The URL can be used to link to this page

30138os IE 3ai�� HYDROLOGY AND RETENTION CALCULATIONS TRACT NO. 30138 La Quinta, California Prepared- by: W & W DESIGN DEVELOPMENT, INC. 79-440 CORPORATE CENTER DRIVE, SUITE 107 LA QUINTA, CA 92253 Lloyd W. Watson R.C.E. 26662 Expires 3 -31 -08 May 18, 2006 � � ��,v ��i • `,:j` ;+tea. � e��;t# �, . y 4`t` � :i�°�- .f �;�, � . TRACT 30138 HYDROLOGY & RETENTION CALCULATIONS INDEX 1 Summary of Report 2 Intensity - Duration Curves Data 3 Time of Concentration 4 Runoff Coefficient Curves 5 Rainfall Patterns in Percent 6 &7 10 -Year Hydrology Calculation 8 &9 100 -Year Hydrology Calculation 10 -14 Pipe Hydraulic Calculation. 15 -16 Size Catch Basins 17 -22 Hydrographs for 3 Year, 6 Year and 100 Year Storms 23 -25 Retention Basin Capacity & Water Surface Calculations 26 -28 Sand Filter Calculations 29 Overflow Map 30 Street Capacity Calculations 31 -32 Soils Report - Percolation Rates SITE DESCRIPTION This site is a 14.79 acre nursery in the City of La Quinta located within the Southeast Quarter of Section 4, Township 6 South, Range 7 East, San Bernardino Meridian. The proposed tract consists of 47 single family residential lots with private streets and gates. The site lies southeasterly of the All American Canal and is bounded by the canal on the North. Two large diameter irrigation mains bisect the tract and due to their shallow cover, no storm drain lines can serve the property North of these mains. The property on the East is being developed as a single. family development and the property on the West is a nursery. The crossing of Avenue 52 at the canal creates a natural high point in the road. As a result, the street drains to the East. Avenue 52 has recently been reconstructed by the Hideaway Country Club development on the South side of Avenue 52, eliminating the natural low point to the East of the project. This raises the road bed approximately 1.5 feet fronting the tract. This creates difficulty providing an emergency overflow for excess storm water flow from this development. PURPOSE OF THIS STUDY: The purpose of this study is to provide calculations to prove that adequate storage has been provided for the worst case 100 -year storm and that the storm drain system is capable of conducting the 100 year storm to the retention basins. A percolation rate of 2- inches per hour is used for the storage and a percolation test is provided as part of this study. The retention basin maximum ponding elevation is 15.76 in Basin No. 1. The maximum depth is 4.96 feet. The storm water at all catch basins is contained in the street section. A maximum ponding elevation of 18.62 allows the storm water emergency overflow to escape. All building pads in the development are a minimum of one foot above this ponding elevation. Retention basin No. 2 at the North east end of the tract, ponds to a maximum elevation of 16.23. The maximum depth is 4.23 feet. This basin is necessary to maintain the relationship to the adjacent tract. It abuts a retention basin that has been constructed on that tract. These basins are necessary due to grading constraints caused by the existing irrigation mains bisecting the tract. As mentioned previously, these large diameter pipes do not allow for gravity mains to cross at reasonable depths. ' Retention Basin No. 3 on Lot D near the Southeast end of the tract, ponds to a maximum elevation of 17.52. No nuisance water is generated in this basin due to landscape setback along Avenue 52, therefore no sand filter is needed. No ' calculations have been provided for this basin in that the total area of runoff is only 0.25 acres. 0.10 acres of this total is retention basin. J m r rTI v Ak- N O 01 � n 0 D 0 cv r ■ RAINFALL INTENSITY- INCHES PER HOUR CATHEDRAL CITY Z VALLEY i CORONA rn DESERT HOT SPRINGS n - YILDOyAR URATION FREQUENCY DURATION FREQUENCY DURATION FREQUENCY DURATION FREQUENCY DURATION FREQUENCY INUTES MINUTES rq D MINUTES p MINUTES I 10 0 D 10 100 l0 100 ]0 0 n � YEAR ! YEAR 0 YEAR YEAR Z YEAR ■ RAINFALL INTENSITY- INCHES PER HOUR CATHEDRAL CITY CHERRY VALLEY CORONA DESERT HOT SPRINGS ELSiNORE - YILDOyAR URATION FREQUENCY DURATION FREQUENCY DURATION FREQUENCY DURATION FREQUENCY DURATION FREQUENCY INUTES MINUTES MINUTES MINUTES MINUTES 10 100 10 100 l0 100 ]0 100 10 100 YEAR ! YEAR YEAR YEAR YEAR YEAR YEAR YEAR YEAR YEAR 5 4.14 6.T6 5 3.65 5.49 5 3.10 4.78 5 4.39 6.76 5 3.23 4.94 6 3.73 6.08 6 3.30 4.97 6 '. 