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35088iwuma� __ IE 3.5oss P.O. Box 1504 LA QUINTA, CALIFORNIA 92247 -1504 PUBLIC WORKS DEPARTMENT 78 -495 CALLE TAMPICO (760) 777 -7075 LA QUINTA, CALIFORNIA 92253 FAX (760) 777 -7155 SUBJECT: ' PCN 08261 MAYER VILLA CAPRI PARCEL MAP 35088 PRELIMINARY HYDROLOGY REPORT DATE: December 5, 2008 INSTRUCTIONS TO APPLICANT: 1) Please provide a written response to each comment on the following pages or in green line on the redlined plans. 2) Please revise originals and reprint Plans and /or Calculations as necessary for corrections. 3) Please return all red - marked Plans, Back -Up Documents, Specifications, Calculations or Reports with the resubmittal. 4) Please assure that each sheet of the resubmitted Plans and the title, cover or signature sheet of the Documents, Specifications, Calculations or Reports include the preparer's name and telephone number and are wet - signed and stamped by the - licensed preparer as prescribed by California Business and Professions Code Section 5536 (Architects) and Section 6735 (Civil Engineers). Resubmittals will not be accepted with signatures missing. 5) Please return this list, your written responses, and all documents listed above with your resubmittal. REQUESTED PUBLIC WORKS CORRECTIONS (1st Round Check to Planning): The preliminary MSA hydrology report, dated October 5, 2006 is approvable for entitlement purposes, but additional engineering definition is required prior to plan submittal to Public Works for 1St round plan check following entitlement. Underground retention volumes are approved at 3.78 acre -ft for Drainage Area "A" and at 3.35 acre -ft for Drainage Area "B ". Above ground retention volumes are approved at 0.26 acre -ft for Drainage Area "A" and at 0.79 acre -ft for Drainage Area "B ". Total retention for the project has been established by the FOR to equal 8.18 acre -ft for the 29.21 acre project tributary area. The FOR should clarify all retention basin volumes in the preliminary report and recheck the precipitation and low loss value assumptions per City Hydrological Engineering Bulletin #06 -16 guidance. Grading and storm drain invert elevations, storm drain inlet locations and other basic design storm drain parameters should be established and reviewed with Public Works Staff prior to 1St round plan check following entitlement. These specific design parameters have not been provided to Public Works to date. Sincerely, Timothy R. Jonasson, P.E. Public Works Director/ City Engineer PRELIMIIVi4RY HYDF�OLOG.Y REPORT For Property Located In a portion of Section 18, T5S., R7E., SBM La Quinta, California OCT 1 8 2006 Parcel Map 35088 October 5, 2006 Prepared for: Mayer Corporation 660 Newport Center Drive Newport Beach, CA 92660 JN 1685 CITY OF LA QUINTA COMMUNITY DEVELOPMFN DEPARTMENT MSA CONSULTING, INC. MAI MRO, SMITH & ASSOCIATES, INC. PLmNma ■ C rim Emmmm ao ■ LAxu SuRvEymo 34200 BOB Hop$ DRM 0 RANCHO MUAaE ■ CA 92270 T mmHoNB (760) 320 -9811 ■ FAx (760) 323 -7893 0 t t � 0 • Project Description The project, PM 35088, is located on the northeast corner of Fred Waring Drive and Washington Street in the city of La Quinta, California, and consists of a 29.2 acre commercial site (see Vicinity Map). Existing Conditions Flood Rate Map: The project area is covered by FIRM Panel No. 060245 2260 D, revised November 20, 1996, which shows that the project area lies within Zone C, indicating the area is subject to minimal flooding (see FEMA map). On -Site: The site is relatively flat and slopes gradually toward the northeast with storm runoff generally characterized as sheet flow. Off -Site: The site is surrounded by existing development which prevents off -site storm runoff from entering the project site. Flood Control Requirements The drainage from this project site falls under the jurisdiction of the City of La Quinta. The project design shall provide for the capture and storage of all storm runoff generated on -site in a 100 -year storm. Proposed Hydrology and Flood Control Improvements Storm runoff will be conveyed via swales or catch basins to above ground and below ground retention basins, as shown on the attached Hydrology Map. The size and • configuration of the basins will be sufficient to store the entirety of the 100 -year storm runoff volume. Run -Off Analysis The Synthetic Unit Hydrograph, Shortcut Method, as prescribed in the RCFC &WCD Hydrology Manual, was used to determine the runoff volumes created from the proposed improvements in a 100 -year storm event. The 3 -hour, 6 -hour and 24 -hour storms were analyzed, with the 24 -hour storm producing the