 7' 48''117° 14' 38''33° 7' 48''
33° 7' 58''117° 14' 47''117° 14' 47''Map Scale: 1:1,540 if printed on A size (8.5" x 11") sheet.
Hydrologic Soil Group—San Diego County Area, California
Natural ResourcesNatural ResourcesNatural ResourcesNatural Resources
Conservation ServiceConservation ServiceConservation ServiceConservation Service
Web Soil Survey
National Cooperative Soil Survey
5/23/2012
Page 1 of 4
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Units
Soil Ratings
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Political Features
Cities
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Map Scale: 1:1,540 if printed on A size (8.5" × 11") sheet.
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 accurate map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov
Coordinate System: UTM Zone 11N NAD83
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, California
Survey Area Data: Version 6, Dec 17, 2007
Date(s) aerial images were photographed: 6/7/2005
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 Survey
National Cooperative Soil Survey
5/23/2012
Page 2 of 4
Hydrologic Soil Group
Hydrologic Soil Group— Summary by Map Unit — San Diego County Area, California (CA638)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
AtC Altamont clay, 5 to 9 percent
slopes
D 4.5 96.0%
AtE Altamont clay, 15 to 30 percent
slopes
D 0.2 4.0%
Totals for Area of Interest 4.7 100.0%
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.
Rating Options
Aggregation Method: Dominant Condition
Hydrologic Soil Group–San Diego County Area, California
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
5/23/2012
Page 3 of 4
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group–San Diego County Area, California
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
5/23/2012
Page 4 of 4
ATTACHMENT 10
Summary Files from the SWMM Model
Pre_Dev_Evap
EPA STORM WATER MANAGEMENT MODEL - VERSION 5.0 (Build 5.0.022)
--------------------------------------------------------------
*********************************************************
NOTE: The summary statistics displayed in this report are
based on results found at every computational time step,
not just on results from each reporting time step.
*********************************************************
****************
Analysis Options
****************
Flow Units ............... CFS
Process Models:
Rainfall/Runoff ........ YES
Snowmelt ............... NO
Groundwater ............ NO
Flow Routing ........... NO
Water Quality .......... NO
Infiltration Method ...... GREEN_AMPT
Starting Date ............ OCT-01-1951 00:00:00
Ending Date .............. SEP-30-2008 22:00:00
Antecedent Dry Days ...... 0.0
Report Time Step ......... 00:30:00
Wet Time Step ............ 00:05:00
Dry Time Step ............ 02:00:00
************************** Volume Depth
Runoff Quantity Continuity acre-feet inches
************************** --------- -------
Total Precipitation ...... 98.344 674.360
Evaporation Loss ......... 7.795 53.449
Infiltration Loss ........ 31.066 213.025
Surface Runoff ........... 59.855 410.435
Final Surface Storage .... 0.000 0.000
Continuity Error (%) ..... -0.378
************************** Volume Volume
Flow Routing Continuity acre-feet 10^6 gal
************************** --------- ---------
Dry Weather Inflow ....... 0.000 0.000
Wet Weather Inflow ....... 59.855 19.505
Groundwater Inflow ....... 0.000 0.000
RDII Inflow .............. 0.000 0.000
External Inflow .......... 0.000 0.000
External Outflow ......... 59.855 19.505
Internal Outflow ......... 0.000 0.000
Storage Losses ........... 0.000 0.000
Initial Stored Volume .... 0.000 0.000
Final Stored Volume ...... 0.000 0.000
Continuity Error (%) ..... 0.000
***************************
Subcatchment Runoff Summary
***************************
------------------------------------------------------------------------------
--------------------------
Total Total Total Total Total
Total Peak Runoff
Precip Runon Evap Infil Runoff
Page 1
Pre_Dev_Evap
Runoff Runoff Coeff
Subcatchment in in in in in
10^6 gal CFS
------------------------------------------------------------------------------
--------------------------
1 674.36 0.00 53.45 213.02 410.44
19.50 2.05 0.609
Analysis begun on: Tue Jun 26 10:06:43 2012
Analysis ended on: Tue Jun 26 10:06:57 2012
Total elapsed time: 00:00:14
Page 2
Post_Dev_Final
EPA STORM WATER MANAGEMENT MODEL - VERSION 5.0 (Build 5.0.022)
--------------------------------------------------------------
*********************************************************
NOTE: The summary statistics displayed in this report are
based on results found at every computational time step,
not just on results from each reporting time step.
