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Appendix F - Preliminary Hydrology Study
Preliminary Hydrology Study For Troutdale Village, LLC Parcel 1 of MB 23/99 Washington & Avenue 50 La Quinta, CA 92253 APN# 646-070-016 Prepared for: Troutdale Village, LLC c/o: Jeff Parker 1800 Blankenship Road, Suite 325 West Linn, Oregon 97068 Prepared by: Egan Civil, Inc. Benjamin Daniel Egan, PE, PLS 46150 Commerce Street, Suite 100 Indio, CA 92201 (760) 404-7663 began@egancivil.com Prepared 01/22/2023 Page 1 of 4 Proiect Location and Surroundings The project consists of 14.03 acres of level terrain located on Avenue 50 just east of Washington Street in La Quinta, CA. The site is bounded on the East by the Coachella Valley Water District Storm Channel industrial land, on the North by single family homes, on the West by Washington Street, and on the south by Avenue 50. The site is not in the vicinity of any hillside or alluvial fan which would contribute any offsite runoff to the site. Method and Approach This is a preliminary study, strictly to evaluate the 100 year design storm runoff from the site with proposed improvements and to size an appropriate storm water retention basin to store 100% of all storm water runoff from this design storm. To analyze required on site storage, the Synthetic Unit Hydrograph method as outlined in the Riverside County Flood Control and Water Conservation District Hydrology Manual of 1978 was used for retention basin sizing. Site area was developed from surveys and the approved site plan, retention basin sizing was developed from the attached preliminary grading plan, and rainfall data was collected from the NOAA 14 online atlas. The site has moderately draining silty/sandy soils, but no infiltration testing was available at the time of the preparation of this report. Therefore, to ensure the basin is adequately sized, and an average percolation rate of 0 inches per hour for losses in the retention basin was used in the calculations. Analysis was completed utilizing a spreadsheet set up to correspond to the plates provided in the 1978 manual. The site is broken down as follows, there is proposed 13.42 acres of apartment building development, 0.61 acres of retention basin, and off-site area of 1.28 acres of Washington Street and Avenue 50 that front the project as shown on the attached hydrology map. Notes about the CVWD Wash Early in planning, the Coachella Valley Water District was contacted about the Wash on the eastern side of the property. The two concerns were as follows: First, what is the HGL of the wash and flood state and what protection or mitigation may be required near the wash, and Second, is lining required. CVWD responded and clarified the HGL of the Wash is 48 feet above sea level, and freeboard requirements apply within 75 feet of the channel right-of-way. The project has therefore been designed not only to keep all buildings out of the setback zone, but also to elevate all buildings on the site with substantial freeboard. CVWD also clarified that no slope protection is required to be installed on the channel as long as no structures are built within the 75 foot setback, with the exception of carports. Since the site design has been developed to accommodate all of CVWD's required constraints, no further analysis of the channel hydraulics or further flood plain review is required at this time. Page 2 of 4 Hydrology and Retention Basin Sizing The 100 year recurrence, 3, 6 and 24 hour storms produce runoff as follows: DURATION 1 HOUR 3 HOUR 6 HOUR 24 HOUR EFF. RAIN 1.38 IN REQ. STORAGE 68,819 FT^3 PEAK FLOW 44.47 CFS 1.58 IN 77,007 FT^3 27.97 CFS 1.52 IN 71,606 FT^3 23.54 CFS 1.57 IN 65,949 FT^3 5.88 CFS Therefore, the size of the retention basin is controlled by the 100 year recurrence, 3 hour design storm from the 1978 RCFC&WCD Hydrology Manual, modified to use the NOAA 14 rainfall data values. Said storm requires that 77,007 cubic feet of runoff be stored in the retention basin. The proposed retention basin consists of a depressed turfed area. The basin has a bottom elevation of 42 feet, and an upper contour elevation of 48 feet. There is no specific freeboard requirement, but the lowest building is located at a pad elevation 2 feet higher than the basin, and the basin is designed to overflow into Washington Street. The basin has a designed capacity of 106,998 cubic feet therefore has adequate capacity to retain all of the runoff from the controlling 100 year 3 hour design storm. Calculations indicate that after rain events the basin should fully percolate all water stored within 48 hours as required by City policy. The off-site tributary areas of Washington Street and Avenue 50 have existing drainage facilities to handle runoff. These drainage facilities are shown and detailed on city of La Quinta Improvement Plan number 99044. There is a catch basin located at the southeast end of the northeast curb return at the intersection of Washington Street and Avenue 50 to collect surface flows and an 18" diameter storm drain pipe conveys flows east to an outlet in the CVWD Stormwater Channel. There is a highpoint in Avenue 50 approximately 400 feet east of the intersection with Washington street. Runoff flowing to the west is collected in the aforementioned catch basin and runoff flowing to the east is directed into the CVWD Stormwater Channel at the existing channel crossing. The engineer and the developer see no need to alter these improvements. However, if the city wishes to redirect some of the 1.28 acre drainage area of Washington Street and Avenue 50 to the project, the proposed on-site retention basin has excess capacity. Rational Hydrology The project has 2 storm drain inlets for connection to drywells placed in the retention basins and minimal lengths of underground pipe, all runoff is surface drained to these structures. From the hydrology map, subareas are defined, and peak flows developed utilizing the rational method in the RCFC&WCD 1978 Hydrology Manual. The conveyance structures consist of ribbon gutters on inverted drive aisle sections, 2 catch basins and approximately 105 LF of 30" diameter underground pipe. Hydraulic Capacity Calculations for these improvements are included in Appendix "C". Page 3 of 4 Summary The preliminary design provides adequate onsite storage for the 100 year design storm in accordance with the recommendations of the RCFC&WCD Hydrology Manual and "first flush" rain events in compliance with currently adopted water quality management practices. The design concept is sound and should upon agency approval be moved forward to final engineering design. Page 4 of 4 Appendix A — NOAA Rainfall Data 9/14/2021 Precipitation Frequency Data Server NOAA Atlas 14, Volume 6, Version 2 (D Location name: La Quinta, California, USA*� Latitude: 33.68630, Longitude: -116.29340 Elevation: 46 ft** source: ESRI Maps ** source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES Sanja Perica, Sarah Dietz, Sarah Heim, Lillian Hiner, Kazungu Maitaria, Deborah Martin, Sandra Pavlovic, Ishani Roy, Carl Trypaluk, Dale Unruh, Fenglin Yen, Michael Yekta, Tan Zhao, Geoffrey Bonnin, Daniel Brewer, Li -Chuan Chen, Tye Parzybok, John Yarchoan NOAA, National Weather Service, Silver Spring, Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS -based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Average recurrence interval (years) Duration 1 2 5 10 25 50 1 100 100 200 500 1000 5 -min 0.068 (0.056-0.082) 0.104 1(0.086-0.126)11(0.132-0.193) 0.159 0.210 0.292 0.364 (0.173-0.257) 1(0.232-0.370)11(0.284-0.472) 0.449 0.549 1(0.342-0.597)11(0.406-0.750)11(0.502-1.01)11(0.585-1.27) 0.709 0.856 10 -min 0.097 (0.081-0.117) 0.149 1(0.124-0.180)11(0.189-0.277) 0.228 0.301 0.418 0.522 (0.248-0.369) 1(0.333-0.530)11(0.407-0.677) -----]F-1-.0-2-]F1.23 0.644 (0.490-0.855) 1 (0.581-1.08) 11(0.719-1.45)1(0.839-1.81) 15 -min 0.117 (0.098-0.142) 0.180 1(0.150-0.218)11(0.229-0.334) 0.275 0.364 0.505 0.632 (0.300-0.446) 1(0.403-0.641)11(0.493-0.818) 0.779 0.952 (0.592-1.03) (0.703-1.30) 1.23 11(0.870-1.75)1(1.01-2.19) 1.48 30 -min 0.171 (0.143-0.207) 0.263 1(0.219-0.319)11(0.335-0.489) 0.403 0.533 0.739 0.925 (0.439-0.653) (0.589-0.938) 1 (0.721-1.20) 1.14 1.39 1 (0.867-1.51) 1 (1.03-1.90) 1.80 11 (1.27-2.56) 2.17 1 (1.49-3.21) 60 -min 0.242 (0.202-0.292) 0.371 1(0.309-0.449)11(0.472-0.690) 0.568 0.751 1.04 1.30 (0.619-0.920) (0.830-1.32) 1 (1.02-1.69) -1.6-1--'F-1.-96- 1 (1.22-2.13) 1 (1.45-2.68) 2.53 (1.79-3.61) 3.06 (2.09-4.53) 2 -hr 0.336 (0.281-0.407) 0.493 (0.411-0.598) 0.732 (0.609-0.890) 0.954 1.30 1.61 (0.787-1.17) (1.04-1.65) 11 ( 1.26-2.09) 1.97 2.38 ( 1.50-2.62) ( 1.76-3.26) 3.03 11(2.15-4.32) 3.62 (2.47-5.35) -----]F--2.72 (1.72-3.00) 1 (2.01-3.72) 4.09 (2.80-6.05) 3 -hr 0.403 (0.337-0.488) 0.583 (0.486-0.706) 0.856 1 (0.711-1.04) 1.11 1.51 1.86 (0.914-1.36) (1.20-1.91) 11 (1.45-2.40) 3.45 (2.44-4.91) 2.84 (2.16-3.78) 11 3.41 (2.52-4.66) 5.06 (3.46-7.48) 6 -hr 0.528 (0.441-0.639) 0.759 (0.633-0.919) 1.11 (0.918-1.34) 1.42 1.92 2.35 (1.17-1.74) (1.53-2.43) (1.83-3.05) 4.29 (3.04-6.12) 3.54 1 (2.69-4.70) 4.21 1 (3.11-5.76) 5.24 (3.71-7.48) 6.14 (4.20-9.07) 12 -hr 0.640 (0.534-0.774) -0-.9-4-2--F--1.