maximum runoff. The data used in the Synthetic Unit Hydrograph calculations are as follows: Soil Group: A, AMC -II Runoff I dex_Nunib 32 (U an- Commercial, Good Cover) filtration Rate (FP): 0.74 in /hr Impervious Area (A;): 90% G U 1 Constant Loss Rate (F): 0.74[1 - 0.9(0.90] = 0.14 in /hr Low Loss Rate: 0.9 — (0.8 x 0.90) = 0.18 in /hr Storm Frequency: Total Adjusted Rainfall i L�5� 100 -Year 24 -Hour: 4.1 inches Ly 6 -Hour: 2.5 inches 3 -Hour: 2.0 inches _ Z o • Results and Conclusions The Synthetic Unit Hydrograph analysis yielded the following values of effective rain for the project site: 24 -Hour 6 -Hour 3 -Hour 3.36" 2.09" 1.71" The corresponding 100 -year storm runoff volumes for the 24 -hour rainfall were then calculated for the project as follows: 24 -Hour: Drainage Area A: 14.42 ac x 3.36 in / 12 in /ft = 4.04 ac -ft Drainage Area B: 14.79 ac x 3.36 in 112 in /ft = 4.14 ac -ft Total runoff = 8.18 ac -ft The Synthetic Unit Hydrograph Hydrology Map illustrates the storm runoff volume of the tributary areas and the storage capacities of the proposed retention basins. As the map indicates, the capacities of the retention basins and underground storage are sufficient to store the entirety of the 100 -year storm volumes of their corresponding tributary areas. It is therefore concluded that the proposed development of the Mayer Corporation meets the hydrologic requirements set forth by the City of La Quinta. • • • • 0 VICINITY MAP 3 • PALM DESEPYT I BERMUDA DUNS HOVLEY LANE I AVENUE 42 • PALM ROYALE FRED WARING DRIVE DRIVE NDM WELLS I LA CUWTA VICINITY MAP N.T.S. • OR/VE Jim 4 LJ • SYNTHETIC UNIT HYDROGRAPH SHORTCUT METHOD CALCULATIONS 0 • • r: R C F C& W C D MVF2)Q @1L @@V ��Q6 "SHORTCUT METHOD" SYNTHETIC UNIT HYDROGRAPH METHOD Unit Hydrograph and Effective Rain Calculation Form Project 1685 Mayer Corporation Sheet By RRR Date Checked Date [1] CONCENTRATION POINT - -- [3] DRAINAGE AREA -ACRES 1.000 [5] UNIT TIME - MINUTES 30 [7] UNIT TIME - PERCENT OF LAG (100'[5]1[6]) -- [9] STORM FREQUENCY & DURATION 100 -YR, 24 -HR [11] VARIABLE LOSS RATE (AVG)•INCHES /HOUR - -- 13 CONSTANT LOSS RATE - INCHES /HOUR 0.14 [2] AREA DESIGNATION [4] ULTIMATE DISCHARGE - CFS- HRSIIN (645'[3]) - -- [6] LAG TIME - MINUTES �.�, [8] S -CURVE _. [10] TOTAL ADJUSTED STORM RAIN- INCHES 4.1 [12] MINIMUM LOSS RATE (FOR VAR. LOSS) -[NVC 14 LOW LOSS RATE - PERCENT - .,3 �jc g UNIT HYDROGRAPH EFFECTIVE RAIN' S M� � 0\( -HYDROGRAPH [15] UNIT TIME PERIOD M [16] TIME PERCENT OF LAG [7]'[15] [17] CUMULATIVE AVERAGE PERCENT OF ULTIMATE DISCHARGE (S- GRAPH) [16] DISTRIB GRAPH PERCENT [17]m- [17]m -1 [17] UNIT HYDROGRAPH CFS- HRS /IN 4 • 18 100.000 [20] PATTERN PERCENT (PL E -5.9) [21] STORM RAIN IN /HR 601`101[201 100[5] [22] LOSS RATE IN /HR S 23] FFECTIVE RAIN IN /HR [21] -[22] [24] FLOW CFS MAX LOW 1 0.5 0.041 1 0.140 0.007 1 0.034 0.034 2 0.7 0.057 0.140 0.010 0.047 0.047 3 0.6 0.049 0.140 0.009 0.040 0.041 4 0.7 0.057 0.140 0.010 0.047 0.047 5 0.8 0.066 0.140 0.012 0.054 0.054 6 1.0 0.082 0.140 0.015 0.067 0.068 7 1.0 0.082 0.140 0.015 0.067 0.068 8 1.1 0.090 0.140 0.016 0.074 0.075 9 1.3 0.107 0.140 0.019 0.087 0.088 10 1.5 0.123 0.140 0.022 0.101 0.102 11 1.3 0.107 0.140 0.019 0.087 0.088 12 1.6 0.131 0.140 0.024 0.108 0.108 13 1.8 0.148 0.140 0.027 0.121 0.122 14 2.0 0.164 0.140 0.030 0.134 0.136 15 2.1 0.172 0.140 0.031 0.141. 0.142 16 2.5 0.205 0.140 0.037 0.168 0.170 17 3.0 0.246 0.140 0.044 0.202 0.203 18 3.3 0.271 0.140 0.049 0.222 0.224 19 3.9 0.320 0.140 0.058 0.262 0.264 20 4.3 0.353 0.140 0.063 0.289 0.292 21 3.0 0.246 0.140 0.044 0.202 0.203 22 4.0 0.328 0.140 0.059 0.269 0.271 23 3.8 0.312 0.140 0.056 0.256 0.258 24 3.5 0.287 0.140 0.052 0.235 0.237 25 5.1 0.418 0.140 0.075 0.343 0.346 26 5.7 0.467 0.140 0.084 0.383 0.386 27 6.8 0.558 0.140 0.100 0.457 0.461 28 4.6 0.377 0.140 0.066 0.309 0.312 29 5.3 0.435 0.140 0.078 0.356 0.359 30 5.1 0.418 0.140 0.075 0.343 0.346 31 4.7 0.385 0.140 0.069 0.316 0.319 32 3.8 0.312 0.140 0.056 0.256 0.258 33 0.8 0.066 0.140 0.012 0.054 0.054 34 0.6 0.049 0.140 0.009 0.040 0.041 35 1.0 0.082 0.140 0.015 0.067 0.068 36 0.9 0.074 0.140 0.013 0.061 0.061 37 0.8 0.066 0.140 0.012 0.054 0.054 38 0.5 0.041 0.140 0.007 0.034 0.034 39 0.7 0.057 0.140 0.010 0.047 0.047 40 0.5 0.041 0.140 0.007 0.034 0.034 41 1 0.6 0.049 0.140 0.009 0.040 0.041 42 1 0.5 0.041 0.140 0.007 0.034 0.034 43 0.5 0.041 0.140 0.007 0.034 0.034 44 0.5 0.041 0.140 0.007 0.034 0.034 45 0.5 0.041 0.140 0.007 0.034 0.034 46 0.4 0.033 0.140 0.006 0.027 0.027 47 0.4 0.033 0.140 0.006 1 0.027 0.027 48 0.4 0.033 0.140 0.006 0.027 0.027 TOTALS 1 100.0 6.724 6.780 EFFECTIVE RAIN = 