MENIFEE VALLEY CAMPUS MASTER PLAN FINAL EIR MT. SAN JACINTO COMMUNITY COLLEGE DISTRICT Appendix Appendix B. Storm Drain System Data June 2017
MENIFEE VALLEY CAMPUS MASTER PLAN FINAL EIR MT. SAN JACINTO COMMUNITY COLLEGE DISTRICT Appendix This page intentionally left blank. PlaceWorks
= Storm Drain System The campus is served by a private on-site storm drainage system consisting of a series of pipes ranging between 4 and 36 in diameter that collect runoff from building roof drains and site area drains. The storm drainage system ultimately ties into an existing 36 storm drain main in La Piedra Road at the northeast end of the campus which drains to a lake northeast of the site, and ultimately to Salt Creek. The proposed on-site storm drainage system shall piggyback off the existing system, and shall be designed in accordance with the requirements of the City of Menifee as well as the Riverside County Flood Control and Water Conservation District s Hydrology Manual and Standard Drawings. The new storm drain pipes will gravity flow to bioretention basins (which will act as both detention basins and water quality BMPs), then ultimately to the existing storm drainage system. Proposed building roof drains and site area drains shall utilize PVC or HDPE pipe. As requested by the City of Menifee, a WQMP (Water Quality Management Plan) for Master Planning is being developed in conjunction with the DEIR. The purpose of the WQMP is to provide supporting studies and calculations indicating whether post-development flows might adversely impact existing receiving facilities, and if mitigation measures are required. The WQMP includes a drainage study analyzing the anticipated post-development flows and comparing to pre-development flows. Should post-development flows exceed pre-development flows, mitigation measures will be required on-site to restrict excess runoff. A summary of the Drainage Study is as follows: Sizing of storm drainage piping is based on post-development 100-year peak flows as determined using the Rational Method in accordance with Riverside County Flood Control and Water Conservation District s Hydrology Manual. The WinTR-55 hydrology modeling program is also used to compare postdevelopment vs. pre-development flows. The difference in runoff amount will be mitigated by the detention characteristics of the proposed bioretention basins. The WinTR-55 hydrology program, developed by the US Department of Agriculture, assumes the following storm data per NOAA Atlas 14, Volume 6, for the 24-hour storm in Menifee: NOAA Atlas 14, Volume 6 for the 24-hour storm Rainfall Return Period (years): 2 5 10 25 50 100 200 Rainfall Amount (inches): 2.08 2.79 3.37 4.17 4.80 5.45 6.13 The following Runoff Index Numbers were assumed for the following cover types: Runoff Index Numbers for Pervious Areas Cover Type: Soil Group: A B C D Commercial Landscaping (good quality): 32 56 69 75 Field, Turf (good quality): 39 61 74 80 Undeveloped Natural Grass, Annual (fair quality): 50 69 79 84 Gravel: 76 85 89 91 Developed Commercial (average 85% impervious): 89 92 94 95 In all cases, soil group D is assumed. Since the project proposes to utilize the three existing off-site discharge points, the site is divided into three sheds (A, B and C). See attached shed maps.