-991.79 (0.785-1.14) 11 (1.15-1.69) 2.41 2.94 1 (1.92-3.05) 11 (2.29-3.81) 24 -hr 0.791 (0.700-0.912) 0.910 (0.805-1.05) 1.20 1 (1.06-1.38) 1.79 11 (1.58-2.07) 2.32 3.12 3.79 (2.03-2.71) (2.64-3.75) 11 (3.15-4.66) 2.74 3.68 4.48 (2.40-3.20) (3.12-4.44) 11 (3.72-5.51) 4.54 1 (3.69-5.72) 5.39 1 (4.25-6.96) 6.65 (5.05-8.95) 7.81 (5.92-10.5) 7.74 (5.68-10.8) 2 -day 1.40 2.11 1 (1.24-1.62) 11 (1.86-2.44) 5.36 6.34 1 (4.35-6.74) 1 (5.01-8.20) 9.05 (6.64-12.6) 3 -day 0.975 (0.863-1.12) 1.51 2.28 (1.33-1.74) (2.01-2.64) -----]F--4.00 4.86 (2.60-3.47) (3.39-4.81) (4.04-5.97) 5.82 6.89 (4.72-7.32) (5.44-8.90) 8.48 ) (6.43-11.4 ( 9.84 7.22-13.7) 4 -day 1.03 (0.914-1.19) 1.60 1 (1.42-1.85) 2.43 11 (2.14-2.81) 3.16 1 (2.76-3.68) 4.25 1 (3.60-5.12) F 6.18 1 (5.01-7.78) 7.32 1 (5.78-9.46) 9.01 (6.84-12.1) 10.5 (7.67-14.5) 7 -day 1.10 (0.969-1.26) 1.70 1 (1.50-1.96) 2.57 11 (2.26-2.97) 3.34 1 (2.92-3.90) 4.49 1 (3.81-5.41) 5.46 11 (4.54-6.71) 6.52 1 (5.29-8.21) 7.71 1 (6.09-9.96) 9.46 11.0 (7.18-12.7) (8.04-15.2) 10 -day 1.12 (0.994-1.30) 1.74 1 (1.54-2.01) 2.65 11 (2.33-3.06) 3.44 1 (3.01-4.02) 4.63 1 (3.93-5.58) 5.63 11 (4.68-6.92) 6.72 1 (5.45-8.46) 7.93 1 (6.26-10.2) 9.72 11.2 (7.38-13.1) (8.24-15.6) 20 -day F--l.-20--]F--l.-89-]F--2.-90--]F--3.79 (1.06-1.38) 1 (1.67-2.18) (2.56-3.36) 1 (3.32-4.42) -----]F--6.-23--]F7.43 1 (4.34-6.17) 11 (5.17-7.65) 1 (6.03-9.35) 8.76 1 (6.92-11.3) 10.7 12.3 (8.11-14.4) (9.03-17.1) 30 -day 1.27 P1.12-1.46) 2.03 1 (1.80-2.35) 3.16 (2.78-3.65) 4.15 1 (3.63-4.84) 5.64 1 (4.78-6.79) 6.87 11 (5.70-8.44) 8.20 (6.65-10.3) 9.65 (7.62-12.5) 11.7 13.5 (8.91-15.8) (9.88-18.7) 45 -day 1.36 (1.21-1.57) 2.23 1 (1.97-2.58) 3.50 11 (3.09-4.06) --4.-64--]F-6-.3-3- 1 (4.05-5.41) 1 (5.36-7.62) 7.73 (6.42-9.50) 9.24 (7.50-11.6) 10.9 (8.58-14.0) 13.2 (10.0-17.8) 15.1 (11.1-21.0) 60 -day 1.44 (1.27-1.66) 2.40 (2.12-2.77) 3.81 (3.36-4.41) 5.06 (4.43-5.91) 6.93 (5.87-8.34) 8.48 (7.04-10.4) 10.2 (8.23-12.8) 11.9 (9.43-15.4) 14.5 (11.0-19.5) 16.6 (12.2-23.0) Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Top PF graphical https://hdsc. nws. noaa. gov/hdsc/pfds/pfds_printpage.html?lat=33.6863&Ion=-116.2934&data=depth&units=engIish&series=pds 1/4 9/14/2021 Precipitation Frequency Data Server PDS -based depth -duration -frequency (DDF) curves Latitude: 33.68631, Longitude= -116.29341 14 c s 12 4. CL 10 4-1v 19 S Z 6 CL 4 9 C: e e_ e_ E E E -E IJ'S OY"I O O 1-4ri rn LD Duration 18 16 14 c s 12 CL -0 10 e O CL 6 IL IL 4 2 0 L Ip Ip fp Ip fp Ip Ip fp fp N rV tf1 v h dI:r O rn O 'i N fY'Y V kD 1 2 5 10 25 50 100 200 500 1000 Average recurrence interval (years) NOAAAtlas 14, Valu me 5, Version 2 Created (GMT): Tue Sep 14 21=26.22 2021 Back to Top Maps & aerials Small scale terrain Average recurrence interval (years} — 1 2 — 5 10 25 — s0 100 200 500 1000 Duration — 5-mtn — 2 -day — 10 -min — 3 -day 15 -min — 4 -day — 30 -min — 7 -day — 60 -min — 10 -day — 2 -hr — 20 -day — "r — 30 -day — 6 -hr — 45 -day — 12 -hr — 60 -day — 24 -hr https://hdsc. nws. noaa. gov/hdsc/pfds/pfds_printpage.html?lat=33.6863&Ion=-116.2934&data=depth&units=engIish&series=pds 2/4 9/14/2021 Precipitation Frequency Data Server rt r e}<fia�� elps, - _lul_, EISENHOWER MOUNTAIN 'La Quinta J i ;Hideaway N GalrClub Lal,�Cahullla . ation Large scale terrain Lancaster0 'Now.0- a • Palmdale Victorville + Lake v t Angeles * Riverside �,q a - ,r�,1. °aeh Anaheim Cathedralcity 1'.s Sant%na PalmDesei�"�T1dib- Murrieta' I Oceanside Sea San Diego �7j 100km M�7CICdii-� 60mi _ _ isRi Large scale map easter .,Palmdale VictorviII& Ham' Santa Clarita Cid LosAngeles Riverside Anaheim Cathedral :acli" Cit} I India SantaAnaii'Qasart Murrieta Oceanside San ❑ieao 100km ex ina 60mi Large scale aerial https://hdsc. nws. noaa. gov/hdsc/pfds/pfds_printpage.htmI?Iat=33.6863&Ion=-116.2934&data=depth&units=engIish&series=pds 3/4 9/14/2021 Precipitation Frequency Data Server Back to Top US Department of Commerce National Oceanic and Atmospheric Administration National Weather Service National Water Center 1325 East West Highway Silver Spring, MD 20910 Questions?: HDSC.Questions@noaa.gov Disclaimer https://hdsc. nws. noaa. gov/hdsc/pfds/pfds_printpage.htmI?Iat=33.6863&Ion=-116.2934&data=depth&units=engIish&series=pds 4/4 Appendix 6 — Synthetic Unit Hydrograph Calculations 45 A B C D 1 RCFCD SYNTHETIC UNIT HYDROGRAPH 11683 2 DATA INPUT SHEET 14612 3 4 5 WORKSHEET PREPARED BY: SPE 6 PROJECT NAME LA QUINTA APARTMENTS 7 ECI Job # 20210635 511 8 27458 9 CONCENTRATION POINT DESIGNATION ISITE RETENTION BASIN 10 JAREA DESIGNATION IONSITE FLOWS 11 12 TRIBUTARY AREAS ACRES 13 14 COMMERCIAL 15 PAVING/HARDSCAPE 16 SF - 1 ACRE 17 SF - 1/2 ACRE 18 SF - 1/4 ACRE 19 IMF - CONDOMINIUMS 20 MF -APARTMENTS 13.42 21 MOBILE HOME PARK 22 LANDSCAPING 23 RETENTION BASIN 0.61 24 GOLF COURSE 25 IMOUNTAINOUS 26 1 LOW LOSS RATE (PERCENT) 90% 27 28 LENGTH OF WATERCOURSE (L) 1000 29 LENGTH TO POINT OPPOSITE CENTROID (Lca) F77 240 30 31 ELEVATION OF HEADWATER 53.4 32 ELEVATION OF CONCENTRATION POINT 48 33 34 JAVERAGE MANNINGS 'N' VALUE 0.02 35 36 STORM FREQUENCY (YEAR) 100 37 38 POINT RAIN 39 1 HOUR 1.61 40.3 -HOUR 2.26 41 6 -HOUR 2.84 42 24-HOUR 4.54 43 44 BASIN CHARACTERISTICS: I ELEVATION I AREA 45 42 8867 46 43 11683 47 44 14612 48 45 17654 49 46 20809 501 471 24077 511 481 27458 52 53 PERCOLATION RATE (in/hr) 0 54 55 DRYWELL DATA 56 NUMBER USED 2 57 1 PERCOLATION RATE cfs 0.12 RCFCD SYNTHETIC UNIT HYDROGRAPH METHOD PROJECT: BASIC DATA CALCULATION FORM ECI JOB# SHORTCUT METHOD BY LA QUINTA APARTMENTS 20210635 SPE DATE 10/25/2022 1 -HOUR 3 -HOUR PHYSICAL DATA 24-HOUR EFFECTIVE RAIN (in) 1.38 [1] CONCENTRATION POINT 1.52 1.57 SITE RETENTION BASIN 70,264 1.61 [2] AREA DESIGNATION 77,186 1.77 80,099 1.84 ONSITE FLOWS 68,819 1.58 [3] AREA - ACRES 71,662 1.65 66,166 1.52 14.030 - (0.00) [4] L -FEET 56 0.00 217 0.00 1000 68,819 1.58 [5] L -MILES 71,606 1.64 65,949 1.51 0.189 44.47 [6] La -FEET 23.54 5.88 240.00 46.48 [7] La -MILES 46.60 46.33 0.045 [8] ELEVATION OF HEADWATER 53.4 [9] ELEVATION OF CONCENTRATION POINT 48 [10] H -FEET 5.4 [11] S-FEET/MILE 28.5 [12] S"0.5 5.34 [13] L*LCA/S^0.5 0.002 [14] AVERAGE MANNINGS'N' 0.02 [15] LAG TIME -HOURS 0.04 [16] LAG TIME -MINUTES 2.5 [17] 100% OF LAG -MINUTES 2.5 [18] 200% OF LAG -MINUTES 5.0 [19] UNIT TIME -MINUTES (100%-200% OF LAG) 5 [24] TOTAL PERCOLATION RATE FOR DRYWELLS (cfs) 0.24 RAINFALL DATA [1] SOURCE [2] FREQUENCY -YEARS 100 [3] DURATION: 3 -HOURS 6 -HOURS 24 -HOURS [4] [5] [6] POINT AREA RAIN INCHES PER NOAA [7] AVERAGE POINT RAIN INCHES [8] POINT RAIN INCHES PER NOAA [9] [10] AREA [11] AVERAGE POINT RAIN INCHES [12] [13] [14] POINT AREA RAIN INCHES PER NOAA [15] AVERAGE POINT RAIN INCHES 2.26 14.030 1.00 2.26 2.84 14.030 1.00 2.84 4.54 14.030 1.00 4.54 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 SUM [5] 14.03 SUM [7] [16] AREA ADJ FACTOR [17] ADJ AVG POINT RAIN 2.26 SUM [9] 14.03 SUM [11] 2.84 SUM [13] 14.03 SUM [15] 4.54 1.000 1.000 1.000 2.26 2.84 4.54 STORM EVENT SUMMARY DURATION 1 -HOUR 3 -HOUR 6 -HOUR 24-HOUR EFFECTIVE RAIN (in) 1.38 1.58 1.52 1.57 FLOOD VOLUME (cu -ft) (acre -ft) 70,264 1.61 80,259 1.84 77,186 1.77 80,099 1.84 ADJ FLOOD VOLUME (cu -ft) (FLOOD VOLUME LESS (acre -ft) LOSS RATES) 68,819 1.58 77,007 1.77 71,662 1.65 66,166 1.52 BASIN PERC LOSSES (cu -ft) (acre -ft) - (0.00) - 0.00 56 0.00 217 0.00 REQ BASIN STORAGE (cu -ft) (acre -ft) 68,819 1.58 77,007 1.77 71,606 1.64 65,949 1.51 PEAK FLOW (cfs) 44.47 27.97 23.54 5.88 MAXIMUM WSEL (ft) 46.48 46.83 46.60 46.33 1 -HOUR [16] [17] POINT AREA RAIN INCHES PER NOAA [18] [19] AVERAGE POINT RAIN INCHES 1.61 14.030 1.00 1.61 0.00 0.00 0.00 0.00 0.00 0.00 SUM [5] 14.03 SUM [19] [16] AREA ADJ FACTOR [17] ADJ AVG POINT RAIN 1.61 1.000 1.61 Plate E-2.1 Page 2 of 20 RCFCD SYNTHETIC UNIT HYDROGRAPH METHOD PROJECT LA QUINTA APARTMENTS CONCENTRATION POINT: SITE RETENTION BASIN BY SPE DATE 10/25/2022 DJUSTED LOSS RATE SOIL GROUP [Plate C-1] LAND USE RI NUMBER [Plate E-6.1] PERVIOUS AREA INFILTRATION RATE (in/hr) [Plate E-6.2] DECIMAL PERCENT OF AREA IMPERVIOUS [Plate E-6.3] ADJUSTED INFILTRATION RATE (in/hr) AREA AVERAGE ADJUSTED INFILTRATION RATE (in/hr) A COMMERCIAL 32 0.74 90% 0.14 0.00 0.000 0.0000 A PAVING/HARDSCAPE 32 0.74 100% 0.07 0.00 0.000 0.0000 A SF - 1 ACRE 32 0.74 20% 0.61 0.00 0.000 0.0000 A SF - 1/2 ACRE 32 0.74 40% 0.47 0.00 0.000 0.0000 A SF - 1/4 ACRE 32 0.74 50% 0.41 0.00 0.000 0.0000 A MF - CONDOMINIUMS 32 0.74 65% 0.31 0.00 0.000 0.0000 A MIF -APARTMENTS 32 0.74 80% 0.21 13.42 0.957 0.1982 A MOBILE HOME PARKS 32 0.74 75% 0.24 0.00 0.000 0.0000 A LANDSCAPING 32 0.74 0% 0.74 0.00 0.000 0.0000 A RETENTION BASINS 32 0.74 0% 0.74 0.61 0.043 0.0322 A GOLF COURSE 32 0.74 0% 0.74 0.00 0.000 0.0000 D MOUNTAINOUS 93 0.95 90% 0.18 0.00 0.000 0.0000 0.00 0.000 0.0000 0.00 0.000 0.0000 0.00 0.000 0.0000 0.00 0.000 0.0000 0.00 0.000 0.0000 0.00 0.000 0.0000 0.00 0.000 0.0000 0.00 0.000 0.0000 0.00 0.000 0.0000 SUMI 14.03 1 SUM 0.2304 VARIABLE LOSS RATE CURVE (24-HOUR STORM ONLY) Fm= 0.115182609 C= 0.00213 Ft=C(24-(T/60))11.55 = 0.00213 (24-(T/60))^1.55 + 0.12 in/hr LOW LOSS RATE (80-90 PERCENT) = 90% Where: T=Time in minutes. To get an average value for each unit time period, Use T=1/2 the unit time for the first time period, T=1 1/2 unit time for the second period, etc. Plate E-2.1 Page 3 of 20 RCFCD SYNTHETIC UNIT HYDROGRAPH METHOD PROJECT: LA QUINTA APARTMENTS 100 YEAR - 3 HOUR STORM EVENT CONCENTRATION POINT: SITE RETENTION BASIN BY: SPE DATE 10/25/2022 EFFECTIVE RAIN CALCULATION FORM DRAINAGE AREA -ACRES 14.03 UNIT TIME -MINUTES 5 LAG TIME - MINUTES 2.50 UNIT TIME -PERCENT OF LAG 199.9 TOTAL ADJUSTED STORM RAIN -INCHES 1.61 CONSTANT LOSS RATE-in/hr 0.23 LOW LOSS RATE - PERCENT 90% TOTAL PERCOLATION RATE (cfs) 0.24 cfs Unit Time Time Pattern Storm Loss Rate Effective Flood Required Period Minutes Hours Percent Rain Rain Hydrograph Storage in/hr in/hr Flow (Plate E-5.9) Max Low in/hr cfs cf 1 5 0.08 3.7 0.715 0.23 0.64 0.48 