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

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.

Page 2 of 8 May 6, 2016 1MTS013200 2. 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.

Page 3 of 8 May 6, 2016 1MTS013200 Table 1 Measure RR 25-Year Overall Hydrology Summary Sub-Area Area (AC) Length (ft) Slope (ft/ft) C Tc (min) 1-A 12.8 2723 0.024 0.85 17 22.9 1-B 2.9 622 0.068 0.91 6 8.6 1-C 4.9 783 0.045 0.85 7 13.5 1-D 6.9 776 0.036 0.85 7 19.0 Q (cfs) 1-E 5.6 708 0.03 0.85 7 15.4 Subarea 1 Total 33.1 - - - - 79.4 2-A 8.2 1013 0.007 0.91 11 18.4 2-B 3.3 639 0.033 0.91 6 9.9 2-C 3.4 708 0.011 0.91 8 8.9 Subarea 2 Total 14.9 - - - - 37.2 3-A 27.3 2575 0.043 0.85 15 51.9 3-B 26.2 1875 0.059 0.85 12 55.5 3-C 5.8 1313 0.045 0.85 10 13.4 3-D 4.1 1741 0.013 0.85 15 7.8 Subarea 3 Total 63.4 - - - - 128.6 4-A 8.1 861 0.037 0.91 8 21.1 4-B 6.2 1465 0.043 0.91 10 14.5 4-C 4.8 1035 0.044 0.85 8 12.5 4-D 14.5 1812 0.012 0.66 15 27.6 4-E 23.2 1540 0.014 0.42 13 46.7 4-F 20.9 1929 0.016 0.66 15 39.7 4-G 9.1 1138 0.13 0.25 7 24.9 4-H 16 1648 0.092 0.25 10 36.5 4-I 12.7 783 0.05 0.89 7 34.9 4-J 2.8 1716 0.012 0.85 15 5.4 Subarea 4 Total 118.3 - - - - 263.8 5-A 32.1 2386 0.017 0.42 17 56.5 5-B 7.8 1074 0.022 0.25 10 18.0 5-C 4.6 1096 0.018 0.25 10 10.6 5-D 10.5 1448 0.039 0.25 11 22.8 5-E 6.3 975 0.010 0.58 11 13.9 5-F 11.5 1235 0.010 0.58 12 24.3 5-G 2.8 600 0.020 0.85 7 7.8 Subarea 5 Total 75.6 - - - - 153.9

Page 4 of 8 May 6, 2016 1MTS013200 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 215 439.3 220.5 506.8 5.5 67.5 2.6% 15.4% LINE B 88.1 169.5 89.7 171.7 1.6 2.2 1.8% 1.3% LINE C 15.1 34.9 14.9 37.2-0.2 2.3-1.3% 6.6% LINE D 32.6 54.6 33.1 79.4 0.5 24.8 1.5% 45.4% Total 350.8 698.3 358.2 795.1 7.4 96.8 2.1% 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.

Page 5 of 8 May 6, 2016 1MTS013200 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 1.50 0.68 2. Physical Education Project Phase 1 32.62 9.79 3. Building 12 2.61 0.26 4. Building 4 0.94 0.08 5. Building 46 0.90 0.00 6. Parking Lot M 9.43 8.68 7. Major Grading (Athletic Complex Hill) 24.00 0.00 8. Business and Computer Technology Center 5.76 0.58 9. Student Success Center 0.92-0.29 10. Design Technology Center 1.70 0.00 Total 19.76

Page 6 of 8 May 6, 2016 1MTS013200 APPENDIX A Appendix A LACDPW Isohyet/25-Year 24-hr Rainfall/Soils Information