The increase in storm water runoff is primarily due to the increase in impervious area. Table 1, below, presents the anticipated increase in impervious area at full-buildout of the campus for the three sheds as well as the overall site: Table 1: Summary of Anticipated Increase of Impervious Area Shed Pre-Development Shed Tributary Area Pre-Development Impervious Area (Percentage) Post-Development Shed Tributary Area at Full-Buildout Page 2 Post-Development Impervious Area (Percentage) at Full-Buildout Shed A 46.7 ac 27.0 ac (57.8%) 50.9 ac 36.3 ac (71.3%) Shed B 4.0 ac 0.2 ac (6.3%) 4.3 ac 3.3 ac (75.4%) Shed C 28.2 ac 4.1 ac (14.6%) 23.7 ac 14.7 ac (62.3%) Overall Site 78.9 ac 31.3 ac (39.7%) 78.9 ac 54.3 ac (68.8%) Table 2, below, summarizes the peak flows at the downstream outlet locations for sheds A, B, and C for the 100-year storm events: Table 2: Summary of Peak Storm Water Flows Shed Pre-Development Shed Tributary Area Pre-Development 100-Year Peak Flow Post-Development Shed Tributary Area at Full-Buildout Post-Development 100-Year Peak Flow Shed A 46.7 ac 42.2 cfs 50.9 ac 49.1 cfs Shed B 4.0 ac 3.5 cfs 4.3 ac 4.9 cfs Shed C 28.2 ac 20.5 cfs 23.7 ac 25.2 cfs Referring to the WinTR-55 program outputs on the following pages, the required detention volumes are estimated as follows: Shed A (Post-Dev Runoff Depth) (Pre-Dev Runoff Depth) x Shed Area = Detention Volume (4.204 inches 4.178 inches) x 50.94 acres = 0.11 acre-ft, or 4,800 cubic feet Shed B (Post-Dev Runoff Depth) (Pre-Dev Runoff Depth) x Shed Area = Detention Volume (4.299 inches 3.781 inches) x 4.34 acres = 0.19 acre-ft, or 8,200 cubic feet Shed C (Post-Dev Runoff Depth) (Pre-Dev Runoff Depth) x Shed Area = Detention Volume (4.097 inches 3.734 inches) x 23.65 acres = 0.72 acre-ft, or 31,200 cubic feet Total Site 4,800 + 8,200 + 31,200 = 44,200 cubic feet Referring to the section titled Water Quality, approximately 2.7 acres of bioretention basins are anticipated for the site. The basins will store water at select locations throughout the site at a depth of 6 inches each. This results in a total detention capacity of 2.7 ac x 43,560 sf/ac x 0.5 ft = 58,800 cubic feet which exceeds the required detention volume of 44, 200 cubic feet.
ALBION LANE ANTELOPE ROAD LA PIEDRA ROAD STORM OUTLET 'A' (N) PERFORMING ARTS STORM OUTLET 'B' STORM OUTLET 'C' LEGEND 1" = 200' STORM DRAIN EXHIBIT - PHASE 1 Menifee Valley Campus June 2017 Mt. San Jacinto Community College District 28237 La Piedra Road Menifee, CA 92584
ALBION LANE ANTELOPE ROAD LA PIEDRA ROAD STORM OUTLET 'A' (N) PERFORMING ARTS STORM OUTLET 'B' STORM OUTLET 'C' LEGEND 1" = 200' STORM DRAIN EXHIBIT - FULL BUILDOUT Menifee Valley Campus June 2017 Mt. San Jacinto Community College District 28237 La Piedra Road Menifee, CA 92584