3.362 INCHES 6:) 0 • R C F C& W C D 12 D3V & @V G MURL "SHORTCUT METHOD" SYNTHETIC UNIT HYDROGRAPH METHOD Unit Hydrograph and Effective Rain Calculation Form Project 1685 Mayer Corporation Sheet By RR R Date Checked Date [1] CONCENTRATION POINT -- [3] DRAINAGE AREA -ACRES 1.000 15] UNIT TIME - MINUTES 10 17) UNIT TIME - PERCENT OF LAG (100- [5]1[6]) - -- [9] STORM FREQUENCY & DURATION 100 -YR, 6 -HR [11] VARIABLE LOSS RATE (AVG)- INCHES /HOUR - -- 13 CONSTANT LOSS RATE- INCHES /HOUR 0.14 [2] AREA DESIGNATION [4] ULTIMATE DISCHARGE - CFS - HRS /IN (645 -[3]) - -- [6] LAG TIME - MINUTES ... [8] S -CURVE - -- [10] TOTAL ADJUSTED STORM RAIN- INCHES 2,5 [12] MINIMUM LOSS RATE (FOR VAR. LOSS) -IN /HR ... 14 LOW LOSS RATE- PERCENT 18 UNIT HYDROGRAPH EFFECTIVE RAIN FLOOD HYDROGRAPH 1151 UNIT TIME PERIOD M [16] TIME PERCENT OF LAG [7]'[15] [17] CUMULATIVE AVERAGE PERCENT OF ULTIMATE DISCHARGE (S- GRAPH) [16] DISTRIB GRAPH PERCENT [17]m- [17]m -1 [17] UNIT HYDROGRAPH CFS - HRS /IN 4f 1 "x181 100.000 [20] PATTERN PERCENT (PL E -5.9) [21] STORM RAIN IN /HR 601r 01[201 100[5] [22] LOSS RATE IN /HR [23] EFFECTIVE RAIN IN /HR [21] -[22] [24] FLOW CFS MAX LOW 1 1.1 0.165 0.140 0.030 1 0.135 0.136 2 1.2 0.180 0.140 0.032 0.148 0.149 3 1.3 0.195 0.140 0.035 0.160 0.161 4 1.4 0.210 0.140 0.038 0.172 0.174 5 1.4 0.210 0.140 0.038 0.172 0.174 6 1.5 0.225 0.140 0.041 0.185 0.186 7 1.6 0.240 0.140 0.043 0.197 0.198 8 1.6 0.240 0.140 0.043 0.197 0.198 9 1.6 0.240 0.140 0.043 0.197 0.198 10 1.6 0.240 0.140 0.043 0.197 0.198 11 1.6 0.240 0.140 0.043 0.197 0.198 12 1.7 0.255 0.140 0.046 0.209 0.211 13 1.7 0.255 0.140 0.046 0.209 0.211 14 1.8 0.270 0.140 0.049 0.221 0.223 15 1.8 0.270 0.140 0.049 0.221 0.223 16 1.8 0.270 0.140 0.049 0.221 0.223 17 2.0 0.300 0.140 0.054 0.246 0.248 18 2.0 0.300 0.140 0.054 0.246 0.248 19 2.1 0.315 0.140 0.057 0.258 0.260 20 2.2 0.330 0.140 0.059 0.271 0.273 21 2.5 0.375 0.140 0.068 0.308 0.310 22 2.8 0.420 0.140 0.076 0.344 0.347 23 3.0 0.450 0.140 0.081 0.369 0.372 24 3.2 0.480 0.140 0.086 0.394 0.397 25 3.5 0.525 0.140 0.095 0.431 0.434 26 3.9 0.585 0.140 0.105 0.480 0.484 27 4.2 0.630 0.140 0.113 0.517 0.521 28 4.5 0.675 0.140 0.122 0.554 0.558 29 4.8 0.720 0.140 0.130 0.590 0.595 30 5.1 0.765 0.140 0.138 0.627 0.633 31 6.7 1.005 0.140 0.181 0.865 0.872 32 8.1 1.215 0.140 0.219 1.075 1.084 33 10.3 1.545 0.140 0.278 1.405 1.417 34 2.8 0.420 0.140 0.076 0.344 0.347 35 1.1 0.165 0.140 0.030 0.135 0.136 36 0.5 0.075 0.140 0.014 0.062 0.062 TOTALS 100.0 12.558 12.662 EFFECTIVE RAIN = 2.093 INCHES Ll • 0 R C F C& W C D pwpQ @1 @ @V MMULM "SHORTCUT METHOD" SYNTHETIC UNIT HYDROGRAPH METHOD Unit Hydrograph and Effective Rain Calculation Form Project 1685 Mayer Corporation Sheet By RRR Date Checked Date [11 CONCENTRATION POINT -- [3] DRAINAGE AREA -ACRES 1.000 15] UNIT TIME - MINUTES 5 [7] UNIT TIME - PERCENT OF LAG (100•[5]1[6]) - [9] STORM FREQUENCY & DURATION 100 -YR, 3 -HR [11] VARIABLE LOSS RATE (AVG). INCHES /HOUR - [131 CONSTANT LOSS RATE- INCHES /HOUR 0.14 [2] AREA DESIGNATION [4] ULTIMATE DISCHARGE - CFS- HRS /IN (645•[3]) - [6] LAG TIME - MINUTES _ [8] S -CURVE - -- [10] TOTAL ADJUSTED STORM RAIN- INCHES 2 [12] MINIMUM LOSS RATE (FOR VAR. LOSS) -IN /HR ... 14 LOW LOSS RATE- PERCENT 18 UNIT HYDROGRAPH EFFECTIVE RAIN FLOOD HYDROGRAPH [15] UNIT TIME PERIOD M [16] TIME PERCENT OF LAG [7]•[151 [17] CUMULATIVE AVERAGE PERCENT OF ULTIMATE DISCHARGE (S- GRAPH) [16) DISTRIB GRAPH PERCENT [17]m- [17]m -1 [17] UNIT HYDROGRAPH CFS- HRS/IN 1`41.1181 100.000 [20] PATTERN PERCENT (PL E -5.9) [21] STORM RAIN IN /HR 601`101[201 100[5] [22] LOSS RATE IN /HR [23] EFFECTIVE RAIN IN /HR [21] -[22] [241 FLOW CFS MAX LOW 1 1.3 0.312 0.140 0.056 0.256 0.258 2 1.3 0.312 0.140 0.056 0.256 0.258 3 1.1 0.264 0.140 0.048 0.216 0.218 4 1.5 0.360 0.140 0.065 0.295 0.298 5 1.5 0.360 0.140 0.065 0.295 0.298 6 1.8 0.432 0.140 0.078 0.354 0.357 7 1.5 0.360 0.140 0.065 1 0.295 0.298 8 1.8 0.432 0.140 0.078 0.354 0.357 9 1.8 0.432 0.140 0.078 0.354 0.357 10 1.5 0.360 0.140 0.065 0.295 0.298 11 1.6 0.384 0.140 0.069 0.315 0.318 12 1.8 0.432 0.140 0.078 0.354 0.357 13 2.2 0.528 0.140 0.095 0.433 0.437 14 2.2 0.528 0.140 0.095 0.433 0.437 15 2.2 1 0.528 0.140 0.095 0.433 0.437 16 2.0 0.480 0.140 0.086 0.394 0.397 17 2.6 0.624 0.140 0.112 0.512 0.516 18 2.7 0.648 0.140 0.117 0.531 0.536 19 2.4 0.576 0.140 0.104 0.472 0.476 20 2.7 0.648 0.140 0.117 0.531 0.536 21 3.3 0.792 0.140 0.143 0.652 0.657 22 3.1 0.744 0.140 0.134 1 0.610 0.615 23 2.9 0.696 0.140 0.125 0.571 0.575 24 3.0 0.720 0.140 0.130 0.590 0.595 25 3.1 0.744 0.140 0.134 0.610 0.615 26 4.2 1.008 0.140 0.181 0.868 0.875 27 5.0 