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1991-1226 H 7r/~5 .-- -~.__.__.~. -- _.-. Category /?-'2--6 ~ Name Plan ck. # Street Address I 30QI) Serial # 14 () IJ IJ-e 0 Description Year . HYDROLOGY EVALUATION FOR THE MONACO SUBDIVISION LOT ONE OF MAP NO. 12049 . BACKGROUND: . This report presents a hydrology comparison between the existing and proposed conditions of lot 1 of the Monaco Subdivision (Map No. 12049) to determine the impact the proposed development may have on the downstream properties. . The study area is a portion of an eleven lot single-family residential subdi vision. Presently, ten residences have been constructed. The study area is the remaining lot of this subdivision which is presently under construction. SUMMARY: . The site is located within a local hydrologic basin known as the "Summit Sump". The southerly sub-basin of the "Summit Sump" is comprised of 38.0 acres and the subject site makes up an area of .35 acres within the southerly sub-basin. RATES . Based on an analysis of a 100 year storm event the southerly sub- basin generates a peak rate flow of 74 cubic feet per second (c.f.s.) and the subject site under existing conditions generates a peak rate of flow of 0.52 c.f.s., which represents 0.70% of the total. Under developed conditions the peak runoff from the site is calculated to be 0.63 c.f.s.. The incremental increase of peak runoff due to development of the subject site is .11 c.f.s., which represents one sixth of one percent of the total runoff for the southerly sub-basin. . VOLUMES . During a 100 year storm event, the total volume of runoff from the southerly sub-basin is 8.3 acre feet. Based on the dimensionless hydrogragh under buildout conditions the incremental increase in volume of runoff from the subject site is 1,818 cubic feet which equals 0.04 acre feet. This incremental increase in runoff volume represents one half of one percent of the total runoff for the southerly sub-basin. . STORAGE The developer proposes to retain 75% of the total incremental increase of storm water runoff during a 100 year twenty-four hour storm, (1,370 cubic feet). . An analysis of the roof area of the proposed home indicates a total area of 2,673 square feet. Assuming a 100 year storm yields 4 JONES . 2 . . inches of rainfall, the total volume of runoff collected by the roof is 891 cubic feet which represents 49% of the incremental increase in runoff which would occur under buildout. An additional 479 cubic feet of runoff from the patio, driveway and parking areas will be collected by placing inlets at collection points on the yard area, the driveway and parking area routing the runoff into the retention system. . A system of perforated pipe in trenches with gravel bed is proposed to store the storm water