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Home My WebLink AboutRP 15-16; 4 + 1 LUXURY LIVING; HYDROLOGY AND HYDRAULICS STUDY 4 + 1 LUXURY LIVING AT 3050 MADISON STREET, CARLSBAD, CALIFORNIA 92008; 2020-01-24L Hydrology & Hydraulics Study 4 + 1 Luxury Living at 3050 Madison Street Carlsbad, California 92008 RP 15-16/CUP 15-37 GR 2017-0042 Dwg. No. 505-BA APN: 203-351-03-00 Prepared For Dr. Bruce Sahba FIRST RM PROPERTIES 1010 Pearl Street #12 La Jolla, CA 92037 Phone: 619-300-5139 Prepared By Landmark Engineering Corporation Lawrence E. Cole, RCE 36292 3443 Camino Del Rio South #204 San Diego, California 92108 Phone 619-260-0420 ~ RECEIVEn RCE36292 Exp. 6/30/22 OCT 22 2020 LAND DEVELOPME ENGiN·---:::.~fNG Project #2403 January 24, 2020 INTRODUCTION PROJECT DESCRIPTION METHODOLOGY TABLE OF CONTENTS Existing Condition Hydrology Post-Development Hydrology HYDROLOGY CALCULATIONS INTENSITY-DURATION DESIGN CHART (100-yr Tc= 5 min.) INTENSITY-DURATION DESIGN CHART (2-yr Tc= 5 min.) RAINFALL ISOPLUVIALS 100-YEAR 6-HOUR PRECIPITATION 100-YEAR 24-HOUR PRECIPITATION 2-YEAR 6-HOURPRECIPITATION 2-YEAR 24-HOUR PRECIPITATION RUNOFF COEFFICIENTS FOR URBAN AREAS (Table 3-1) HYDRAULIC CALCULATIONS CONCLUSION CERTIFICATION REFERENCES ATTACHMENTS DRAINAGE MAPS DRAINAGE MAP (EXISTING) DRAINAGE MAP (PROPOSED) INTRODUCTION The proposed project site is located in the City of Carlsbad, County of San Diego. The project is located at on the east side of Madison Street between Carlsbad Village Drive and Oak Avenue. It is bordered to the west by Madison Street, to the east by an unnamed alley, and to the north and south by existing developed properties. The Assessor's Parcel number for the project lot is 203- 351-03-00. The project proposes grading and improvements for a mixed use consisting of one new commercial/retail store and four residential units. This drainage study calculates the peak stormwater discharge entering and leaving the project site (onsite and offsite drainage) in the existing condition and after development. PROJECT SITE DESCRIPTION The project proposes a 1,105 sf commercial/retail floor plan and 4 residential units comprised of a total floor area of 9,748 sf with a deck area of 3,644 sf. The building can be conveniently accessed through an elevator from each of the floors. The off-street parking has direct access from the unnamed alley and located at the rear of the retail area. It allows for residential parking to the residents. There is also on-street parking in Madison Street. METHODOLOGY Stormwater runoff was calculated using the Rational Method as outlined in the San Diego County Hydrology Manual, dated June 2003. Stormwater runoff was calculated for an existing and post- development condition resulting from the 100-year, 6-hour storm event for the project and its drainage area. Standard intensity-duration curve data was used for the San Diego region supplied in the Manual. The soil group used for the site and in the drainage area is soil hydrologic Group B from Map Soil Hydrology Groups in County Hydrology Manual. EXISTING CONDITION HYDROLOGY The existing project site drainage area is approximately 0.224 acres. The site varies