-117º 52' 30'' -- BALDWIN PARK 1-H1.21 W 34º 07' 30'' -006 007 013 N S 006 007 013 006-007 006-017 002 089-002 002-017 002 003 014 013 017 E 015 002 017-017- 089 089 016 017 002 089 002 002-017- 016 7.2-017 DPA - 6-016 007 002 016 013 002 002 089 --016-002 SOIL CLASSIFICATION AREA INCHES OF RAINFALL DEBRIS POTENTIAL AREA -002 011 006 007 002 013 DPA - 7 002 002 003 006 002 GLENDORA 1-H1.32 DPA - 6 090 003-016- 002-017- 006 DPA - 7 090 002 003 002 007 013 003 016 002 007 0 ---016 089 YORBA LINDA 1-H1.12 003 7.2 013 017 6.8 7.0 006-7.4 6.6 090 003 016 003 006 007 012 012 003 DPA - 6 088-017- 003-016- 007 1 0 1 2 Miles 25-YEAR 24-HOUR ISOHYET REDUCTION FACTOR: 0.878 10-YEAR 24-HOUR ISOHYET REDUCTION FACTOR: 0.714 SAN DIMAS 50-YEAR 24-HOUR ISOHYET 6.4 012 089 007 007 007 002-007 002 016-006 006 1-H1.22 DPA - 2- ------ 007 017 007-------- 007 003 007 34º 00' 00'' 08 0130 - ONTARIO 1-H1.23-117º 45' 00''

Page 7 of 8 May 6, 2016 1MTS013200 APPENDIX B Appendix B Overall Existing Hydrology Results and Hydrographs

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) 2723.0 Flow Path Slope (vft/hft) 0.024 Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) 2.0335 Undeveloped Runoff Coefficient (Cu) 0.7609 Developed Runoff Coefficient (Cd) 0.8791 Time of Concentration (min) 17.0 Clear Peak Flow Rate (cfs) 22.8833 Burned Peak Flow Rate (cfs) 22.8833 24-Hr Clear Runoff Volume (ac-ft) 5.0934 24-Hr Clear Runoff Volume (cu-ft) 221869.8211

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) 622.0 Flow Path Slope (vft/hft) 0.068 Percent Impervious 0.91 Soil Type 16 Peak Intensity (in/hr) 3.3177 Undeveloped Runoff Coefficient (Cu) 0.8657 Developed Runoff Coefficient (Cd) 0.8969 Time of Concentration (min) 6.0 Clear Peak Flow Rate (cfs) 8.6294 Burned Peak Flow Rate (cfs) 8.6294 24-Hr Clear Runoff Volume (ac-ft) 1.2153 24-Hr Clear Runoff Volume (cu-ft) 52938.7926

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) 783.0 Flow Path Slope (vft/hft) 0.045 Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) 3.0858 Undeveloped Runoff Coefficient (Cu) 0.8538 Developed Runoff Coefficient (Cd) 0.8931 Time of Concentration (min) 7.0 Clear Peak Flow Rate (cfs) 13.476 Burned Peak Flow Rate (cfs) 13.476 24-Hr Clear Runoff Volume (ac-ft) 1.9464 24-Hr Clear Runoff Volume (cu-ft) 84785.4708

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) 776.0 Flow Path Slope (vft/hft) 0.036 Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) 3.0858 Undeveloped Runoff Coefficient (Cu) 0.8538 Developed Runoff Coefficient (Cd) 0.8931 Time of Concentration (min) 7.0 Clear Peak Flow Rate (cfs) 19.0152 Burned Peak Flow Rate (cfs) 19.0152 24-Hr Clear Runoff Volume (ac-ft) 2.7465 24-Hr Clear Runoff Volume (cu-ft) 119635.9404

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) 708.0 Flow Path Slope (vft/hft) 0.03 Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) 3.0858 Undeveloped Runoff Coefficient (Cu) 0.8538 Developed Runoff Coefficient (Cd) 0.8931 Time of Concentration (min) 7.0 Clear Peak Flow Rate (cfs) 15.4326 Burned Peak Flow Rate (cfs) 15.4326 24-Hr Clear Runoff Volume (ac-ft) 2.229 24-Hr Clear Runoff Volume (cu-ft) 97095.8357

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) 1013.0 Flow Path Slope (vft/hft) 0.007 Percent Impervious 0.91 Soil Type 17 Peak Intensity (in/hr) 2.4952 Undeveloped Runoff Coefficient (Cu) 0.8731 Developed Runoff Coefficient (Cd) 0.8976 Time of Concentration (min) 11.0 Clear Peak Flow Rate (cfs) 18.3651 Burned Peak Flow Rate (cfs) 18.3651 24-Hr Clear Runoff Volume (ac-ft) 3.4584 24-Hr Clear Runoff Volume (cu-ft) 150646.0569