ANTELOPE ROAD LEGEND LA PIEDRA ROAD STORM OUTLET 'A' STORM OUTLET 'B' SHED A1.1 STORM OUTLET 'C' SHED A1.3 SHED AREA = 10.67 ac LANDSCAPE = 2.61 ac SHED A1.6 SHED AREA = 9.76 ac LANDSCAPE = 1.69 ac SHED A1.2 SHED AREA = 3.61 ac LANDSCAPE = 1.28 ac SHED A1.4 SHED AREA = 1.56 ac LANDSCAPE = 0.58 ac SHED A1.5 SHED AREA = 5.84 ac LANDSCAPE = 1.24 ac SHED AREA =2.73 ac LANDSCAPE =0.73 ac SHED B1.1 SHED AREA = 4.02 ac LANDSCAPE = 0.01 ac UNDEVELOPED = 3.54 ac GRAVEL = 0.22 ac SHED C1.2 SHED AREA = 21.00 ac UNDEVELOPED = 17.17 ac ATHLETIC FIELD = 3.70 ac SHED C1.1 SHED AREA = 7.16 ac LANDSCAPE = 1.24 ac UNDEVELOPED = 1.71 ac FIELD = 0.05 GRAVEL = 0.19 ac DRAINAGE STUDY SHED MAP - PRE DEVELOPMENT Menifee Valley Campus Mt. San Jacinto Community College District 28237 La Piedra Road Menifee, CA 92584 June 2017 SHED A1.7 SHED AREA = 12.57 ac UNDEVELOPED = 11.55 ac 1" = 200' ALBION LANE
LA PIEDRA ROAD REACH 0-1 REACH 2-3 REACH 1-2 SHED A1.1 STORM OUTLET 'A' STORM OUTLET 'B' REACH 0-1 STORM OUTLET 'C' ANTELOPE ROAD SHED A1.3 SHED AREA = 10.67 ac LANDSCAPE = 2.61 ac SHED A1.6 SHED AREA = 9.76 ac LANDSCAPE = 1.69 ac REACH 6-7 SHED A1.2 SHED AREA = 3.61 ac LANDSCAPE = 1.28 ac SHED A1.4 SHED AREA = 1.56 ac LANDSCAPE = 0.58 ac REACH 5-6 SHED A1.5 SHED AREA = 5.84 ac LANDSCAPE = 1.24 ac SHED AREA =2.73 ac LANDSCAPE =0.73 ac REACH 4-5 REACH 1-4 SHED B1.1 SHED AREA = 4.02 ac LANDSCAPE = 0.01 ac UNDEVELOPED = 3.54 ac GRAVEL = 0.22 ac SHED C1.2 SHED AREA = 21.00 ac UNDEVELOPED = 17.17 ac ATHLETIC FIELD = 3.70 ac SHED C1.1 REACH 0-1 REACH 1-2 SHED AREA = 7.16 ac LANDSCAPE = 1.24 ac UNDEVELOPED = 1.71 ac FIELD = 0.05 GRAVEL = 0.19 ac TR-55 MODEL - PRE DEVELOPMENT Menifee Valley Campus Mt. San Jacinto Community College District 28237 La Piedra Road Menifee, CA 92584 June 2017 SHED A1.7 SHED AREA = 12.57 ac UNDEVELOPED = 11.55 ac 1" = 200' ALBION LANE
LEGEND STORM OUTLET 'A' LA PIEDRA ROAD STORM OUTLET 'B' STORM OUTLET 'C' SHED B2.1 SHED AREA = 3.38 ac LANDSCAPE = 0.84 ac SHED AREA = 4.35 ac LANDSCAPE = 1.07 ac SHED C2.2 SHED A2.3 SHED A2.4 SHED AREA = 10.50 ac LANDSCAPE = 1.91 ac SHED AREA = 1.85 ac LANDSCAPE = 1.02 ac SHED AREA = 1.57 ac LANDSCAPE = 0.49 ac SHED A2.6 SHED AREA = 2.92 ac LANDSCAPE = 0.55 ac SHED A2.5 ANTELOPE ROAD DRAINAGE STUDY SHED MAP - POST DEVELOPMENT Menifee Valley Campus SHED A2.2 SHED AREA =2.64 ac LANDSCAPE =1.18 ac SHED C2.1 SHED AREA = 2.38 ac LANDSCAPE = 0.40 ac SHED AREA = 6.00 ac LANDSCAPE = 1.67 ac SHED A2.8 SHED AREA = 8.41 ac LANDSCAPE = 2.38 ac SHED A2.7 SHED AREA = 3.16 ac LANDSCAPE = 1.10 ac SHED C2.3 SHED AREA = 6.94 ac LANDSCAPE = 1.42 ac ATHLETIC FIELD = 1.32 ac SHED A2.9 SHED AREA = 2.03 ac LANDSCAPE = 0.88 ac SHED C2.5 (N) PERFORMING ARTS SHED AREA = 1.26 ac LANDSCAPE = 0.31 ac Mt. San Jacinto Community College District 28237 La Piedra Road Menifee, CA 92584 SHED A2.1 June 2017 SHED C2.4 SHED A2.10 SHED AREA = 10.32 ac LANDSCAPE = 3.63 ac ALBION LANE SHED C2.6 SHED AREA = 5.19 ac LANDSCAPE = 1.49 ac SHED AREA = 6.03 ac LANDSCAPE = 1.09 ac ATHLETIC FIELD = 1.86 ac 1" = 200'