2.84 4.38 6 3.95 6.08 6 2.96 4.53 7 3.411 5.56 7 3.03 4.56 7 _ 2.64 4.07 7 3.62 5.56 7 2.75 4.21 6 3.15 S.1S 8 2.82 4.24 8' 2.47 3.81 8 3.35 5.15 8 2.58 3.95 9 2.95 4.81 9 2.64 3.97 9 2.34 3.60. 9 3.13 4.81 9 2.44 3.73 10 2.77 1 4.52• 10 2.49 3.75 10 2.22 3.43 10 2.94 4.52 10 2.32 3.54 31 2.62 4.28 11 2.36 3.56 11 2.12 3:27 11 2.78 4.28 11 2.21 3.39 12 2.44. 4.07 12 2.25 3.39 12 2.04 3.14: 12 2.61s 4.07 12 2.12 3.25 13 2.38 3.•88 13 2.16 3.25 13 1.96 3.02 13 2.53 3.88 13 2.04 3.13 14 2.28 3.72 14 2.OT 3.12 14 1.89 2.92 14 2.42 3.72 14 1.97 3.02 IS 2.19: 3.58 15 1.99 3.00 15 1.83 2.82 15 2.32 3.58 15 1.91 2.92 16 2.11 3.44 16 1.92 2.90 16 1.77 2.73 16 2.24 3.44 16 1.85 2.83 i 17 2.04 3.32 17 1.86 2.80 17 1.72 2.66 17 2.16 3.32 17 1.80 2.75 18 1.97 3.22 i8 1.80 2.71 18 1.68 2.58 18 2.09 3.22 18 1.75 2.67 19 i 1.91 3.12 19 1.75 2.64 19 1.63 2.52 19 2.03 •3.12 19 1.70 2.60 4 20 1.85 3.03 20 1.70 2.56 20 1.59 2.46 20 1.97 3.03 20 1.66 2.54 22 1.75 2.86 22 1.61 2.43 22 1.52 2.35 22 1.86 2.86 22 1.59 2.43 24 1.67 2.72 24 1.54 2.32 24 1.46 2.25 24 1.77 2.72 24 1.52 2.33 26 1.59 2.60 26 1.47 2.22 26 1.40 2.17. 26 1.69 2.60 26 1.46 2.24 28 1.52 2.49 28 1.41 2.13 28 1.36 2.09 28 1.62 2.49 28 1.41 2.16 1 30 1.46 2.39 30 1.36 2.05 30 1.31 2.02 30 •1.55 2.39 30 1.37 2.09 1 32 1.41 2.30 32 1.31 1.98 32 1.27 I.96 32 1.50 2.30 32 1.33 2.03 34 1.36 2.22 34 1.27 1.91 34 1.23 1.90 34 1.45 2.22 34 1.29 1.97 36 1.32 2.15 36 1.23 1.85 36 1.20 1.85 36 1.40 2.15 - 36 1.25 1.92 I 38 1.28 2.09 38 1.20 1.80 38 1.17 1:81 38 1.36 2.09 38 1.22 1.87 40 1.24 2.02 40 1.16 .1.75 40 1.14 1.76 40 1.32 2.02 40 1.19 1.82 45 1.16 1.89 45 1.09 1.64 45 1.06 1.66 45 1.23 1.89 45 1.13 1.72 50 1.09 1.78 50 1.03 1.45 SO 1.03 1.58 50 1.16 1.78 50 1.07 1.64 55 1.03 1:68 55. .99 1.47 55 .98 1.51 55 1.09 1.68 55 1.02 1.56 60 .98 1.60 60 .93 1.40 60 .94 1.-45 60 1.04 1.60 60 .98 1.50 65 .94 1.53 65 .89 1.34 65 .90 1.40 65 .99 1.53 65 .94 1.44 TO .90 1.46 70 as 1.29 70 .87 1.35 TO .95 1:46 TO .91 1.39 75 .86 1.41 TS ..82 1.24 75 .84 1.30 75 .91 1.41 75 .88 1.35 80 .83 1.35 80 .T9 1.20 80 .82 1.26 80 .88 1.35 BO .85 1.31 85 .90 1.31 85 .77 1.16 85 .80 1.23 85 as 1.31 85. .63 ;. 1.27 SLOPE - .550 SLOPE '= .550 SLOPE ..480 SLOPE = .580 SLOPE .480 W N 4 LIMITATIONS: TC1 . I. Maximum length __100 2. Maxirmith 1000 —90' Undeveloped Undeveloped - —900 —80 H 800 Undeveloped 700 — 60 Poor Cover -- ° _ 2 30Q 6r 00 50 (1/4 Acre)- 0 0 E Cdihmdrcial_ 1UV 0 —500 8 60 0 QL6 35 40 30 o 06 400 c 30 20 350 25 6 K Ai ...m E- 20 _-250 x: - 15 2-00 —14 112 2 113 II 150 9 E P 6 4 LIMITATIONS: I. Maximum length =1000 2. Maxirmith area = 10 Acres Undeveloped Undeveloped - 1,0 H Undeveloped Sac) 400 Poor Cover -- ° _ 2 30Q -2 (1/4 Acre)- 200 0 E Cdihmdrcial_ 1UV 0 4U 8 60 0 50 E 40 30 o 06 20 6 K Ai ...m Undeveloped. Good Cover 2 Undeveloped Undeveloped - 1,0 r Cover Undeveloped .5 .4 Poor Cover -- ° _ 2 Single Family > (1/4 Acre)- -50 Cdihmdrcial_ 4U RC_FC &I WCD HYDF?oLoGy 1\11.ANUAL I I .KEY L---H --TG - K - T C' TC 5---1 6 ri a CD 8 ;Q. E az 910 E O 12 16 -Z 17 E t8 c 12 20-- O 25— C 0 30.- EXAMPLE: E (D (1) L =550 , H =5.0, K = Single Family 35-.:-- Development , Tc 12-6 min. _ (2) L =550'1 H =5.0', K = Comm Development - -'-' ercial 401 _.____...,Tq=9, 7.fnjn.. Reference: Bibliog.roohy item No. 35. TIME OF CONCENTRATION FOR INITIAL SUB-AREA PLATE D-3 a ■% r m M 1 tD i v RAINFALL PATTERNS IN PERCENT L 3-HOUR.. b1oKM -HOUR- STORM I 24 -HOUR STORM `- �Y ^ TINE PERIOD 1 5 -NIN PERIOD 1.3 !0 -MIN PERI00 2.6 IS -MIN PERIOD 3.1 30 -MIN PER100 B.5 TINE PEaI00 5 -NIN PERIOD 10 -MIN PERt00 IS -MiN PERTOD 30 -MIN PERIOD LINE PERIOD 5 -MIN PERIOD TIME PER100 15 -MIN PERIOD 30 -NIN PERIOD 60 -NIN PERIOO 1 .5 1.1 1.1 3.6 ♦9 1.1 1 .2 .5 1.2 ` J 2 1.3 1.1 2.6 3.3 ♦.8 5.1 10.0 13.9 2 .6 1.2. 1.9 ♦.3 50 1.8 2 .3 .7 l.3 v 3 ♦ 1.5 3.] ♦.9 17.♦ 3 ♦ .6 .6 1.] 1.♦ 2.l 2.2 ♦.B i. 9 51 52 1.9 2.0 3 t .3 ,♦ .6 .7 1.8 2.1 ` 5 1.5 3.3 6.6 29.9 5 .6 1.♦ 2•♦ 5.3 53 2.1' S .3 .8 2.B �7 6 l.B 3.4 7.3 20.3 6 .7 1.5 2.♦ 5.8 51 2.1 6 .3 1.0 2.9 l.5 ♦.♦ B.♦ 7 .7 1.6 2.