6.80 1967.15 2 10 0.17 4.8 0.927 0.23 0.83 0.70 9.78 2861.65 3 15 0.25 5.1 0.985 0.23 0.89 0.75 10.59 3105.60 4 20 0.33 4.9 0.947 0.23 0.85 0.72 10.05 2942.97 5 25 0.42 6.6 1.275 0.23 1.15 1.04 14.66 4325.37 6 30 0.50 7.3 1.410 0.23 1.27 1.18 16.56 4894.60 7 35 0.58 8.4 1.623 0.23 1.46 1.39 19.54 5789.09 8 40 0.67 9.0 1.739 0.23 1.56 1.51 21.16 6277.00 9 45 0.75 12.3 2.376 0.23 2.14 2.15 30.11 8960.49 10 50 0.83 17.6 3.400 0.23 3.06 3.17 44.47 13270.34 11 55 0.92 16.1 3.111 0.23 2.80 2.88 40.41 12050.57 12 60 1.00 4.2 0.811 0.23 0.73 0.58 8.15 2373.74 EFFECTIVE RAIN & FLOOD VOLUMES SUMMARY EFFECTIVE RAIN (in) FLOOD VOLUME (acft) FLOOD VOLUME (cuft) REQUIRED STORAGE (acft) REQUIRED STORAGE (cuft) PEAK FLOW RATE (cfs) 1.38 1.61 70263.56 1.58 68818.59 44.47 Plate E-2.2 Page 4 of 20 RCFCD SYNTHETIC UNIT HYDROGRAPH METHOD 100 YEAR - 3 HOUR STORM EVENT PROJECT: LA QUINTA APARTMENTS CONCENTRATION POINT: SITE RETENTION BASIN BY: SPE DATE 10/25/2022 EFFECTIVE RAIN CALCULATION FORM DRAINAGE AREA -ACRES UNIT TIME -MINUTES LAG TIME - MINUTES UNIT TIME -PERCENT OF LAG TOTAL ADJUSTED STORM RAIN -INCHES CONSTANT LOSS RATE-in/hr LOW LOSS RATE - PERCENT 14.03 5 2.50 199.9 2.26 0.23 90% TOTAL PERCOLATION RATE (cfs) 0.24 cfs Unit Time Time Period Minutes Hours Pattern Percent (Plate E-5.9) Storm Rain in/hr Loss Rate in/hr Max Low Effective Rain in/hr Flood Hydrograph Flow cfs Required Storage cf 1 5 0.08 1.3 0.353 0.23 0.32 0.12 1.71 442.32 2 10 0.17 1.3 0.353 0.23 0.32 0.12 1.71 442.32 3 15 0.25 1.1 0.298 0.23 0.27 0.07 0.95 214.02 4 20 0.33 1.5 0.407 0.23 0.37 0.18 2.48 670.61 5 25 0.42 1.5 0.407 0.23 0.37 0.18 2.48 670.61 6 30 0.50 1.8 0.488 0.23 0.44 0.26 3.62 1013.06 7 35 0.58 1.5 0.407 0.23 0.37 0.18 2.48 670.61 8 40 0.67 1.8 0.488 0.23 0.44 0.26 3.62 1013.06 9 45 0.75 1.8 0.488 0.23 0.44 0.26 3.62 1013.06 10 50 0.83 1.5 0.407 0.23 0.37 0.18 2.48 670.61 11 55 0.92 1.6 0.434 0.23 0.39 0.20 2.86 784.76 12 60 1.00 1.8 0.488 0.23 0.44 0.26 3.62 1013.06 13 65 1.08 2.2 0.597 0.23 0.54 0.37 5.14 1469.65 14 70 1.17 2.2 0.597 0.23 0.54 0.37 5.14 1469.65 15 75 1.25 2.2 0.597 0.23 0.54 0.37 5.14 1469.65 16 80 1.33 2.0 0.542 0.23 0.49 0.31 4.38 1241.35 17 85 1.42 2.6 0.705 0.23 0.63 0.47 6.66 1926.24 18 90 1.50 2.7 0.732 0.23 0.66 0.50 7.04 2040.39 19 95 1.58 2.4 0.651 0.23 0.59 0.42 5.90 1697.95 20 100 1.67 2.7 0.732 0.23 0.66 0.50 7.04 2040.39 21 105 1.75 3.3 0.895 0.23 0.81 0.66 9.32 2725.28 22 110 1.83 3.1 0.841 0.23 0.76 0.61 8.56 2496.98 23 115 1.92 2.9 0.786 0.23 0.71 0.56 7.80 2268.69 24 120 2.00 3.0 0.814 0.23 0.73 0.58 8.18 2382.84 25 125 2.08 3.1 0.841 0.23 0.76 0.61 8.56 2496.98 26 130 2.17 4.2 1.139 0.23 1.03 0.91 12.75 3752.61 27 135 2.25 5.0 1.356 0.23 1.22 1.13 15.79 4665.80 28 140 2.33 3.5 0.949 0.23 0.85 0.72 10.09 2953.58 29 145 2.42 6.8 1.844 0.23 1.66 1.61 22.64 6720.46 30 150 2.50 7.3 1.980 0.23 1.78 1.75 24.54 7291.20 31 155 2.58 8.2 2.224 0.23 2.00 1.99 27.97 8318.54 32 160 2.67 5.9 1.600 0.23 1.44 1.37 19.22 5693.13 33 165 2.75 2.0 0.542 0.23 0.49 0.31 4.38 1241.35 34 170 2.83 1.8 0.488 0.23 0.44 0.26 3.62 1013.06 35 175 2.92 1.8 0.488 0.23 0.44 0.26 3.62 1013.06 36 180 3.00 0.6 0.163 0.23 0.15 0.02 0.23 0.00 EFFECTIVE RAIN & FLOOD VOLUMES SUMMARY EFFECTIVE RAIN (in) FLOOD VOLUME (acft) FLOOD VOLUME (tuft) REQUIRED STORAGE (acft) REQUIRED STORAGE (cuft) PEAK FLOW RATE (cfs) 1.58 1.84 80259.04 1.77 77006.94 27.97 Plate E-2.2 Page 5 of 20 RCFCD SYNTHETIC UNIT HYDROGRAPH METHOD 100 YEAR - 6 HOUR STORM EVENT PROJECT: CONCENTRATION POINT: BY: SPE LA QUINTA APARTMENTS SITE RETENTION BASIN DATE: 10/25/2022 EFFECTIVE RAIN CALCULATION FORM DRAINAGE AREA -ACRES UNIT TIME -MINUTES LAG TIME - MINUTES UNIT TIME -PERCENT OF LAG TOTAL ADJUSTED STORM RAIN -INCHES CONSTANT LOSS RATE-in/hr LOW LOSS RATE - PERCENT 14.03 5 2.50 199.9 2.84 0.230 90% TOTAL PERCOLATION RATE (cfs) 0.24 cfs Unit Time Time Period Minutes Hours Pattern Percent (Plate E-5.9) Storm Rain in/hr Loss Rate in/hr Max Low Effective Rain in/hr Flood Hydrograph Flow cfs Required Storage cf 1 5 0.08 0.5 0.170 0.23 0.15 0.02 0.24 0.00 2 10 0.17 0.6 0.204 0.23 0.18 0.02 0.29 14.07 3 15 0.25 0.6 0.204 0.23 0.18 0.02 0.29 14.07 4 20 0.33 0.6 0.204 0.23 0.18 0.02 0.29 14.07 5 25 0.42 0.6 0.204 0.23 0.18 0.02 0.29 14.07 6 30 0.50 0.7 0.239 0.23 0.21 0.01 0.11 0.00 7 35 0.58 0.7 0.239 0.23 0.21 0.01 0.11 0.00 8 40 0.67 0.7 0.239 0.23 0.21 0.01 0.11 0.00 9 45 0.75 0.7 0.239 0.23 0.21 0.01 0.11 0.00 10 50 0.83 0.7 0.239 0.23 0.21 0.01 0.11 0.00 11 55 0.92 0.7 0.239 0.23 0.21 0.01 0.11 0.00 12 60 1.00 0.8 0.273 0.23 0.25 0.04 0.59 105.93 13 65 1.08 0.8 0.273 0.23 0.25 0.04 0.59 105.93 14 70 1.17 0.8 0.273 0.23 0.25 0.04 0.59 105.93 15 75 1.25 0.8 0.273 0.23 0.25 0.04 0.59 105.93 16 80 1.33 0.8 0.273 0.23 0.25 0.04 0.59 105.93 17 85 1.42 0.8 0.273 0.23 0.25 0.04 0.59 105.93 18 90 1.50 0.8 0.273 0.23 0.25 0.04 0.59 105.93 19 95 1.58 0.8 0.273 0.23 0.25 0.04 0.59 105.93 20 100 1.67 0.8 0.273 0.23 0.25 0.04 0.59 105.93 21 105 1.75 0.8 0.273 0.23 0.25 0.04 0.59 105.93 22 110 1.83 0.8 0.273 0.23 0.25 0.04 0.59 105.93 23 115 1.92 0.8 0.273 0.23 0.25 0.04 0.59 105.93 24 120 2.00 0.9 0.307 0.23 0.28 0.08 1.07 249.38 25 125 2.08 0.8 0.273 0.23 0.25 0.04 0.59 105.93 26 130 2.17 0.9 0.307 0.23 0.28 0.08 1.07 249.38 27 135 2.25 0.9 0.307 0.23 0.28 0.08 1.07 249.38 28 140 2.33 0.9 0.307 0.23 0.28 0.08 1.07 249.38 29 145 2.42 0.9 0.307 0.23 0.28 0.08 1.07 249.38 30 150 2.50 0.9 0.307 0.23 0.28 0.08 1.07 249.38 31 155 2.58 0.9 0.307 0.23 0.28 0.08 1.07 249.38 32 160 2.67 0.9 0.307 0.23 0.28 0.08 1.07 249.38 33 165 2.75 1.0 0.341 0.23 0.31 0.11 1.55 392.82 34 170 2.83 1.0 0.341 0.23 0.31 0.11 1.55 392.82 35 175 2.92 1.0 0.341 0.23 0.31 0.11 1.55 392.82 36 180 3.00 1.0 0.341 0.23 0.31 0.11 1.55 392.82 37 185 3.08 1.0 0.341 0.23 0.31 0.11 1.55 392.82 38 190 3.17 1.1 0.375 0.23 0.34 0.14 2.03 536.26 39 195 3.25 1.1 0.375 0.23 0.34 0.14 2.03 536.26 40 200 3.33 1.1 0.375 0.23 0.34 0.14 2.03 536.26 41 205 3.42 1.2 0.409 0.23 0.37 0.18 2.51 679.71 42 210 3.50 1.3 0.443 0.23 0.40 0.21 2.98 823.15 43 215 3.58 1.4 0.477 0.23 0.43 0.25 3.46 966.59 44 220 3.67 1.4 0.477 0.23 0.43 0.25 3.46 966.59 45 225 3.75 1.5 0.511 0.23 0.46 0.28 3.94 1110.03 46 230 3.83 1.5 0.511 0.23 0.46 0.28 3.94 1110.03 47 235 3.92 1.6 0.545 0.23 0.49 0.31 4.42 1253.48 48 240 4.00 1.6 0.545 0.23 0.49 0.31 4.42 1253.48 49 245 4.08 1.7 0.579 0.23 0.52 0.35 4.90 1396.92 50 250 4.17 1.8 0.613 0.23 0.55 0.38 5.37 1540.36 51 255 4.25 1.9 0.648 0.23 0.58 0.42 5.85 1683.80 52 260 4.33 2.0 0.682 0.23 0.61 0.45 6.33 1827.25 53 265 4.42 2.1 0.716 0.23 0.64 0.49 6.81 1970.69 54 270 4.50 2.1 0.716 0.23 0.64 0.49 6.81 1970.69 55 275 4.58 2.2 0.750 0.23 0.67 0.52 7.29 2114.13 56 280 1 4.67 2.3 0.784 0.23 0.71 0.55 7.77 2257.58 Plate E-2.2 Page 6 of 20 RCFCD SYNTHETIC UNIT HYDROGRAPH METHOD 100 YEAR - 6 HOUR STORM EVENT PROJECT: CONCENTRATION POINT: BY: SPE LA QUINTA APARTMENTS SITE RETENTION BASIN DATE: 10/25/2022 EFFECTIVE RAIN CALCULATION FORM DRAINAGE AREA -ACRES UNIT TIME -MINUTES LAG TIME - MINUTES UNIT TIME -PERCENT OF LAG TOTAL ADJUSTED STORM RAIN -INCHES CONSTANT LOSS RATE-in/hr LOW LOSS RATE - PERCENT 14.03 5 2.50 199.9 2.84 0.230 90% TOTAL PERCOLATION RATE (cfs) 0.24 cfs Unit Time Time Period Minutes Hours Pattern Percent (Plate E-5.9) Storm Rain in/hr Loss Rate in/hr Max Low Effective Rain in/hr Flood Hydrograph Flow cfs Required Storage cf 57 285 4.75 2.4 0.818 0.23 0.74 0.59 8.24 2401.02 58 290 4.83 2.4 0.818 0.23 0.74 0.59 8.24 2401.02 59 295 4.92 2.5 0.852 0.23 0.77 0.62 8.72 2544.46 60 300 5.00 2.6 0.886 0.23 0.80 0.66 9.20 2687.90 61 305 5.08 3.1 1.056 0.23 0.95 0.83 11.59 3405.12 62 310 5.17 3.6 1.227 0.23 1.10 1.00 13.98 4122.33 63 315 5.25 3.9 1.329 0.23 1.20 1.10 15.42 4552.66 64 320 5.33 4.2 1.431 0.23 1.29 1.20 16.85 4982.99 65 325 5.42 4.7 1.602 0.23 1.44 1.37 19.24 5700.20 66 330 5.50 5.6 1.908 0.23 1.72 1.68 23.54 6991.19 67 335 5.58 1.9 0.648 0.23 0.58 0.42 5.85 1683.80 68 340 5.67 0.9 0.307 0.23 0.28 0.08 1.07 249.38 69 345 5.75 0.6 0.204 0.23 0.18 0.02 0.29 14.07 70 350 5.83 0.5 0.170 0.23 0.15 0.02 0.24 0.00 71 355 5.92 0.3 0.102 0.23 0.09 0.01 0.14 0.00 72 360 6.00 0.2 0.068 0.23 0.06 0.01 0.10 0.00 EFFECTIVE RAIN & FLOOD VOLUMES SUMMARY EFFECTIVE RAIN (in) FLOOD VOLUME (acft) FLOOD VOLUME (cuft) REQUIRED STORAGE (acft) REQUIRED STORAGE (cuft) PEAK FLOW RATE (cfs) 1.52 1.77 77186.24 1.65 71661.92 23.54 Plate E-2.2 Page 7 of 20 RCFCD SYNTHETIC UNIT HYDROGRAPH METHOD 100 YEAR - 24 HOUR STORM EVENT PROJECT: CONCENTRATION POINT: BY: SPE LA QUINTA APARTMENTS SITE RETENTION BASIN DATE: 10/25/2022 EFFECTIVE RAIN CALCULATION FORM DRAINAGE AREA -ACRES UNIT TIME -MINUTES LAG TIME - MINUTES UNIT TIME -PERCENT OF LAG TOTAL ADJUSTED STORM RAIN -INCHES 14.030 15 2.50 599.6 4.54 CONSTANT LOSS RATE-in/hr VARIABLE LOSS RATE (AVG) in/hr MINIMUM LOSS RATE (for var. loss) - in/hr LOW LOSS RATE - DECIMAL C PERCOLATION RATE (cfs) n/a 0.2304 0.115 0.90 0.00213 0.24 Unit Time Time Period Minutes Hours Pattern Percent (Plate E-5.9) Storm Rain in/hr Loss Rate in/hr Max Low Effective Rain in/hr Flood Hydrograph Flow cfs Required Storage cf 1 15 0.25 0.2 0.036 0.407 0.033 0.004 0.05 0.00 2 30 0.50 0.3 0.054 0.402 0.049 0.005 0.08 0.00 3 45 0.75 0.3 0.054 0.397 0.049 0.005 0.08 0.00 4 60 1.00 0.4 0.073 0.393 0.065 0.007 0.10 0.00 5 75 1.25 0.3 0.054 0.388 0.049 0.005 0.08 0.00 6 90 1.50 0.3 0.054 0.383 0.049 0.005 0.08 0.00 7 105 1.75 0.3 0.054 0.379 0.049 0.005 0.08 0.00 8 120 2.00 0.4 0.073 0.374 0.065 0.007 0.10 0.00 9 135 2.25 0.4 0.073 0.370 0.065 0.007 0.10 0.00 10 150 2.50 0.4 0.073 0.365 0.065 0.007 0.10 0.00 11 165 