Subject: Mt. San Antonio College- Measure RR Updated Hydrology Study

Transcription

1 To: Cc: Mike Klein Mt. San Antonio College Sidney Lindmark, AICP Mt SAC Environmental Consultant From: Alysen Weiland, PE - Psomas Date: May 6, 2016 Subject: Mt. San Antonio College- Measure RR Updated Hydrology Study As part of the campuswide stormwater analysis, Psomas has prepared a concept level hydrology study to reflect the Mount San Antonio College (Mt. SAC) Measure RR built-out condition. Mt. SAC s diverse uses include general college buildings, agricultural facilities and athletic facilities. Psomas has reviewed and incorporated the Measure RR project site and grading plans for the following projects either under construction or in design: 1. Food Services Building (complete) 2. Physical Education Project Phase 1 (currently under DSA review) 3. Building 12 (complete) 4. Building 4 (complete) 5. Building 46 (complete) 6. Parking Lot M (currently under construction) 7. Major Grading (Athletic Complex Hill) (Complete) 8. Business and Computer Technology Center (currently under construction) 9. Student Success Center (complete) 10. Design Technology Center (complete) The site conditions consist of approximately 60 buildings, parking lots, roads, a new athletic complex (Physical Education Project Phase 1), and undeveloped hill terrain, all spread across 300 acres. The site varies in slope from 1% to 13%. Elevation ranges from approximately 850 to 660 feet above mean sea level. In the existing condition storm water runoff predominantly drains to the south west and is gathered by multiple storm drains catch basins/inlets and collected into 5 main public storm drain lines that ultimately discharge out into two creeks. The project site is located on Los Angeles County s San Dimas isohyet map. The 50-year, 24-hour isohyet is 6.9 in, (See Appendix A). The site s soil type is identified as Type 2, 16, 17 (see Appendix A). METHODOLOGY Drainage calculations follow the methodology outlined in the Los Angeles County Department of Public Works Hydrology Manual. The Rational Method was used in this study to determine onsite flows using the County provided HydroCalc program. As described in the Hydrology Manual for Los Angeles County, discharge was computed using the following steps. 1. On-site drainage areas were determined by a review of the topographic information.

2 Page 2 of 8 May 6, MTS Rainfall data was determined using the LACDPW Isohyetal Maps for a 50-Year 24-Hour storm (see Appendix A). 3. Soils data was found for the project site. (Appendix A) 4. The Los Angeles County Department of Public Works HydroCalc computer program was used for Modified Rational Method calculations to find values for Time of Concentration, Intensity (see Appendix B). 5. Flows were calculated for each drainage area using Q = CiA Where: Q is the design runoff (cfs) C is the runoff coefficient I is the intensity (in/hr) A is the drainage area (ac) MEASURE RR EPT HYDROLOGY ANALYSIS The hydrologic analysis was performed by studying five major areas within the project site. Within Mt Sac, there are four existing public storm drain line and a creek that serve as 5 major discharge points. The areas were determined by dividing the project site into its own individual section according to which public storm drain line (A, B, C, D) the rainfall was discharging into. The 4 public storm drain lines and snow creek are identified in the Hydrology Map. The 5 areas were then sub-divided to study flow paths lengths and flow path slopes. The average imperviousness (C-value) was determined for each sub-drainage area and from all of the values that were obtained we determined an accurate discharge values using HydroCalc. The following table and attached Exhibit 2 summarize the results of the Measure RR 25-year hydrology analysis.

3 Page 3 of 8 May 6, MTS Table 1 Measure RR 25-Year Overall Hydrology Summary Sub-Area Area (AC) Length (ft) Slope (ft/ft) C Tc (min) 1-A B C D Q (cfs) 1-E Subarea 1 Total A B C Subarea 2 Total A B C D Subarea 3 Total A B C D E F G H I J Subarea 4 Total A B C D E F G Subarea 5 Total