collected from the roof and driveway. Enclosed is a lot layout illustrating the area for a trench system to be installed. A detail of the trench is also included. The remainder of the incremental increase in runoff, attributable to construction of the home is equal to 1/8 of 1% of the overall volume of runoff generated by the southerly sub-basin. This relative increase should be considered negligible. . CRITERIA: . The design standards, basic criteria and procedures will be based upon the San Diego Flood Control District Hydrology Design and Procedure manual. The existing and proposed conditions will be evaluated for the worst-case scenario (100 year storm) to analyze the most severe impact the development will have on downstream properties. COMPUTATIONS: (100 YEAR STORM, 24 HOUR DURATION) . RUNOFF FOR NATURAL CONDITIONS Q = CIA C = 0.45 (Appendix "A"IX . "D" SOIL GROUP A = 0.35 ACRES P6 = 2.5 in./100 yr. (Appendix "A" XI-E) . P24 = 4.0 in./100 yr. (Appendix "A" XI-H) tc = 15.0 min. (Appendix "A" X-A) I = 3.3 in./hr. (Appendix "A" XI-A) . Q(NAT.) = (0.45) (3.3 in./hr.) (0.35 ac.) Q(NAT.) = 0.52 c.f.s. . . JONES 3 . RUNOFF FOR DEVELOPED CONDITION Q = CIA . C = 0.55 (Appendix "A" XI-A) "D" SOIL GROUP A = 0.35 ac. . tc = 15 min. (Appendix "A" X-C) i = 3.3/hr. (Appendix "A" XI-A Q(DEV) = (0.55) (3.3) (0.35 ac.) . Q(DEV) = 0.63 c.f.s. INCREASE IN RUNOFF RATE BY PROPOSED DEVELOPMENT . Q(DEV) - Q(NAT) = INCREASE RUNOFF BY DEVELOPMENT (0.63) - (0.52) = 0.11 c.f.s. For 100 year storm SOUTH SUB-BASIN . PEAK FLOW* = Q100 = 74 c.f.s.* INCREASE IN PEAK FLOW BY SITE DEVELOPMENT = Q100 = 0.11 c.f.s. . = 0.15% OF TOTAL SUB-BASIN PEAK FLOW OR 1/6 OF 1% . . . * Per Hydrology study for proposed 11 Lot Subdivision TM 4603, 7/31/86 by Conway & Associates (with no ground infiltration.) . JONES 4 . VOLUME OF SOUTHERLY SUB-BASIN V = 8.3 ac-ft * . VOLUME INCREASE OF SITE BY DEVELOPMENT V = (1,818 c.f.) (1 ac./4,3560 s.f.) V = 0.04 ac-ft . = .5% OF TOTAL SUB-BASIN VOLUME . . . . . . . * Per ASL Consulting Engineers Master Drainage Plan City of Encinitas July, 1989. . 5 JONES . . . . . . . . . . TRIANGULAR DIMENSIONLESS HYDROGRAPH >-; (jj H-; <J '-' v--f?E.Ak FLOW 'JOl.-UME: 1NC.lZEP6E:. OF !7fiV~D CONDITIO'\! -. -VS. ~XI~N~ C1>NtJlTloN ~15I11fj~ c.Of,J17I11rN _ ..~l>U)~O CO}..Jl7111Dt-J lL lL C> :2 :::l tI:: :: Tp Tb hi TIME (hrs.) Tp = Time to Peak, (hrs.) o = Duration, (6 hrs.) L = Lag Time, 0.6 (Tc); (hrs.) EMPIRICAL EOUATIONS FOR HYDROGRAGH CONSTRUCTION Tp = 0/2 + L Tb = 2.67 (Tp) RUNOFF FLOWS Q 100 (DEV) = 0.63 Q 100 (NAT) = 0.52 c.f.s. Tc = 15 min. (0.25 hr.) Tc = 15 min. (0.25 hr.) TIME TO PEAK Tp (DEV) = 6/2 + 0.6(0.25) = 3.15 hr. Tp (NAT) = 6/2 + 0.6(0.25) = 3.15 hr. TIME BASE Tb (DEV) = 2.67 (3.15) = 8.4 hr. Tb (NAT) = 2.67 (3.15) = 8.4 hr. JONES . 