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) 639.0 Flow Path Slope (vft/hft) 0.033 Percent Impervious 0.91 Soil Type 17 Peak Intensity (in/hr) 3.3177 Undeveloped Runoff Coefficient (Cu) 0.9047 Developed Runoff Coefficient (Cd) 0.9004 Time of Concentration (min) 6.0 Clear Peak Flow Rate (cfs) 9.8581 Burned Peak Flow Rate (cfs) 9.8581 24-Hr Clear Runoff Volume (ac-ft) 1.3918 24-Hr Clear Runoff Volume (cu-ft) 60626.9239

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) 708.0 Flow Path Slope (vft/hft) 0.011 Percent Impervious 0.91 Soil Type 17 Peak Intensity (in/hr) 2.8981 Undeveloped Runoff Coefficient (Cu) 0.8886 Developed Runoff Coefficient (Cd) 0.899 Time of Concentration (min) 8.0 Clear Peak Flow Rate (cfs) 8.858 Burned Peak Flow Rate (cfs) 8.858 24-Hr Clear Runoff Volume (ac-ft) 1.434 24-Hr Clear Runoff Volume (cu-ft) 62463.4363

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) 2575.0 Flow Path Slope (vft/hft) 0.043 Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) 2.1568 Undeveloped Runoff Coefficient (Cu) 0.7741 Developed Runoff Coefficient (Cd) 0.8811 Time of Concentration (min) 15.0 Clear Peak Flow Rate (cfs) 51.8793 Burned Peak Flow Rate (cfs) 51.8793 24-Hr Clear Runoff Volume (ac-ft) 10.8639 24-Hr Clear Runoff Volume (cu-ft) 473231.0065

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) 1875.0 Flow Path Slope (vft/hft) 0.059 Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) 2.3952 Undeveloped Runoff Coefficient (Cu) 0.7996 Developed Runoff Coefficient (Cd) 0.8849 Time of Concentration (min) 12.0 Clear Peak Flow Rate (cfs) 55.5341 Burned Peak Flow Rate (cfs) 55.5341 24-Hr Clear Runoff Volume (ac-ft) 10.427 24-Hr Clear Runoff Volume (cu-ft) 454200.8583

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) 1313.0 Flow Path Slope (vft/hft) 0.045 Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) 2.6095 Undeveloped Runoff Coefficient (Cu) 0.8192 Developed Runoff Coefficient (Cd) 0.8879 Time of Concentration (min) 10.0 Clear Peak Flow Rate (cfs) 13.4384 Burned Peak Flow Rate (cfs) 13.4384 24-Hr Clear Runoff Volume (ac-ft) 2.3084 24-Hr Clear Runoff Volume (cu-ft) 100554.857

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) 1742.0 Flow Path Slope (vft/hft) 0.013 Percent Impervious 0.85 Soil Type 16 Peak Intensity (in/hr) 2.1568 Undeveloped Runoff Coefficient (Cu) 0.7741 Developed Runoff Coefficient (Cd) 0.8811 Time of Concentration (min) 15.0 Clear Peak Flow Rate (cfs) 7.8484 Burned Peak Flow Rate (cfs) 7.8484 24-Hr Clear Runoff Volume (ac-ft) 1.6435 24-Hr Clear Runoff Volume (cu-ft) 71591.3574

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) 861.0 Flow Path Slope (vft/hft) 0.037 Percent Impervious 0.91 Soil Type 2 Peak Intensity (in/hr) 2.8981 Undeveloped Runoff Coefficient (Cu) 0.8792 Developed Runoff Coefficient (Cd) 0.8981 Time of Concentration (min) 8.0 Clear Peak Flow Rate (cfs) 21.083 Burned Peak Flow Rate (cfs) 21.083 24-Hr Clear Runoff Volume (ac-ft) 3.4717 24-Hr Clear Runoff Volume (cu-ft) 151225.2453

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) 1465.0 Flow Path Slope (vft/hft) 0.043 Percent Impervious 0.91 Soil Type 2 Peak Intensity (in/hr) 2.6095 Undeveloped Runoff Coefficient (Cu) 0.8664 Developed Runoff Coefficient (Cd) 0.897 Time of Concentration (min) 10.0 Clear Peak Flow Rate (cfs) 14.5123 Burned Peak Flow Rate (cfs) 14.5123 24-Hr Clear Runoff Volume (ac-ft) 2.6573 24-Hr Clear Runoff Volume (cu-ft) 115750.3007