in elevation from a high of 45 .25 through the property to a low of 41.54 at the southwest gutter of Madison Street and from a high of 46.64 through the property to a low of 45.35 at the southeast alley swale. The calculation, the 0.224 acre drainage area in the existing condition is divided into 3 separate basins (see Drainage Map (See Drainage Map (Existing)) each described as follows: Area E 1 is a portion of Madison Street and a westerly portion of the property on the east side of Madison Street. The stormwater sheet flows to the easterly gutter in Madison Street and then southerly away from the site. The stormwater is concentrated to POC#l at a point in the easterly gutter of Madison Street and includes stormwater from Area El A described below. The runoff flows southerly to the northwesterly gutter of Oak A venue the surface flow southwesterly along Oak A venue through a series of cross gutters toward the Pacific Ocean. Area ElA is a central portion of the site which surface flows to a drain in an existing parking lot and then through a pipe to the easterly gutter in Madison Street and then southerly away from the site. The stormwater is concentrated to POC#l at the existing drain. The runoff flows southerly to the northwesterly gutter of Oak A venue the surface flow southwesterly along Oak A venue through a series of cross gutters toward the Pacific Ocean. Area E2 is an easterly portion of the property on the west side of an unnamed alley. The stormwater sheet flows easterly to the center swale in the unnamed alley and then southerly away from the site. The stormwater is concentrated to POC#2 at a point in the unnamed alley. The runoff flows southerly to the northwesterly gutter of Oak Avenue the surface flow southwesterly along Oak Avenue through a series of cross gutters toward the Pacific Ocean. Area E4 is an onsite drainage area that sheet drains southerly over the south boundary into the adjacent developed property. There is no POC for this area. L METHODOLOGY ( continued) POST-DEVELOPMENT HYDROLOGY The project site drainage area is approximately 0.224 acres. Toe calculations for, the 0.224 acre drainage area that is graded or disturbed is divided into 8 separate basins (see Drainage Map (See Drainage Map (Proposed)) each described as follows: Area Pl is a portion of Madison Street and a westerly portion of the property on the east side of Madison Street. The stormwater sheet flows to the easterly gutter in Madison Street and then southerly away from the site. The stormwater is concentrated to POC# 1 at a point in the easterly gutter of Madison Street and includes stormwater from Areas P2 described below. The runoff flows southerly to the northwesterly gutter of Oak A venue the surface flow southwesterly along Oak A venue through a series of cross gutters toward the Pacific Ocean. Area P2 is a westerly portion of the project which consists of roofs and deck areas which are carried in roof drains to planters which provide both treatment and detention the discharge into the easterly gutter in Madison Street. The stormwater is concentrated to POC#l at a point in the easterly gutter of Madison Street and includes stormwater