6 . . . ~ U) 7.M 2~~ - +l ~~Ii: Cl- 0 Ii:\ ~~" - C(\ u..~C; ~~3 I II \\ / U) ~ d) ! a W <i\ i :27 :z I 0 \J) ):- - I. ~..::: r' E ~inll / ; .4=. l ~\O ~ ~ ~ . :z ~e, C> -:1. . :i' "-> f1 ::>1 & ~ ~.. m ~ I..J ~ ~~ '" ~ -0 ' , "W' 1 I ill 2 . ~ .;: \I ~ h u 0 ,...,.~ z-=- -;;~ ~ - --..I. w~ D~ ! I '-.../ I 0 ~ / Q~ , ~ , 13 e p :2.Jl S~ ....Hv ;;1~ ~II Z . . . . . . , , . . o ~ \t\ c \t'> <::S o \... <;oj':)) ..;:i.,.::K;' N ClC:f7 o ~ Inl ih~ !.\!~ lt~" ~ <:l:) 1:- ~ --:-1 [Q \.t\ :r .....; w ~ .2 ~ "" .,.. o . METHOD OF ELIMINATING INCREASED RUNOFF: . The increase in runoff is due mainly to the building and driveway. Collecting and storing the rainfall from the roof of the building will significantly reduce potential increases in runoff. This can be accomplished with roof drains connected to perforated pipe/french drains that will allow the runoff to seep into the ground in the lower yard area. The driveway area also contributes to the increase in runoff. The developer proposes to collect and store a portion of these areas where feasible. To minimize the increase in runoff from this project the proposed retention system will collect and store all of the roof area and a portion of the driveway area so that a minimum of 75% of the incremental increase of runoff will be stored on site. . . RUNOFF STORAGE Volume of Incremental Increase in Runoff V = 1,818 c.f. = 0.04 ac-ft . 75% x 1,818 c.f. = 1,370 c.f. = 0.03 ac-ft Total Required Storaqe Volume Lot 1 Storage Volume = 1,370 c.f. . Lot 1 Storaqe 1370 c.f. Roof Area = 2,750 s.f. x 0.33 ft. of precipitation = 891 c.f. = 0.02 ac-ft Remaining Volume to be stored = 462 c.f. = 0.01 ac-ft . 462 c.f. 0.33 ft. = 1400 s.f. of driveway area to be collected, (See Drainage Plan.) STORAGE CALCULATIONS FOR PERFORATED PIPE I FRENCH DRAIN: . VOLUME OF PIPE PER LINEAR FOOT: A =.0- r2 6" P.V.C. R= 0.25 ft. A = (3.14) (0.25) . A = 0.19 c.t. AT 1/2 Full = A = 0.10 c.f. . . JONES 8 . VOLUME OF VOIDS . = Ve (He) e = void ratio e 0.5 (pea gravel) . VOLUME OF VOID PER CUBIC FOOT: = (1 cefe) lO.5) 1 + 0.5 . = 0.33 c.f./c.f. VOLUME OF TRENCH: H = 4.0 (See typical detail.) h = 2.5' = storage area . w = 4' V = HWL . V = hw V = (2.5 s.f.) (4 s.t.) V = 10 c.f. . TOTAL VOLUME OF TRENCH & DRAIN PIPE PER LINEAR FOOT: VOLUME = (VOLUME OF TRENCH) (VOLUME OF VOID) + VOLUME OF PIPE V = (10 c.f.) (0.33 c.f. Ic.f.) + 0.10 c.f. . V = 3.40 c.t. I l.t. LOT 1: REQUIRED STORAGE = 1,370 c.t. . LENGTH OF STORAGE TRENCH REQUIRED: ~. L = 1370 C.F. 3.40 c.f. I lof. L = 403 lof. . JONES 9 . . MONACO SUBDIVISION I LOT HYDROLOGY STUDY COST ESTIMATE FOR STORAGE I DISSIPATION TRENCH . 1. 6" P.V.C. PERFORATED DRAIN PIPE @ $15.00/1.f. LOT 1 = 371 L.F. @ $15.00/1.f. = 6,045.00 . 