♦ 6.8 55' 2.2 7 .3 1.0 3.8 B 1.8 4.2 7.0 B .7 1.6 2.5 9.0 56 2.3 B .♦ 1.1 ♦.6- 9 I.8 5.3 12.3 9 .7 1.6' 2.6 11.6 57 2.4 9 .♦ 1.3 6.3 10 1.5 5.1 17.6 10 .7 1.6 2.7 14.1 5B 2.4 10 .♦ 1.5 8.2 Il 1.6 6.♦ 16.1 11 .7 1.6 2.8 25:1 59 2.5 11 .S 1.3 1.0 12 1.8 5.9 4.2 12 .8 1.1 3.0 ♦•♦ 60 2.5 12 .5 1.6 1.3 13 2.2 1.3 13 .B 1.7 3.2 61 3.l 13 .5 1.6 IO.B 14 . 2.2 B.5 14 .8 1.8 3.6 62 3.6 1♦ .5 ^c.0 11.♦ 15 2.2 1 ♦.1 IS :8 1.6 ♦.3 63 3.9 15 .5 2.1 10.♦ 16 2.0 1 ♦.1 16 .8 1.8 ♦.1 6♦ 2 16 .6 2.5 B.S IT 2.6 3.8 lT .B 2.0 5.♦ 6s ♦ 7 IT .6 3.0 1.4 1 8 2.1 2.4 18 .8 2.0' 6.2 66 5.6 1B .7 3.3 1.9 19 2.4 19 .8 2.1 6.9 67 1.9 19 .7 7.9 1.3 20 2.7 20 .8 2.2 7.5- 68 ,9 20 .8 4 .3 1.2 21 3.3 21 .8 2.5 10.6 69 .6 21 .6 3.0 1.1 22 3.1 22 .8 2.8 1i.5 70 ,5 22 .1 4 .0 1.0 23 2.9 23 .8 3.0 3.♦ 7l .3 23 .8 3.8 .9 24 3.0 24 .9 3.2 1.0 72 .2 24 .8 3.5 .6 25 3.1 25 .8 3.5 25 .9 5.1 26 ♦•2 26 .9 3.9 - 26 .9 5.1 27 5.0 - 27 .9 i.2 27 1.0 6.B 28 3.5 28 . 9 4.S 28 1.0 t.6 _ 29 6.8 29 .9 ♦.8 29 1.0 5.3 T 30 7.3 30 .9 S.l 30 1.1 5.1 il! 31 8.2 31 .9 6.7 31 1.2 ♦.7 D 32 5.9 32 .9 B.1 32 1.3 3.8 37 2.0 33 1.0- 10.3 33 I.5 .8 Z 34 1.8 34 1.0 2.8 34 1.5 .6 Z 75 I.8 35 .1.0 1.1 35 1.6 1.0 D 36 .6 36 1.0 .5 36 1.7 .9 37 1.6 37 38 1.9 2 0 .8 5 r 1.1 -v r t.t m 1.1 . n 1.2 D 1 .3 ' 43 I.♦ ♦♦ 1.♦ Z m 1.5 ' ♦6 1.5 ♦7 1 6 Z 1.6'i 38 1.1 39 t.t ♦0 1.1 . ♦1 1.2 42 1 .3 ' 43 I.♦ ♦♦ 1.♦ ♦5 1.5 ' ♦6 1.5 ♦7 1 6 ♦8 1.6'i NOTES: I. 3 and 6 -hour patterns based on the Indio.area thunderstorm of September 24,1939. 2. 24 -hour patterns based on the general storm of March 2 a 3,1938. 3 t ♦ ♦ ♦ ♦ 9 2.1 .7 0 2.2 .5 1 1.5 .6 2 1.5 .5 3 2.0 .5 ♦ 2.0 S 5 1.9 .5 6 1.9 ♦ 7 1.1 B 1.6 TIME 15 -MIN PER100 •PERIOD FICK i& VC D HYDROLOGY kJANUAL RATIONAL METHW CALCULATION FORM PROJECT 74447' Alf-.3013,5 FREQUENCY1 110:4e4v 6AP"'v Ch,ecked. bv Shool;No,-L of 32Sh'"Is DRAINAGE AREA soil a Development A: Acres I Ih /Iw C: AQ CF's s Qi OFS SLOK SIVION v FPSi L 'FT. T MIN.. E:Y REMARKS A -/p 04'ff 7 A -$0 1#74 7134..667. 2,Q" -g -so 0,57 2,70 671 t.0 /o,5 1-.2 ml A -go Of Z Z-73 16173 0116 Z; .1 E e.g. 5--eo Ia. f.w 1(161. /1 //,I Tti ko z. F to A t I. 0,6 *5 A -so 2 .4 ,4 0 � :1 14 L f, 0,12,! 53 3 r 0, 4 OB q3 610,58 &67. 2,o fo eS. -*3 i A -50 480' 0,7 he I I"f 4 #z 4 f .01 0.7 .4 r w ;4 61. 07) R C F 11%; ' W C 0 HYDROLOGY MANUAL RATIONAL ;METHOD: CALCULATION FORM PROJECT 7-ycal AP 30138 FREQUEOICY1 Waisted! by th,acked' bv of 2LSh'sols DRAINAGE R AEA • ;BREHM , REMARKS M off, 13 Fri - ®�� ram�� mmmm mmmm mmmm mmm mmm mmm mmmm mmm mm ® ®�� ®®®�►� 4ADiotir Q m .Z *1 R C FC & WC D HymOLOGY MANUAL RATIONAL METHOD. CALCULATION FORM PROJECT _ Te,4c7' /✓" SO/38 FREQUENCY1 !00 V441, 61veof Sheet No, 8 of 2-1-Sheets Colculeted. by -„ P 17 ZVt_ -- Cheeked bv ----------- Rr * - -- DRAINAGE s soil a A A I I C C A A 0 1 1 G S SECTION v v > >_ T T E E T REMARKS A io. ex- A A - 5o / /,2G 3 3.85 , ,7!/ 3 3,45 I !3 2 J J,,A.t ee,? 1.7 5 4Ll= 2,8-f' I i i ! a D C,B A A - 5o 0 0.57 1 14,4o , ,727 / /,8 i l0.5 � �i�(%ir¢=i L =zg'0 3 3 45 4 io,sx / /8s l 4 ` , C o C�. B. `' A A - 5o o of 4 4 # #710 3 3.5 ` 1. ' '?d"41.Avq 1 =9V/ &q 3,8' , 1 D �o C,15'0 �o. A A-50 0 0-4z , ,45 , ,728 / /. 4 � �►a rt w � � (��' � . 4.7c& 3 3,5 - --o x / / • •7C ! o C! 8. -0 - -,5-0 / /06 4 4,01 !l,4 ' ' n, At Arta, 1 =36o A$4: I � I I i F 40 I A - So 0 0,9� , , , ,vl� 2 2 ,6 Lp 0,13 �5 A A —50 6 6,52 4 4.30 , ,723 l l,lo , a, A A.t6r l= 3sg Q�= 7, .2c 2 2,7 _ ,o� a ,2 � �5 f 0,5- i 14 2.P A A - 5o 0 0,/2 5 546 . .750 1 15 0 C' �s d� 7 ?3 RCFC l&; ,'WG D HYDRO LQGY MANUAL RATIONAL. ;METHOD, CALCULATION FORM PROJECT )V-2 38 FREQUENCY1 Shat fiNo...f.." of &Sh*eets CoAculated! bi..—.0— Ckocked' by 'fA 040tl 0 7 � q , • 14 ya, rau ' ! Try 24 D . HDf �. _,oil a E 1� !w V= 7�,4 = 2.14 cm fL'�.5� - ' _ tk ! ! _ 1G:L3 a . a. G N .G. - -� • i L-- _G4,ic, 116tt.0 , .�_ _.. �.. - Qr.��K �QCd_�d: e�s_� ►... P!(ae4a Clt;'sAt I '____ —� : -- CDv_�nPu 1— = -��,• 64TwQ�1�! ' - = �� _ _. __._. _. ,___ _.. _ _.__._ ._._ _.1f_ " � Z•�� fps t�v • z S _ , neo7il� AL N�. V.L. � �urw��a�n .0 = ..9N.S.C�,�3 /as;ti •{- �-aSt- � �- 23.1' ✓_ =' .... ..•--- ._•.__ .. . - - -. _ tz,TL -t , 04- 4� D...1.2. , • 6 a %wtd A ��av►�,�-ioH N= `� � _ L° ,B .�?l.._ �- ._;.. _,.. _. {_,. � -- -- � - 1 - _ O1 A N pf' � s._ n.. _ ._ -.D 1.1_ OV_ -7 I r i FI (,LCD )cT'�Z ,� #- 1 231 l ✓_ -177 1 I j ! j J • , { �- �Ga±N► .u�c�± __.1�,.