REACH 6-7 REACH 4-6 ANTELOPE ROAD SHED A2.3 SHED AREA = 10.50 ac LANDSCAPE = 1.91 ac LA PIEDRA ROAD SHED A2.8 SHED AREA = 8.41 ac LANDSCAPE = 2.38 ac SHED A2.4 REACH 0-1 REACH 2-3 REACH 1-2 SHED A2.2 SHED AREA = 3.38 ac LANDSCAPE = 0.84 ac SHED AREA = 1.57 ac LANDSCAPE = 0.49 ac SHED A2.5 SHED A2.9 SHED A2.1 SHED AREA =2.64 ac LANDSCAPE =1.18 ac REACH 4-5 SHED AREA = 6.00 ac LANDSCAPE = 1.67 ac SHED AREA = 2.03 ac LANDSCAPE = 0.88 ac REACH 7-8 REACH 1-4 SHED C2.5 SHED B2.1 SHED AREA = 4.35 ac LANDSCAPE = 1.07 ac SHED A2.7 SHED AREA = 3.16 ac LANDSCAPE = 1.10 ac SHED AREA = 1.26 ac LANDSCAPE = 0.31 ac STORM OUTLET 'A' STORM OUTLET 'B' SHED A2.6 REACH 0-1 SHED AREA = 2.92 ac LANDSCAPE = 0.55 ac SHED C2.2 SHED AREA = 1.85 ac LANDSCAPE = 1.02 ac SHED C2.3 SHED C2.1 SHED AREA = 2.38 ac LANDSCAPE = 0.40 ac SHED AREA = 6.94 ac LANDSCAPE = 1.42 ac ATHLETIC FIELD = 1.32 ac REACH 4-5 REACH 0-2 STORM OUTLET 'C' REACH 0-1 REACH 1-3 REACH 3-4 TR-55 MODEL - POST DEVELOPMENT Menifee Valley Campus Mt. San Jacinto Community College District 28237 La Piedra Road Menifee, CA 92584 June 2017 SHED C2.4 SHED A2.10 SHED C2.6 SHED AREA = 6.03 ac LANDSCAPE = 1.09 ac ATHLETIC FIELD = 1.86 ac SHED AREA = 10.32 ac LANDSCAPE = 3.63 ac SHED AREA = 5.19 ac LANDSCAPE = 1.49 ac 1" = 200' ALBION LANE
WinTR-55 Current Data Description --- Identification Data --- User: P. Herzer, LPA Date: 5/30/2017 Project: Menifee Master Planning Units: English SubTitle: Shed A, Pre Development Areal Units: Acres State: California County: Riverside Filename: C:\Users\pherzer\AppData\Roaming\WinTR-55\Menifee Shed A Pre.w55 --- Sub-Area Data --- Name Description Reach Area (ac) RCN Tc (hr) 10-Yr (cfs) 100-Yr (cfs) ------------------------------------------------------------------------------------------------------------------------------------------- Shed A1.1 Reach 0-1 2.73 90 0.081 1.64 3.08 Shed A1.2 Reach 1-2 3.61 88 0.098 1.98 3.87 Shed A1.3 Reach 2-3 10.67 90 0.454 5.71 10.79 Shed A1.4 Reach 1-4 1.56 88 0.103 0.85 1.67 Shed A1.5 Reach 4-5 5.83 91 0.130 3.65 6.73 Shed A1.6 Reach 5-6 9.76 91 0.168 6.08 11.20 Shed A1.7 Reach 6-7 12.57 85 0.752 4.47 9.50 Total area: 46.73 (ac) --- Storm Data -- Rainfall Depth by Rainfall Return Period 2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr 200-Yr (in) (in) (in) (in) (in) (in) (in) ---------------------------------------------------------------------------------------------- 2.08 2.79 3.37 4.17 4.80 5.45 6.13 Area or Drainage Rain Gage Runoff ----------------------- Peak Flow ------------------------ Reach Area ID or Amount Elevation Time Rate 10-Yr Rate 100-Yr Identifier (sq mi) Location (in) (ft) (min) (cfs) (cfs) OUTLET 0.073 4.178 34.04 21.92 42.17 WinTR-20 Version 1.10 Page 1 5/30/2017 12:38
WinTR-55 Current Data Description --- Identification Data --- User: P. Herzer, LPA Date: 5/30/2017 Project: Menifee Master Planning Units: English SubTitle: Shed A, Post Development Areal Units: Acres State: California County: Riverside Filename: C:\Users\pherzer\AppData\Roaming\WinTR-55\Menifee Shed A Post.w55 --- Sub-Area Data --- Name Description Reach Area (ac) RCN Tc (hr) 10-Yr (cfs) 100-Yr (cfs) ------------------------------------------------------------------------------------------------------------------------------------------- Shed