1.200 0.140 0.216 1.060 1.069 28 3.5 0.840 0.140 0.151 0.700 0.706 29 6.8 1 1.632 0.140 0.294 1.492 1.504 30 7.3 1.752 0.140 0.315 1.612 1.625 31 8.2 1.968 0.140 0.354 1.828 1.843 32 5.9 1.416 0.140 0.255 1.276 1.287 33 2.0 0.480 0.140 0.086 0.394 0.397 34 1.8 0.432 0.140 0.078 0.354 0.357 35 1.8 0.432 0.140 0.078 0.354 0.357 36 0.6 0.144 0.140 0.026 0.118 0.119 TOTALS 100.0 20.469 20.640 EFFECTIVE RAIN = 1.706 INCHES • 0 RCFC AND WCD REFERENCE PLATES c: INSTRUCTIONS FOR SYNTHETIC UNIT HYL)ROGRAPH METHOD HYDROLOGY CALCULATIONS A. Synthetic Unit Hydrograph Development 1. On a USGS topographic quandrangle sheet or other map of suit- able scale, outline the proposed drainage system and outline the area or subareas tributary to it. 2. From the map of the drainage system, determine the following basin physical factors and enter them on Sheet 1 of Plate E -2.1. A = Drainage area - square miles L = Length of longest watercourse - miles Lca = Length along the longest watercourse, measured upstream to a point opposite the centroid of the area - miles - H = Difference in elevation between the concentration point a.Td the most remote point-of the basin -feet S = Overall slope of longest watercourse between headwaters and concentration point - feet per mile (S = H/L) 3. Determine lag time using Plate E -3 or the following expression (See Sheet 1 of Plate E -2.1): Lag (hours) = 24n [L_Lca](.38) S �t where: n = The visually estimated mean of the n (Mannings formula) values of all collection streams and channels within the watershed. 4. Select a unit time period. To adequately define the unit hydro - graph the unit time period should be about 25- percent of lag time, and never more than 40- percent of lag time. For ease of calculation, the unit time should match the times for which .pre- cipitation patterns are available (Plate E -5.9). Also see Sheet 1 of Plate E -2.1. 5. Utilizing the S -graph applicable to the drainage basin (Plates E -4.1 through E -4.4), determine the average percentage of the ultimate discharge for each unit period. In reading-the percentage of discharge from the S- graph, the average ordinate over the t-ime RCFC fk WCD ] YDROLO Y J\/JA NUAL ENO ATC C_1 1 to _Z r% 1 4. For 3 and 6 -hour c'.srat:.on storms assume the weighted average loss rate is a constant defining the maximum loss rate for each unit time period. For 24 -hour storms use the variable loss rate function below to compute the maximum loss rate for each unit time period: 1.55 FT'(inches/hour) = C (24-(T /60)) + Fm where: C = (F - Fm) /54 F = Adjusted loss rate - inches/hour (as previously defined) T = Time from beginning of storm - minutes Fm = Minimum value on loss rate curve - inches/hour (typically 50 to 75- percent of F) The time "T" used should be from the start of the storm to the middle of each unit time period, i.e., for a unit time of 3Q- minutes the maximum loss rate would be computed for T=15-min- utes for period one, T=45- minutes for period two, etc. Enter the maximum loss rates (constant or variable) on Column 22 of Plate E -2.2. 5. Compute the low loss rate for .each unit time period where the maximum loss rate exceeds the rainfall rate for that period. The low loss rate should normally be 80 to 90- percent times the rainfall rate. See Column 22 of Plate E -2.2. 6. Compute the effective rainfall rate for each unit time period by subtracting the loss rate from the rainfall rate. See Column 23 of Plate E -2.2. Be sure to use the low loss rate where the maximum lgss rate exceeds unit period intensity. 7. Compute the flood hydrograph using one of the following two methods. Do not use the simplified method until the long form method is thoroughly understood: (a) Long form method (use Plate E -2.3): (1) Multiply the effective rainfall rate for the first unit time period times each synthetic unit hydrograph value to determine the flood hydrograph which would result from that rainfall increment. (2) Repeat the above process for each suceeding effective rainfall value, advancing the resultant flood hvdrographs one unit time period for each cycle. HYDROLOGY 1\/JANUAL 02 ATC C_1 1 12 -4 r • • m. -�., EXAMPLE OF SIMPLIFIED METHOD OF FLOOD HYDROGRAPH COMPUTATION 9 Flood 7 Hydrograph 9 7 [23] �24] 7 7 Effective Flaw 17 Rain cfs 14 In /Hr 17 [2.1� — [22] Separate Sheet 21 Plate E -2.2 24 26 .13 10 31 .21 54 38 .23 145 45 .22 254 50 .35 343 64 .40 430 Unit Graph Values 85 .48 545 Listed in Reverse 109 .53 680 The position of the unit Order 158 .77 827 graph values on the sep- 257 1.17 1037 arate sheet in this exam - 479 1.06 1344 ple gives the value of 515 .17 1615 1188 cfs in column C 4] 288 1579 , To get all of the values 78 118 for the flood hydrograph 758 the separate sheet must 513 moved from the top to the 382 bottom of column [23] . 