2. GRAVEL TRENCH @ $0.50 s.f. with filter fabric (4' x 4' TRENCH TYPICAL) = 16 s.f./l.f. = $8.00/1.f. LOT 1 = 371 l.f. @ $8.00/ l.f. = 3,224.00 . LOT 1 TOTAL $ 9,269.00 . . . . . JONES . 10 . . , . FINISH G;Ri)UND . -C) ::i ~~ ~"4' PVc. ~1EP Pl~ C,- 0 6 ,,0 'Z J10 Tf o. o "" " . o " d - FJ t:TElZ \D FABRIC - Cl -~f ~ II :r ~ ~ GRAVeL " J:: o Q C t9 . o o " <- , W=40 ~ . (I.) TOP OF 1l<rncH WILL r=,E. A MINIMUM OF Z f!X;T ~ -rn~ Ft:b11N(;\, tZ,)T11e:: ~CR CFlHE:. -rRENC.H WIU, E7fi: A MINIMUM OF S FEET AWAY Fl<VM BUlWINGI, WAL-l-S J Pl<OPIS"R1'{ ecuNDARY) AND TOP Cf' SLDf'!:;:. (B,} lA<AIN PIPE WIlL r%' -r1~HT' L/NE'D TO A MINIMUM OF IOfEtT fROM l'fiE:: l7UILDINc,. (4.) ALL. c.cNS1RUc.nOJ,AND MA1ER\ALS SHALL BE:: ~ SAN I;\e<::;o CCUNrY ~/CNAL STANDARDS. . . TYPICAL STOr<AGtf./ t/!0WA11t-J~ 1KENCl-t. N.I.S. . . JONES 11 . . , . APPENDIX "A" . . . . . . . . JONES o' . RUNOFF COEFFICIENTS (RATIONAL METHOD) . LAND USE Coefficient, C Soil Group (1) , A B C D - @ Undeveloped .30 .35 .40 . Resident ial: Rural .30 .35 .40 .45 Single Family .40 .45 .50 @ . Multi-Units .45 .50 .60 .70 Mobile Homes (2) .45 .50 .55 .65 Conunercial (2) .70 .75 .80 .85 . 80% Impervious Industrial ( 2) .80 .85 .90 .95 90% Impervious . NOTES: . (1) Obtain soil group from maps on file with the Department of Sanitat:on and Flood Control. . (2) i~,e,e actual conditions deviate significantly from the tabulated iI:Jperviousness values of 80% or 90%, the values given for coefficier.: C, may be revised by multiplying 80% or 90% by the ratio of accual imperviousness to the tabulated imperviousness. However, in no C:1~(' shJll cne final coefficient be less than 0.50. For example: Cons.J~l" commercial property on D soil group. Actual imperviousness = 50% ie I Tabulated imperviousness = 80% Revised C = ~ X 0.85 = 0.53 I. I JONES I- . II F",,,,/ ( saaa 4aaa . 3aaO 21717a . EGLI/lTlOA/ Tc. eljJL J) ..385 lC = 7/m~ 0/ conc~n/n:u'/o/7 L. L"'nt;11! or war..r.s-h..d /I. f)1/kr~/7ce In ~/..vaf/dn alon~ ",/1'.-.:-1'1"" slo.ae /In.. (S.... /l,o"",n"yx :t.B) ;; L C Af//~.s F~~r #O(/,.:s M~nu/~.1 4 240 10 ~ 1171711 900 800 700 GOO "- . soo "- .5 "- 400 'Q- 4- ~ ~ .3 3/JO "-~~ " . "- 200 "- 2 '- '- ( "- "- lOa I . .5"0 as . to . 30 N GTE [FOR~ATURALWAiiRSHW~ 20 n ADD TEN MINUTES TO COMPUTED TIME OF coj CENTRATION. ~ 10 . 5 \ H . SAr4 01 EGO COUNTY DEPARTMENT OF SPECIAL DISTRICT SERVICES DE SIGN MANUAL APPROVED ,j././.p~",~ . .3 18d 2 /20 100 50 8IJ 70 I 60 5"0 40 30 '- 5t:JOtJ '4~11 20 "- 18 30ao " IG "- I<f "- 2000 "- /2 1800 "- 1600 10 I~OO 9 /2tJO 8 1000 7 900 800 (; TOO 600 5 sot) ". 400 300 J 200 L 1C NOMOGRAPH FOR DETERMINATrON OF TIME OF CONCENTRATION (Te) FOR NATURAL WATERSHEDS DATE /2./1/6 '1 APPENDIX X-A V-A-IO Rev. 5/81 . . . 7-" ~3 - f- ~ I- - (..~~ - ~ f.l,J ~ (;l. ...... _~ 0 ::J o :i:: I c:.<:) ~ ~ Lt.J >- I o <::::) ~ . . . . . '" z o ~ f- 0"" "'~ ..,z ~< o V> z........J ",,00 V> '" u.