(�a.....•..b�a.�G�_.- J4��:o,n tit - , pp � # # '!_ivy 77 , ' i j , � d-1.�• �.,� C. �.' �I, W � ode l� JG�, �• � (.I S } ��Z3 1.}-t/.6 , , 1 � � � ; , - .__ ; _ ! _� - _.. ___. �_ ..... _ _boacvc _ ►:34Y- 1G.�q - _- 0,3r___ —w - -- - -•- • r ' _ T2 Acc,7- 30138 1 JfA' 0 C-64 to (e-" Tr 1-" DIA 14 -PPE AI 2.573 Le 2q, (�&Lg 4A"b 4v + L Si 1.2ske, bu Rde C-0, 8z (vic, I 11 11 CS" Pik Agpe oil vq�. 141 4:p 0.16' ... Vq 3- Do 301/1 r 16-so: vA 4-1 4.1 c h 9,(o e. UP !Y vy, b. L. Q -4C.T. t'Z = Neal A- tIe S0'4 Wvo + 14, (OIL. 6? 1 6T. I 1AS + W(7- L. @ JCT, N= 30138 °_.. ' �. -1 i a15 4f; �Ar-k tt�t,6 ' Met. -tA t L-A'M t' CJ�2 ji - - LZ s QIA to I s- - oorl o .. 1,486r 2.3 I i ! i (r. I, Q C-5: N= 0 _ 4.uLGG gat 4- L) SI + i 16,7 4, ♦ 25,40 • �o►�i, /1,23. O'..I�Ot _ �_: �_ .. __.. ... .._ - - ' ISIS 10 4, .C, ,.old i -. 1_ ! _ 5�_ �l ► ¢8 (o - , by 1;0 y Faaboctrc I I TV- A Ur PJS 3 0 14-1 Aeautlir'-,;, C 3 4.SJt.44-oc-k =S-ScAe. Tr-j 14"'DIA HoFe r1r,011 t �3= A�oo- 2--1 1 0- YVI 14 4-(*60. 06 0-010) "23)(0, I I tv u 14 zr F. L C 5 Free 6m,-J II—.ZS — 1&.5$. 6.4-7 1 -- -' _ _ - _ —Q;�+ ,= 4-D r 1.58 u 4 dt 14 F✓u bmv c4 = 11.14 - IG-11 0,55� I , , ._ ..I- ' i-- • - - -�. f. '. I }y day ILL° lLt�a��auad .- f -A li c4lcl 6a.s wN , rQ iV% �uou odw oo� �j5st�w+Eei_ i Po.hd'a C,*�Vrb All c 6i. ba'iot;lov Wtod ° cA �. ' ,I ' ! _ i � LI�b...;- iCd.L6.- � �Tk �Q�i , .. - _.t.� oPLK•�✓� A..t� __ I • _`_. �a6w+..1�., ` _ .Q �naC� �a�i.� ,��_..... wid�t+; evil. 3.0 4. I 4' I 4-w f i 414 2- OL . Lr � I 1 • i i 4 I I ! i i.o!� T75 . !.0 Cf S . K de .7 Af- Qmi r D t, / 00, ,p8 �• 25 .04 ./ 12 PROJECT: ILOCATION: CLIENT: PAGE 17 OF TRACT 30138 JOB NO: BY: DEL BOYER DATE: 05/10/06 FLOW IN OFFSITE STORM DRAIN TO RETENTION HYDROGRAPH AREA # 1 IN TENTATIVE TRACT NO. 30138 'USE RCFCD HYDROLOGY MANUAL PLATE E -5.9 FOR RAINFALL PATTERN. PLATE E -5.6 INDICATES 100 -YEAR 24 -HOUR PRECIPITATION = 4.5" SOIL TYPE "A" � I 1 (2) (3) INCL. NET '(1) PERIOD RAINFALL Q VOL. PREY. STOR. PERC. CUM. STOR. (HOUR) % INS. (PER HR) C C.F.S. (C. F.) (C.F.) (C. F.) (C.F.) � I 1 1.2 0.054 0.461 0.303 1,092 1,092 0 1,092 2 1.3 0.058 0.463 0.327 1,178 2,271 379 1,892 3 1.8 0.081 0.467 0.461 1,660 3,552 593 2,959 4 2.1 0.094 0:469 0.537 1,935 4,894 817 4,077 5 2.8 0.126 0.472 0.725 2,610 6,686 1,116 5,570 6 2.9 0.130 0.473 0.750 2,698 8,269 1,371 6,898 7 3.8 0.171 0.480 1.001 3,602 10,500 1,653 8,847 8 4.6 0.207 0.487 1.229 4,424 13,271 1,767 11,504 9 6.3 0.284 0.497 1.721 6,194 17,698 1,886 15,812 10 8.2 0.369 0.508 2.285 8,226 24,038 2,059 21,979 11 7.0 0.315 0.501 1.924 6,926 28,905 2,192 26,713 12 7.3 0.328 0.503 2.011 7,240 33,953 2,317 31,636 13 10.8 0.486 0.520 3.081 11,090 42,726 2,476 40,250 14 11.4 0.513 0.525 3.283 11,819 52,069 2,674 49,395 15 10.4 0.468 0.520 2.967 10,680: 60,075 2,863 57,212_ 16 8.5 0.382 0.508 2.366 8,516 65,728 2,942 62,786 17 1.4 0.063 0.464 0.356 1,283 64,069 2,942. 61,127 18 1.9 0.086 0.468 0.491 1,766. 62,893. 2,930 59,963 19 1.3 0.058 0.463 0.327 1,178 61,141' 2,888 58,253 20 1.2 0.054 0.461 0.303 1,092 59,346 2,846 56,500 21 1.1 0.050 0.461 0181 1,012 57,511- 2,802- 54,709:, 22 1.0 0.045 0.460 0.252 908 55,618 2,758. 52,860 23 0.9- 0.040' 0.459 0.224 806 53,665 2,700 50,965 24 0.8 0.038. 0.458 0.212 764 51,729 2,666 49,063- (1) RAINFALL = % OF TOTAL PERCIPITATION I' (2) Q= RAINFALL x C x A (INS. PER HOUR) (3)V= Qx3600= c.f. /HR 1(4 . ) PERC RATE = 2 " /HR = 0167'/HR II G:/Administration/COST ESTIMATES /HYDROGRAPH.wb3 A = 12.19 C = COEFF. FOR 50GL. SGL FAM 'PROJECT: LOCATION: CLIENT: PAGE 18 OF 32 TRACT 30138 JOB NO: BY: DEL BOYER DATE: 05/10/06 FLOW IN OFFSITE STORM DRAIN TO RETENTION - HYDROGRAPH AREA # 1 IN TENTATIVE TRACT NO. 30138 'USE RCFCD HYDROLOGY MANUAL PLATE E -5.9 FOR RAINFALL PATTERN. PLATE E -5.6 INDICATES 100 -YEAR 6 -HOUR PRECIPITATION = 2.75" SOIL TYPE "A" '(1) PERIOD (HOUR) RAINFALL % INS. (PER 1/4 HR) C (2) Q C.F.S. (3) VOL. (C.F.) INCL. PREY. STOR. (C.F.) PERC. (C. F.) NET CUM. STOR. (C.F.) 1 1.2 0.047 0.461 0.264 951 951 0 951 2 1.3 0.052 0.488 0.309 1,114 2,064 86 1,978 3 1.8 0.058 0.490 0.346 1,247 3,226 135 3,091 ' 4 2.1 0.061 0:492 0.366 1,317 4,408 184 4,224 5 2.8 0.066 0.496 0.399 1,437 5,660 236 5,424 6 2.9 0.066 0.496 0.399 1,437 6,861 286 6,575 7 3.8 0.066 0.496 0.399 1,437 8,011 335 7,676 ' 8 4.6 0.069 0.498 0.419 1,508 9,184' 414 8,770, 9 6.3 0.072 0.499 0.438 1,577 10,347 422 9,925 10 8.2 0.074 0.500 0.451 1,624 11,549 430 11,119 11 7.0 0.077 0.502 0.471 1,696. 