from Areas Pl described above. The runoff flows southerly to the northwesterly gutter of Oak Avenue the surface flow southwesterly along Oak A venue through a series of cross gutters toward the Pacific Ocean. Area P3 is an easterly portion of the project which consists of roofs and deck areas which are carried in roof drains to planters which provide both treatment and detention the discharge into the unnamed alley. The storm water is concentrated to POC#2 at a point in the unnamed alley. The runoff flows southerly to the northwesterly gutter of Oak A venue the surface flow southwesterly along Oak A venue through a series of cross gutters toward the Pacific Ocean. HYDROLOGY CALCULATIONS Area< 0.5 square miles. Use Rational Formula Q100 = CIA ~ =N33°09' 38" A. = Wll 7 ° 2 O ' 4 6" From Hydrology Manual Soils Map -Soils Group B Developed Site (Existing) 79.2% impervious C = 0.76 Commercial & Residential (Proposed) 89.6% impervious C = 0.84 From INTENSITY-DURATION DESIGN CHART Loo= 6.59 in/hr. Tc= Smin From Existing Drainage Map POC#l POC#2 POC#l Area El: Area E2: Area E4: POC#2 Area E3: POC#l Area El: Area E2: Area E4: POC#2 Area E3: h = 2.90 in/hr. Area El = 0.131 acre Area E2 = 0.046 acres Area E4 = 0.002 acres O.l 79acres Area E3 = 0.045 acres 0.045 acres Q100 =CIA= (0.76)(6.59)(0.131) = 0.66 cfs Q100 =CIA= (0.76)(6.59)(0.046) = 0.23 cfs Q,oo =CIA= (0.76)(6.59)(0.002) = 0.01 cfs 0.90 cfs Q100 =CIA = (0.76)(6.59)(0.045) = 0.23 cfs 0.23 cfs Q2 =CIA= (0.76)(2.90)(0.131) = 0.29 cfs Q2 =CIA= (0.76)(2.90)(0.046) = 0.10 cfs Q2 =CIA= (0.76)(2.90)(0.002) = 0.00 cfs 0.39 cfs Q2 =CIA = (0.76)(2.90)(0.045) = 0.10 cfs 0.10 cfs HYDROLOGY CALCULATIONS (CONTINUED) From Proposed Drainage Map POC#l POC#2 POC#l POC#2 POC#l POC#2 Area Pl = 0.053 acres Area P2 = 0 .102 acres 0.155 acres Area P3 = 0.069 acres 0.069 acres Area Pl: Q100 =CIA= (0. 84)(6.59)(0.053) = 0.29 cfs Area P2: Q100 = CIA = (0. 84)(6.59)(0.102) = 0.56 cfs 0.85 cfs Area P3: Q100 =CIA= (0.84)(6.59)(0.069) = 0.38 cfs 0.38 cfs Area Pl: Q2 =CIA= (0.84)(2.90)(0.053) = 0.13 cfs Area P2: Q2 =CIA= (0.84)(2.90)(0.102) = 0.25 cfs 0.38 cfs Area P3: Q2 = CIA = (0.84)(3 .95)(0.069) = 0.17 cfs 0.17 cfs 'I~™l!!ll!\!lilli!l!ll!ll!!l!l!!!!l!H!!!H[i : 1.: ~ ! i. I! i!! 11!1i!llili~ 6.oF"~,; !::-+-J N"¾1-LI't-l"N~·ll,llld1il~II I Ii tlt1:1ll~!11I 5.0N,. j i ""'..J I 'J: i "),.;,_N,l.fN.l1'-l.l~Pl!II ii I I I; Ii ii ii!!~ 2.01 f"i-...1 I I : : NI i I i IN-kl:' j I I :111;.b!IHJ"N..1 i l?t: i l~l;!·kni-.£ i~' i I i 11 . I I! Ii:: l rl Id ;I "' ::i:: 0 C: .., ~ ~ ~ ~ 5 -i ul ~ LH-++Whi+-+--HH-~~~~~H;~tit:~ttttttt~ti:t~tt~~~,~~-5-5 = g '· 0tj=:tw=:tc~~~trn~~Ft~Wfij]]£rft~id::t!t$tt~~m~~i s.o g ';:o.gt::!::tih!P:PA:~~~R~~ittfr:r~ti:rrfjti~ft!!ttta:~m~~t 4·5 '§' ~ 0 ~ o.at=:::t=t=r+n~~~~tHHMR~~f~itW-rr+t~tt~fj;trtttt:n~Il~l 4'0 i Cl) 5 "' _§0.7 ( 3. - ' j ' • o.6 , : . . . .,,. ··'"II ' , 4" .. l I ' Fl'-!.±!; H1ilJU::Nt 3,o 11 1 1 I :tllltl!ill,ll1ll:1!Hlilllilll:i:1~,!;-,t1 ! .-t:.~ .... 0.51 j ! I . . .. ' . . ' ' I'. l'l'l-k!IJ'! 'I 2.5 1111 I 1· 11 '"l•''''!ffi~ I I I I~ 11 I I . '· 0_11 I l 1 :lll1i1!1IIPil:ll1il!I; '1 ;t;i ,n,,.~ ' ~ 2 _ 0 0.3 r-::;_ + -t . -:i:T,:t-: ;: + ·_i_, i-•·'7" i ' -~ • 0·2t : I ±-i=U-_LJ:l J:W:U-Wl'.