300 Start with 78 adjacent 241 to .13 and finish with 9 202 adjacent to .17. The 172 flood hydrograph ordin- 145 ate for any position of 124 the separate sheet is 107 the sum of the products 94 of all adjacent unit 80 graph and effective rain 67 values. The computed 58 flow value is entered 48 opposite the bottom unit 36 graph value (78 in this 32 case) for any position 30 of the separate sheet. 27 20 it 2 R C F C ai W C D SYNTHETIC UNIT HYDROL DrBY 1\AANUAL HYDROGRAPH METHOD INSTRUCTIONS m. -�., INSTRUCIMNS FOR SHORT CUT SYNTHETIC HYDROGRAPH HYDROLOGY CALCULATIONS 1. Determine drainage area and lag time. Use Steps A -1 through A -3 on Plate E -1.1. 2. Determine that the area is suitable for development of a Short Cut hydrograph, i.e., the area is no more than 100 to 200 -acres in size, and lag time is less than 7 to 8- minutes. 3. Select a suitable unit time equal to from 100 to 200 - percent of lag. Normally, 5 to 10- minutes for 3 and 6 -hour storms, and 15- minutes for 24 -hour storms will be adequate. 4. Compute effective rainfall rates using steps B -1 through B -6 on Plate E -1.1. 5. Compute flood hydrograph ordinates for each unit time period by multiplying the effective rainfall rate_ (inches per hour) times the drainage area in acres. The resultant values are discharge in cfs. 6. The three hour storm peak discharge should normally compare well with rational peaks. If adjustments are necessary, use a shorter unit time period to raise the peak, and a longer unit time period to lower them. RCFC & WCD HYDROLOGY 1\11ANJAL PLATE E-1.2 0 • • RUNOFF INDEX NUMBERS OF HYDROLOGIC SOIL -COVER COMPLEXES FOR PERVIOUS AREAS -AMC II Cover Type (3) Quality of Cover (2) Soil Group A B C D NATURAL COVERS - Barren 78 86 91 93 (Rockland, eroded and graded land) Chaparrel, Broadleaf Poor 53 70 80 85 (Manzonita, ceanothus and scrub oak) Fair 40 63 75 81 Good 31 57 71 78 Chaparrel, Narrowleaf Poor 71 82 88 91 (Chamise and redshank) Fair 55 72 81 86 Grass, Annual or Perennial Poor 67 78 86 89 Fair 50 69 79 84 Good 38 61 74 80 Meadows or Cienegas Poor 63 77 85 88 (Areas with seasonally high water table, Fair 51 70 80 84 principal vegetation is sod forming grass) Good 30 58 72 78 Open Brush Poor 62 76 84 88 (Soft wood shrubs - buckwheat, sage, etc.) Fair 46 66 77 83 Good 41 63 75 81 Woodland Poor 45 66 77 83 (Coniferous or broadleaf trees predominate. Fair 36 60 73 79 Canopy density is at least 50 percent) Good 28 55 70 77 Woodland, Grass Poor 57 73 82 86 (Coniferous or broadleaf trees with canopy Fair 44 65 77 82 density from 20 to 50 percent) Good 33 58 72 79 URBAN COVERS - 56 69 75 Residential or Commercial Landscaping Good 32 (Lawn, shrubs, etc.) 74 83 87 Turf Poor 58 (Irrigated and mowed grass) Fair 44 65 77 82 Good 33 58 72 79 AGRICULTURAL COVERS - Fallow 76 85 90 92 (Land plowed but not tilled or seeded) R C F C a W C D RUNOFF INDEX NUMBERS HYDROLOGY MANUAL FOR PERVIOUS AREAS PLATE E -6.1 0 of 2) • • C RUNOFF INDEX NUMBERS OF HYDROLOGIC SOIL -COVER COMPLEXES FOR PERVIOUS AREAS -AMC II Quality of Soil Group Cover Type (3) Cover (2) A B C D AGRICULTURAL COVERS (cont.) - Legumes, Close Seeded Poor 66 77 85 89 (Alfalfa, sweetclover, timothy, etc.) Good 58 72 81 85 Orchards, Deciduous See Not 4 (Apples, apricots, pears, walnuts, etc.) Orchards, Evergreen Poor 57 73 82 86 (Citrus, avocados, etc.) Fair 44 65 77 82 Good 33 58 72 79 Pasture, Dryland Poor 67 78 86 89 (Annual grasses) Fair 50 69 79 84 Good 38 61 74 80 Pasture, Irrigated Poor 58 74 83 87 (Legumes and perennial grass) Fair 44 65 77 82 Good 33 58 72 79 Row Crops Poor 72 81 88 91 (Field crops - tomatoes, sugar beets, etc.) Good 67 78 85 89 Small Grain Poor 65 76 84 88 (Wheat, oats, barley, etc.) Good 63 75 83 87 Vineyard See Note 4 Notes: 1. All runoff index (RI) numbers are for Antecedent Moisture Condition (AMC) II. 2. Quality of cover definitions: Poor - Heavily grazed or regularly burned areas. Less than 50 per- cent of the ground surface is protected by plant cover or brush and tree canopy. Fair - Moderate cover with 50 percent to 75 percent of the ground sur- face protected. Good -Heavy or dense cover with more than 75 percent of the ground surface protected. 3. See Plate C -2 for a detailed description of cover types. 4. Use runoff index numbers based on ground cover type. See discussion under "Cover Type Descriptions" on Plate C -2. 