~~ o LlJ ci >-~u 1::"'0 _",,0 =>"-0 OW...J uo..... . . . . '" c::: :::;) o :: , c:.c '" - o "" c::: r;:;.C ~ >- I C C --- . r-- - ,,--.;,. - - <-.- a '^ ~ z ~ " u > " " ~ " " zi= 0< ;:" <~ w e:~ u ~ z 0:::: 7. 0 w:ii: :;; 0-< :>:: <;z 0::: > u ,0 >. U. :: 3 &J 0 c: c . . " 0: Z. e- w f-- = .. ..,.. < Lo.. ll.;:co 0 Ct:: Zt,j CV'\ < U d:~;: w z "- o ~ 0 . u =" '" 0 u ::i ~ ~. ~~ -~ ~ ~ z a ~ ~ ~ .J - I o o ...... . . z a H f- a':: <:)H "-' ~ H< o<n Zl1..-1 <00 <n '" l1..~~ OL:J 0 :--~u f-"''''' :2:<0 :::>0..0 OW...J UOu... . . . '" "" e:: :=l o I '<:l~ ~ c::: <: w.J ;;- I o o ...... !,.,',... C C-" -J c:=<: > ::::l -J C'.. o c/j " = ~ \ .,- ~ , /. I w z < ~ " l r '" - o '" '" . '" '" Revised 1/85 , . ~ '=' ,. ,. ~ c: 2 U. " " ~ <:, u '" , Q C u < " , ,..... c- '" -'T ~ u > " ~ ~ " ~ z;: 0< j:~ < ,,~ WI- -' I u ,,0 >"-~S ~ 0 ~ ~ I' I :.... C ;: ~ ~ ~-: I :.. ;: 0 0 ~ ~ ~ ~ ~:;: :.:..J z:" oS O. g . u = V) 0 :.J =:i ..J ~ i ~ o ~ - ^ ~ ~ < - z 0 o ~ ~ c ~, ~ < u ~ ~ ~ APPENDIX Xl-II / JilAJES ENGINEERS.IN:ORPORATED CONS8L TIN8-=. E~,GIN==RS -. 1 If~3/? ~~ J5I ~ C~~ d~c:/P ~/m 4://f iY~;?J 1 ! j ,- ~~ ." ,: 1.~. t:-";::: ,__to ':::',. ?,,:Y'-,7" f .;; C,. - ," _'.; : -:;::' .,""" .... ....~_-:> " -- ".," .... 10..:. . .~ -- I j 3320 Kempe, Street, #204 San Diego. California 92110 . . (619' 223-9333. FOCUSED DRAINAGE STUDY FOR THE MONACO SUBDIVISION TM 4603 LOTS 1 , 2 Prepared By: JONES ENGINEERS INC. 3320 Kemper street Suite 204 San Diego, CA 92110 Revised July 30, 1990 1,,', . -, _. '." ~ ~ . ." l'- - ~. < Prepared for: The city of '-Encinitas Department of Public Works r.l. &.-0 . - -, . , . I I. ,-~. ~ \U~' . 6 2199D 1L:J: . . CriY OF ENCiNITAS Be -/ ~ DI?- w~t'T1L6 6A-9 CIVil.. E~'<'::;' ;~:::H:"':G': LA~~:' Sf...JR""~YING . -. HYDROLOGY EVALUATION FOR THE MONACO SUBDIVISION , I I \ BACKGROUND: This report presents a hydrology comparison between the existing and- proposed conditions of lots 1 & 2 of the Monaco Subdivision (TM 4603) to determine the impact the proposed development may have on the downstream properties. The study area is a portion of an eleven lot single-family residential subdivision. Presently, nine residences have been constructed. The study area is the remaining two lots of this subdivision which are presently vacant. SUMMARY: The site is located within a local hydrologic basin known as the "sUlllInit Sump". The southerly sub-basin of the "Summit Sump" is comprised of 38.0 acres and the subject site makes up an area of .70 acres within the southerly sub-basin. RATES Based on an analysis of a 100 year storm event the southerly sub-basin generates a peak rate of flow of 74 cubic feet per second (c.f.s.) and the subject site under existing conditions generates a peak rate of flow of 1.04 