-U-1' 1111:i;W!lrt:l:J+U -t--+' , '. ~' I 1 1 : l:t ! I. ,.:=:; ig~4IJfjflrf Hff);!iW"H +e,,~f~nt bl 0.1. ' ,, ., "' 5 6 7 8 9 10 15 20 30 Minutes 40 50 Duration 2 3 H01Jrs 4 5 1.5 1.0 6 lntensity..Ouration Design Chart• Template Direction.& for Application: (1) From precipitation maps determine 6 hr and 24 hr amounts for the selected frequency. These maps are included in the County Hydrology Manual (10, 50, and 100 yr maps included in the Design and Procedure Manual). (2) Adjust 6 hr precipitation (if necessary} so that it is Within the range of 45% to 65% of the 24 hr precipitation (not applicaple to Desert). (3) Plot 6 hr precipitation on the right side of the chart. (4) Draw a line through the point parallel to the plotted lines. (5) This line ts the intensity-duration curve for the location being analyzed. Application Fonn: (a) Selected frequency _!QQ_ year (b) Ps"' __33__ in., p24 "' ~ .:s "' 50.9 %(2) 24 (c) Adjusted p6<2l = _12.._ in. (d) tx = _5_ min. (e) I = .2l.!_ in./hr. Calculated by formula Note; This chart replaces the Intensity-Duration-Frequency curves used since 1965. PS 1 1.S 2 2.!:i 3 3.5 4 4.5 5 5.5 6 D,m,tfon I . j" T ··r r ·, j J f r i s 2.63 .3.95 s.:n·G.1,9·1.00·9.22'10.s4•11,00··13.1r144911o'>.a1 7 fi2 ·:Ulf,{24 5.30 e.se 7;42 8.48 9.54 · 10.00: 1t.se, 12-12 1o t:Gii :iisif iri31 4.i!f 'i,.& 5.eo a.i4 1:ss a.42 · 9.21 · io.11 1_is_ 1,:io __ ·r~f 2A9 ·n{ :f~ I~f fiJ _·5:~-~:~f :na. 1.tt ; . ~:: ;::~: !1~J:;;_ t~tit ~{l ;:;t !:~r , t-: l;! 30 0.83 t?.4,1,8f;i,,?,ffi: .IA1! 2.9Cl, 3-:3.J 3}!3-~-·'.?. 4,56 4_.98 40 0.69 1.03 1.38 t.72 2.0/ 2.41 2.76 :310 3 45 3.71! 4,13 so o.s0 .o.oo· 1.m 1.49 1.79 2.09 2.39 2.69 2.98 a.2a 3.ss' 60 0.53 0.80 iJ'iG i".33· 1 59. 1.86 2.12 2.39 2:ss 2.92 3.18 s~ o.4i_ p.tii .Q~?. I,i:l?. ! .2~ 1.~3 L~ 1.s•. 2,Q:4_ 2.:2_5 2.45_, 120 o.:w o.s, o.es o.as 1.02 1.19 1.36 1.53 no 1.a1 2.~ 1so 0.29 .o.44 o:sg o.;::i o.as 1.03 1.1B L32 1.◄r 1.62 1.76 180 ·(l,26 ·o.3if(f52 ··o:65 (),78 0.91. 1.04 1.i8 1.31 1.44 ·1.67 I 240 Q,?? O.,~;~.:i,3 J~~ 0,6? 0:7-s o.87 o.~ ,~a \19 1,~i 300 .o. Hl () 2fc:1.3_8 0,4! 0 58_ O,!jS ().7!S .0.•lffi.. O.~-~ 1,Q3 1,13 1 360 o. 17 0 2:, · 0.33. 0.42 0.50 0.56 0.67 0 75 0.84 . 0.92 1.00 , FIGURE 3ml ,g~liill!!ll!IH!l!lll:l!l!!!!l!!!!~i!i!i!:11,1: I.:!:: 1::;: I !!itll1!'l 2.0 ,:::- 5 s:;; i s:;; g1.o =0.9 z, µ ' I i ~ "'0 iil 0 L-...... i.....~-!--i.....-.......;....,.+11--l-!-+-.-i-:~e-!+!-l++l+l..+l-!-H+l++..:.+lH+iel+~!+i+...H?.l.t!--~"-t-+lfllki-f*rl'!~PN;:-f!'l,i;l,i;I-a.o I l-+-i-H......i--l--+++-......;+++++++++~W*-''4+14+!-14-+-A-~..,.t-l-4~~~14-r,d-+:~:H-f't~-r'!-fd-ltt.fi'e 5·5 "' 5.0 g j0.8 i.s0.7 4.5 5' J.-.,_,!.._.....,>-l-4-4..;..-1-~+.W.++--l-++++H+IJ~4!l~l+!#-l++++l-14~#,;4#H-t"~+---+:!!,,::-H--""c:!'+H+i1d-tl~t o 4.0 ffi I I I I I i 0.6 J.-,!,-1--;-l,-l-i--l---,...+-;,-++ll+H-+-l-!+H+t++...!+l-4tli'l#ll+~lie!-41-Httt++~n.,..rt-Hl-+-?°'lc:t-tt+4-i.t11-t-1-M:ffitr!t 3.5 .!!!. 0.5 0.4 I i i l 11 ! : j I 11 11 Ii! 11jl 1;wlj 1111 '.11p11iif:t~tff I :~ : i r~n,1,m 30 . I : 'I '. . .. 1,i' ,' ·, . ; l. ; . . I Li I .! . I . i 1 • I 1 1 , ., I. 1:l1111n l:llahl:11 ilil::i:l!:lah::i!Jl!,l..d ! Ii; N-l::i!!lrnYl,l!:12.s 2.0 1.5 -t--i.