5. Reference Bibliography item 17. R C F C& W C D RUNOFF INDEX NUMBERS r�YDRGLOGY MANUAL FOR PERVIOUS AREAS PLATE E -6.1 (2of 2) • • 0 ACTUAL IMPERVIOUS COVER Recommended Value Land Use (1) Range- Percent For Average Conditions- Percent(2 Natural or Agriculture 0 - 10 0 Single Family Residential: (3) 40,000 S. F. (1 Acre) Lots 10 - 25 20 20,000 S. F. (31 Acre) Lots 30 - 45 40 7,200 - 10,000 S. F. Lots 45 - 55 50 Multiple Family Residential: Condominiums 45 - 70 65 Apartments 65 - 90 80 Mobile Home Park 60 - 85 75 Commercial, Downtown 80 -100 90 Business or Industrial Notes: 1. Land use should be based on ultimate development of the watershed. Long range master plans for the County and incorporated cities should be reviewed to insure reasonable land use assumptions. 2. Recommended values are based on average conditions which may not apply to a particular study area. The percentage impervious may vary greatly even on comparable sized lots due to differences in dwelling size, improvements, etc. Landscape practices should also be considered as it is common in some areas to use ornamental grav- els underlain by impervious plastic materials in place of lawns and shrubs. A field investigation of a study area should always be made, and a review of aerial photos, where available may assist in estimat- ing the percentage of impervious cover in developed areas. 3. For typical horse ranch subdivisions increase impervious area 5 per- cent over the values recommended in the table above. RCFC a WCD HYDROLOGY MANUAL IMPERVIOUS COVER FOR DEVELOPED AREAS PLATE E-6.3 • • RETENTION BASIN VOLUME CALCULATIONS 0 • • • (f� RETENTION BASIN VOLUME CALCULATIONS NISSIH (r �F.ow C-"v rvD BASIN A BASIN B DEPTH VOLUME CUM. VOL. ELEVATION AREA (SF) AREA (AC) (FT) (AC -FT) (AC-FT) 134.3 3,886.12 0.089 0.26 134.0 3,641 :72 :'...:: :.. ':0.084 '.' ; : 0.3 0.03 ' :0.23 133.0 2,859.12 0.066 1,0 0.08. ... 0.15 . :.. ... ..... 132.0. ...... ....... ... 2,169.25 .. , . . 0.050 1.0 0.06 , ..:0.09 131.0 1,572.15 0.036 1.0 0.04 0.05 130.0 :. . 1,067.35.. :: ` : 0.025 1.0 0.03 .::: ., .. ... . 0.02 . 119.0 . ; :. '.;.4,073.95 0.094 0.7 0.02 0.00 129.3 768.67 0.018 0.00 BASIN B DEPTH VOLUME CUM. VOL. ELEVATION AREA (SF) AREA (AC) (FT) (AC -FT) (AC -FT) 124.0 10,029.30 0.230 0.79 .... ,123:0... 8;646:98..: .. -0.199 :: 1.0 0.21 .::0.58 122.0 7,361.80 0.169 .1..0 0.18 0.40 121.0. ' :; ' :.;': ' :`6,172.1,4 ::.:.: '::'0.142 1.0 0.1.6. .; 0.24 :: 120.0 5,076.70 0.117 0.11 1.0 0.11 119.0 . ; :. '.;.4,073.95 0.094 0.00 • C FEMA MAP I I s, ll-- L�0 \ i� -- -- —�r _ J u� . `, ,� APPROXIMATE SCALE IN FEET 2000 0 2000 ZONE C NATIONAL FLOOD INSURANCE PROGRAM II SITE FIRM l FLOOD INSURANCE RATE MAP RIVERSIDE COUNTY, CALIFORNIA (UNINCORPORATED AREAS) u�. MILES AVENUE _ - - - -- ZONE A ZONE C "= « •- RZ.. �;�' PANEL INDEX F R F 36000T PRINTED) ZONE C WES7INARD`' � �� HO:'• City of Indian Wells COMMUNITY-PANEL NUMBER AREA NOT INCLUDED 060245 2260 D MAP REVISED: NOVEMBER 20, 1996 City of Man)) UQuinta Federal Emergency Management Agency AREA NOT This Is an official copy of a potion of the abode referenced flood map. It was extracted using F-MIT on -Line. This map does not reflect changes INCLUDED - ' or amendments which may have been made subsequent to the date on the title dock. For the latest product information about National Flood Insurance Program flood maps check the FEMA Flood Map Store at www.msc.fema.gov • :7 SOIL SURVEY MAP • SHEET NO. ii RIVERSIDE COUNTY, CALIFORNIA, COACHEI (LA QUINTA QUADRANGLE) 9N . cn . j Tn MOD -;M D.. W!k Tca MOB ��verside County, C •a '\ QI'}f r. ,�':i �i j��Y�'��'r'�I }I }. i . "i 'n-'J }G/ i�3j �t,S� '{•�nJ�I, VFj ,Fy / �� x�. • ` 3\ # tit ,r -yx ! E 1�� y ♦ "�i''- t ! /�;l .,� �• /,%r \l e, .� :.4i t uuk- s r �. s� .n_""F"� -�'�v rL9`rf�__i��"._y�d�� r. :y r S�{�" -•� .6'y`°'th.�� 'L,rY+'a' �2.,�.n�..:: -�� 'TU' �..J' �t` ;ir.r �+a; %�'. �h, -' �� i ®' �..i! y. F� �t r ., •,;,Fj- •yRy' �' 1 I S {'{ �• a �, �' yr r :, ice: ''q .,�-. • y t� s � .. t� :. / r j' ' °�rv��1• , ,'i �� i ,` �y�•et "sue / rd. f �'` I s `,'faT. .�,. r':5. 0 �4�G•q�i,}'" r."%' "�'�'..::r�j. v.l�.. .,. •>y:�' �..y1' -c., � \'•�: :�},��; „�:. ' �'. •�� _ _ .,- the ";.;; $°• :': -, rE:;. � � ' ', !fir �`;,,: � �•_ , '' � V-1 ' s �r P R �" �rr � �1✓": � `ts 'i�a. �.-� �F° r �,�,'Rr..r �S�C �,3�, }{ih � � _ -. 1 r�.. Wes,'' -, ai < � +.P -"£�- •% Z � .�� se ORIN9 r - ,tS �� ±,��ti`"" .q��l" ... h. Yt' f cy' ' �'"�..? r; ' . •„ Y' �k s 'Y�}L- �c�.