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) 1035.0 Flow Path Slope (vft/hft) 0.044 Percent Impervious 0.85 Soil Type 2 Peak Intensity (in/hr) 2.8981 Undeveloped Runoff Coefficient (Cu) 0.8792 Developed Runoff Coefficient (Cd) 0.8969 Time of Concentration (min) 8.0 Clear Peak Flow Rate (cfs) 12.4762 Burned Peak Flow Rate (cfs) 12.4762 24-Hr Clear Runoff Volume (ac-ft) 1.9868 24-Hr Clear Runoff Volume (cu-ft) 86546.7989

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) 1812.0 Flow Path Slope (vft/hft) 0.012 Percent Impervious 0.66 Soil Type 2 Peak Intensity (in/hr) 2.1568 Undeveloped Runoff Coefficient (Cu) 0.8464 Developed Runoff Coefficient (Cd) 0.8818 Time of Concentration (min) 15.0 Clear Peak Flow Rate (cfs) 27.5755 Burned Peak Flow Rate (cfs) 27.5755 24-Hr Clear Runoff Volume (ac-ft) 5.327 24-Hr Clear Runoff Volume (cu-ft) 232044.1867

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) 1540.0 Flow Path Slope (vft/hft) 0.014 Percent Impervious 0.42 Soil Type 2 Peak Intensity (in/hr) 2.3068 Undeveloped Runoff Coefficient (Cu) 0.853 Developed Runoff Coefficient (Cd) 0.8727 Time of Concentration (min) 13.0 Clear Peak Flow Rate (cfs) 46.7075 Burned Peak Flow Rate (cfs) 46.7075 24-Hr Clear Runoff Volume (ac-ft) 7.1608 24-Hr Clear Runoff Volume (cu-ft) 311922.5943

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) 1929.0 Flow Path Slope (vft/hft) 0.016 Percent Impervious 0.66 Soil Type 2 Peak Intensity (in/hr) 2.1568 Undeveloped Runoff Coefficient (Cu) 0.8464 Developed Runoff Coefficient (Cd) 0.8818 Time of Concentration (min) 15.0 Clear Peak Flow Rate (cfs) 39.7467 Burned Peak Flow Rate (cfs) 39.7467 24-Hr Clear Runoff Volume (ac-ft) 7.6782 24-Hr Clear Runoff Volume (cu-ft) 334463.6898

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) 1138.0 Flow Path Slope (vft/hft) 0.13 Percent Impervious 0.25 Soil Type 2 Peak Intensity (in/hr) 3.0858 Undeveloped Runoff Coefficient (Cu) 0.8857 Developed Runoff Coefficient (Cd) 0.8893 Time of Concentration (min) 7.0 Clear Peak Flow Rate (cfs) 24.9723 Burned Peak Flow Rate (cfs) 24.9723 24-Hr Clear Runoff Volume (ac-ft) 2.4318 24-Hr Clear Runoff Volume (cu-ft) 105928.2608

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) 1648.0 Flow Path Slope (vft/hft) 0.092 Percent Impervious 0.25 Soil Type 2 Peak Intensity (in/hr) 2.6095 Undeveloped Runoff Coefficient (Cu) 0.8664 Developed Runoff Coefficient (Cd) 0.8748 Time of Concentration (min) 10.0 Clear Peak Flow Rate (cfs) 36.5252 Burned Peak Flow Rate (cfs) 36.5252 24-Hr Clear Runoff Volume (ac-ft) 4.2738 24-Hr Clear Runoff Volume (cu-ft) 186165.5661

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) 1877.0 Flow Path Slope (vft/hft) 0.12 Percent Impervious 0.25 Soil Type 2 Peak Intensity (in/hr) 2.6095 Undeveloped Runoff Coefficient (Cu) 0.8664 Developed Runoff Coefficient (Cd) 0.8748 Time of Concentration (min) 10.0 Clear Peak Flow Rate (cfs) 94.0524 Burned Peak Flow Rate (cfs) 94.0524 24-Hr Clear Runoff Volume (ac-ft) 11.005 24-Hr Clear Runoff Volume (cu-ft) 479376.3328