--=+····· • ~ • I :,t-' .. 1,.: :. o.z~ ~4B:.=a+:-i:,,t;7i · .!.I .. L( fl ltJ· '' 1 ~t+.f J~--1.0 ' ++ · • -! -1-.t";.tttt·. 0.1! I ! ! I:• '[!111j 1 'il•1'1 11H•,itill,1,j-1·•l11'"'·1;,i;,q,: I 111•l•·wl'•li1pid•1! 40 2 4 5 6 5 6 7 8 9 10 15 20 30 Minutes 50 Duration 3 Hours Intensity-Duration DesJgn Chart -Template Directions for Application: ( 1) From precipitation maps determine 6 hr and 24 hr amounts for the selected frequency. These maps are included in the County Hydrology Manual (10, 50, and 100 yr maps included in the Design and Procedure Manual). (2) Adjust 6 hr precipitation (if necessary) so that it is within the range of 45% to 65% of the 24 hr pracipitation (not applicaple to Desert). (3) Plot 6 hr precipitation on the right side of the chart. (4) Draw a line through the point parallel to the plotted lines. (5) This line is the intensity-duration curve for the location being analyzed. .Application Form: (a) Selected frequency _2_ year p (b) P6;;: ~ in., P24 = ___l.:L .~ :::: ~ %(2) 24 (c) Adjusted p6(2l = _l._l _ in. (d) ½<"' _5_ min. (e) I = _b2Q_ in./hr. Calculated by formula Note: This chart replaces the lnte.nsity~Duration•Frequency curves used since 1965. I I P6 T tJ Ji 2.5 .3 3,S 4 4.5 $ s.s ~ Ovmtloll . I i I 1 I I l I , I I , I ... ··:~ .. ~-~ ,,!,~~ .. 9:?? 6.58 7.90. 9.Zp0~4: 11.00 1~17;14.48] 15.8il, 7 2,12 3.18· 4.2<1 5.30 6.3ti 7.42, 8.48 9.54 10.80: 1~.66, 12.72 10 ··nre·:Is3 :L31· 4.21 s.os s.oo• a.i4 i:sa ·a.42 · e.21 ,o:h .!~ ~·3ll. :t9~ .• tl:il! 3.24 .3.69 ~•?!., 5.1~ ~'~ a,~ .r1.~ P.t 20 I.OB 1.62 2 15 2.69 3.23 3.17' 4.31 4.85 5,$9 5.93 6.46 ~ ~.e..1. ,,~:ff!?. 2.aa 2.ao :1.2f 3.i~-4_,20 {1ft ·;;.ii s.i;_ci __ 1 30 D.-.~ I 24 1_.6§ 2.07 2.49 2.90 ~ .. :J.?.. t\.:~ .~,15 4,?6 4.!l!I , 40 0.69 l .03 1.':18 l 72 2.u/ 2.41 2.76 3.10 3.45 3.79 4.13 so o:oo .o.oo· 1.19 :.49 '.79 2.09 2.39 :/.69 2.98 3.28 3.56 oo ti.!>3 o.ao· 1.os ,.33 , 59 i.86 ::i_~2 :;;;39 2.6!i fs2 i3.fa ~ ·il~J j>,~1· i:f~.? ur.~ 1.23 1.~· ,.~~ .. 1 .. ~ 2,9.4. 2,g~ .2 .. 4~., 120 0.34 ·0.51 0.68 0.85 1.02 1.19 1.36 1 53 1.70 1.87 2,04 i 1:so. · ... Q)is .. o .. 1.◄ .. :~,s9. o.73 o.aa , o~ 1.1s ,A,·2·.· i.:,i···.·.1.·· 1.e2 .. 1,1s . 1ao 0.26 .o.39:o.s2 o.es o.ro 0,91 1.04 us 1.31 1.« 1.s, ·~~ :.Q~ :Q¥1_\i,~ o.-~4 (}.ss. O-?ll o.a1 o:ga 1:9~ ~,,s 1,:3!>. J ~ .o.~9 .o 2a,o.,~ o.47. o.56 o.66 o.7!i o.._as ~-~~ .,.,~3 1,13 , ~ 0.11 o.2s,o.33 0.42 o.so o.sa o.&L ors . o.s4 . o.92 1.001 l FIGURE 3-1 '---------·-' .. .. L -c f ~' ~ ., :·t-=- ~. ol t , .a. ~ ,~ 1' ___ ,,._ .. :: t·! .. •·-~-.... ' • --,- (} ·t ·" .. -i-11!1 •i--.. _ • ·c-· --• :a I I ... ,,.: .. ... .. '\ ; ~,. \ ""·,__,- ...... ,, \I),. "# J \' v:~v . -. ' ~ ( i i . ' ,.,.,,,,!'~ ,-JC)· -!Cl) . :z· !Lii· .it:)_ :0 •V .,,/i .. r San Diego County Hydrology Manual Date: June 2003 Table 3-1 RUNOFF COEFFICIENTS FOR URBAN AREAS Land Use I NRCS Elements Coun Elements % IMPER. A Undisturbed Natural Terrain (Natural) Permanent Open Space O* 0.20 Low Density Residential (LDR) Residential, 1.0 DU/A or less 10 0.27 Low Density Residential (LOR} Residential, 2.0 DU/A or less 20 0.34 Low Density Residential (LOR) Residential, 2.9 DU/A or less 25 0.38 Medium Density Residential (MDR} Residential, 4.3 DU/A or less 30@ 0.41 Medium Density Residential (MOR) Residential, 7 .3 DU/A or less 40 0.48 Medium Density Residential (MDR) Residential, 10.9 DU/A or less 45 0.52 Medium Density Residential (MOR) Residential, 14.5 DU/A or less 50 0.55 High Density Residential (HOR) Residential, 24.0 DU/A or less 65 0.66 High Density Residential (HOR) Residential, 43.0 DU/A or less 80 0.76 Commercial/Industrial (N. Com) Neighborhood Commercial 80 0.76 Commercial/Industrial (G. Com) General Commercial 85 0.80 Commercial/Industrial (0.P. Com) Office Professional/Commercial 90~ 0.83 Commercial/Industrial (Limited I.) Limited Industrial 90 0.83 Commercial/Industrial {General I.) General Industrial 95 0.87 Section: Page: Runoff Coefficient "C" Soil Ty~e B 0.25 0.32 0.38 0.41 0.45(QB) 0.47 0.51 0.54 0.58 0.67 0.77 0.77 0.80 0.84® 0.84 0.87 C 0.30 0.36 0.42 0.45 0.48 0.54 0.57 0.60 0.69 0.78 0.78 0.81 0.84 0.84 0.87 3 6 of 26 D 0.35 0.41 0.46 0.49 0.52 0.57 • 0.60 0.63 0.71 0.79 0.79 0.82 0.85 0.85 0.87 *The values associated with 0% impervious may be used for direct calculation of the runoff coefficient as described in Section 3.1.2 (representing the pervious runoff coefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given that the area will remain natural forever (e.g., the area is located in Cleveland National Forest). DU/A= dwelling units per acre NRCS = National Resources Conservation Service Cp=0.90x(%imper)+oim])er( I -%imper) Exist Cp=0.90xl,332)+.25(.668)=0.47 Proposed Cp=0.90x(. 742)+.25(.258)=0. 76 3-6 HYDRAULIC CALCULATIONS The only existing hydraulic feature that exists on the site is the private Area Drain 12"X12" located in the existing parking lot of which the project proposes both the drain and the parking lot pavement be removed. Area Drain 12"X12" A= Q/2 (sump condition) Q = 2A = 2.00 cfs Area: ElA0 Q = 0.23 cfs Capacity Area Drain= 2.00 cfs > 0.23 cfs area drains OK! Circular Pipes Planter flow-through Q = 0 .23 cfs ( existing) 4" PVC @ 1.00% min. d= 4" Slope= .01 n= 0.012 A=0.087 R= 0.083 Wetted perimeter (full) = 1. 04 7 Calculated capacity Q100 = 0.22 cfs < 0.23 cfs OK! CONCLUSION I. The proposed project does not substantially alter the existing drainage pattern of the site or area. No flooding will occur due to development. 2. With no reduction in Time of Concentration, the peak Q at POC#l is decreased from 0.90 cfs to 0.85 cfs, or by 0.05 cfs or 5.6%. The peak Q at POC#2 is increased from 0.23 cfs to 0.38 cfs, or by 0.15 cfs or 18.7%. The use of a restricted flowofstorrnwaterthrough planters using 4" PVC @ 1.00% provides detention that reduces the post-construction Q at POC#2 from 0.38 cfs to 0.22 cfs which is less than the pre-construction Q of 0.23 cfs. The planters will also provide landscaped surface area to treat the runoff adequately. Added Time of Concentration increased by the planter detention will reduce Intensity sufficiently to also be satisfactory. 3. The proposed project does not create or contribute any runoff water which would exceed the current capacity of existing storm water drainage systems. 