�'��* ��"r'� 1 • • • ?8 SOIL SURVEY TABLE 12. Soil and water features— Continued ' This mapping unit is made up of two or more dominant kinds of soil. See mapping unit description for the composition and behavior of the whole mapping unit. parent; and the months of the year that the water table commonly is high. Only saturated zones above a depth of 5 or 6 feet are indicated. Information about the seasonal high water table helps in assessing the need for specially designed foundations, the need for specific kinds of drainage systems, and the need for footing drains to insure dry basements. Such information is also needed to decide whether or not construction of basements is feasible and to determine how septic tank absorption fields and other underground installations will function. Also, a seasonal high water table affects ease of excavation. Depth to bedrock is shown for all soils that are underlain by bedrock at a depth of 5 to 6 feet or less. For many soils, the limited depth to bedrock is a part of the definition of the soil series. The depths shown are based on measurements made in many soil borings and on other observations during the mapping of the soils. The kind of bedrock and its hardness as related to ease of excavation is also shown. Rippable bedrock can be excavated with a single -tooth ripping attach- ment on a 200 - horsepower tractor, but hard bedrock generally requires blasting. Formation, Morphology, and Classification of the Soils This section contains descriptions of the major fac- tors of soil formation as they occur in the Coachella Valley Area, a summary of significant morphological characteristics of the soils of the Area, an "explanation of the current system of classifying soils'by categories broader than the series, and a table showing the clas- Hydro - Flooding High water table Bedrock Soil name and logic Frequency Duration Months Depth Kind Months Depth Hardness map symbol group Ft la MvO Ma 13, MaD --------- -- A None - - - - -- None - - -- -- -- ---- -- --- - -- -------- - - - --- -- --- - - - - - -- ------ -- -- -- >6.0 1.5 -5.0 - -- -- -- - - -- -- Apparent - - - -- ----- - -- - --- Jan - Dec - - -- >60 >60 ---- -- ---- ---- --- - -- c 0 ----------- - - - - -- Niland: NaB-- --- ----- - - - - - -, C None - -- - -- ---- --- - - --- -- --- --- - - - - -- >6.0 ------ --- - - - -- -- --- - - --- -- >60 NbB----------------- C None - - - - -- -------- - - - - -- -- ---- -- - - -- 1.5 -5.0 Apparent - - - -- Jan- Dec - - -- >60 - --- - - - --- ---- - - - --- Dmstott: OmD---------- - ----- C None - - - - -- -- --- -- - - - - - -- ------ - - - - -- >8.0 -------------------------- 4-20 Rippable. O rl: Omstott part - - -- - -. Rock C None -- -- -- -- ---- -- - -- --- ----- --- - - -- >6.0 ---- -- -- --- - -- - -- --- - - - - -- 4-20 Rippable. outcrop part. Etiverwash: RA. lock outcrop: RO. RTi: Rock outcrop part. Lithic Torripsamments part. D None - - - - -- -------- -- - - -- --------------- ------ - - - - -- 1 -10 Hard. lubble land: RU. Talton: Sa, Sb---- ---- - -- -- -- D None - - - - -- ------ ---- ------- -- - --- --- 2.0 -5.0 Apparent-- --- Jan- Dec- - -- >60 --- -- -- --- ;oboba: SOD, SpE-- ---- - - - - -- A None - - - - -- ---- ---- - - - - -- ------ -- - - -- >6.0 --- -- --- - - - - -- ----- - - - - -- >60 ---- - - - - -- Corriorthents: TO 1: Torriorthents part. Rock outcrop part. ..uiun a: TpE, TrC, TsB- - - - - -- A None - - -- --- -- - - -- -- - -- --- -- - - -- >6.0 ----- - -- - -- -- ------ - - - - -- >60 ---- - - -- -- ' This mapping unit is made up of two or more dominant kinds of soil. See mapping unit description for the composition and behavior of the whole mapping unit. parent; and the months of the year that the water table commonly is high. Only saturated zones above a depth of 5 or 6 feet are indicated. Information about the seasonal high water table helps in assessing the need for specially designed foundations, the need for specific kinds of drainage systems, and the need for footing drains to insure dry basements. Such information is also needed to decide whether or not construction of basements is feasible and to determine how septic tank absorption fields and other underground installations will function. Also, a seasonal high water table affects ease of excavation. Depth to bedrock is shown for all soils that are underlain by bedrock at a depth of 5 to 6 feet or less. For many soils, the limited depth to bedrock is a part of the definition of the soil series. The depths shown are based on measurements made in many soil borings and on other observations during the mapping of the soils. The kind of bedrock and its hardness as related to ease of excavation is also shown. Rippable bedrock can be excavated with a single -tooth ripping attach- ment on a 200 - horsepower tractor, but hard bedrock generally requires blasting. Formation, Morphology, and Classification of the Soils This section contains descriptions of the major fac- tors of soil formation as they occur in the Coachella Valley Area, a summary of significant morphological characteristics of the soils of the Area, an "explanation of the current system of classifying soils'by categories broader than the series, and a table showing the clas- • RCFC &WCD HYDROLOGY MANUAL REFERENCE PLATES �'' - ;�•=� �� -�--� x.