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) 1716.0 Flow Path Slope (vft/hft) 0.012 Percent Impervious 0.85 Soil Type 2 Peak Intensity (in/hr) 2.1568 Undeveloped Runoff Coefficient (Cu) 0.8464 Developed Runoff Coefficient (Cd) 0.892 Time of Concentration (min) 15.0 Clear Peak Flow Rate (cfs) 5.3672 Burned Peak Flow Rate (cfs) 5.3672 24-Hr Clear Runoff Volume (ac-ft) 1.1548 24-Hr Clear Runoff Volume (cu-ft) 50301.2023

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) 2386.0 Flow Path Slope (vft/hft) 0.017 Percent Impervious 0.42 Soil Type 2 Peak Intensity (in/hr) 2.0335 Undeveloped Runoff Coefficient (Cu) 0.8409 Developed Runoff Coefficient (Cd) 0.8657 Time of Concentration (min) 17.0 Clear Peak Flow Rate (cfs) 56.5125 Burned Peak Flow Rate (cfs) 56.5125 24-Hr Clear Runoff Volume (ac-ft) 9.9059 24-Hr Clear Runoff Volume (cu-ft) 431498.8286

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) 1074.0 Flow Path Slope (vft/hft) 0.022 Percent Impervious 0.25 Soil Type 17 Peak Intensity (in/hr) 2.6095 Undeveloped Runoff Coefficient (Cu) 0.8776 Developed Runoff Coefficient (Cd) 0.8832 Time of Concentration (min) 10.0 Clear Peak Flow Rate (cfs) 18.0226 Burned Peak Flow Rate (cfs) 18.0226 24-Hr Clear Runoff Volume (ac-ft) 1.6432 24-Hr Clear Runoff Volume (cu-ft) 71578.0756

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) 1096.0 Flow Path Slope (vft/hft) 0.018 Percent Impervious 0.25 Soil Type 17 Peak Intensity (in/hr) 2.6095 Undeveloped Runoff Coefficient (Cu) 0.8776 Developed Runoff Coefficient (Cd) 0.8832 Time of Concentration (min) 10.0 Clear Peak Flow Rate (cfs) 10.6015 Burned Peak Flow Rate (cfs) 10.6015 24-Hr Clear Runoff Volume (ac-ft) 0.9666 24-Hr Clear Runoff Volume (cu-ft) 42104.7503

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) 1448.0 Flow Path Slope (vft/hft) 0.039 Percent Impervious 0.25 Soil Type 2 Peak Intensity (in/hr) 2.4952 Undeveloped Runoff Coefficient (Cu) 0.8613 Developed Runoff Coefficient (Cd) 0.871 Time of Concentration (min) 11.0 Clear Peak Flow Rate (cfs) 22.8203 Burned Peak Flow Rate (cfs) 22.8203 24-Hr Clear Runoff Volume (ac-ft) 2.8044 24-Hr Clear Runoff Volume (cu-ft) 122159.1376

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) 975.0 Flow Path Slope (vft/hft) 0.01 Percent Impervious 0.58 Soil Type 2 Peak Intensity (in/hr) 2.4952 Undeveloped Runoff Coefficient (Cu) 0.8613 Developed Runoff Coefficient (Cd) 0.8838 Time of Concentration (min) 11.0 Clear Peak Flow Rate (cfs) 13.8927 Burned Peak Flow Rate (cfs) 13.8927 24-Hr Clear Runoff Volume (ac-ft) 2.1914 24-Hr Clear Runoff Volume (cu-ft) 95455.9437

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) 1235.0 Flow Path Slope (vft/hft) 0.01 Percent Impervious 0.58 Soil Type 2 Peak Intensity (in/hr) 2.3952 Undeveloped Runoff Coefficient (Cu) 0.8569 Developed Runoff Coefficient (Cd) 0.8819 Time of Concentration (min) 12.0 Clear Peak Flow Rate (cfs) 24.2923 Burned Peak Flow Rate (cfs) 24.2923 24-Hr Clear Runoff Volume (ac-ft) 4.0 24-Hr Clear Runoff Volume (cu-ft) 174238.9184

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) 600.0 Flow Path Slope (vft/hft) 0.02 Percent Impervious 0.85 Soil Type 2 Peak Intensity (in/hr) 3.0858 Undeveloped Runoff Coefficient (Cu) 0.8857 Developed Runoff Coefficient (Cd) 0.8979 Time of Concentration (min) 7.0 Clear Peak Flow Rate (cfs) 7.7577 Burned Peak Flow Rate (cfs) 7.7577 24-Hr Clear Runoff Volume (ac-ft) 1.159 24-Hr Clear Runoff Volume (cu-ft) 50486.6816