4. Hydrology Report Summary: EXPECTED RUNOFF DISCHARGES cal 5 minutes Outlet Tributary Area QlO0Peak Q2 Peak Discharge (Acres) Discharge ( cfs) (cfs) Pre Post Pre Post Pre Post POC# 1 Madison A venue 0.179 0.155 0.90 0.85 0.39 0.38 *POC#2 Alley 0.045 0.069 0.23 0.38 0.10 0.17 Total 0.224 0.224 1.13 1.23 0.49 0.55 Outlets shown are based on changes per development of the project site. Stormwater runoff was calculated using the Rational Method as outlined in the San Diego County Hydrology Manual, dated June 2003. Stormwater runoff was calculated for an existing and post-development condition resulting from the 100-year, 6-hour storm event for the project and its drainage area. Standard intensity-duration curve data was used for the San Diego region supplied in the Manual. *POC#2 is the only one which requires mitigation to reduce Post to below Pre. See conclusion no. 2 above. CERTIFICTION Report Preparation I certify that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to ensure that qualified personnel properly gathered and evaluated the information submitted. Based on my inquiry of the person or persons who manage the system or those persons directly responsible for gathering the information, to the best of my knowledge and belief, the information submitted is true, accurate, and complete. CIVIL ENGINEER awrence E. Cole, RCE 36292 January 24, 2020 Date L REFERENCES 1. County of San Diego Department of Public Works Flood Control Section, San Diego County Hydrology Manual dated June 2003. 2. County of San Diego Stormwater Standards Manual. I ~-k-----tt--Jc L 1/?1 .2 1 o· EX. FH. C I 7 FL 41.27 +I . 0 (J) N I I I I I I I I I I I I I I I I I I I I I I I s \ 40' 30' I I I I I \ I (/J (/J I I s I I I I I j I <t.:,2 I ' I I I I I I 'I I II (/J (/J I I "' I I I I I I I I I I I I 40' 30' TC 42.32 FL 41.68 j j ' PLANTER#1. j I Q 100 0.85 CFS POC•1 IP1,P2I C( ,;1.95 I I j j ~ ?" 0 3! ~ ~ ~ >' "' w 0 0 x " w x w Ex. ce 5'± c::, CV I ,,. .: I:} "' I I I I PARCEL 1 PM 3339 L EX. BLDG __ ___j- EX. ASPH. 1 EX. CONC. DRIVE:WA Y \ I i _l I ~ EX. CONC. P2 3RD FLOOR FF 7 4.85 4435.0942 SF 2ND FLOOR FF 64.85 0.1D2 AC PLANTER#6 1 ST FLOOR FF 54.85 GAR!\GE FLR GF 45.85 PLANTER#5 PLANTER#7 PLANTER#8 7L I EX. BLDG 139.55 7 EX. BLDG I I ___ _J L ______ __J i I 7 L__ i ___J t __J <s .,, w 8 u z w ~ x w 7 I I I I I I _J u z 0 u x w EX. TRASH l 0 6 u x w cc ~ ~ ~ x w '{r""Jr_, . --· ,-- w _J _J <( 1 o· _,_ ____________ \ 6 LOT AREA 6994.7419 SF PLANTER#1 20.7779 SF PLAN TER#2 20 . 7089 SF PLANTER#3 45.8520 SF PLANTER#4 15.7422 SF PLANTER#5 10.0148 SF PLAN TER#6 10. 0095 SF PLANTER#7 275.74 SF PLANTER#8 274. 78 SF IMPERVIOUS AREA 6944.2426/6268.4505 SF 89.6% IMPERVIOUS BMP NOTES: IMPERVIOUS AREA = 6944 SF X .04 = 278 SF REQUIRED PLANTER SURFACE AREA = 647 SF PROVIDED GRADING NOTES: 1.) PROJECT PROPOSES GRADING 100 PERCENT OF OF THE SITE. 2.) PROJECT PROPOSES TO DRAIN ROOF DRAI NS TO LANDSCAPED AREAS AN D PLANTERS. THEN THROUGH A SIDEWALK UNDERORAIN 0-27. 3.) EXCAVATION-217 C.Y. FILL: 97 C.Y. EX PO RT/IMPORT: 120 C.Y. BENCH MARK CLSB-130 SET 2.5" DISK IN SOUTHEAST CORNER OF DRAINAGE BOX INLET AT THE END OF CURB RETURN IN THE NORTHEAST CORNER OF GRAND A VEN UE AND WASHINGTON ST. NGVD29 ELEV.: 40.9 1 u z I~ u z 0 u x w 'd' 46.so ~ I I I I ~ I ?