>, � �.� :�riy �" ` { ,.{fiC.E'�, i- _- r*:R °�f • `� r� C R•gE �'I•' Q.r,.� s `- r��4r''.•t a��" - � ��'`�; -C I.'. 1 , c � � .�� '�' i � � I �� x,.o " ' '-,,, 7 - t ?.s' s r? a f �'�.;� v 'ti,� ,-�' .lz T rt c r �„` •r3_1! �I• _ r .. 1_ � I ._ . �- --- �, .,.;, fx r J ' ..! - i.,•a,,�,- z Y .��,,� � t h.' t,� r�,�"'� r. t ° Eh�N.Web -- ! .L.�:� 4.11_ _._ _.�.�.:��....:.._..- ,.�,�..� �. �Jy J!`a ° ,�r � 5v'',a k�� rf, a .�. t ^��" � ILV! r _s 3: ,�1 ,liu •Tt s F �_ ,. -��-• r. �"... 4 � ' . � 7.�'� 1 �- ^�,t+sts � .Tj.. c ! ? y _ .. k.�x� �ir:•�- - -_ - - - - - -'L - - F - - f,�p� 'Hein- `-,7r ;1 •e.6j ;` 1 �$ �"" f.> 51.11 j '� ✓ Ci�: -7N {•.J4 / LJ�VT- f, Y�'= �• ,�- ,� I fe ,! t1: {�.g. .. 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I 1 - -- tc-a!` 7•-- - rr.,`S.._- - y �- «. .:: ,::.,.•nc• >'a '= 14G.- '•' *,y.,' _ _ -, .._�:: ,� -r.J:; ice- I _ �•, ; ;. =*:c _. �•�.. !._ :1,.,..: fri / `• :-{'. � .'+�• �..er; .� ' _. ::5:.,c�dc ... - .`.R,,. �.,,,'.;;r+�?�c._ -::. �, . ;�..oRRES +{A :T-. '!� �`:�•- ^- is -%Y.. � _1 .=eti .. �`• C<,m ,YCN` �. �t- 'a _ �'..I � _.'k: ,1- . �'aE. - .. �� paa�: z_.,. .;;; . w7''�:y. •::�: °,`� _ f :=e. .. ",� •'gii4ty. S\ 'tsr` "v, .��'• •.�� i = 'Y`•s�'�`�� "�+TSS�?_'. ans. Z- ^L s . ��•. , RNf '�f:OU V•I!'•'�'� 'Z ', - !.'1', -�.� - RNER ..... v.n•r. :d = - `'' RIVERSIDE COUNTY FLOOD CONTROL WATER CONSERVATION DISTRICT +` 1 `3~:' �.._ .`" `•°� . , . J ` . q -" IOG -YEAR 3-HOUR PRECIPITATION - '�.:q }' . . ..' •� �roREST - -: �r�- '�,•,V �<�. '..r.c `; 1,,:!� ^< -',a =r •` . -''_ 1 'O> .S: _�•; r :•y^ J., _'f' �c1�...�= -�-i-F :; r i. ,'+ ,.r I•. �.:,'y:.:,..rti:.. c; '::z..:;. .. - E 7 f—ifl.' f, 'j, M: 7 ER . 4L. . . . . . . . . . . . . . . v VV 7 T 7, 4, Ay Y t-` .. ;Y >. -X u i <V, — 1` t - „4ti ` ?, __ M nk; Ni Mlll� eVP s ti y'� • tic •t r 7� -MF Mu t rf I1't4' N- X_ T." I i A R 71 . Z-4- %;R_ 4 TV f3*1 RR . ......... idi cl 10 CAHLJIW; . . . . . . . ..... Q, vAT T "�7/Yv 1`'' A rL RIVERSIDE COUNTY FLOOD CONTROL A N D A w, WATER CONSERVATION DISTRICT lit— 'A c. —YEAR— 6—HOUR 100 Ila PRECIPITATION RZE -K4 W, 4L SAN IN 17' IWA se INDIAN OW y RIVERSIDE COUNTY FLOOD CONTROL WATER CONSERVATION DISTRICT PRECIPITATION efofiEsr --- LIN 17' IWA se INDIAN OW y RIVERSIDE COUNTY FLOOD CONTROL WATER CONSERVATION DISTRICT PRECIPITATION efofiEsr --- 0 • • SYNTHETIC UNIT HYDROGRAPH HYDROLOGY MAP • • SYNTHETIC UNIT HYDROGRAPH HYDROLOGY MAP 0 II _ t t law Y)\ `�5;. 'r- «-...:::. w f - _^-.._..\ ` .y1 •� } �. v I , - .._,....— ...._.._..._..... -� �,,,,. -,..a� ��- _- «. -.�..- - _— ..._.+' ✓' f. ,JS..- wrr+w,N-J J-y � �` ! � �". i. ." ✓'" vueV- tw,J✓\ I 147 ''\\ . C, 11 �' � %' °,� o / �'� .�If`j � � n ._-! ��, ! 1 jj .,-�" ��'_ ,r 4`i yr, ----� •.,� ,� � t 5 IL 4 J i o i�^� J. V , YP v (y l . ry IN J\ t /- - -. Jf(j '^.....jr I..� �✓' �,,.,..^' -' i�� j � +/yy ol qq�\ � �`'• `'� �..�. >,� _' ..._.✓"°- _.�"". —�./ I � \ � f^„ 'ti. s �'\ {..:-""� /-� � ,rte � .✓ v._. IN, lip C:7 Li Hill r , y i t� 24 J � Y 0 Q IX %.. \WSEioo \1 Z. QO L U A-0, E "'AR 14.j79--, - - -kGR 2 :r , Nos '0 \ — y , a } r• �. e J - r^ -- d - v 0 ,.^ a _.-- cl C 1 lug i � 2. 2,70 3. Zo �(� ZS ,la m m PALM DESERT HOVLEY LANE R 11� Z 0 0 Z x Q CALLE LAS BRISAS / FRED WARING DRIVE INDIAN WELLS BEFILMA DUNES AVENUE 42 PALM ROYALE DRIVE LA OUINTA VICINITY MAP N.T.S. O R'C 0, 80' 160'. 240° 320' SCALE 1"=80' RAINAGE AREA "A" AREA RUNOFF ZCIAL 14.42 4.04 AC —FT TOTAL 4.04 AC —FT TENTION STORAGE ON BASIN CAPACITY 5 DEEP 0.26 AC —FT WATER SURFACE ELEVATION = 134.30 ON BASIN BOTTOM ELEVATION = 129.30 ROUND STORAGE CAPACITY 3.78 AC —FT 1RAINAGE AREA "B" AREA RUNOFF RCIAL 14.79 4.14 AC —FT TOTAL 4.14 AC —FT JENTION STORAGE ON BASIN CAPACITY 5 DEEP 0.79 AC —FT WATER SURFACE ELEVATION = 124.00 ION BASIN BOTTOM ELEVATION = 119.00 ROUND STORAGE CAPACITY 3.35 AC —FT LEGEND DRAINAGE DIRECTION TRIBUTARY DRAINAGE AREA BOUNDARY PROPOSED STORM DRAIN UNDERGROUND RETENTION STORAGE L., !l 1 V- V V I Lw w %a MSA CONSULTING INC DESIGN BY EAK CITY OF LA QUINTA, CALIFORNIA MAnqmRo, Smm & AssocrAm ING DRAWN BY SYNTHETIC UNIT HYDROGRAPH PuNmm ■ Qm Emummmo ■ LA m SmvEymo EAK HYDROLOGY MAP 34200 13oB Hope DRm ■ RANcAo Mao$ ■ CA 92270 CHECK BY PARCEL MAP NO. 35088 Ta><smom (760); 320 -9811 ■ FAx (760) 323 -7893 RRR