12,815 439 12,376 12 7.3 0.082 0.504 0.504- 1,814 14,190 448 13,742 13 10.8 0.088 0.506 0.543 1,954 15,696 458 15,238 14 11.4 0.099 0.510 0.615 2,216 17,453' 470 16,983 15 10.4 0.118 0.518 0.745 2,682. 19,666 485 .. 19,181 -. 16 8.5 0.129 0.526 0.827 2,978. 22,159 502 21,657 17 1.4 0.148 0.532 0.960 3,455. 25,112• 522• 24,590 18 1.9 0.170 0.543 1.125 4,051 28,641 546 28,095 19 1.3 0.190 0.550 1.274 4,586 32,681' 574` 32,107 20 1.2 0.206 0.557 1.399 5,035 37,142 594 36,548 ' 21 1.1 0.292 0.585 2.082. 7,496. 44,044. 625.: 43,419 - 22 1.0 0.399 0.618 3.006 10,821 54,240 681 53,559 23 0.9 0.094 0.508 0.582 2,096 55,655 690 54,965 ' 24 0.8. 0.028 0.472. 0.161 580 55,545 689 54,856 ' (1) RAINFALL = % OF TOTAL PERCIPITATION A = 12.19 (2) Q = RAINFALL x C x A C = COEFF. FOR 50GL. SGL FAM ' (INS. PER HOUR) (3)V= Qx3600= c.f. /HR t(4) " PERC RATE = 2 /HR = 0167'/HR !Administration /COST ESTIMATES /HYDROGRAPH.wb3 SUBJECT: TRACT 30138 PAGE 19 OF 32 PROJECT: JOB NO: LOCATION: BY: DEL BOYER CLIENT: DATE: 05/10/06 'FLOW IN OFFSITE STORM DRAIN TO RETENTION HYDROGRAPH AREA #1 IN TENTATIVE TRACT NO. 30138 'USE RCFCD HYDROLOGY MANUAL PLATE E -5.9 FOR RAINFALL PATTERN. PLATE E -5.2 INDICATES 100 -YEAR 3 -HOUR PRECIPITATION = 2.2" SOIL. TYPE "A" (1) (2) (3) INCL. NET RAINFALL Q VOL. PREY, STOR. PERC. CUM. STOR. 'PERIOD (15min) % INS. (PER HR) C C.F.S. (C.F.) (C.F.) (C. F.) (C.F.) 1 3.7 0.081 0.502 0.496 1,784 1,784 0 1,784 t 2 4.8 0.106 0.513 0.663 2,386 4,171 174 3,997 3 5.1 0.112 0.516 0.704 2,536 6,533 273 6,260 4 4.9 0.108 0.515 0.678 2,441 8,701 363 8,338 5 6.6 0.145 0.531 0.939 3,379 11,717 431 11,286 ' 6 7.3 0.161 0.538 1.056 3,801 15,087 454 14,633 7 8.4 0.185 0.548 1.236 4,449 19,082 481 18,601 8 9.0 0.198 0.551 1.330 4,788 23,388 510 22,878 ' 9 12.3 0.271 0.572 1.890 6,803 29,681 553 29,128 10 17.6 0.387 0.615 2.901 10,445' 39,572' 605 38,967 11 16.1 0.354 0.603 2.602 9,368` 48,335 646 47,689 i' 12 4.2 0.092 0.508 0.570 2,051 _ 49,740 655 49,085 (1) RAINFALL = % OF TOTAL PERCIPITATION A = 12.19 ACRE SOIL TYPE "A" (2) Q= RAINFALL x C x A (INS. PER HOUR) C = COEFF. FOR 50 GAL -SGL FAM '(3) V = Q x 3600 = c.f. / HR ' (4) PERC RATE = 2.0 /HOUR =.167'/HOUR '' G: /Administration /COST ESTIMATES /HYDROGRAPH3 SAMPLE.wb3 ' (2) SUBJECT: INCL. PROJECT: PERIOD RAINFALL LOCATION: CLIENT: TRACT 30138 PAGE 20 JOB NO: BY: DEL BOYER DATE: 05/10/06 FLOW IN OFFSITE STORM DRAIN TO RETENTION ' HYDROGRAPH AREA # 2 IN TENTATIVE TRACT NO. 30138 32 USE RCFCD HYDROLOGY MANUAL PLATE E -5.9 FOR RAINFALL PATTERN. ' PLATE E -5.6 INDICATES 100 -YEAR 24 -HOUR PRECIPITATION = 4.5" SOIL TYPE "A" (1) (2) (3) INCL. NET PERIOD RAINFALL Q VOL. PREV. STOR. PERC. CUM. STOR. (HOUR) % INS. (PER HR) C C.F.S. (C. F.) . (C. F.) (C.F.) (C. F.) I I !Administration /COST ESTIMATES /HYDROGRAPH.wb3 1 1.2 0.054. 0.461 0.077 278 278 0 278 2 1.3 0.058 0.463 0.083 300 578 96 482 3 1.8 0.081 0.467 0.117 422 904 151 753 4 2.1 0.094 0:469 0.137 492 1,245 207 1,038 ' 5 2.8 0.126 0.472 0.184 664 1,701 284 1,417 6 2.9 0.130 0.473 0.191 686 2,104 408 1,696 7 3.8 0.171 0.480 0.254 916 2,612 430 2,182 ' 8 4.6 0.207 0.487 0.313 1,125 3,307' 459: 2,84& 9 6.3 0.284 0.497 0.438 1,575 4,423: 506 3,917 10 8.2 0.369 0.508 0.581 ' 2,092 6,009: 578' 5,431. 11 7.0 0.315 0.501 0.489. 1,761. 7,192'. 633 6,559. ' 12 7.3 0.328: 0.503.: 0.511 1,841 8,400' 688: 7,712: 13 10.8 0.486 0.520 0.781 2,820: 10,533::: 786. 9,747: 14 11.4 0.513 0.525 0.835 3,006 12,752: 887. 11,865;. 15 10.4 0.468' 0.5201 0.754. 2,716: 14,581:.. 976..= ..,.... .. 13,605:. = -.• -..- 16 8.5 0.382' 0.508 -. 0.602. 2,166: 15,771. 1,036-1. 14,73&, ; . 17 1.4 0.063 0.464 0.091 326 15,061, 1,0011. _ 14,060'.,., ' 18 1.9 0.086: 0.468 0.125: 449. 14,509. 973' 13,536; 19 1.3 0.058: 0.463: 0.081 300' 13,836!" 939' 12,897` 20 1.2 0.054 0.461 0.077 278 13,175` 906 12,269- 21 1.1 0.050 0.461 0.071 257. 12,526., .. 877 -. 