c.f.s., which represents 1.4% of the total. Under developed conditions the peak runoff from the site is calculated to be 1.27 c.f.s.. The incremental increase of peak runoff due to development of the subject site is .23 c. f. s., which represents one third of one percent of the total peak run off for the southerly sub-basin. VOLUMES During a 100 year storm event, the total volume of runoff from the southerly sub-basin is 8.3 acre feet. Based on the dimensionless hydrograph under buildout conditions the incremental increase in volume of runoff from the subject site is 3,654 cubic feet which equals .08 acre feet. This incremental increase in runoff volume represents one percent of the total runoff for the southerly sub-basin. STORAGE 6A - \0 \d The developer proposes to retain incremental increase of storm water runoff twenty-four hour storm, (2,740 cubic feet). 75% of the total during a lOG year, JONES ,- ~ '.' 1 An analysis of the roof area of each proposed home indicates a total area of 5,470 square feet. Assuming a 100 year storm yields 4 inches of rainfall, the total volume of runoff collected by the roofs is 1,806 cubic feet which represents 50% of the incremental increase in runoff which would occur under buildout. An additional 913 cubic feet of runoff from the driveway areas will be collected by placing an inlet at collection points on each driveway and routing the runoff into the retention system. 1 A system of perforated pipe placed in trenches with a gravel bed is proposed to store the storm water collected from the roofs and driveways. Enclosed are lot layouts illustrating the areas for trench systems to be installed. A Detail of the trench is also included. The remainder of the incremental increase in runoff, attributable to the construction of the two homes is equal to 1f4 of 1% of the overall volume of runoff generated by the southerly sub-basin. This relative increase should be considered negligible. CRITERIA: The design standards, basic criteria, and procedures will be based upon San Diego County Flood Control District Hydrology Design and Procedure Manual. The existing and proposed conditions will be evaluated for the worst-case scenario (100 year storm) to analyze the most severe impact the development will have on the downstream proper~ies. COMPUTATIONS: (100 year storm, 24 hour duration) RID,OFF FOR NATURAL CONDITION , , Q = CIA C = 0.45 (Appendix "A" IX) "0" SOIL GROUP A=0.7ac. P6 = 2.5 in.f100 yr. (Appendix "A" XI-E) P24 = 4.0 in.f100 yr. (Appendix "A" XI-H) tc = 15.0 min. (Appendix "A" X-Jl.) I = 3.3 in.fhr. (JI.ppendix "A" XI-A) ,? 6A-\\ JUNES 10--- Q(NAT.) = (O.