2.75 0.5 0.091 0.361 0.082 0.009 0.13 0.00 12 180 3.00 0.5 0.091 0.356 0.082 0.009 0.13 0.00 13 195 3.25 0.5 0.091 0.352 0.082 0.009 0.13 0.00 14 210 3.50 0.5 0.091 0.348 0.082 0.009 0.13 0.00 15 225 3.75 0.5 0.091 0.343 0.082 0.009 0.13 0.00 16 240 4.00 0.6 0.109 0.339 0.098 0.011 0.15 0.00 17 255 4.25 0.6 0.109 0.335 0.098 0.011 0.15 0.00 18 270 4.50 0.7 0.127 0.330 0.114 0.013 0.18 0.00 19 285 4.75 0.7 0.127 0.326 0.114 0.013 0.18 0.00 20 300 5.00 0.8 0.145 0.322 0.131 0.015 0.20 0.00 21 315 5.25 0.6 0.109 0.318 0.098 0.011 0.15 0.00 22 330 5.50 0.7 0.127 0.314 0.114 0.013 0.18 0.00 23 345 5.75 0.8 0.145 0.310 0.131 0.015 0.20 0.00 24 360 6.00 0.8 0.145 0.305 0.131 0.015 0.20 0.00 25 375 6.25 0.9 0.163 0.301 0.147 0.016 0.23 0.00 26 390 6.50 0.9 0.163 0.297 0.147 0.016 0.23 0.00 27 405 6.75 1.0 0.182 0.293 0.163 0.018 0.25 13.31 28 420 7.00 1.0 0.182 0.289 0.163 0.018 0.25 13.31 29 435 7.25 1.0 0.182 0.285 0.163 0.018 0.25 13.31 30 450 7.50 1.1 0.200 0.282 0.180 0.020 0.28 36.24 31 465 7.75 1.2 0.218 0.278 0.196 0.022 0.31 59.17 32 480 8.00 1.3 0.236 0.274 0.212 0.024 0.33 82.10 33 495 8.25 1.5 0.272 0.270 0.245 0.002 0.03 0.00 34 510 8.50 1.5 0.272 0.266 0.245 0.006 0.09 0.00 35 525 8.75 1.6 0.291 0.263 0.262 0.028 0.39 137.02 36 540 9.00 1.7 0.309 0.259 0.278 0.050 0.70 413.03 37 555 9.25 1.9 0.345 0.255 0.311 0.090 1.26 917.92 38 570 9.50 2.0 0.363 0.252 0.327 0.112 1.57 1193.09 39 585 9.75 2.1 0.381 0.248 0.343 0.133 1.87 1467.82 40 600 10.00 2.2 0.400 0.244 0.360 0.155 2.18 1742.12 41 615 10.25 1.5 0.272 0.241 0.245 0.031 0.44 181.54 42 630 10.50 1.5 0.272 0.237 0.245 0.035 0.49 225.65 43 645 10.75 2.0 0.363 0.234 0.327 0.129 1.81 1415.86 44 660 11.00 2.0 0.363 0.231 0.327 0.133 1.86 1459.09 45 675 11.25 1.9 0.345 0.227 0.311 0.118 1.65 1272.57 46 690 11.50 1.9 0.345 0.224 0.311 0.121 1.70 1314.89 47 705 11.75 1.7 0.309 0.220 0.278 0.088 1.24 898.14 48 720 12.00 1.8 0.327 0.217 0.294 0.110 1.54 1168.85 49 735 12.25 2.5 0.454 0.214 0.409 0.240 3.37 2814.93 50 750 12.50 2.6 0.472 0.211 0.425 0.261 3.67 3084.71 51 765 12.75 2.8 0.508 0.208 0.458 0.301 4.22 3583.31 52 780 13.00 2.9 0.527 0.204 0.474 0.322 4.52 3852.12 53 795 13.25 3.4 0.617 0.201 0.556 0.416 5.84 5037.68 54 810 13.50 3.4 0.617 0.198 0.556 0.419 5.88 5076.21 55 825 13.75 2.3 0.418 0.195 0.376 0.222 3.12 2591.88 56 840 14.00 2.3 0.418 0.192 0.376 0.225 3.16 2629.42 57 855 14.25 2.7 0.490 0.189 0.441 0.301 4.22 3583.67 58 870 14.50 2.6 0.472 0.187 0.425 0.286 4.01 3390.89 59 885 14.75 2.6 0.472 0.184 0.425 0.288 4.05 3426.89 60 900 15.00 2.5 0.454 0.181 0.409 0.273 3.83 3233.06 61 915 15.25 2.4 0.436 0.178 0.392 0.258 3.62 3038.70 Plate E-2.2 Page 8 of 20 RCFCD SYNTHETIC UNIT HYDROGRAPH METHOD 100 YEAR - 24 HOUR STORM EVENT PROJECT: CONCENTRATION POINT: BY: SPE LA QUINTA APARTMENTS SITE RETENTION BASIN DATE: 10/25/2022 EFFECTIVE RAIN CALCULATION FORM DRAINAGE AREA -ACRES UNIT TIME -MINUTES LAG TIME - MINUTES UNIT TIME -PERCENT OF LAG TOTAL ADJUSTED STORM RAIN -INCHES 14.030 15 2.50 599.6 4.54 CONSTANT LOSS RATE-in/hr VARIABLE LOSS RATE (AVG) in/hr MINIMUM LOSS RATE (for var. loss) - in/hr LOW LOSS RATE - DECIMAL C PERCOLATION RATE (cfs) n/a 0.2304 0.115 0.90 0.00213 0.24 Unit Time Time Period Minutes Hours Pattern Percent (Plate E-5.9) Storm Rain in/hr Loss Rate in/hr Max Low Effective Rain in/hr Flood Hydrograph Flow cfs Required Storage cf 62 930 15.50 2.3 0.418 0.175 0.376 0.242 3.40 2843.80 63 945 15.75 1.9 0.345 0.173 0.311 0.172 2.42 1960.44 64 960 16.00 1.9 0.345 0.170 0.311 0.175 2.46 1993.75 65 975 16.25 0.4 0.073 0.167 0.065 0.007 0.10 0.00 66 990 16.50 0.4 0.073 0.165 0.065 0.007 0.10 0.00 67 1005 16.75 0.3 0.054 0.162 0.049 0.005 0.08 0.00 68 1020 17.00 0.3 0.054 0.160 0.049 0.005 0.08 0.00 69 1035 17.25 0.5 0.091 0.158 0.082 0.009 0.13 0.00 70 1050 17.50 0.5 0.091 0.155 0.082 0.009 0.13 0.00 71 1065 17.75 0.5 0.091 0.153 0.082 0.009 0.13 0.00 72 1080 18.00 0.4 0.073 0.151 0.065 0.007 0.10 0.00 73 1095 18.25 0.4 0.073 0.148 0.065 0.007 0.10 0.00 74 1110 18.50 0.4 0.073 0.146 0.065 0.007 0.10 0.00 75 1125 18.75 0.3 0.054 0.144 0.049 0.005 0.08 0.00 76 1140 19.00 0.2 0.036 0.142 0.033 0.004 0.05 0.00 77 1155 19.25 0.3 0.054 0.140 0.049 0.005 0.08 0.00 78 1170 19.50 0.4 0.073 0.138 0.065 0.007 0.10 0.00 79 1185 19.75 0.3 0.054 0.136 0.049 0.005 0.08 0.00 80 1200 20.00 0.2 0.036 0.134 0.033 0.004 0.05 0.00 81 1215 20.25 0.3 0.054 0.133 0.049 0.005 0.08 0.00 82 1230 20.50 0.3 0.054 0.131 0.049 0.005 0.08 0.00 83 1245 20.75 0.3 0.054 0.129 0.049 0.005 0.08 0.00 84 1260 21.00 0.2 0.036 0.128 0.033 0.004 0.05 0.00 85 1275 21.25 0.3 0.054 0.126 0.049 0.005 0.08 0.00 86 1290 21.50 0.2 0.036 0.125 0.033 0.004 0.05 0.00 87 1305 21.75 0.3 0.054 0.123 0.049 0.005 0.08 0.00 88 1320 22.00 0.2 0.036 0.122 0.033 0.004 0.05 0.00 89 1335 22.25 0.3 0.054 0.121 0.049 0.005 0.08 0.00 90 1350 22.50 0.2 0.036 0.120 0.033 0.004 0.05 0.00 91 1365 22.75 0.2 0.036 0.119 0.033 0.004 0.05 0.00 92 1380 23.00 0.2 0.036 0.118 0.033 0.004 0.05 0.00 93 1395 23.25 0.2 0.036 0.117 0.033 0.004 0.05 0.00 94 1410 23.50 0.2 0.036 0.116 0.033 0.004 0.05 0.00 95 1425 23.75 0.2 0.036 0.116 0.033 0.004 0.05 0.00 96 1440 24.00 0.2 0.036 0.115 0.033 0.004 0.05 0.00 EFFECTIVE RAIN & FLOOD VOLUMES SUMMARY EFFECTIVE RAIN (in) FLOOD VOLUME (acft) FLOOD VOLUME (tuft) REQUIRED STORAGE (acft) REQUIRED STORAGE (tuft) PEAK FLOW (cfs) 1.57 1.84 80099.08 1.52 66166.46 5.88 Plate E-2.2 Page 9 of 20 PROJECT: LA QUINTA APARTMENTS ECI JOB# 20210635 SITE RETENTION BASIN BASIN CHARACTERISTICS CONTOUR INCR (ft) DEPTH TOTAL (ft) AREA INCR (sf) TOTAL (sf) INCR (cuft) VOLUME TOTAL (cuft) (acre -ft) 42 0 0 0.15 8867 0 0 0.00 43 1 1 2816 11683 10275 10275 0.24 44 1 2 2929 14612 13148 23423 0.54 45 1 3 3042 17654 16133 39556 0.91 46 1 4 3155 20809 19232 58787 1.35 47 1 5 3268 24077 22443 81230 1.86 48 1 1 6 3381 1 274581 25768 1 106998 1 2.46 PERCOLATION CALCULATIONS PERCOLATION RATE 0 in/hr 0.00000 cfs per square foot of perc area DRYW ELLS NUMBER USED 2 RATE/DRYW ELL 0.12 cfs TOTAL DISSIPATED 0.24 cfs TOTAL DRYWELL PERCOLATION RATE 0.24 cfs INTERPOLATION TABLE FOR RETENTION BASIN DEPTH/AREA/VOLUME LOOKUP CONTOUR DEPTH AREA INCR TOTAL INCR TOTAL INCR (ft) (ft) (sf) (sf) (cuft) 42.00 42.03 42.05 42.08 42.10 42.13 42.15 42.18 42.20 42.23 42.25 42.28 42.30 42.33 42.35 42.38 42.40 42.43 42.45 42.48 42.50 42.53 42.55 42.58 0 0 0.025 0.02 0.025 0.05 0.025 0.07 0.025 0.10 0.025 0.12 0.025 0.15 0.025 0.17 0.025 0.20 0.025 0.22 0.025 0.25 0.025 0.27 0.025 0.30 0.025 0.32 0.025 0.35 0.025 0.37 0.025 0.40 0.025 0.42 0.025 0.45 0.025 0.47 0.025 0.50 0.025 0.52 0.025 0.55 0.025 0.57 0 8867 0 70 8937 223 70 9008 225 70 9078 227 70 9149 229 70 9219 230 70 9289 232 70 9360 234 70 9430 235 70 9501 237 70 9571 239 70 9641 241 70 9712 242 70 9782 244 70 9853 246 70 9923 247 70 9993 249 70 10064 251 70 10134 253 70 10205 254 70 10275 256 70 10345 258 70 10416 259 70 10486 261 VOLUME TOTAL (cuft) (acre -ft) 0 0.00 223 0.01 449 0.01 675 0.02 904 0.02 1134 0.03 1366 0.03 1600 0.04 1835 0.04 2072 0.05 2311 0.05 2552 0.06 2794 0.06 3038 0.07 3284 0.08 3531 0.08 3780 0.09 4031 0.09 4284 0.10 4538 0.10 4794 0.11 5052 0.12 5311 0.12 5572 0.13 Basin Characteristics Page 10 of 20 42.60 42.63 42.65 42.68 42.70 42.73 42.75 42.78 42.80 42.83 42.85 42.88 42.90 42.92 42.95 42.97 43.00 43.03 43.05 43.08 43.10 43.13 43.15 43.18 43.20 43.23 43.25 43.28 43.30 43.33 43.35 43.38 43.40 43.43 43.45 43.48 43.50 43.53 43.55 43.58 43.60 43.63 43.65 43.68 43.70 43.73 43.75 43.78 43.80 43.83 43.85 43.88 43.90 43.92 43.95 43.97 44.00 44.03 0.025 0.60 0.025 0.62 0.025 0.65 0.025 0.67 0.025 0.70 0.025 0.72 0.025 0.75 0.025 0.77 0.025 0.80 0.025 0.82 0.025 0.85 0.025 0.87 0.025 0.90 0.025 0.92 0.025 0.95 0.025 0.97 0.025 1.00 0.025 1.03 0.025 1.05 0.025 1.08 0.025 1.10 0.025 1.12 0.025 1.15 0.025 1.17 0.025 1.20 0.025 1.22 0.025 1.25 0.025 1.27 0.025 1.30 0.025 1.32 0.025 1.35 0.025 1.37 0.025 1.40 0.025 1.42 0.025 1.45 0.025 1.47 0.025 1.50 0.025 1.52 0.025 1.55 0.025 1.57 0.025 1.60 0.025 1.62 0.025 1.65 0.025 1.67 0.025 1.70 0.025 1.72 0.025 1.75 0.025 1.77 0.025 1.80 0.025 1.82 0.025 1.85 0.025 1.87 0.025 1.90 0.025 1.92 0.025 1.95 0.025 1.97 0.025 2.00 0.025 2.03 70 10557 263 5835 0.13 70 10627 265 6100 0.14 70 10697 266 6366 0.15 70 10768 268 6634 0.15 70 10838 270 6904 0.16 70 10909 271 7176 0.16 70 10979 273 7449 0.17 70 11049 275 7724 0.18 70 11120 277 8000 0.18 70 11190 278 8279 0.19 70 11261 280 8559 0.20 70 11331 282 8840 0.20 70 11401 283 9124 0.21 70 11472 285 9409 0.22 70 11542 287 9696 0.22 70 11613 289 9985 0.23 70 11683 290 10275 0.24 73 11756 294 10569 0.24 73 11829 296 10865 0.25 73 11903 297 11162 0.26 73 11976 299 11461 0.26 73 12049 301 11762 0.27 73 12122 303 12065 0.28 73 12196 305 12370 0.28 73 12269 306 12676 0.29 73 12342 308 12984 0.30 73 12415 310 13294 0.31 73 12488 312 13606 0.31 73 12562 314 13919 0.32 73 12635 315 14234 0.33 73 12708 317 14552 0.33 73 12781 319 14870 0.34 73 12855 321 15191 0.35 73 12928 322 15514 0.36 73 13001 324 15838 0.36 73 13074 326 16164 0.37 73 13148 328 16492 0.38 73 13221 330 16821 0.39 73 13294 331 17153 0.39 73 13367 333 17486 0.40 73 13440 335 17821 0.41 73 13514 337 18157 0.42 73 13587 339 18496 0.42 73 13660 340 18836 0.43 73 13733 342 19178 0.44 73 13807 344 19522 0.45 73 13880 346 19868 0.46 73 13953 347 20215 0.46 73 14026 349 20564 0.47 73 14099 351 20915 0.48 73 14173 353 21268 0.49 73 14246 355 21623 0.50 73 14319 356 21979 0.50 73 14392 358 22337 0.51 73 14466 360 22697 0.52 73 14539 362 23059 0.53 73 14612 364 23423 0.54 76 14688 367 23790 0.55 Basin Characteristics