11,649 -.. t 22 1.0 0.045 0.460 0.064 231 11,880 847 11,033 23 0.9 0.040` 0.459 0.057 205 11,238- 818 10,420 24 0.8 0.038 0.458 0.054 194 10,614 789 9,825 ' (1) RAINFALL = % OF TOTAL PERCIPITATION A = 11 (2) Q = RAINFALL x C x A C = COEFF. FOR 50GL. SGL FAM (INS. PER HOUR) (3)V= Qx3600= c.f. /HR ,(4) " PERC RATE = 2 /HR = 0167'/HR I I !Administration /COST ESTIMATES /HYDROGRAPH.wb3 ' SUBJECT: PROJECT: 'LOCATION: CLIENT: TRACT 30138 PAGE 21 JOB NO: BY: DEL BOYER DATE: 05/10/06 FLOW IN OFFSITE STORM DRAIN. TO RETENTION ' HYDROGRAPH AREA # 2 IN TENTATIVE TRACT N.O. 30138 'USE RCFCD HYDROLOGY MANUAL PLATE E -5.9 FOR RAINFALL PATTERN. PLATE E -5.6 INDICATES 100 -YEAR 6 -HOUR PRECIPITATION = 2.75" SOIL TYPE "A" ' (2) (3) INCL. NET '(1) PERIOD RAINFALL Q VOL. PREV. STOR. PERC. CUM. STOR. (HOUR) % INS. (PER 1/4 HR) C C.F.S. (C.F.) (C.F.) (C.F.) (C.F.) ' 1 1'.2 0.047 0.461 0.067 242 242 0 2 1.3 0.052 0.488 0.079 283 525 22 3 1.8 0.058 0.490 0.088 317 820 35 4 2.1 0.061 0.492 0.093 335 1,120 48 ' 5 2.8 0.066 0.496 0.101 365 1,437 61 6 2.9 0.066 0.496 0.101 365 1,742 73 7 3.8 0.066 0.496 0.101 365 2,034 101 t8 4.6 0.069 0.498 0.107 383 2,317 104 9 6.3 0.072 0.499 0.111 401 2,614 110 10 8.2 0.074 0.500 0.115 413 2,916 113 ' 11 7.0 0.077 0.502 0.120 431 3,235 116 12 7.3 0.082 0.504 0.128_ 461 3,580.. 120 13 10.8 0.088 0.506 .0.138 497 3,957 124 14 11.4 0.099 0.510 0.157 563 4,396' 129 ' 15 10.4 0.118 0.518 0.189 682 4,950. 135. 16 8.5 0.129 0.526 0.210 757 5,572 142 17 1.4. 0.148 0.532 0.244 879 6,309• 151. ' 18 1.9 0.170 0.543 0.286 1,030 7,188 161 19 1.3 0.190 0.550 0.324 1,166 8,193' 172 20 1.2 0.206 0.557 0.356 1,281 9,301. 185 21 1.1 0.292 0.585 0.530 1,906. 11,023., 205- ' 22 1.0 0.399 0.618 0.764 2,752 13,570 234 23 0.9 0.094 0.508' 0.148 533 13,869 238 ' 24 0.8 0.028. 0.472 0.041 147 13,778 237 '0) RAINFALL = % OF TOTAL PERCIPITATION A = (2) Q= RAINFALL x C x A C= ' (INS. PER HOUR) (3)V= Qx3600= c.f. /HR '(4) PERC RATE = 2 " /HR = 0167'/HR II /Administration /COST ESTIMATES /HYDROGRAPH.wb3 3.1 242 503 785 1,072 1,376 1,669 1,933 2,213` 2,504 2,803. 3,119 3,460- 3,833 4,267 4,815_;... .. 5,430 6,158. 7,027 8,021, 9,116 10,818:., 13,336. _ 13,631 13,541 COEFF. FOR 50GL. SGL FAM SUBJECT: TRACT 30138 PAGE 22 OF 32 PROJECT: JOB NO: LOCATION: BY: DEL BOYER CLIENT: DATE: 05/10/06 FLOW IN OFFSITE STORM DRAIN TO RETENTION HYDROGRAPH - AREA # 2 IN TENTATIVE TRACT NO. 30138 USE RCFCD HYDROLOGY MANUAL PLATE E -5.9 FOR RAINFALL PATTERN. PLATE E -5.2 INDICATES 100 -YEAR 3 -HOUR PRECIPITATION = 2.2" SOIL TYPE "A" ' 1 () 2 () (3 ) INCL. NET RAINFALL Q VOL. PREV. STOR. PERC. CUM. STOR. 'PERIOD (15 min)_ % INS. (PER HR) C C.F.S. (C.F.) (C.F.) (C.F.) (C.F.) 1 3.7 0.081 0.502 0.126 454 454 0 454 2 4.8 0.106 0.513 0.169 607 1,061 36 1,025 3 5.1 0.112 0.516 0.179 645 1,670 57 1,613 4 4.9 0.108 0.515 0.172 621 2,233 72 2,161 5 6.6 0.145 0.531 0.239 859 3,021 112 2,909 ' 6 7.3 0.161 0.538 0.269 967 3,875 121 3,754 7 8.4 0.185 0.548 0.314 1,131 4,886 132 4,754 8 9.0 0.198 0.551 0.338 1,218 5,971 144 5,827 9 12.3 0.271 0.572 0.481 1,730 7,557 162 7,395 ' 10 17.6 0.387 0.615 0.738 2,656 10,051 191 9,860 11 16.1 0.354 0.603 0.662 2,382 12,242 216 12,026 _ .12 4.2 0.092 0.508 0.145 522 12,548 219 12,329 II (1) RAINFALL= % OF TOTAL PERCIPITATION A = 3.1 ACRE I' (2) Q= RAINFALL x C x A (INS. PER HOUR) '(3)V= Q.x3600= c.f. /HR (4) PERC RATE = 2.0 /HOUR =.167'/HOUR II C = COEFF. FOR 50 GAL -SGL FAM ir: /Administration /COST ESTIMATES /HYDROGRAPH3 SAMPLEM133 3A,i Ak C -LC- v AiLc -A vol-UH -c- COL A,- (I On? _ _ -. _PE2 'G2 ►a lipgo 5F 13-0 2432 SF 2 p5 �'�' : _' _ 4-oco Rs 15.0 144- -5p, F.- B48a 54�5& 4F I 'L�o.: X04 3' _ 1234 ` .C'?64b, N A. SF X1053} �__ 1�73'3�-- ' - - ~ -- , Ai2o (11:41 S,F ..10, _t IL + ' i u 11. - -1 - 11 2fo� 3z MARQUIS LANE - WEST ■ SANDFILTER SIZING CALCULATIONS Calculation #1 Determines how many standard size sandfilters are needed'. No.* of Sandfilters = 21 homes _ 40 homes / sandfilter ` Round all fractions up to the nearest whole number I . 