4 Page 4 of 8 May 6, MTS HYDROLOGY COMPARISON A hydrology comparison between the 2012 Utility Infrastructure Master Plan and the Measure RR build out can be found in the following table. Table 2 Hydrology Comparison Between 2012 Utility Infrastructure Master Plan Conditions and Measure RR Build Out Conditions Utility Infrastructure Master Plan 2012 Line Area (Ac) Q25 (cfs) Measure RR Difference Percent Change Area (Ac) LINE A % 15.4% LINE B % 1.3% LINE C % 6.6% LINE D % 45.4% Total % 13.9% Q25 (cfs) Area (Ac) Q25 (cfs) Area (Ac) Q25 (cfs) A detailed breakdown of the hydrology comparison can be found in Appendix C. Reference Exhibits 1, 2, and 3 for the corresponding Hydrology Maps. The calculations show that the areas tributary to Line A and Line D have the greatest increase in the 25-year storm flows. Line A The subareas 1-A, 11-B, and 4-C from the Utility Infrastructure Master Plan showed the largest increase in the 25-Year design frequency flow rates (Q25) from tributary Measure RR and Farm Precinct subareas. However, no new development occurred in these areas between 2012 and Measure RR Conditions. The differences may be derived from varying hydrology methods, including different subareas sizes and boundaries between the two studies (e.g. Measure RR and Farm Precinct studies included additional subareas). Line D The Utility Infrastructure Master Plan subarea 1-A showed the greatest increase in Q25 the most when compared to the Measure RR analysis. The Food Services building is the only Measure RR new development in this area and should not have increased the runoff volume by the amount indicated in the calculations. The difference may have to do with varying hydrology methods, including increased subareas between the studies (e.g. Measure RR study included additional subareas.) For the purpose of the Mt. SAC Supplemental Environmental Impact Report (SEIR), it may be helpful to analyze the difference in conditions within these subareas in order to provide site specific hydrology analysis for the 2012 conditions using the same subareas and methodology as was employed for the Measure RR conditions study.

5 Page 5 of 8 May 6, MTS IMPERVIOUS AREA At completion of the Measure RR implementation, the impervious area is expected to increase by approximately 20 acres, which is roughly 5% of the entire campus, including the Farm Precinct. A majority of the increase of impervious area is a result of Parking Lot M and the Physical Education Project Phase 1, as shown in the following table. Building Name Area (acres) Difference in Impervious Area (Acres) 1. Food Service Physical Education Project Phase Building Building Building Parking Lot M Major Grading (Athletic Complex Hill) Business and Computer Technology Center Student Success Center Design Technology Center Total 19.76

6 Page 6 of 8 May 6, MTS APPENDIX A Appendix A LACDPW Isohyet/25-Year 24-hr Rainfall/Soils Information

7 -117º 52' 30'' -- BALDWIN PARK 1-H1.21 W 34º 07' 30'' N S E DPA SOIL CLASSIFICATION AREA INCHES OF RAINFALL DEBRIS POTENTIAL AREA DPA GLENDORA 1-H1.32 DPA DPA YORBA LINDA 1-H DPA Miles 25-YEAR 24-HOUR ISOHYET REDUCTION FACTOR: YEAR 24-HOUR ISOHYET REDUCTION FACTOR: SAN DIMAS 50-YEAR 24-HOUR ISOHYET H1.22 DPA º 00' 00'' ONTARIO 1-H º 45' 00''

8 Page 7 of 8 May 6, MTS APPENDIX B Appendix B Overall Existing Hydrology Results and Hydrographs

9 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 1-A.pdf Subarea ID 1-A Area (ac) 12.8 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 17.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

10 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 1-B.pdf Subarea ID 1-B Area (ac) 2.9 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.91 Soil Type 16 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 6.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

11 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 1-C.pdf Subarea ID 1-C Area (ac) 4.89 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 7.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

12 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 1-D.pdf Subarea ID 1-D Area (ac) 6.9 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 7.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

13 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 1-E.pdf Subarea ID 1-E Area (ac) 5.6 Flow Path Length (ft) Flow Path Slope (vft/hft) 0.03 Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 7.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

14 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 2-A.pdf Subarea ID 2-A Area (ac) 8.2 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.91 Soil Type 17 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 11.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

15 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 2-B.pdf Subarea ID 2-B Area (ac) 3.3 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.91 Soil Type 17 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 6.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