~5) (3.3 in.fhr.) (0.7 ac.) Q(NAT.) = 1.04 c.f.s. \ RUNOFF FOR DEVELOPED CONDITION Q = CIA C = 0.55 (Appendix "A" IX) "D" SOIL GROUP A = 0.7 "ac. 1 , tc = 15 min. (Appendix "A" X-C) i = 3.3/hr. (Appendix "A" XI-A) Q(DEV) = (0.55) (3.3) (0.7 ac.) Q(DEV) = 1.27 c.f.s. INCREASE IN RUNOFF RATE BY PROPOSED DE\'ELOPMENT Q(DEV) - Q(NAT) = INCREASE RUNOFF BY DEVELOPMENT (1.27) - (1.04) = 0.23 c.f.s. For 100 year storm SOUTH SUB-BASIN PEAK FLOW* = Q100 = 74 c.f.s.* INCREASE IN PEAK FLOW BY SITE DEVELOPMENT = Q100 = 0.23 c.f.s. -1 j = 0.31% OF TOTAL SUB-BASIN PEAK FLOW or 1/3 of 1% * Per Hydrology study for proposed 11 Lot Subdivision TM 4603 7/31/86 By Conway & Associates (with no ground infiltration. ) 6A - \2- JONES I--~.' I ! 3 / . . VOLUME OF SOUTHERLY SUB-BASIN V = 8.3 ac-ft * VOLUME INCREASE OF SITE BY DEVELOPMENT -- V = (3,654 c-.f.) (1 ac./4,3560 s.!.) V = 0.08 ac-ft = 1% OF TOTAL SUB-BASIN VOLUME j 1, ,. j o- J 1 * Per ASL Consulting Engineers Master Drainage Plan city of Encinitas July, 1989. bA-13 JONES / 4 ~- >--; <I, 1 k-: I '<J '-' ll.. 1 lL C> 2 => rx:: 1 J 'r . . TRIANGULAR DIMENSIONLESS HYDROGRAPH ~_f:.cAl<. FLDW :'JOl-UME: 1~1<.EA5~ OF l?~V--~D COIJDIT/O"-l ' '_ -VS. ~XI::rnNUI CDNOLTIOt>.! ~lSII/fJ6; c.OfJl7l11CN .. ,- t7~V~L.Orw COlJl7lllDIJ :: Tp Tb TIME ( hrs .) Tp = Time to Peak, (hrs.) D = Duration, (6 hrs.) L = Lag Time, 0.6 (Tc) ; (hrs.) EMPIRICAL EQUATIONS FOR HYDROGRAPH CONSTRUCTION Tp = D/2 + L Tb = 2.67 (Tp) RUNOFF FLOWS Q 100 (DEV) = 1.27 Q 100 (NAT) = 1.04 c.f.s. Tc = 15 min. (0.25 hr.) Tc = 15 min. (0.25 hr.) TIME TO PEAK Tp (DEV) = 6/2 + 0.6(0.25) = 3.15 hr. Tp (NAT) = 6/2 + 0.6(0.25) = 3.15 hr. TIME BASE Tb (DEV) = 2.67 (3.15) = 8.4 hr. Tb (NAT) = 2.67(3.15) = 8.4 hr. 6A~/l1 JONES .? 5 ,4 "Z "' -ctc- -.::' t<)-r- o~ N /f:\- II \\ 0,...... '2 ,; ::J J: ~~ ~~ ~.e. gf \Ut.. ~ ~.t ill .. "'J .S \.$'I U ~-..9 N..n Z~. 0) :2 o ~ ~ :z c "-> '.D 2r-~ 3~t! 9L" \J..~c; u. :f o \J Z~j (l~~ \.ll - ~ I- t<' .~~ II ~ -:1. c.'Q U r- N II . ........'li. "7~ W,l) Ot\) '-' o ~ 2~ \J ~ r- . If) o \:L Z -:::I:o ,..;J,.~t: \;(-:D :ztOz --../" 0 ~ ~~\) ,,,,-0- -l rf ::J !;;i :z o ~ ~ c ~ <5 o \5,:P) ~..:i<d N eY,:f '.>:l ~ .~ ~ ~ " . . ......... Vl 1:1.' I -.....J w .2 \-- "I "" o 6A-1? JONES 6 . . METHOD OF ELIMINATING INCREASED RUNOFF: 1 The increase in runoff is due mainly to the buildings and driveways. Collecting and storing the rainfall from the roofs of the buildings will significantly reduce potential increases in runoff. This can be accomplished with roof drains connected to perforated pipe/french drains that will allow the runoff to seep into the ground in the yard areas. The driveway areas also contribute to the increase in runoff. The developer proposes to collect and store a portion of these areas where feasible. To minimize the increase in runoff from this project the proposed retention system will collect and store all of the roof area and a portion of the driveway areas