< n I 0 z n I 21 ----7 ~'D\ ,+-- Q'--' ~X. '3LDG 0v I • __J 'G' 0 \ I - EX. CURB 3 ,---\ EX.A =SP~H. __ _ \ \ \ \ Q ■ 0.38 CFS 20· 1 o· PO •2 IP3I \ \ EX. ASPk \ REVISIONS i I I I I I I ; I I No. Description Approved Date 22 EX. ASPH. EX. BLDG >E A.R 4) EX. BLDG FF 46.36 23 26 EX. FE " LEGAL DESCRIPTION: ! I VICINITY MAP NO SCALE EX. ASPH. t- LOTS 9 AND 10 BLOCK 48 OF CARLSBAD, IN THE Cl1Y OF CARLSBAD , COUN1Y OF SAN DIEGO, STATE OF CALIFORNIA, ACCORDING TO MAP THEREOF NO. 535 AND 7 75, FI LED IN THE OFFICE OF THE COUN1Y RECORDER OF SAN DIEGO COUN1Y MAY 2, 1888 AND FEBRUARY 15, 1894, RESPECTIVELY. ASSESSOR'S PARCEL NUMBER: 203-351-03-00 DRAINAGE MAP (PROPOSED) FOR: 3050 MADISON STREET Carlsbad, CA CDP 15-37 PREPARED FOR: FIRST RM PROPERTIES 1010 PEARL STREET #12 LA JOLLA, CA 92037 L E C LANDMARK ENGINEERING CORPORATION 3443 Camino Del Rio South Suite 204 San Diego, CA 9210B (619) 260-0420 Sht 1 of 1 Date:B/05/15 Own. MC Apr. LEC Dwg. No. 2403-PGP-1 I I I I I I I I [/) I I I I I I [/) I I I I I ,:;;: e I I I I I 3 \ Ifs ~ FL ,,.4/?r , ;:; 0 I I I ~ x w 1S I ·,:, / 1rc,.,, r'[ 4-7.27"" I I I I I ' I I • I ~l I • I \ ' I I I I I \ I 'I I II I v ~ ' [/) I [/) I I I I I I I "' I I I I I I I "'I 11- I W ./W ,~ I (f) I z 0 (f) - 0 <( 3 2 ~ 3 TC 42.J2 rl 41.68 1 C 4t6~ 1~,·" \C • . I /) ~ ,- j j ;:; 0 x w 'S < ~ w :,: x w \ ' I I I EX. ASPH. EX. GAS o PARCEL 1 PM 3339 5690.689 SF 0.131 AC EX. 81 >E.. .50 EX. BLDG I L ______ __J i - I I N55'32~ . I ) ' ,:;;: s ~ I L - I I I I i L " I TC 45.13 § r "T"T,U• n \ ~ EX. BLDG 7 ~ ;,< n 0 z n 2021.691 SF \ 0.046 AC j 1, __ ~ i ' ---___J ' '.'-)'0 _J '0 () ~ 0 v EX. ASPH. I ' ' ,_ I I I I I _J 1 0 8 7 EX. TRASH E3 1946.598 SF 0.045 AC ~'{' -_y I 6 0 z I 0 u x w BENCH MARK CLSB-130 le 4,,, p 1Ssf.- rn ~ ~ cc u ~ x ~ < w ~ w ' h, "''R, 4-5_ 5f, ~':> 1 · ;< 'l ,;>-w _J _J <( - , 1 o· , - - SET 2.5" DISK IN SOUTHEAST CORNER OF DRAINAGE BOX INLET AT TH[ END OF CURB RETURN IN TH[ NORTHEAST CORNER OF GRAND A VENUE AND WASHINGTON ST. NGVD29 ELEV 40.91 0 z 0 u x w I No. - -20' 1 o' , I I I ---7 EX. BLDG I I I ' I I _J_ ' I i I I I EX. ASPH, EX. BLDG E> 46 .!.1 21 23 24 "' LOT AREA 6994. 7 419 SF LSCP AREA 585.1714 SF LSCP AREA 195.3235 SF LSCP AREA 69.9108 SF LSCP AREA 98.1132 SF LSCP AREA 8.5485 SF LSCP AREA 498. 0191 SF IMPERVIOUS AREA 5539.6554 SF 79.2% IMPERVIOUS .,,, -0 )( I I I " § n I I I I ~ ~ I ai I / I 0 EX. ASPH. __f _25_ 71--,0 ~ I~ ( I is cc,--/--j-1 -.-- EX. ASPk ---- No. 5097 Exp. 06 /30 /19 I I I I 1 I I I ~} \ )( ~ 7 I I REVISIONS Description Approved Date EX. BLDG FF 46.36 26 EX. FE c. LEGAL DESCRIPTION: I I I LOTS 9 AND 10 BLOCK 48 OF CARLSBAD, IN THE CITY OF CARLSBAD, COUNTY OF SAN DIEGO, STATE OF CALIFORNIA, ACCORDING TO MAP THEREOF NO. 535 AND 775, FILED IN THE OFFICE OF THE COUNTY RECORDER OF SAN DIEGO COUNTY MAY 2, 1888 AND FEBRUARY 15, 1894, RESPECTIVELY. ASSESSOR'S PARCEL NUMBER: 203-351-03-00 DRAINAGE MAP (EXISTING) FOR: 3050 MADISON STREET Carlsbad, CA CDP 15-37 PREPARED FOR: FIRST RM PROPERTIES 1010 PEARL STREET #12 LA JOLLA, CA 92037 L E C LANDMARK ENGINEERING CORPORATION 3443 Camino Del Rio South Suite 204 San Diego, CA 92108 (619) 260-0420 Sht 1 of 1 Date:8/05/15 Dwn. MC Apr. LEC Dwg. No. 2403-TOP0-1