16 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 2-C.pdf Subarea ID 2-C Area (ac) 3.4 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.91 Soil Type 17 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 8.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

17 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 3-A.pdf Subarea ID 3-A Area (ac) 27.3 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 15.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

18 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 3-B.pdf Subarea ID 3-B Area (ac) 26.2 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 12.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

19 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 3-C.pdf Subarea ID 3-C Area (ac) 5.8 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 10.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

20 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 3-D.pdf Subarea ID 3-D Area (ac) 4.13 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 15.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

21 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 4-A.pdf Subarea ID 4-A Area (ac) 8.1 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.91 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 8.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

22 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 4-B.pdf Subarea ID 4-B Area (ac) 6.2 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.91 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 10.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

23 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 4-C.pdf Subarea ID 4-C Area (ac) 4.8 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.85 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 8.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

24 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 4-D.pdf Subarea ID 4-D Area (ac) 14.5 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.66 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 15.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

25 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 4-E.pdf Subarea ID 4-E Area (ac) 23.2 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.42 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 13.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

26 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 4-F.pdf Subarea ID 4-F Area (ac) 20.9 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.66 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 15.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

27 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 4-G.pdf Subarea ID 4-G Area (ac) 9.1 Flow Path Length (ft) Flow Path Slope (vft/hft) 0.13 Percent Impervious 0.25 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 7.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

28 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 4-H.pdf Subarea ID 4-H Area (ac) 16.0 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.25 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 10.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

29 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 4-I.pdf Subarea ID 4-I Area (ac) 41.2 Flow Path Length (ft) Flow Path Slope (vft/hft) 0.12 Percent Impervious 0.25 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 10.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

30 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 4-J.pdf Subarea ID 4-J Area (ac) 2.79 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.85 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 15.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

31 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 5-A.pdf Subarea ID 5-A Area (ac) 32.1 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.42 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 17.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

32 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 5-B.pdf Subarea ID 5-B Area (ac) 7.82 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.25 Soil Type 17 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 10.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

33 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 5-C.pdf Subarea ID 5-C Area (ac) 4.6 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.25 Soil Type 17 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 10.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

34 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 5-D.pdf Subarea ID 5-D Area (ac) 10.5 Flow Path Length (ft) Flow Path Slope (vft/hft) Percent Impervious 0.25 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 11.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

35 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 5-E.pdf Subarea ID 5-E Area (ac) 6.3 Flow Path Length (ft) Flow Path Slope (vft/hft) 0.01 Percent Impervious 0.58 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 11.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

36 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 5-F.pdf Subarea ID 5-F Area (ac) 11.5 Flow Path Length (ft) Flow Path Slope (vft/hft) 0.01 Percent Impervious 0.58 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 12.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

37 File location: W:/Mt_SAC//ENGR/CALCS/HydroCalcs/25 year/ - 5-G.pdf Subarea ID 5-G Area (ac) 2.8 Flow Path Length (ft) Flow Path Slope (vft/hft) 0.02 Percent Impervious 0.85 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 7.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

38 Page 8 of 8 May 6, MTS APPENDIX C Appendix C Hydrology Comparison Breakdown and Exhibits

39 HYDROLOGY COMPARISON BETWEEN 2012 UTILITY INFRASTRUCTURE MASTER PLAN CONDITIONS AND MEASURE RR BUILD OUT CONDITIONS (25-YEAR DESIGN FREQUENCY) MEASURE RR CONDITIONS Exhibit 1 Utility Infrastructure Master Plan (UIMP) (2012) Exhibit 3 Farm Precinct Exhibit 2 Hydrology Map - Overall Total Measure RR Conditions Difference Between Measure RR Conditions and UIMP (2015) 2016 Subarea Area (ac) Q25 (cfs) Subarea Area (ac) Q25 (cfs) Subarea Area (ac) Q25 (cfs) Area (ac) Q25 (cfs) Area (ac) Q25 (cfs) 4-A B A B C C Total E A A Total D B D Total LINE A B C C C Total D A J Total B F Total B E G Total B H I Total Total Area and Flow In Line A A B Total LINE B 2-A D Total A A Total A A Total Total Area and Flow In Line B LINE C 2-A B C Total Total Area and Flow In Line C A B A C D E Total Total Area and Flow In Line D LINE D Notes: 1-A Measure RR subarea 4-I flow path and tributary area extends outside of study limit. For the purpose of this comparison, only onsite Q was taken into consideration. See attached calculation for comparable onsite Q only. 2. Measure RR area 3-C is tributary to Line B. However, 2012 UIMP shows it tributary to Line A. For the purpose of this comparison, 3-C is shown tributary to Line A. 3. Measure RR areas 5-B, 5-C, 5-D, 5-E, 5-F and 5-G omitted from Hydrology Comparison. 4. Farm Precinct area D-3 was omitted from Hydrology Comparison since it is outside the project study.