A2.1 Reach 0-1 2.63 86 0.081 1.30 2.66 Shed A2.2 Reach 1-2 3.39 90 0.098 2.04 3.83 Shed A2.3 Reach 2-3 10.50 91 0.454 5.89 10.89 Shed A2.4 Reach 1-4 1.57 89 0.103 0.90 1.72 Shed A2.5 Reach 4-5 6.00 89 0.130 3.43 6.59 Shed A2.6 Reach 4-6 2.93 91 0.108 1.84 3.39 Shed A2.7 Reach 6-7 3.16 88 0.136 1.72 3.37 Shed A2.8 Reach 6-7 8.41 89 0.478 4.23 8.18 Shed A2.9 Reach 7-8 2.03 86 0.113 1.00 2.05 Shed A2.10 Reach 7-8 10.32 88 0.482 4.93 9.74 Total area: 50.94 (ac) --- Storm Data -- Rainfall Depth by Rainfall Return Period 2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr 200-Yr (in) (in) (in) (in) (in) (in) (in) ---------------------------------------------------------------------------------------------- 2.08 2.79 3.37 4.17 4.80 5.45 6.13 Area or Drainage Rain Gage Runoff ----------------------- Peak Flow ------------------------ Reach Area ID or Amount Elevation Time Rate 10-Yr Rate 100-Yr Identifier (sq mi) Location (in) (ft) (min) (cfs) (cfs) OUTLET 0.080 4.204 25.50 25.47 49.12 WinTR-20 Version 1.10 Page 1 5/30/2017 10:36
WinTR-55 Current Data Description --- Identification Data --- User: P. Herzer, LPA Date: 5/30/2017 Project: Menifee Master Planning Units: English SubTitle: Shed B, Pre Development Areal Units: Acres State: California County: Riverside Filename: C:\Users\pherzer\AppData\Roaming\WinTR-55\Menifee Shed B Pre.w55 --- Sub-Area Data --- Name Description Reach Area (ac) RCN Tc (hr) 10-Yr (cfs) 100-Yr (cfs) ------------------------------------------------------------------------------------------------------------------------------------------- Shed B1.1 Reach 0-1 4.02 85 0.463 1.86 3.89 Total area: 4.02 (ac) --- Storm Data -- Rainfall Depth by Rainfall Return Period 2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr 200-Yr (in) (in) (in) (in) (in) (in) (in) ---------------------------------------------------------------------------------------------- 2.08 2.79 3.37 4.17 4.80 5.45 6.13 Area or Drainage Rain Gage Runoff ----------------------- Peak Flow ------------------------ Reach Area ID or Amount Elevation Time Rate 10-Yr Rate 100-Yr Identifier (sq mi) Location (in) (ft) (min) (cfs) (cfs) OUTLET 0.006 3.781 27.78 1.65 3.49 WinTR-20 Version 1.10 Page 1 5/30/2017 01:59
WinTR-55 Current Data Description --- Identification Data --- User: P. Herzer, LPA Date: 5/30/2017 Project: Menifee Master Planning Units: English SubTitle: Shed B, Post Development Areal Units: Acres State: California County: Riverside Filename: C:\Users\pherzer\AppData\Roaming\WinTR-55\Menifee Shed B Post.w55 --- Sub-Area Data --- Name Description Reach Area (ac) RCN Tc (hr) 10-Yr (cfs) 100-Yr (cfs) ------------------------------------------------------------------------------------------------------------------------------------------- Shed B2.1 Reach 0-1 4.34 90 0.105 2.61 4.90 Total area: 4.34 (ac) --- Storm Data -- Rainfall Depth by Rainfall Return Period 2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr 200-Yr (in) (in) (in) (in) (in) (in) (in) ---------------------------------------------------------------------------------------------- 2.08 2.79 3.37 4.17 4.80 5.45 6.13 Area or Drainage Rain Gage Runoff ----------------------- Peak Flow ------------------------ Reach Area ID or Amount Elevation Time Rate 10-Yr Rate 100-Yr Identifier (sq mi) Location (in) (ft) (min) (cfs) (cfs) OUTLET 0.007 4.299 6.30 2.61 4.89 WinTR-20 Version 1.10 Page 1 5/30/2017 02:17