54.N4 FILTER, REQ'0 Each sandfilter has 48 sf of filter surface (ie 6'x 8'); assume the incoming nuisance water will ' percolate through the sand at the rate of 4' '16 inches per hour. The sandfitter must be sized to handle the "surge inflow rate" of 0.458 cf /house /hour, which is based on the assumption that, on average, each house releases 12 gallons in a 3.5 hour "surge" period. Therefore, each sandfilter is capable of handling 18.4 cf /hour. As a result, each,sandfilter can handle the nuisance water released by 40 homes (18.4/0.458 =40).. Calculation #2 - Determines how long the leach line must be. 2 Leach Line Length* = homes. x 1.9 If/home (sandy soil) " In feet to be divided evenly,between the number of sandfilters 5 Leach Line Length* = 2 homes x 3:8 If/home (silty soil) ` In feet to be divided evenly between the number of sandfilters -79.$ LF MIN Fj0., PROVIDED The critical aspect in sizing the leach line length is related to its ability to maintain a sustained` percolation rate (ie 24-7 -365) in saturated soil, therefore,.forthe purposes of this calculation, itig :. assumed that the sustained percolation rate in saturated soil is 0.25 in/hr .(Note: if the soil, is ;silty." more than 5% by weight passing the 200 sieve, the percolation rate shall be reduced to 0.125 Whr). The leach line arch provides 2.8 sf of percolation surface per lineal foot of leach line. length. If the average nuisance water discharge per house in the neighborhood is 20 gallons per day that means each house must have 5.35 sf of.percolabon area in the leach field to percolate its 24-hr nuisance water discharge. Therefore, the leach line length must be 1.9 If/home. APPROVED STAROARU 013` 21 Ol GHR1hS, A. VOGT Ti�- Oda r ,, CITY EtdGiN !!! 370 t. AcFF' 44250 SAND FILTER SHEET 6': OF 7 µ z ?t i .y 2113-11. N AA RQuiS LANE - NO R,T4 SANDFILTER SIZING CALCULATIONS Calculation #1 Determines how many standard size sandfilters are needed. No.* of Sandfilters = 9 homes _ 40 homes / sandfilter * Round all fractions up to the nearest whole number SANDFILT6-j;?_ RE'4 (jj1 e—r Each sandfilter has 48 sf of filter surface (ie 6' x 8'); assume the incoming nuisance water will percolate through the sand at the rate of:4 fi pch s- per ..hqur.. The sandfilter must be sized to handle the "surge inflow rate" of 0.458 cf/house /hour, which is based on the assumption that, on average, each house releases 12 gallons in a 3.5 hour "surge" period. Therefore, each sandfilter is capable of handling 18.4 cf/hour. As a result, each,sandfilter can handle the nuisance water released by 40 homes (18.4/0.458 =40). Calculation #2 - Determines how long the leach line must be. Leach Line Length* = T:.hornes x' T- 91f1home (sandy soil) In feet to be divide: e'ye01l ..b6veeri tile° number of sandfilters Leach Line Length* = 9 .'h'o'me's- x 3:8 If /home (silty sail) In feet to be divided evenly between "the number of sandfilters 34.2. I_F: KAIN 35 l,f pRavte�g The critical aspect in sizing the leach line length is related to.its ability to maintain a sustained percolation rate Cie 24-7 -365) in saturated soil, therefgre,.forthe. purposes of this calculation, it is assumed that the sustained percolation rate in saturated'soili§ 025 in/hr.(Note: if the soil is silty;: more than 5% by weight passing the 200 sieve, t1i &-percOlation rate shall be reduced to. 0.125 in/hr). The leach line arch provides 2.8 sf of percolation surface per lineal foot of leach line length. If the average nuisance water discharge per house in the neighborhood is 20 gallons per day that means each house must have.5;35 sf percolatioA.area in the leach field to percolate its 24-hr nuisance water discharge. There fore,'the leach [in' ne length must be 1.9 If/home. APPROVED STANOARQ OB 21 O1 _ CHRIS. A. VOGT r� CITY' ENGINEER �%. RCE 44250 SAND FILTER SHEET ffli. OF' 7 28/32 MARQUE SSA LaNE SANDFILTER SIZING CALCULATIONS Calculation #1 Determines how many standard size sandfilters are needed. No.