40 File location: W:/Mt_SAC/1MTS013200/ENGR/CALCS/1MTS I.pdf 1MTS Subarea ID 4-I Area (ac) 12.7 Flow Path Length (ft) Flow Path Slope (vft/hft) 0.05 Percent Impervious 0.25 Soil Type 2 Peak Intensity (in/hr) Undeveloped Runoff Coefficient (Cu) Developed Runoff Coefficient (Cd) Time of Concentration (min) 7.0 Clear Peak Flow Rate (cfs) Burned Peak Flow Rate (cfs) Hr Clear Runoff Volume (ac-ft) Hr Clear Runoff Volume (cu-ft)

41 Utility Infrastructure Master Plan Figure 2b - Existing Utility Map - Hydrology Distribution AREA DISCHARGE TO GRAND AVENUE VIA LINE D AREA DISCHARGE TO TEMPLE AVENUE VIA LINE C AREA DISCHARGE TO MT SAC WAY VIA LINE B AREA DISCHARGE TO SERVICE ROAD VIA LINE A AREA DISCHARGE TO SNOW CREEK ADJACENT TO GRAND AVE. WATERSHED BOUNDARY SUBAREA-BOUNDARY EXISTING STORM DRAIN FLOWPATH SUBAREA DISCHARGE POINT > CONFLUENCE POINT CUMULATIVE PEAK FLOW RATE, Q TOTAL TRIBUTARY AREA AREA PEAK FLOW RATE, Q AREA (AC.) HYDROLOGIC INFORMATION SOIL TYPE: 000,016, YEAR 24-HR ISOHYET : 6.8 IN. 0' Mt. San Antonio College 1100 N. Grand Ave. Walnut, CA Mt. San Antonio College P2S Engineering, Inc. 200' 400' EXHIBIT 1 UTILITY INFRASTRUCTURE MASTER PLAN (2012) (25 - YEAR RAINFALL FREQUENCY FIGURE 2b - EXISTING UTILITY MAP - HYDROLOGY DISTRIBUTION Chapter 2 Storm Drain System 2 8