Page 8 of 8 May 6, 2016 1MTS013200 APPENDIX C Appendix C Hydrology Comparison Breakdown and Exhibits

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 8.1 21.1 4-B 6.2 14.5 1-A 28.6 56.6 B-1 5.0 12.9 4-C 4.8 12.5 3-C 5.8 13.4 Total 28.6 56.6 5.0 12.9 24.9 61.5 29.9 74.4 1.3 17.8 E-1 8.0 19.5 2-A 13.4 29.7 A-1 6.0 14.7 Total 13.4 29.7 14.0 34.2 14.0 34.2 0.6 4.5 D-2 16.3 37.0 3-B 22.2 44.0 D-1 13.6 37.1 Total 22.2 44.0 29.9 74.1 29.9 74.1 7.7 30.1 LINE A B-2 24.0 55.6 4-C 47.2 100.3 C-1 5.0 12.8 C-2 18.5 40.0 Total 47.2 100.3 47.5 108.4 47.5 108.4 0.3 8.1 4-D 14.5 27.6 7-A 19.8 33.9 4-J 2.8 5.4 Total 19.8 33.9 17.3 33.0 17.3 33.0-2.5-0.9 8-B 20.9 40.1 4-F 20.9 39.7 Total 20.9 40.1 20.9 39.7 20.9 39.7 0.0-0.4 9-B 35.9 77.3 4-E 23.2 46.7 4-G 9.1 24.9 Total 35.9 77.3 32.3 71.6 32.3 71.6-3.6-5.7 11-B 27.0 57.4 4-H 16.0 36.5 4-I 12.7 34.9 Total 27.0 57.4 28.7 71.4 28.7 71.4 1.7 14.0 Total Area and Flow In Line A 215.0 439.3 96.4 229.6 124.1 277.2 220.5 506.8 5.5 67.5 1-A 22.0 46.7 3-B 26.2 55.5 Total 22.0 46.7 26.2 55.5 26.2 55.5 4.2 8.8 LINE B 2-A 4.1 7.9 3-D 4.1 7.8 Total 4.1 7.9 4.1 7.8 4.1 7.8 0.0-0.1 3-A 28.6 54.8 3-A 27.3 51.9 Total 28.6 54.8 27.3 51.9 27.3 51.9-1.3-2.9 4-A 33.4 60.1 5-A 32.1 56.5 Total 33.4 60.1 32.1 56.5 32.1 56.5-1.3-3.6 Total Area and Flow In Line B 88.1 169.5 89.7 171.7 89.7 171.7 1.6 2.2 LINE C 2-A 8.2 18.4 2-B 3.3 9.9 2-C 3.4 8.9 Total 15.1 34.9 14.9 37.2 14.9 37.2-0.2 2.3 Total Area and Flow In Line C 15.1 34.9 14.9 37.2 14.9 37.2-0.2 2.3 1-A 12.8 22.9 1-B 2.9 8.6 1-A 32.6 54.6 1-C 4.9 13.5 1-D 6.9 19.0 1-E 5.6 15.4 Total 32.6 54.6 33.1 79.4 33.1 79.4 0.5 24.8 Total Area and Flow In Line D 32.6 54.6 33.1 79.4 33.1 79.4 0.5 24.8 LINE D Notes: 1-A 15.1 34.9 1. 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.

File location: W:/Mt_SAC/1MTS013200/ENGR/CALCS/1MTS013200-4-I.pdf 1MTS013200 Subarea ID 4-I Area (ac) 12.7 Flow Path Length (ft) 783.91 Flow Path Slope (vft/hft) 0.05 Percent Impervious 0.25 Soil Type 2 Peak Intensity (in/hr) 3.0858 Undeveloped Runoff Coefficient (Cu) 0.8857 Developed Runoff Coefficient (Cd) 0.8893 Time of Concentration (min) 7.0 Clear Peak Flow Rate (cfs) 34.8515 Burned Peak Flow Rate (cfs) 34.8515 24-Hr Clear Runoff Volume (ac-ft) 3.3938 24-Hr Clear Runoff Volume (cu-ft) 147833.9464