Page 11 of 20 44.05 44.08 44.10 44.13 44.15 44.18 44.20 44.23 44.25 44.28 44.30 44.33 44.35 44.38 44.40 44.43 44.45 44.48 44.50 44.53 44.55 44.58 44.60 44.63 44.65 44.68 44.70 44.73 44.75 44.78 44.80 44.83 44.85 44.88 44.90 44.92 44.95 44.97 45.00 45.03 45.05 45.08 45.10 45.13 45.15 45.18 45.20 45.23 45.25 45.28 45.30 45.33 45.35 45.38 45.40 45.43 45.45 45.48 0.025 2.05 0.025 2.08 0.025 2.10 0.025 2.12 0.025 2.15 0.025 2.17 0.025 2.20 0.025 2.22 0.025 2.25 0.025 2.27 0.025 2.30 0.025 2.32 0.025 2.35 0.025 2.37 0.025 2.40 0.025 2.42 0.025 2.45 0.025 2.47 0.025 2.50 0.025 2.52 0.025 2.55 0.025 2.57 0.025 2.60 0.025 2.62 0.025 2.65 0.025 2.67 0.025 2.70 0.025 2.72 0.025 2.75 0.025 2.77 0.025 2.80 0.025 2.82 0.025 2.85 0.025 2.87 0.025 2.90 0.025 2.92 0.025 2.95 0.025 2.97 0.025 3.00 0.025 3.03 0.025 3.05 0.025 3.08 0.025 3.10 0.025 3.12 0.025 3.15 0.025 3.17 0.025 3.20 0.025 3.22 0.025 3.25 0.025 3.27 0.025 3.30 0.025 3.32 0.025 3.35 0.025 3.37 0.025 3.40 0.025 3.42 0.025 3.45 0.025 3.47 76 14764 369 24159 0.55 76 14840 371 24530 0.56 76 14916 373 24902 0.57 76 14992 375 25277 0.58 76 15068 376 25653 0.59 76 15144 378 26032 0.60 76 15220 380 26412 0.61 76 15296 382 26794 0.62 76 15373 384 27178 0.62 76 15449 386 27563 0.63 76 15525 388 27951 0.64 76 15601 389 28340 0.65 76 15677 391 28731 0.66 76 15753 393 29125 0.67 76 15829 395 29520 0.68 76 15905 397 29916 0.69 76 15981 399 30315 0.70 76 16057 401 30716 0.71 76 16133 402 31118 0.71 76 16209 404 31522 0.72 76 16285 406 31928 0.73 76 16361 408 32336 0.74 76 16437 410 32746 0.75 76 16513 412 33158 0.76 76 16589 414 33571 0.77 76 16665 415 33987 0.78 76 16741 417 34404 0.79 76 16817 419 34823 0.80 76 16894 421 35244 0.81 76 16970 423 35667 0.82 76 17046 425 36091 0.83 76 17122 427 36518 0.84 76 17198 428 36946 0.85 76 17274 430 37377 0.86 76 17350 432 37809 0.87 76 17426 434 38243 0.88 76 17502 436 38678 0.89 76 17578 438 39116 0.90 76 17654 439 39556 0.91 79 17733 443 39999 0.92 79 17812 445 40444 0.93 79 17891 447 40891 0.94 79 17970 449 41340 0.95 79 18048 451 41791 0.96 79 18127 453 42244 0.97 79 18206 455 42699 0.98 79 18285 457 43156 0.99 79 18364 459 43614 1.00 79 18443 461 44075 1.01 79 18522 463 44537 1.02 79 18601 464 45002 1.03 79 18679 466 45468 1.04 79 18758 468 45936 1.05 79 18837 470 46407 1.07 79 18916 472 46879 1.08 79 18995 474 47353 1.09 79 19074 476 47829 1.10 79 19153 478 48307 1.11 Basin Characteristics Page 12 of 20 45.50 45.53 45.55 45.58 45.60 45.63 45.65 45.68 45.70 45.73 45.75 45.78 45.80 45.83 45.85 45.88 45.90 45.92 45.95 45.97 46.00 46.03 46.05 46.08 46.10 46.13 46.15 46.18 46.20 46.23 46.25 46.28 46.30 46.33 46.35 46.38 46.40 46.43 46.45 46.48 46.50 46.53 46.55 46.58 46.60 46.63 46.65 46.68 46.70 46.73 46.75 46.78 46.80 46.83 46.85 46.88 46.90 46.92 0.025 3.50 0.025 3.52 0.025 3.55 0.025 3.57 0.025 3.60 0.025 3.62 0.025 3.65 0.025 3.67 0.025 3.70 0.025 3.72 0.025 3.75 0.025 3.77 0.025 3.80 0.025 3.82 0.025 3.85 0.025 3.87 0.025 3.90 0.025 3.92 0.025 3.95 0.025 3.97 0.025 4.00 0.025 4.03 0.025 4.05 0.025 4.08 0.025 4.10 0.025 4.12 0.025 4.15 0.025 4.17 0.025 4.20 0.025 4.22 0.025 4.25 0.025 4.27 0.025 4.30 0.025 4.32 0.025 4.35 0.025 4.37 0.025 4.40 0.025 4.42 0.025 4.45 0.025 4.47 0.025 4.50 0.025 4.52 0.025 4.55 0.025 4.57 0.025 4.60 0.025 4.62 0.025 4.65 0.025 4.67 0.025 4.70 0.025 4.72 0.025 4.75 0.025 4.77 0.025 4.80 0.025 4.82 0.025 4.85 0.025 4.87 0.025 4.90 0.025 4.92 79 19232 480 48786 1.12 79 19310 482 49268 1.13 79 19389 484 49752 1.14 79 19468 486 50238 1.15 79 19547 488 50725 1.16 79 19626 489 51214 1.18 79 19705 491 51706 1.19 79 19784 493 52199 1.20 79 19863 495 52694 1.21 79 19941 497 53191 1.22 79 20020 499 53691 1.23 79 20099 501 54192 1.24 79 20178 503 54694 1.26 79 20257 505 55199 1.27 79 20336 507 55706 1.28 79 20415 509 56215 1.29 79 20494 511 56725 1.30 79 20572 513 57238 1.31 79 20651 514 57752 1.33 79 20730 516 58269 1.34 79 20809 518 58787 1.35 82 20891 522 59309 1.36 82 20972 524 59833 1.37 82 21054 526 60360 1.39 82 21136 528 60888 1.40 82 21218 530 61418 1.41 82 21299 532 61950 1.42 82 21381 534 62484 1.43 82 21463 536 63021 1.45 82 21544 538 63559 1.46 82 21626 540 64099 1.47 82 21708 542 64641 1.48 82 21789 544 65185 1.50 82 21871 546 65731 1.51 82 21953 548 66279 1.52 82 22035 550 66829 1.53 82 22116 552 67382 1.55 82 22198 554 67936 1.56 82 22280 556 68492 1.57 82 22361 558 69050 1.59 82 22443 560 69610 1.60 82 22525 562 70172 1.61 82 22606 564 70736 1.62 82 22688 566 71302 1.64 82 22770 568 71870 1.65 82 22852 570 72440 1.66 82 22933 572 73012 1.68 82 23015 574 73586 1.69 82 23097 576 74162 1.70 82 23178 578 74740 1.72 82 23260 580 75320 1.73 82 23342 582 75902 1.74 82 23423 584 76486 1.76 82 23505 586 77072 1.77 82 23587 588 77660 1.78 82 23669 590 78250 1.80 82 23750 592 78842 1.81 82 23832 594 79436 1.82 Basin Characteristics Page 13 of 20 46.95 46.97 47.00 47.03 47.05 47.08 47.10 47.13 47.15 47.18 47.20 47.23 47.25 47.28 47.30 47.33 47.35 47.38 47.40 47.43 47.45 47.48 47.50 47.53 47.55 47.58 47.60 47.63 47.65 47.68 47.70 47.73 47.75 47.78 47.80 47.83 47.85 47.88 47.90 47.92 47.95 47.971 48.001 0.025 4.95 82 82 82 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 23914 23995 24077 24162 24246 24331 24415 24500 24584 24669 24753 24838 24922 25007 25091 25176 25260 25345 25429 25514 25598 25683 25768 25852 25937 26021 26106 26190 26275 26359 26444 26528 26613 26697 26782 26866 26951 27035 27120 27204 27289 27373 27458 596 598 600 604 606 608 610 612 614 616 618 620 623 625 627 629 631 633 635 637 639 641 643 645 647 649 651 653 656 658 660 662 664 666 668 670 672 674 676 678 680 682 684 80032 80630 81230 81834 82440 83048 83658 84271 84885 85501 86120 86740 87363 87987 88614 89243 89873 90506 91141 91778 92417 93058 93701 94347 94994 95643 96295 96948 97604 98261 98921 99583 100246 100912 101580 102250 102922 103596 104272 104951 105631 106313 106998 1.84 1.85 1.86 1.88 1.89 1.91 1.92 1.93 1.95 1.96 1.98 1.99 2.01 2.02 2.03 2.05 2.06 2.08 2.09 2.11 2.12 2.14 2.15 2.17 2.18 2.20 2.21 2.23 2.24 2.26 2.27 2.29 2.30 2.32 2.33 2.35 2.36 2.38 2.39 2.41 2.42 2.44 2.46 0.025 4.97 0.025 5.00 0.025 5.03 0.025 5.05 0.025 5.08 0.025 5.10 0.025 5.12 0.025 5.15 0.025 5.17 0.025 5.20 0.025 5.22 0.025 5.25 0.025 5.27 0.025 5.30 0.025 5.32 0.025 5.35 0.025 5.37 0.025 5.40 0.025 5.42 0.025 5.45 0.025 5.47 0.025 5.50 0.025 5.52 0.025 5.55 0.025 5.57 0.025 5.60 0.025 5.62 0.025 5.65 0.025 5.67 0.025 5.70 0.025 5.72 0.025 5.75 0.025 5.77 0.025 5.80 0.025 5.82 0.025 5.85 0.025 5.87 0.025 5.90 0.025 5.92 0.025 5.95 0.025 5.97 0.025 1 6.00 Basin Characteristics Page 14 of 20 SITE RETENTION BASIN ECI JOB # 20210635 100 YEAR - 1 HOUR STORM EVENT TIME UNIT (min) PERIOD FLOW IN (cfs) VOLUME IN (cuft) PERC AREA DEPTH (ft) BASIN VOL PRE-PERC (cuft) PERC AREA (sf) PERC OUT (cuft) POST PERC BASIN DEPTH (ft) BALANCE IN BASIN (cuft) (acre -ft) 1 5 6.56 1,967 42.23 1,967 9501 0 42.23 1,967 0.05 2 10 9.54 2,862 42.50 4,829 10275 0 42.50 4,829 0.11 3 15 10.35 3,106 42.80 7,934 11120 0 42.80 7,934 0.18 4 20 9.81 2,943 43.05 10,877 11829 0 43.05 10,877 0.25 5 25 14.42 4,325 43.40 15,203 12855 0 43.40 15,203 0.35 6 30 16.32 4,895 43.78 20,097 13953 0 43.78 20,097 0.46 7 35 19.30 5,789 44.18 25,886 15144 01 44.18 25,886 0.59 8 40 20.92 6,277 44.58 32,163 16361 0 44.58 32,163 0.74 9 45 29.87 8,960 45.10 41,124 17970 0 45.10 41,124 0.94 10 50 44.23 13,270 45.78 54,394 20099 0 45.78 54,394 1.25 11 55 40.17 12,051 46.35 66,445 21953 0 46.35 66,445 1.53 12 60 1 7.911 2,374 1 46.481 68,819 1 22361 0 46.48 68,819 1.58 Basin Depth Analysis Page 15 of 20 SITE RETENTION BASIN ECI JOB # 20210635 100 YEAR - 3 HOUR STORM EVENT TIME UNIT PERIOD (min) FLOW IN (cfs) VOLUME IN (cuft) PERC AREA DEPTH (ft) BASIN VOL PRE-PERC (cuft) BASIN PERC AREA PERC OUT (cuft) POST PERC BASIN DEPTH (ft) BALANCE IN BASIN (cuft) (acre -ft) 1 5 1.47 442 42.05 442 9008 0 42.05 442 0.01 2 10 1.47 442 42.10 885 9149 0 42.10 885 0.02 3 15 0.71 214 42.13 1,099 9219 0 42.13 1,099 0.03 4 20 2.24 671 42.20 1,769 9430 0 42.20 1,769 0.04 5 25 2.24 671 42.28 2,440 9641 0 42.28 2,440 0.06 6 30 3.38 1,013 42.38 3,453 9923 0 42.38 3,453 0.08 7 35 2.24 671 42.43 4,124 10064 0 42.43 4,124 0.09 8 40 3.38 1,013 42.53 5,137 10345 0 42.53 5,137 0.12 9 45 3.38 1,013 42.63 6,150 10627 0 42.63 6,150 0.14 10 50 2.24 671 42.70 6,820 10838 0 42.70 6,820 0.16 11 55 2.62 785 42.78 7,605 11049 0 42.78 7,605 0.17 12 60 3.38 1,013 42.85 8,618 11261 0 42.85 8,618 0.20 13 65 4.90 1,470 42.97 10,088 11613 0 42.97 10,088 0.23 14 70 4.90 1,470 43.10 11,557 11976 0 43.10 11,557 0.27 15 75 4.90 1,470 43.23 13,027 12342 0 43.23 13,027 0.30 16 80 4.14 1,241 43.33 14,268 12635 0 43.33 14,268 0.33 17 85 6.42 1,926 43.48 16,195 13074 0 43.48 16,195 0.37 18 90 6.80 2,040 43.63 18,235 13514 0 43.63 18,235 0.42 19 95 5.66 1,698 43.75 19,933 13880 0 43.75 19,933 0.46 20 100 6.80 2,040 43.90 21,973 14319 0 43.90 21,973 0.50 21 105 9.08 2,725 44.08 24,699 14840 0 44.08 24,699 0.57 22 110 8.32 2,497 44.25 27,196 15373 0 44.25 27,196 0.62 23 115 7.56 2,269 44.40 29,464 15829 0 44.40 29,464 0.68 24 120 7.94 2,383 44.55 31,847 16285 0 44.55 31,847 0.73 25 125 8.32 2,497 44.70 34,344 16741 0 44.70 34,344 0.79 26 130 12.51 3,753 44.92 38,097 17426 0 44.92 38,097 0.87 27 135 15.55 4,666 45.18 42,763 18206 0 45.18 42,763 0.98 28 140 9.85 2,954 45.35 45,716 18758 0 45.35 45,716 1.05 29 145 22.40 6,720 45.68 52,437 19784 0 45.68 52,437 1.20 30 150 24.30 7,291 46.05 59,728 20972 0 46.05 59,728 1.37 31 155 27.73 8,319 46.43 68,046 22198 0 46.43 68,046 1.56 32 160 18.98 5,693 46.68 73,739 23015 0 46.68 73,739 