*********************************************************
****************
Analysis Options
****************
Flow Units ............... CFS
Process Models:
Rainfall/Runoff ........ YES
Snowmelt ............... NO
Groundwater ............ NO
Flow Routing ........... YES
Ponding Allowed ........ NO
Water Quality .......... NO
Infiltration Method ...... GREEN_AMPT
Flow Routing Method ...... KINWAVE
Starting Date ............ OCT-17-1948 08:00:00
Ending Date .............. SEP-30-2005 23:00:00
Antecedent Dry Days ...... 0.0
Report Time Step ......... 01:00:00
Wet Time Step ............ 00:15:00
Dry Time Step ............ 04:00:00
Routing Time Step ........ 60.00 sec
************************** Volume Depth
Runoff Quantity Continuity acre-feet inches
************************** --------- -------
Total Precipitation ...... 94.752 649.730
Evaporation Loss ......... 0.000 0.000
Infiltration Loss ........ 23.690 162.446
Surface Runoff ........... 71.842 492.631
Final Surface Storage .... 0.001 0.010
Continuity Error (%) ..... -0.824
************************** Volume Volume
Flow Routing Continuity acre-feet 10^6 gal
************************** --------- ---------
Dry Weather Inflow ....... 0.000 0.000
Wet Weather Inflow ....... 71.842 23.411
Groundwater Inflow ....... 0.000 0.000
RDII Inflow .............. 0.000 0.000
External Inflow .......... 0.000 0.000
External Outflow ......... 71.832 23.408
Internal Outflow ......... 0.000 0.000
Storage Losses ........... 0.000 0.000
Initial Stored Volume .... 0.000 0.000
Final Stored Volume ...... 0.000 0.000
Continuity Error (%) ..... 0.014
********************************
Highest Flow Instability Indexes
********************************
All links are stable.
*************************
Page 1
Post_Dev_Final
Routing Time Step Summary
*************************
Minimum Time Step : 60.00 sec
Average Time Step : 60.00 sec
Maximum Time Step : 60.00 sec
Percent in Steady State : 0.00
Average Iterations per Step : 1.00
***************************
Subcatchment Runoff Summary
***************************
------------------------------------------------------------------------------
--------------------------
Total Total Total Total Total
Total Peak Runoff
Precip Runon Evap Infil Runoff
Runoff Runoff Coeff
Subcatchment in in in in in
10^6 gal CFS
------------------------------------------------------------------------------
--------------------------
BASIN_BYPASS 649.73 0.00 0.00 217.18 436.97
6.53 0.65 0.673
DEV_A 649.73 0.00 0.00 137.36 518.14
16.88 1.43 0.797
******************
Node Depth Summary
******************
---------------------------------------------------------------------
Average Maximum Maximum Time of Max
Depth Depth HGL Occurrence
Node Type Feet Feet Feet days hr:min
---------------------------------------------------------------------
PC-1 OUTFALL 0.00 0.00 0.00 0 00:00
BASIN STORAGE 0.01 4.82 4.82 19902 09:00
*******************
Node Inflow Summary
*******************
------------------------------------------------------------------------------
-------
Maximum Maximum Lateral
Total
Lateral Total Time of Max Inflow
Inflow
Inflow Inflow Occurrence Volume
Volume
Node Type CFS CFS days hr:min 10^6 gal
10^6 gal
------------------------------------------------------------------------------
-------
PC-1 OUTFALL 0.65 2.08 19902 09:00 6.526
23.406
BASIN STORAGE 1.43 1.43 19902 09:00 16.883
16.883
Page 2
Post_Dev_Final
**********************
Node Surcharge Summary
**********************
Surcharging occurs when water rises above the top of the highest conduit.
---------------------------------------------------------------------
Max. Height Min. Depth
Hours Above Crown Below Rim
Node Type Surcharged Feet Feet
---------------------------------------------------------------------
BASIN STORAGE 499263.02 4.825 0.175
*********************
Node Flooding Summary
*********************
No nodes were flooded.
**********************
Storage Volume Summary
**********************
------------------------------------------------------------------------------
--------------
Average Avg E&I Maximum Max Time
of Max Maximum
Volume Pcnt Pcnt Volume Pcnt
Occurrence Outflow
Storage Unit 1000 ft3 Full Loss 1000 ft3 Full days
hr:min CFS
------------------------------------------------------------------------------
--------------
BASIN 0.002 0 0 1.551 99 19902
09:00 1.43
***********************
Outfall Loading Summary
***********************
-----------------------------------------------------------
Flow Avg. Max. Total
Freq. Flow Flow Volume
Outfall Node Pcnt. CFS CFS 10^6 gal
-----------------------------------------------------------
PC-1 2.69 0.06 2.08 23.406
-----------------------------------------------------------
System 2.69 0.06 2.08 23.406
********************
Link Flow Summary
********************
-----------------------------------------------------------------------------
Maximum Time of Max Maximum Max/
Max/
|Flow| Occurrence |Veloc| Full
Full
Link Type CFS days hr:min ft/sec Flow
Depth
Page 3
Post_Dev_Final
-----------------------------------------------------------------------------
3 DUMMY 1.43 19902 09:00
*************************
Conduit Surcharge Summary
*************************
No conduits were surcharged.
Analysis begun on: Wed May 30 13:24:10 2012
Analysis ended on: Wed May 30 13:24:36 2012
Total elapsed time: 00:00:26
Page 4