WinTR-55 Current Data Description --- Identification Data --- User: P. Herzer, LPA Date: 5/30/2017 Project: Menifee Master Planning Units: English SubTitle: Shed C, Pre Development Areal Units: Acres State: California County: Riverside Filename: C:\Users\pherzer\AppData\Roaming\WinTR-55\Menifee Shed C Pre.w55 --- Sub-Area Data --- Name Description Reach Area (ac) RCN Tc (hr) 10-Yr (cfs) 100-Yr (cfs) ------------------------------------------------------------------------------------------------------------------------------------------- Shed C1.1 Reach 0-1 7.15 89 0.081 4.11 7.86 Shed C1.2 Reach 1-2 21.00 83 0.633 7.02 15.65 Total area: 28.15 (ac) --- Storm Data -- Rainfall Depth by Rainfall Return Period 2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr 200-Yr (in) (in) (in) (in) (in) (in) (in) ---------------------------------------------------------------------------------------------- 2.08 2.79 3.37 4.17 4.80 5.45 6.13 Area or Drainage Rain Gage Runoff ----------------------- Peak Flow ------------------------ Reach Area ID or Amount Elevation Time Rate 10-Yr Rate 100-Yr Identifier (sq mi) Location (in) (ft) (min) (cfs) (cfs) OUTLET 0.044 3.734 39.30 9.59 20.54 WinTR-20 Version 1.10 Page 1 5/30/2017 02:36
WinTR-55 Current Data Description --- Identification Data --- User: P. Herzer, LPA Date: 5/30/2017 Project: Menifee Master Planning Units: English SubTitle: Shed C, Post Development Areal Units: Acres State: California County: Riverside Filename: C:\Users\pherzer\AppData\Roaming\WinTR-55\Menifee Shed C Post.w55 --- Sub-Area Data --- Name Description Reach Area (ac) RCN Tc (hr) 10-Yr (cfs) 100-Yr (cfs) ------------------------------------------------------------------------------------------------------------------------------------------- Shed C2.1 Reach 0-1 2.38 92 0.065 1.56 2.82 Shed C2.2 Reach 0-2 1.86 84 0.063 0.83 1.77 Shed C2.3 Reach 1-3 6.93 88 0.089 3.79 7.42 Shed C2.4 Reach 3-4 6.03 87 0.079 3.14 6.28 Shed C2.5 Reach 4-5 1.26 90 0.060 0.76 1.42 Shed C2.6 Reach 4-5 5.19 89 0.140 2.96 5.69 Total area: 23.65 (ac) --- Storm Data -- Rainfall Depth by Rainfall Return Period 2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr 200-Yr (in) (in) (in) (in) (in) (in) (in) ---------------------------------------------------------------------------------------------- 2.08 2.79 3.37 4.17 4.80 5.45 6.13 Area or Drainage Rain Gage Runoff ----------------------- Peak Flow ------------------------ Reach Area ID or Amount Elevation Time Rate 10-Yr Rate 100-Yr Identifier (sq mi) Location (in) (ft) (min) (cfs) (cfs) OUTLET 0.037 4.097 25.40 12.91 25.21 WinTR-20 Version 1.10 Page 1 5/30/2017 03:48