* of Sandfilters = 17 homes -- 40 homes /san It dfi er Round all fractions up to the nearest whole number. I SAND FIL.TE P, REC4' ID Each sandfilter has 48 sf of filter surface (ie 6' x 8); assume the incoming nuisance water will percolate through the sand at the rate of 4.6 inches per hour. The sandfitter must be sized to handle the "surge inflow rate" of 0.458 cf /house/hour, which is based on the assumption that, on average, each house releases 12 gallons in a 3.5 hour "surge" period. Therefore, each sandfilter is capable of handling 18.4 cf /hour. As a result, each,sandfilter can handle the nuisance water released by 40. homes (18.4/0.458 =40). Calculation #2 - Determines how long the leach line must be. Leach Line Length* = homes x 1.9 If /home (sandy soil) In feet to be divided even ly.between the number of sandfilters Leach Line Length* _ 17 homes x -18 If /home (silty soil) ' In feet to be divided evenly between the number of sandfilters LF M %N G5 ct= .9(Z0V%DE0 The critical aspect in sizing the leach line length is related to its ability to maintain a sustained percolation rate (e 24 -7 -365) in saturated soil, therefore, for the purposes of this calculation, itis. assumed that the sustained percolation rate in saturated soil is 0.25 in/hr.(Note: if the soil'is silty-, more than 5% by weight passing the 200 sieve, the percolation rate shall be reduced to 0:125'° .�• ... in/hr). The leach line arch provides 2.8 sf of percolation surface per lineal foot of leach line length. If the average nuisance water discharge per house in the neighborhood is 20 gallons per day that means each house must have 5.35 sf of percolation area in the leach field to percolate its 24-hr nuisance water discharge. Therefore, the leach line length must be 1.9 If /home. APPROVED CHRIS A. VOGT CITY: ENGINEER ICE 4 250 r��7 t SAND FILTER STANDARD 37.0 SHEET fft OF 7 a� ul n D r m II O O m T T m 0 z 07 7 ,re �a 4. CITY OF II`4DIO 50TH AVENUE 52ND AVENUE ... -. 2113 0 n °- 0 0 Z -n- Lon — p m C z m O D TOACT NO. 30(:36 5NEfT.GAPAUTY CALCUL*Ti0XJe7 I Rw i ?C n � u ✓o I u ��t�ed �d T.C. A 3 ,° I' R ALFA 2 I p WRBF.CH ' 15,09 0. 030 ' >� A D D R W j- � D p D D D D •� � V � o, 0,33 � uw I R :.Y7 = �. s3 0, 30 +0,03 A rill To I YoIea mo, = 3.50 V0jLlfr7e _ 1Na �ilr� Pare ev►¢ I"dr i 1 Q: +O LIP b 0. 514 ±2.00-7:+ 1,6,001+,03D 1 -- LJ w P -' 3,5� ►f8� i 1a,5� = �`�'�t�o 1o7) , n ;alp 2,ic� fps _ 1 0= VA (o,45 cis No Qloo occurs, on a y Iz 11Y2Ql 41,t f ex and ,,? a,48 c4 me cap � 1� 6fYddf j6 1 ►¢p G , T ra�ov� qll 5-Ire-&46 Lui ",.w ✓4e_- will Garr Q y � 1- q Sladden Engineering 8782 Stanton Ave., Suite A, Buena Park, CA 90621 (714) 523 -0952 Fax (714) 523 -1369 39 -725 Garand Ln., Suite G, Palm Desert, CA 92211 (760) 772 -3803 Fax (760) 772 -3895 August 30, 2004 Project No. 544 -2097 04 -08 -599 Alpine Real Property Equity Croup, Inc. 41 -800 Washington Street, #13105 -220 Bermuda Dunes, California 92203 Attention. Mr. Bob Davis Project: Proposed Residential Development . Avenue 52 — Tract 30138 La Quinta, California i; ' Subject. Infiltration Testing for Stormwater Retention As requested, we have performed infiltration testing on the subject site in order to determine the ' percolation potential of the surface soils. The percolation /infiltration rates determined should'be useful in assessing stormwater retention needs. It. is our' understanding that onsite stormwater /nuisance water retention is required. It (s proposed to collect runoff within shallow ' retention basins. Infiltration testing was performed within test holes excavated to the expected: depths of the ' retention basins. Infiltration testing was performed on August 1.6, 2004. Test resul summarized below, ts are Test Location Percolation Rate A 8 inches /hour B 7.5 inches /hour 1 It should be noted that the infiltration rates determined by testing are ultimate rates based upon Short duration field test results in the specific test locations. An appropriate safety factor should be applied prior to use in design to account for- potential subsoil inconsistencies, possible compaction related to site grading, and potential silting of the percolating soils. The safety factor ' should be determined with consideration to other factors in the stormwater retention system design, (particularly stormwater volume estimates) and the safety factors associated with those design components. � i 011y (3(lli 1 U.Un WIvA hi)nnN1r i,wvj 31! 32': August 30, 2004 -2- Project No. 544 -2097 04 -08 -599 If there are any questions regarding this memo, please contact the undersigned. Respectfully submitted, SLADDEN ENGINEERING �• o � -�:o. , -• .,; :,;rye , ANUF� M Brett L. Anderso w Exp. 913=6 M Principal Engineer *) Perc /pc Copies - 2 /Alpine Real property Equity Group, Jnc.- 1 /AMC Civil Design Sladdeto E1r[�inecriec, I UIOI/1 iilv:l ulnnu,n. W. AU i 3232