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: 000,016,017 50-YEAR 24-HR ISOHYET : 6.8 IN. 0' Mt. San Antonio College 1100 N. Grand Ave. Walnut, CA 91789 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

HYDROLOGIC INFORMATION OFFSITE Q25=420.0 cfs PER CITY OF WALNUT IMPROVEMENT PLANS FOR TRACT 40533 & TRACT 44019 AND M.T.D. 1192 48 48 36 36 48 795 797 790 ' S=0. 044 51 775 45 S=0.0 771 18 L=1035 770 13' L=13 5' 30 L=18 7 8.63 CFS 4.13AC 51 3-D 18 60 36 63 30 24 24 24 36 30 30 6 18 81 L=23 86' 60 ' S =0.0 22 24 30 S=0.0 17 08' 36.0 S=0 L=7 24 84 11 L= ' 38 0 S=.13 30 24 81 30 11 L=1 074 01 ' S=0. L=1929 81 725 60 730 36 STOP 740 48 735 720 719 36 GE LDIN BUI 36 735 740 745 18 749 750 740 18 18 755 750 751 750 725 STORM DRAIN 890.0 ' S =0 715 848.0.09 84 24 51 24 FLOWPATH 36.53 CFS 16.0AC 4-I 730 725 735 9 BENCH 18 760 761 S=0.02 711.0 30 690 60 720 715 710 34.9 CFS 12.7AC 24 60 UD 5-F 24.29 CFS 11.5AC 710.0 695 700 705 710 715 720 762 725 695.8 730 709.0 2 4-H 36 ABAND. 705 700 759 755 750 L=600' 3 =0.0 ' S 695 745 740 735 762 7.76 CFS 2.8AC 730 700 763 5-G 725 L=1 648 715 715 L=1235' S=0.01 448 L=1 710 715 705 720 730 725 735 735 740 745 755 750 762 18 WATERSHED BOUNDARY SUBAREA-BOUNDARY 730 725 720 BENCH 759 761 770 719.0 726 725 759 765 775 780 785 716.0 OFFSITE Q 18 18 30 730 760 763 765 4-G FIRE LANE 720 13.89 CFS 6.3AC 770 PUBLIC STORM DRAIN LINE 24.97 CFS 9.1AC 30 720 5-E 39.75 CFS 20.9AC > 755 735 750 745 740 761 762 18 8 18 30 36 725 715 710 720 735 730 725 36 759 30 730 > L=975' S=0.01 760 22.82 CFS 10.5AC 763 759 0 ND. 5-D 728 725 690.00 695.00 700.00 705.00 18 745 755 24 14 1 730 24 ABA 759 750 755 760 765 755 752 745 745 24 24 40' S=0.0 L=15 723.6 4-F 750 733.0 740 735 LANE 36 24 755 42 745 750 745 740.012 46.71 CFS 23.2 AC FIRE 725 705.00 D 726.0 745 745 S=0 4-E TB TB 699.0 740 18 TB 730 710.00 730 745 735 12' 745 708.00 18 735 730 747.0 745 706.00 750 755 730 759 735 740 745 775 770 765 790 785 780 740 750 726.0 42 725 18 YIELD 703.00 707.00 24 18 42 42 705.00 705.00 704.00 740 706.00 704.00 705.00 763.0 755 750 3 735 760 775 790 785 770 780 765 716.0 725 L=18 740 8 36 36 735 761. 01 18 YIELD PUBLIC LINE A 740 S= 0 AREA 5 DISCHARGE TO SNOW CREEK ADJACENT TO GRAND AVE. 764.3 740 5-C L 10.60 CFS =109 6' 4.6AC 754.0 TB TB TB 735 18.02 CFS 7.82AC OFFSITE Q 750 27.58 CFS 14.5AC 735.5 56.51 CFS 32.1AC PUBLIC LINE B 716.5 5-B 741.6 4-D 5-A 723.0 721.1 18 6' S=0.012 48 4-J 5.37 CFS 2.79AC L=17 1 3 24 48 722.0 1 =0.0 ' S 27 745 740 8.86 CFS 3.4AC 718.5 84 719.0 2-C 41 L=17 AREA 4 DISCHARGE TO SERVICE ROAD VIA LINE A 27 60 743.0 740.0 728.0 24 24 780 785 30 780 775 771 780 30.059 L= 9 L=63 36 13.44 CFS 5.8AC 36 36 24 18 24 UD UD UD UD UD 0.037 L=861' S= S=0.043 L=1465' 24 18 S2=40.0 43 24 L=2245 75' 18 48 18 18 18 18 18 24 24 18 24 763 3-C 735 24 36 24 S=0.045 764 740 24 42 36 18L=622' S=0.068 42 L=783' S=0 765 B-D 42.036 S=0 776' 33 =0.0 ' S 766 740 767 740 57 S=0.030 57 L=708' 769 768 735 57 770 765 18 18 0.007 L=1013' S= 55.53 CFS 26.2AC 735.0 84 18 772-GB D 730 18 12.48 CFS 4.8AC 775 774-GB 773-GB 775 36 24 780 775 D 750 42 771 YEIL D 785 745 42 4-C 786 3-B 724.0 PUBLIC LINE C 84 30 48 788 787 2-A 18.37 CFS 8.2AC 18 794.5 789 720.0 27 785.0 R 790 780 24 42 790 GB GB 785 RD 785 51.88 CFS 27.3AC AREA 3 DISCHARGE TO MT SAC WAY VIA LINE B 795 730 722.0 798 36 9.86 CFS 3.3AC 800 799 36 2-B 30 790 800 36 24 800 795 3-A 741.0 30 723.0 801 790 775 24 15.43 CFS 30 5.6AC 18 802 771 24 30 803 737.0 1-E 18 18 24 14.51 CFS 6.2AC 795 1-D 19.02 CFS 6.9AC AREA 2 DISCHARGE TO TEMPLE AVENUE VIA LINE C RD 18 18 UD 765.0 UD. 24 RD 18 UD 821.1 4-B BAND 18 742.0 78 18 766.0 747.0 PUBLIC LINE D 832.0 4-A 21.08 CFS 8.1AC 755 1-C 13.48 CFS 4.9AC 839.0 30 A 8.63 CFS 2.9AC 784.5 30 30 30 755 S 1-B 42 755 36D 760 24 24 42 22.88 CFS 12.8AC 801.4 750 786.0 847.5 18 18 24 853.0 STOP 34 1-A 753 24 24 24 AREA 1 DISCHARGE TO GRAND AVENUE VIA LINE D 754 S=0.024 L=2723' 748 18 18 48 48 854.0 SOIL TYPE: 002,016,017 50-YEAR 24-HR ISOHYET : 6.9 IN. 755 750 745 740 735 BENCH 711.0 735 660.0 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 FREQUENCY) @ 11X17 5/6/2016