1.69 33 165 4.14 1,241 46.73 74,981 23178 0 46.73 74,981 1.72 34 170 3.38 1,013 46.78 75,994 23342 0 46.78 75,994 1.74 35 175 3.38 1,013 46.83 77,007 23505 0 46.83 77,007 1.77 36 180 -0.01 (4) 46.83 77,003 23505 01 46.83 77,003 1.77 Basin Depth Analysis Page 16 of 20 SITE RETENTION BASIN ECI JOB # 20210635 100 YEAR - 6 HOUR STORM EVENT TIME UNIT PERIOD (min) FLOW IN (cfs) VOLUME IN (cuft) PERC AREA DEPTH (ft) BASIN VOL PRE-PERC (cuft) BASIN PERC AREA PERC OUT (cuft) POST PERC BASIN DEPTH (ft) BALANCE IN BASIN (cuft) (acre -ft) 1 5 0.00 (0) 42.00 (0) 8867 0 42.00 - 0.00 2 10 0.05 14 42.00 14 8867 0 42.00 14 0.00 3 15 0.05 14 42.00 28 8867 0 42.00 28 0.00 4 20 0.05 14 42.00 42 8867 01 42.00 42 0.00 5 25 0.05 14 42.00 56 8867 0 42.00 56 0.00 6 30 -0.13 (38) 42.00 19 8867 0 42.00 19 0.00 7 35 -0.13 38 42.00 19 8867 0 42.00 - 0.00 8 40 -0.13 (38) 42.00 (38) 8867 0 42.00 - 0.00 9 45 -0.13 (38) 42.00 (38) 8867 0 42.00 - 0.00 10 50 -0.13 (38) 42.00 (38) 8867 0 42.00 - 0.00 11 55 -0.13 (38) 42.00 (38) 8867 0 42.00 - 0.00 12 60 0.35 106 42.00 106 8867 0 42.00 106 0.00 13 65 0.35 106 42.03 212 8937 0 42.03 212 0.00 14 70 0.35 106 42.03 318 8937 0 42.03 318 0.01 15 75 0.35 106 42.05 424 9008 0 42.05 424 0.01 16 80 0.35 106 42.05 530 9008 0 42.05 530 0.01 17 85 0.35 106 42.08 636 9078 0 42.08 636 0.01 18 90 0.35 106 42.08 742 9078 0 42.08 742 0.02 19 95 0.35 106 42.10 847 9149 0 42.10 847 0.02 20 100 0.35 106 42.10 953 9149 0 42.10 953 0.02 21 105 0.35 106 42.13 1,059 9219 01 42.13 1,059 0.02 22 110 0.35 106 42.13 1,165 9219 0 42.13 1,165 0.03 23 115 0.35 106 42.15 1,271 9289 0 42.15 1,271 0.03 24 120 0.83 249 42.18 1,521 9360 0 42.18 1,521 0.03 25 125 0.35 106 42.18 1,627 9360 0 42.18 1,627 0.04 26 130 0.83 249 42.20 1,876 9430 0 42.20 1,876 0.04 27 135 0.83 249 42.23 2,125 9501 0 42.23 2,125 0.05 28 140 0.83 249 42.25 2,375 9571 0 42.25 2,375 0.05 29 145 0.83 249 42.28 2,624 9641 0 42.28 2,624 0.06 30 150 0.83 249 42.30 2,873 9712 0 42.30 2,873 0.07 31 155 0.83 249 42.33 3,123 9782 0 42.33 3,123 0.07 32 160 0.83 249 42.35 3,372 9853 0 42.35 3,372 0.08 33 165 1.31 393 42.40 3,765 9993 0 42.40 3,765 0.09 34 170 1.31 393 42.45 4,158 10134 0 42.45 4,158 0.10 35 175 1.31 393 42.48 4,551 10205 0 42.48 4,551 0.10 36 180 1.31 393 42.53 4,943 10345 0 42.53 4,943 0.11 37 185 1.31 393 42.55 5,336 10416 0 42.55 5,336 0.12 38 190 1.79 536 42.60 5,873 10557 0 42.60 5,873 0.13 39 195 1.79 536 42.65 6,409 10697 0 42.65 6,409 0.15 40 200 1.79 536 42.70 6,945 10838 0 42.70 6,945 0.16 41 205 2.27 680 42.78 7,625 11049 0 42.78 7,625 0.18 42 210 2.74 823 42.85 8,448 11261 0 42.85 8,448 0.19 43 215 3.22 967 42.92 9,415 11472 0 42.92 9,415 0.22 44 220 3.22 967 43.00 10,381 11683 0 43.00 10,381 0.24 45 225 3.70 1,110 43.10 11,491 11976 0 43.10 11,491 0.26 46 230 3.70 1,110 43.20 12,601 12269 0 43.20 12,601 0.29 47 235 4.18 1,253 43.30 13,855 12562 0 43.30 13,855 0.32 48 240 4.18 1,253 43.40 15,108 12855 0 43.40 15,108 0.35 49 245 4.66 1,397 43.50 16,505 13148 0 43.50 16,505 0.38 50 250 5.13 1,540 43.63 18,045 13514 0 43.63 18,045 0.41 51 255 5.61 1,684 43.75 19,729 13880 0 43.75 19,729 0.45 52 260 6.09 1,827 43.88 21,556 14246 0 43.88 21,556 0.49 Basin Depth Analysis Page 17 of 20 SITE RETENTION BASIN ECI JOB # 20210635 100 YEAR - 6 HOUR STORM EVENT TIME UNIT PERIOD (min) FLOW IN (cfs) VOLUME IN (cuft) PERC AREA DEPTH (ft) BASIN VOL PRE-PERC (cuft) BASIN PERC AREA PERC OUT (cuft) POST PERC BASIN DEPTH (ft) BALANCE IN BASIN (cuft) (acre -ft) 53 265 6.57 1,971 44.00 23,527 14612 0 44.00 23,527 0.54 54 270 6.57 1,971 44.15 25,498 15068 0 44.15 25,498 0.59 55 275 7.05 2,114 44.28 27,612 15449 0 44.28 27,612 0.63 56 280 7.53 2,258 44.43 29,870 15905 0 44.43 29,870 0.69 57 285 8.00 2,401 44.58 32,271 16361 0 44.58 32,271 0.74 58 290 8.00 2,401 44.73 34,672 16817 0 44.73 34,672 0.80 59 295 8.48 2,544 44.88 37,216 17274 0 44.88 37,216 0.85 60 300 8.96 2,688 45.03 39,904 17733 0 45.03 39,904 0.92 61 305 11.35 3,405 45.20 43,309 18285 0 45.20 43,309 0.99 62 310 13.74 4,122 45.43 47,431 18995 01 45.43 47,431 1.09 63 315 15.18 4,553 45.68 51,984 19784 0 45.68 51,984 1.19 64 320 16.61 4,983 45.90 56,967 20494 0 45.90 56,967 1.31 65 325 19.00 5,700 46.18 62,667 21381 0 46.18 62,667 1.44 66 330 23.30 6,991 46.50 69,658 22443 0 46.50 69,658 1.60 67 335 5.61 1,684 46.58 71,342 22688 0 46.58 71,342 1.64 68 340 0.83 249 46.60 71,592 22770 0 46.60 71,592 1.64 69 345 0.05 14 46.60 71,606 22770 0 46.60 71,606 1.64 70 350 0.00 (0) 46.60 71,605 22770 0 46.60 71,605 1.64 71 355 -0.10 (29) 46.58 71,576 22688 0 46.58 71,576 1.64 72 360 -0.14 (43) 46.58 71,533 22688 0 46.58 71,533 1.64 Basin Depth Analysis Page 18 of 20 SITE RETENTION BASIN ECI JOB # 20210635 100 YEAR - 24 HOUR STORM EVENT TIME UNIT (min) PERIOD FLOW IN cfs) VOLUME IN (cuft) PERC AREA DEPTH (ft) BASIN VOL PRE-PERC (cuft) BASIN PERC AREA PERC OUT cuft POST PERC BASIN DEPTH ft) BALANCE IN BASIN (cuft) (acre -ft 1 15 -0.19 (170) 42.00 (170) 8867 0 42.00 - 0.00 2 30 -0.16 (147) 42.00 (147) 88671 0 42.00 - 0.00 3 45 -0.16 147 42.00 147 8867 0 42.00 - 0.00 4 60 -0.14 124 42.00 124 8867 0 42.00 - 0.00 5 75 -0.16 (147) 42.00 (147) 8867 0 42.00 - 0.00 6 90 -0.16 (147) 42.00 (147) 8867 0 42.00 - 0.00 7 105 -0.16 147 42.00 147 8867 0 42.00 - 0.00 8 120 -0.14 (124) 42.00 (124) 8867 0 42.00 - 0.00 9 135 -0.14 (124) 42.00 (124) 8867 0 42.00 - 0.00 10 150 -0.14 124 42.00 124 8867 0 42.00 - 0.00 11 165 -0.11 (101) 42.00 (101) 8867 0 42.00 - 0.00 12 180 -0.11 (101) 42.00 (101) 8867 0 42.00 - 0.00 13 195 -0.11 (101) 42.00 (101) 8867 0 42.00 - 0.00 14 210 -0.11 101 42.00 101 8867 0 42.00 - 0.00 15 225 -0.11 (101) 42.00 (101) 8867 0 42.00 - 0.00 16 240 -0.09 (78) 42.00 (78) 8867 0 42.00 - 0.00 17 255 -0.09 78 42.00 78 8867 0 42.00 - 0.00 18 270 -0.06 55 42.00 55 8867 0 42.00 - 0.00 19 285 -0.06 (55) 42.00 (55) 8867 0 42.00 - 0.00 20 300 -0.04 33 42.00 33 8867 0 42.00 - 0.00 21 315 -0.09 78 42.00 78 8867 0 42.00 - 0.00 22 330 -0.06 (55) 42.00 (55) 88671 0 42.00 - 0.00 23 345 -0.04 (33) 42.00 (33) 88671 0 42.00 - 0.00 24 360 -0.04 33 42.00 33 88671 0 42.00 - 0.00 25 375 -0.01 (10) 42.00 (10) 8867 0 42.00 - 0.00 26 390 -0.01 (10) 42.00 (10) 8867 0 42.00 - 0.00 27 405 0.01 13 42.00 13 8867 0 42.00 13 0.00 28 420 0.01 13 42.00 27 8867 0 42.00 27 0.00 29 435 0.01 13 42.00 40 8867 0 42.00 40 0.00 30 450 0.04 36 42.00 76 8867 0 42.00 76 0.00 31 465 0.07 59 42.03 135 8937 0 42.03 135 0.00 32 480 0.09 82 42.03 217 8937 0 42.03 217 0.00 33 495 -0.21 (187) 42.00 30 8867 0 42.00 30 0.00 34 510 -0.15 139 42.00 109 8867 0 42.00 - 0.00 35 525 0.15 137 42.03 137 8937 0 42.03 137 0.00 36 540 0.46 413 42.05 550 9008 0 42.05 550 0.01 37 555 1.02 918 42.15 1,468 9289 0 42.15 1,468 0.03 38 570 1.33 1,193 42.28 2,661 9641 0 42.28 2,661 0.06 39 585 1.63 1,468 42.43 4,129 10064 0 42.43 4,129 0.09 40 600 1.94 1,742 42.60 5,871 10557 0 42.60 5,871 0.13 41 615 0.20 182 42.63 6,053 10627 0 42.63 6,053 0.14 42 630 0.25 226 42.65 6,278 10697 0 42.65 6,278 0.14 43 645 1.57 1,416 42.78 7,694 11049 0 42.78 7,694 0.18 44 660 1.62 1,459 42.90 9,153 11401 0 42.90 9,153 0.21 45 675 1.41 1,273 43.03 10,426 11756 0 43.03 10,426 0.24 46 690 1.46 1,315 43.13 11,741 12049 0 43.13 11,741 0.27 47 705 1.00 898 43.20 12,639 12269 0 43.20 12,639 0.29 48 720 1.30 1,169 43.30 13,808 12562 0 43.30 13,808 0.32 49 735 3.13 2,815 43.50 16,623 13148 0 43.50 16,623 0.38 50 750 3.43 3,085 43.75 19,707 13880 0 43.75 19,707 0.45 51 765 3.98 3,583 44.00 23,291 14612 0 44.00 23,291 0.53 52 780 4.28 3,852 44.25 27,143 15373 0 44.25 27,143 0.62 53 1 795 1 5.601 5,038 1 44.58 1 32,180 1 16361 0 44.58 32,180 0.74 Basin Depth Analysis Page 19 of 20 SITE RETENTION BASIN ECI JOB # 20210635 100 YEAR - 24 HOUR STORM EVENT TIME UNIT (min) PERIOD FLOW IN cfs) VOLUME IN (cuft) PERC AREA DEPTH (ft) BASIN VOL PRE-PERC (cuft) BASIN PERC AREA PERC OUT cuft POST PERC BASIN DEPTH ft) BALANCE IN BASIN (cuft) (acre -ft 54 810 5.64 5,076 44.88 37,257 17274 0 44.88 37,257 0.86 55 825 2.88 2,592 45.03 39,848 17733 0 45.03 39,848 0.91 56 840 2.92 2,629 45.18 42,478 18206 0 45.18 42,478 0.98 57 855 3.98 3,584 45.35 46,062 18758 0 45.35 46,062 1.06 58 870 3.77 3,391 45.53 49,452 19310 0 45.53 49,452 1.14 59 885 3.81 3,427 45.70 52,879 19863 0 45.70 52,879 1.21 60 900 3.59 3,233 45.88 56,112 20415 0 45.88 56,112 1.29 61 915 3.38 3,039 46.03 59,151 20891 0 46.03 59,151 1.36 62 930 3.16 2,844 46.15 61,995 21299 0 46.15 61,995 1.42 63 945 2.18 1,960 46.25 63,955 21626 0 46.25 63,955 1.47 64 960 2.22 1,994 46.33 65,949 21871 0 46.33 65,949 1.51 65 975 -0.14 (124) 46.33 65,825 218711 0 46.33 65,825 1.51 66 990 -0.14 (124) 46.33 65,700 21871 0 46.33 65,700 1.51 67 1005 -0.16 147 46.33 65,553 21871 0 46.33 65,553 1.50 68 1020 -0.16 (147) 46.30 65,406 21789 0 46.30 65,406 1.50 69 1035 -0.11 (101) 46.30 65,305 21789 0 46.30 65,305 1.50 70 1050 -0.11 101 46.30 65,203 21789 0 46.30 65,203 1.50 71 1065 -0.11 (101) 46.30 65,102 21789 0 46.30 65,102 1.49 72 1080 -0.14 (124) 46.30 64,978 21789 0 46.30 64,978 1.49 73 1095 -0.14 124 46.28 64,853 21708 0 46.28 64,853 1.49 74 1110 -0.14 124 46.28 64,729 21708 0 46.28 64,729 1.49 75 1125 -0.16 (147) 46.28 64,582 21708 0 46.28 64,582 1.48 76 1140 -0.19 (170) 46.28 64,412 21708 0 46.28 64,412 1.48 77 1155 -0.16 147 46.25 64,265 21626 0 46.25 64,265 1.48 78 1170 -0.14 (124) 46.25 64,140 21626 0 46.25 64,140 1.47 79 1185 -0.16 (147) 46.25 63,993 21626 0 46.25 63,993 1.47 80 1200 -0.19 170 46.23 63,823 215441 0 46.23 63,823 1.47 81 1215 -0.16 (147) 46.23 63,676 21544 0 46.23 63,676 1.46 82 1230 -0.16 (147) 46.23 63,529 21544 0 46.23 63,529 1.46 83 1245 -0.16 (147) 46.23 