42 HYDROLOGIC INFORMATION OFFSITE Q25=420.0 cfs PER CITY OF WALNUT IMPROVEMENT PLANS FOR TRACT & TRACT AND M.T.D ' S= S= L= ' L=13 5' 30 L= CFS 4.13AC 51 3-D L=23 86' 60 ' S = S= ' 36.0 S=0 L= L= ' 38 0 S= L= ' S=0. L= STOP GE LDIN BUI STORM DRAIN ' S = FLOWPATH CFS 16.0AC 4-I BENCH S= CFS 12.7AC UD 5-F CFS 11.5AC H 36 ABAND L=600' 3 =0.0 ' S CFS 2.8AC G 725 L= L=1235' S= L= WATERSHED BOUNDARY SUBAREA-BOUNDARY BENCH OFFSITE Q G FIRE LANE CFS 6.3AC 770 PUBLIC STORM DRAIN LINE CFS 9.1AC E CFS 20.9AC > > L=975' S= CFS 10.5AC ND. 5-D ABA ' S=0.0 L= F LANE CFS 23.2 AC FIRE D S=0 4-E TB TB TB ' YIELD L= YIELD PUBLIC LINE A 740 S= 0 AREA 5 DISCHARGE TO SNOW CREEK ADJACENT TO GRAND AVE C L CFS =109 6' 4.6AC TB TB TB CFS 7.82AC OFFSITE Q CFS 14.5AC CFS 32.1AC PUBLIC LINE B B D 5-A ' S= J 5.37 CFS 2.79AC L= =0.0 ' S CFS 3.4AC C 41 L=17 AREA 4 DISCHARGE TO SERVICE ROAD VIA LINE A L= 9 L= CFS 5.8AC UD UD UD UD UD L=861' S= S=0.043 L=1465' S2= L= ' C S= L=622' S= L=783' S=0 765 B-D S=0 776' 33 =0.0 ' S S= L=708' L=1013' S= CFS 26.2AC GB D CFS 4.8AC GB 773-GB D YEIL D C B PUBLIC LINE C A CFS 8.2AC R GB GB 785 RD CFS 27.3AC AREA 3 DISCHARGE TO MT SAC WAY VIA LINE B CFS 3.3AC B A CFS AC E CFS 6.2AC D CFS 6.9AC AREA 2 DISCHARGE TO TEMPLE AVENUE VIA LINE C RD UD UD. 24 RD 18 UD B BAND PUBLIC LINE D A CFS 8.1AC C CFS 4.9AC A 8.63 CFS 2.9AC S 1-B D CFS 12.8AC STOP 34 1-A AREA 1 DISCHARGE TO GRAND AVENUE VIA LINE D 754 S=0.024 L=2723' SOIL TYPE: 002,016, YEAR 24-HR ISOHYET : 6.9 IN BENCH L=783.9' S=0.05 OFFSITE Q Flow path and tributary area extends outside of study limits. Total Flow Length; 1877' Total Slope: 0.12 Total Area: 41.2 AC Total Q25:94.05 CFS AREA 5-2A 22 CFS 0.4 AC PEAK FLOW RATE,25Q AREA (AC.) UN-ASSIGNED AREA Area north of the project limits drains offsite and does not impact hydrology study MT. SAN ANTONIO COLLEGE SUBAREA DISCHARGE POINT EXHIBIT 2 HYDROLOGY MAP - OVERALL MEASURE RR (2016) (25-YEAR RAINFALL 11X17 5/6/2016

43 DECK DECK STAIRS DECK TANK DECK TANK DECK TANK DECK TANK TANK DECK DECK TANK MISC DECK MISC TANK DECK DECK DECK ASPH TANK PIPE TANK DRAINAGE BASIN COLOR VARIES FLOW PATH LEGEND > EXISTING STORM DRAIN LINE PROPERTY LINE BASIN B-1 AREA = 5.02 AC. C = 0.25 Q = CFS 25 BASIN C-2 AREA = AC. C = 0.08 Q = CFS 25 BASIN D-2 AREA = AC. C = 0.01 Q = CFS 25 BASIN D-3 AREA = AC. C = 0.01 Q = CFS 25 EXISTING DIRT ROAD BASIN BASIN SUMMARY AREA (AC) Q25 (CFS) EDINGER WAY BONITA DRIVE BONITA DRIVE 36 BASIN B-2 AREA = AC. C = 0.17 Q = CFS 25 BASIN A-1 AREA = 5.98 AC. C = 0.87 Q = 14.7 CFS 25 BASIN C-1 AREA = 4.99 AC. C = 0.22 Q = CFS 25 BASIN E-1 AREA = 8.00 AC. C = 0.65 Q = CFS 25 MT. SAN ANTONIO COLLEGE WEST TEMPLE AVE. BASIN D-1 AREA = AC. C = 0.01 Q = CFS ' 200' 0' 400' 800' GRAPHIC SCALE: 11X17 A SUBAREA TOTAL B B SUBAREA TOTAL C C SUBAREA TOTAL D D D SUBAREA TOTAL E SUBAREA TOTAL TOTAL EXHIBIT 3 HYDROLOGY MAP - OVERALL EXISTING FARM PRECINCT (2015) (25-YEAR RAINFALL FREQUENCY) 5/6/2016 Plotted - 5/6/2016 2:08:01 PM :: Saved - 5/4/ :04:03 PM :: W:\Mt_SAC\1MTS013200\ENGR\SHEETS\MSAC-01-Exist Hydro.dwg :: tina.tse