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 = 12.87 CFS 25 BASIN C-2 AREA = 18.52 AC. C = 0.08 Q = 39.95 CFS 25 BASIN D-2 AREA = 16.34 AC. C = 0.01 Q = 36.96 CFS 25 BASIN D-3 AREA = 37.78 AC. C = 0.01 Q = 71.54 CFS 25 EXISTING DIRT ROAD BASIN BASIN SUMMARY AREA (AC) Q25 (CFS) EDINGER WAY BONITA DRIVE BONITA DRIVE 36 BASIN B-2 AREA = 24.41 AC. C = 0.17 Q = 55.55 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 = 12.78 CFS 25 BASIN E-1 AREA = 8.00 AC. C = 0.65 Q = 19.53 CFS 25 MT. SAN ANTONIO COLLEGE 24 27 WEST TEMPLE AVE. BASIN D-1 AREA = 13.58 AC. C = 0.01 Q = 37.12 CFS 25 400' 200' 0' 400' 800' GRAPHIC SCALE: 1=400' @ 11X17 A-1 5.98 14.70 SUBAREA TOTAL 5.98 14.70 B-1 5.02 12.87 B-2 24.41 55.55 SUBAREA TOTAL 29.43 68.42 C-1 4.99 12.78 C-2 18.52 39.95 SUBAREA TOTAL 23.51 52.73 D-1 13.58 37.12 D-2 16.34 36.96 D-3 37.78 71.54 SUBAREA TOTAL 67.70 145.62 E-1 8.00 19.53 SUBAREA TOTAL 8.00 19.53 TOTAL 134.62 301 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 - 5/4/2016 12:04:03 PM :: W:\Mt_SAC\1MTS013200\ENGR\SHEETS\MSAC-01-Exist Hydro.dwg :: tina.tse