63,381 21544 0 46.23 63,381 1.46 84 1260 -0.19 170 46.20 63,211 21463 0 46.20 63,211 1.45 85 1275 -0.16 (147) 46.20 63,064 21463 0 46.20 63,064 1.45 86 1290 -0.19 (170) 46.20 62,894 21463 0 46.20 62,894 1.44 87 1305 -0.16 147 46.18 62,747 21381 0 46.18 62,747 1.44 88 1320 -0.19 (170) 46.18 62,577 21381 0 46.18 62,577 1.44 89 1335 -0.16 (147) 46.18 62,429 21381 0 46.18 62,429 1.43 90 1350 -0.19 170 46.18 62,259 213811 0 46.18 62,259 1.43 91 1365 -0.19 170 46.15 62,089 212991 0 46.15 62,089 1.43 92 1380 -0.19 (170) 46.15 61,919 212991 0 46.15 61,919 1.42 93 1395 -0.19 (170) 46.15 61,749 21299 0 46.15 61,749 1.42 94 1410 -0.19 170 46.13 61,579 21218 0 46.13 61,579 1.41 95 1425 -0.19 (170) 46.13 61,409 21218 0 46.13 61,409 1.41 96 1 1440 -0.19 (170) 46.13 61,238 21218 0 46.13 61,238 1.41 Basin Depth Analysis Page 20 of 20 Appendix C — Rational Method and Hydraulic Calculations for Street Sections RATIONAL METHOD General - The Rational method is commonly used for determining peak discharge from relatively small drainage areas. For areas in excess of 300 to 500 -acres the Synthetic Unit Hydrograph method should normally be used. Before attempting to apply the information in this section, the engineer should become thoroughly familiar with sections A, B and C of this manual. Rational Equation - The Rational method is based on the following equation: Q = CIA where: Q = Peak discharge - cfs C = Coefficient of runoff I = Rainfall intensity (inches/hour) corresponding to the time of concentration A = Area — acres Time of Concentration - If rain were to fall continuously at a constant rate and be uniformly distributed over an impervious surface, the rate of runoff from that surface would reach a maximum rate equivalent to the rate of rainfall. This maximum would occur when all parts of the surface were contributing runoff to the concentration point. The time required to reach the maximum or equilibrium runoff rate is defined as the time of concentration. The time of concentration is a function of many variables including the length of the flow path from the most remote point of an area to the concentration point, the slope and other characteristics of natural and improved channels in the area, the infiltration characteristics of the soil, and the degree and type of development. In District Rational tabling, the time of concentration for an initial sub -area can be estimated from the nomograph on Plate D-3. The time of concentration for the next downstream subarea is computed by adding to the initial time, the time required for D-1 the computed peak flow to travel to the next concentration point. Time of concentration is computed for each subsequent subarea by computing travel time between subareas and adding the cumulative sum. Travel time may be estimated using the tabling aids on Plates D-6 through M To avoid distortion of travel time large subareas should be avoided. Where extremely large subareas are used, peak flow entering a travel reach may be much lower than the flow leaving that reach. Velocity normally increases with discharge, therefore travel time computed using the average flow over a reach may be significantly lower than travel time computed using inflow to the reach. Since rainfall intensity is inversely proportional to time, flow rates would be consistently underestimated by use of large subareas. Intensity -Duration Curves - Rainfall intensity, "I", is determined using District intensity - duration curves for the area under study. Standard intensity -duration curves have been prepared for many population centers in the District. Intensity -duration data for these standard curves is given in tabular form on Plate D-4.1. The standard curves for these areas may be reproduced by plotting the 10 and 60 -minute values on Plate D-4.2, and drawing a straight line through them. For areas where curves have not been published, Plates D-4.3 through D-4.7 should be used to develop design intensity -duration curves. Plates D-4.3 and D-4.4 are isohyetal maps of the maximum 2 -year 1 -hour and 100 -year 1 - hour precipitation respectively. One-hour point rain for intermediate return periods can be determined from Plate D-4.5. The slope of the intensity duration curve can be obtained from Plate D-4.6. Intensity duration curves for a particular area can be easily developed using Plate D-4.7, plotting the 1 -hour point rain value for the desired return period, and drawing a straight line through the 1 -hour value parallel to the required slope. The isohyetal maps and return period diagram are based on NOAA Atlas 2 discussed in more detail in Section B of this report. The map of intensity -duration curve slope is based on D-2 District analysis of all available recording rain gauge records in and near the District. This material is also discussed in Section B of this manual. Coefficient of Runoff Curves - The coefficient of runoff is intended to account for the many factors which influence peak flow rate. The co -efficient depends on the rainfall intensity, soil type and cover, percentage of impervious area, antecedent moisture condition, etc. To account for the difference between actual and effective impervious area it is assumed the maximum runoff rate which can occur from impervious surfaces is 90 -percent of the rainfall rate. The runoff from pervious surfaces is further reduced by infiltration. Runoff coefficient curves can be developed using the relationship: C = 0.9 A; + I -F,, Ap I where: C = Runoff coefficient I = Rainfall intensity - inches/hour Fp = Infiltration rate for pervious areas - inches/hour Ai = Impervious area (actual) - decimal percent AP = Pervious area (actual) - decimal percent and AP = 1.00 - A; The infiltration rate for pervious areas, "Fp", can be estimated using the methods discussed in Section C of this manual for various combinations of soil type, cover type and antecedent moisture condition (AMC). In practice it is not necessary for the engineer to make these computations, as runoff coefficient curve data has been tabulated by the District on Plate D-5.7 for the working range of runoff index (RI) numbers. Runoff coefficient curves can be developed for any combination of conditions by simply plotting the data from Plate D-5.7 on Plate D-5.8. D-3 In addition, for the common case of urban landscaping type cover, runoff coefficient curves have been plotted on Plates D-5.1 through D-5.4. WO COVER TYPE DESCRIPTIONS N1• i i► ■� 7: Barren - Areas with 15 percent or less of the ground surface covered by plants or litter. It includes rockland, eroded land, and shaped or graded land. Barren land does not include fallow land. Chaparral, Broadleaf - Areas on which the principal vegetation consists of ever- green shrubs with broad, hard, stiff leaves such as manzonita, ceanothus and scrub oak. The brush cover is usually dense or moderately dense. Chaparral, Narrowleaf -- Land on which the principal vegetation consists of dif- fusely branched evergreen shrubs with fine needle-like leaves such as chamise and redshank. The shrubs are usually widely spaced and low in growth. If the narrowleaf chaparral shrubs are dense and high; the land should be included with broadleaf chaparral cover. Grass, Annual - Land on which the principal vegetation consists of annual grass and weeds such as annual bromes, wild barley, soft chess, ryegrass and filaree. Grass, Perennial - Areas on which the principal vegetation consists of perennial grass, either native or introduced, and which grows under normal dryland condi- tions. Examples are Stipa or needle grass, Harding grass and wheat grass. It does not include irrigated and meadow grasses. Meadow -- Land areas with seasonally high water table, often called cienegas. Principal vegetation consists of sod -forming grasses interspersed with other plants. Open Brush - Principal vegetation consists of soft wood shrubs, usually grayish in color. Examples include California buckwheat, California sagebrush, black sage, white sage and purple sage. It also includes vegetation on desert facing slopes where broadleaf chaparral predominate in an open shrub cover. Woodland - Areas on which coniferous or broadleaf trees predominate. The crown or canopy density, the amount of ground surface shaded at high noon, is at least 54 percent. Open areas may have a cover of annual or perennial grasses or of brush. Plant cover under the trees is usually sparse because of leaf or needle litter accumulation. Woodland, Grass - Areas with an open cover of broadleaf or coniferous trees usu- ally live oak and pines, with the intervening ground space occupied by annual grasses or weeds. The trees may occur singly or in small clumps. Canopy den- sity,the amount of ground surface shaded at high noon,is from 20 to 50 percent. Residential or Commercial Landscaping - The pervious portions of commercial establishments, single and multiple family dwellings, trailer parks and schools where the predominant land cover is lawn, shrubbery and trees. RCFC & WCD HYDROLOGY NIA NUAL PLATE C-2 0 of 2) COVER TYPE DESCRIPTIONS COVERS (cont.) - Turf - Golf courses, parks, cemeteries, and similar lands where the predominant cover is irrigated mowed close --grown turf grass. Parks in which trees are dense may be classified as woodland. AGRICULTURAL COVER - Fallow -- Fallow land is land plowed but not yet seeded or tilled. It is more effective than barren land in reducing storm runoff. Legumes, Close Seeded - Alfalfa, sweetclover, timothy, etc. and combinations, either planted in close rows or broadcast. Orchards, Deciduous - Land planted to such deciduous trees as apples, apricots, pears, walnuts and. almonds. The ground cover during the rainy reason alters the hydrologic response to storm rainfall. Ground cover may be annual grass or perennial grass with or without legumes. Occasionally legumes are used alone. Use runoff index numbers which apply to the land use or the kind and condition of cover during storm periods. If orchards are kept bare by disking, or through the use of herbicides, fallow applies. Orchards, Evergreen - Land planted to evergreen trees which include citrus and avocado orchards and coniferous plantings. The effectiveness of this kind of land use is in part determined by the tree, the litter and the ground cover. In these groves the ground cover may be legumes alone or annual or perennial grasses with or without legumes. The ground cover may be entirely litter if the tree canopy is sufficiently dense to produce a substantial quantity of fallen leaves or needles. As with deciduous orchards, management practices affect the runoff potential of evergreen orchards. Pasture, gryland - Equivalent to annual grass. Land on which the principal veg- etation consists of annual grasses and weeds such as annual bromes, wild barley, soft chess, ryegrass and f ilaree. Pasture, Irrigated - Irrigated land planted to perennial grasses and legumes for production of forage and which is cultivated only to establish or renew the stand of plants. Raw Crops -- Lettuce, tomatoes, sugar beets, tulips or any field crop planted in rows far enough apart that most of the soil surface is exposed to rainfall im- pact throughout the growing season. At plowing, planting and harvest times it is equivalent to fallow. Small Grain - Wheat, oats, barley, flax, etc. planted in rows close enough that the soil surface is not exposed except during planting and shortly thereafter. Vineyards - As with orchards, ground cover and land condition must be consider- ed in estimating runoff potential. Use runoff index numbers which apply to the kind and condition of cover. For example either annual grass or fallow may apply. Reference: Bibliography item No. 17 RCFC & WCD HYDROLOGY NIA NUAL PLATE C-2 t2 of 2) n m 0 i N PROJECT R C F C a W C D r1YDROLOGY ]MANUAL RATIONAL METHOD CALCULATION FORM FREQUENCY Sheet No.— of Sheets Calculated by __________ __ '�ATI Checked by -6ZyT---- DRAINAGE AREA .. , om OMER mm M D TO i M W^ a - O d m;z Lnm dT U11•IN Nm U11 O 11.11.11 �O Olm F1 N1 NN f BOO f T m.r1 > O < T U1 NT1 U11' I 1O . T 1 1 .O 112 "t lto 1V -� O OP 0: 9! m1 IO N U1 11'11' I1 O U o W < 2 d f mm P1 1'1 1'1 1'1 1'1 N NNN N N NNN N N N — .r -• -• — — -• — — — — — — S W O O 7 m O O J W Q In U1md M-�N d 1 ;:U10m0 .OTN 1O .� 11.17 UIN TI.11 Nm f -gym U11'1 K O < N0 1 UI f 1'1N -.OT Tmm11 .O 1(11!1 f f to 1•IN NN -.00T TTmmm f W — W Y 1.1 N N N N NN N N — ——.. -- -•- -- — -+-•- --+ -• -•- — 11 1 W W z a ao In o O W J 2 H•- In O1 OD O m 4,0 w OMom. M-000 (n < Z) N NN NN 1.11.11.1(.11.1 f f U1 UI .O .011 m m m Q 2 J I •+ W O S Om.O U1 .� Nm1mN m1NNN In O NOT TO NU T NT mmO MD UI Y o < 1 OU1 -+m UIN Om1 UI 11'1N-. 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Y O < 1 O U1 -+m U1N Om1 U11 I'1N-+ Om1101 /'1 • J PIN.ti% O m 11010 "111 /'11'1 O W • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Z 1010 mN f f / f m mmm mm I•1N NNN NN NNN N-+.-. .-.-.-.-.-.-.-. > W p ~_ Z) m O U W Q f 1'1 -y U1 UI 1NT mm T -.f F.- UI U11 TN 10 -. 10 Nm f 10 Ttnm 10 0MO Q • 1• f -• T• 11011•IN -+O TT m110 UI U1 11'1 f•IN TT m mm J U- < 1'1 1'1 I'1 N N NNN N N N N -. -.-..-..-. -+ -. .-. -.-....... --• ..w ..., ..., it !Y O W W Z i 4 O U1 O Ln 10 1 m TO .ti N 1'1 1 U1 10 1 m T O N E 10 m O (V Q �O m O U1 O U1 o m O m O m UI U < O .ti -w •+ -+ -• -.� ...1 -.1 -.� .r N N N N N to 1.1 1.1 In 1.1 1 f U1 U1 10 10 1 1 m m � Z O S RCFC & WCD HYDROLOGY JMANIJAL PLATE D-4.1 (2 of 6) L 1000 900 800 700 .M• y- k- 400 a F 350 v a F 300 c "- r 250 J L v� J 200 150 K• TC' 100 90 80 70 60 c E 50 CL 0 a� C v 35 CL N 0 30 0 N 25 c E c_ 20 19 18 17 r6 0 15 14 O C:13 12 0 11 w- 0 0 9 E 8 7 6 5 LIMITATIONS: I. Maximum length =1000' 2. Maximum area = 10 Acres a H .. U 500 Y CP 400 300 c 0' '> 0 --200 c N E v E 100 0 - so C 0 50 30 E CL CP 0 N CL o c c 20 Q10 a_ 3 8 6 K Ai t— 4 RCFC & WCD HYDROLOGY 1\/]ANUAL Undeveloped Good Cover Undeveloped Fair Cover Undeveloped Poor Cover Single Family (1/4 Acre) Commercial, (Pav TC 5 —1 6 � v` Q 7 c a� 8— a 0 a� 9 0 10 E 0 U - II a� 12 in 0 14 '~ N 15 16 17 E 18 19 U 20 ~ C 0 0 C 25 C KEY L --H Tc —K —Tc' 0 30 a� EXAMPLE; E (1) L =550, H =5.0, K = Single Family(1/4 Ac.) 35 Development , Tc = 12.6 min. (2) L =550', H =5.0', K = Commercial 40 Development , Tc = 9.7 min. Reference: Bibliography item No. 35. PLATE D-3 Channel Report Hydraflow Express by Intelisolve Monday, Jan 17 2022 20210635 - Troutdale Village - 32' Driveway - Area 'A' User -defined Highlighted Invert Elev (ft) = 0.55 Depth (ft) = 0.50 Slope (%) = 0.50 Q (cfs) = 19.34 N -Value = 0.013 Area (sqft) = 6.94 Velocity (ft/s) = 2.79 Calculations Wetted Perim (ft) = 31.92 Compute by: Known Q Crit Depth, Yc (ft) = 0.51 Known Q (cfs) = 19.34 Top Width (ft) = 31.82 EGL (ft) = 0.62 (Sta, EI, n)-(Sta, EI, n)... (0.00, 1.50)-(0.10, 1.00, 0.013)-(14.00, 0.72, 0.013)-(16.00, 0.55, 0.013)-(18.00, 0.72, 0.013)-(31.90, 1.00, 0.013)-(32.00, 1.50, 0.013) Elev (ft) Section 2.00 1.50 v 1.00 0.50 0.00 -5 0 5 10 15 20 25 30 35 40 Sta (ft) Depth (ft) 1.45 0.45 -0.05 -0.55 Inlet Report Hydraflow Express by Intelisolve Drop Inlet at Draiange Area A Drop Grate Inlet = 19.34 Location = Sag Curb Length (ft) = -0- Throat Height (in) = -0- Grate Area (sqft) = 9.00 Grate Width (ft) = 3.00 Grate Length (ft) = 3.00 Gutter = 19.34 Slope, Sw (ft/ft) = 0.020 Slope, Sx (ft/ft) = 0.020 Local Depr (in) = -0- Gutter Width (ft) = 4.00 Gutter Slope (%) = -0- Gutter n -value = -0- All dimensions in feel Monday, Jan 17 2022 Calculations Compute by: Known Q Q (cfs) = 19.34 Highlighted Q Total (cfs) = 19.34 Q Capt (cfs) = 19.34 Q Bypass (cfs) = -0- Depth at Inlet (in) = 7.93 Efficiency (%) = 100 Gutter Spread (ft) = 70.07 Gutter Vel (ft/s) = -0- Bypass Spread (ft) = -0- Bypass Depth (in) = -0- Channel Report Hydraflow Express by Intelisolve Monday, Jan 17 2022 20210635 - Troutdale Village - 30" Drainage Pipe -AREA A Circular Highlighted Diameter (ft) = 2.50 Depth (ft) = 1.21 Q (cfs) = 19.34 Area (sqft) = 2.36 Invert Elev (ft) = 42.00 Velocity (ft/s) = 8.20 Slope (%) = 1.00 Wetted Perim (ft) = 3.85 N -Value = 0.013 Crit Depth, Yc (ft) = 1.50 Top Width (ft) = 2.50 Calculations EGL (ft) = 2.26 Compute by: Known Q Known Q (cfs) = 19.34 Elev (ft) 45.00 44.50 44.00 43.50 43.00 42.50 42.00 41.50 Section 0 1 2 3 4 Reach (ft) L 1000 900 800 700 .M• y- k- 400 a F 350 v a F 300 c "- r 250 J L v� J 200 150 K• TC' 100 90 80 70 60 c E 50 CL 0 a� C v 35 CL N 0 30 0 N 25 c E c_ 20 19 18 17 r6 0 15 14 O C:13 12 0 11 w- 0 0 9 E 8 7 6 5 LIMITATIONS: I. Maximum length =1000' 2. Maximum area = 10 Acres a H .. U 500 Y CP 400 300 c 0' '> 0 --200 c N E v E 100 0 - so C 0 50 30 E CL CP 0 N CL o c c 20 Q10 a_ 3 8 6 K Ai t— 4 RCFC & WCD HYDROLOGY 1\/]ANUAL Undeveloped Good Cover Undeveloped Fair Cover Undeveloped Poor Cover Single Family (1/4 Acre) Commercial, (Pav TC 5 —1 6 � v` Q 7 c a� 8— a 0 a� 9 0 10 E 0 U - II a� 12 in 0 14 '~ N 15 16 17 E 18 19 U 20 ~ C 0 0 C 25 C KEY L --H Tc —K —Tc' 0 30 a� EXAMPLE; E (1) L =550, H =5.0, K = Single Family(1/4 Ac.) 35 Development , Tc = 12.6 min. (2) L =550', H =5.0', K = Commercial 40 Development , Tc = 9.7 min. Reference: Bibliography item No. 35. PLATE D-3 Channel Report Hydraflow Express by Intelisolve Monday, Jan 17 2022 20210635 - Troutdale Village - 32' Driveway - Area 'B' User -defined Highlighted Invert Elev (ft) = 0.55 Depth (ft) = 0.52 Slope (%) = 0.50 Q (cfs) = 23.46 N -Value = 0.013 Area (sqft) = 7.58 Velocity (ft/s) = 3.10 Calculations Wetted Perim (ft) = 31.96 Compute by: Known Q Crit Depth, Yc (ft) = 0.54 Known Q (cfs) = 23.46 Top Width (ft) = 31.83 EGL (ft) = 0.67 (Sta, EI, n)-(Sta, EI, n)... (0.00, 1.50)-(0.10, 1.00, 0.013)-(14.00, 0.72, 0.013)-(16.00, 0.55, 0.013)-(18.00, 0.72, 0.013)-(31.90, 1.00, 0.013)-(32.00, 1.50, 0.013) Elev (ft) Section 2.00 1.50 v 1.00 0.50 0.00 -5 0 5 10 15 20 25 30 35 40 Sta (ft) Depth (ft) 1.45 0.45 -0.05 -0.55 Inlet Report Hydraflow Express by Intelisolve Drop Inlet at Draiange Area B Drop Grate Inlet = 23.46 Location = Sag Curb Length (ft) = -0- Throat Height (in) = -0- Grate Area (sqft) = 9.00 Grate Width (ft) = 3.00 Grate Length (ft) = 3.00 Gutter = 23.46 Slope, Sw (ft/ft) = 0.020 Slope, Sx (ft/ft) = 0.020 Local Depr (in) = -0- Gutter Width (ft) = 4.00 Gutter Slope (%) = -0- Gutter n -value = -0- All dimensions in feel Monday, Jan 17 2022 Calculations Compute by: Known Q Q (cfs) = 23.46 Highlighted Q Total (cfs) = 23.46 Q Capt (cfs) = 23.46 Q Bypass (cfs) = -0- Depth at Inlet (in) = 9.02 Efficiency (%) = 100 Gutter Spread (ft) = 79.15 Gutter Vel (ft/s) = -0- Bypass Spread (ft) = -0- Bypass Depth (in) = -0- Channel Report Hydraflow Express by Intelisolve Monday, Jan 17 2022 20210635 - Troutdale Village - 30" Drainage Pipe - AREA B Circular Highlighted Diameter (ft) = 2.50 Depth (ft) = 1.36 Q (cfs) = 23.46 Area (sqft) = 2.73 Invert Elev (ft) = 42.00 Velocity (ft/s) = 8.59 Slope (%) = 1.00 Wetted Perim (ft) = 4.15 N -Value = 0.013 Crit Depth, Yc (ft) = 1.65 Top Width (ft) = 2.49 Calculations EGL (ft) = 2.51 Compute by: Known Q Known Q (cfs) = 23.46 Elev (ft) 45.00 44.50 44.00 43.50 43.00 42.50 42.00 41.50 Section 0 1 2 3 4 Reach (ft) Appendix D — Hydrology Map