so that a minimum of 75% of the incremental increase of runoff will be stored on site. RUNOFF STORAGE Volume of Incremental Increase in Runoff I j V = 3,654 c.f. = .08 ac-ft 75% x 3,654 c.f. = 2,740 c.f. = .06 ac-ft Total Recruired Storacre Volume = 2,740 c.f. Lot 1 storage Volume = 1,370 c.f. Lot 2 storage Volume = 1,370 c.f. Lot 1 Storacre: 1370 c.f. -, ! Roof Area = 2,750 s.L x .33 ft. of precip. = 908 c.L = .02 ac-ft Remaining Volume to be stored = 462 c.f. = .01 ac-ft 462 c.f. .33 ft. = 1400 s.f. of driveway area to be collected, (See page 12). LOT 2 STORAGE: 1370 c.f. Roof Area = 2,720 s.L x .33 ft. of precip. = 898 c.L = .02 ac-ft Remaining Volume to be stored = 472 c.f. = .01 ac-ft 472 c.f. .33 ft. = 1430 s.f. of driveway area to be collected, (See page 13). - i I -' I ;A-/b JONES 7 . . STORAGE CALCULATIONS FOR PERFORATED PIPE I FRENCH DRAIN: VOLUME OF PIPE PER LINEAR FOOT: A = 1r rt A = (3.14) (0.5 Ls.) 6" P.V.C. = 0.5 ft. A = 0.79 c.f. AT 1/2 FULL = A = 0.39 c.f. VOLUME OF VOIDS = -Y.L (1 + e) e = void ratio e = 0.5 (pea gravel) VOLUME OF VOID PER CUBIC FOOT: = (loC.F.I (0.51 1 + 0.5 = 0.33 c.L / c.L VOLUME OF TRENCH: H = 4.0 (See Typical detail. ) h = 2.5' = storage area w = 4 ' V = HWL j V = hw I I V = (2.5 ft.) (4 ft. ) J V = 10 s.L , tA-/7 1 JONES 8 TOTAL VOLUME OF TRENCH & DRAIN PIPE PER LINEAR FOOT: VOLUME = (VOLUME OF TRENCH) (VOLUME OF VOID) + VOLUME OF PIPE V = (10 s.f.)(0.33 c.f. / c.f.) + 0.39 c.f. V = 3.69 c.f. / l.f. LOT 1: REQUIRED STORAGE = 1,370 c.f. LENGTH OF STORAGE TRENCH REQUIRED: L = 1370 c.f. 3.69 c.f. / l.f. L = 371 l.f. LOT 2: . REQUIRED STORAGE = 1370 c.f. LENGTH OF STORAGE TRENCH REQUIRED L = 1370 c.!. 3.69 c.!. / l.f. L = 371 l.f. -\ ! , i I --1 r- \ 6A-I7; JONES 9 / --..... l MONACO SUBDIVISION I 2 LOT HYDROLOGY STUDY COST ESTIMATE FOR STORAGE I DISSIPATION TRENCH j 1 l 1. 6" P.V.C. PERFORATED DRAIN PIPE @ $15.00/L.F. LOT 1 = 371 L.F. @ $15.00/L.F. = $ 5,565.00 LOT 2 = 371 L.F. @ $15.00/L.F. = $ 5,565.00 TOTAL = $11,130.00 2. GRAVEL TRENCH @ $0.50/S.F. WITH FILTER FABRIC (4'X 4' TRENCH TYPICAL) = 16 S.F./L.F. = $8.00/L.F. i -1 LOT 1 = 371 L.F. @ $8.00/L.F. = $ 2,968.00 LOT 2 = 3.71 L.F. @ $8.00/L.F. = $ 2,962_.00 TOTAL = $ 5,936.00 LOT 1 TOTAL = $ 8,533.00 LOT 2 TOTAL = $ 8,533.00 TOTAL COST FOR STORAGE DISSIPATION TRENCH' = $17,066.00 . i -' ! tA-19 JONES 10 / l l , ; , I X@' ,t FINISH ~' GROUND J //~\V ~y .0 !;t ~I~ '(o"f PVC ~1ED f'li"E' ~ -'-' ^ ~ '8 c2 t5 0 c;) ,- C> - _____ FI L1ElZ \l) fAeR1C "':'1 G I i _ X,- ~ \D. r-~a ";;-! __ _.__.~V_ _.'S<._ ~ ' , 6' 0 l~ 0 va C> v o C 6 o o " ! o 0 o ~ o (, o '-; 0'"" - 'l\~ .^- : I : I j / ",: 4.0 ): '\.~- ..._- .---- ..--.. - _. ------, , (I.) -PP OF TRENCH \IIILL iS€. A MINIMtJiv1 CF Z rtE:T ~ IHE: n::tm~, l2.JlllE: ~CR crlllC -rKENCH WILL E% A MINIMUM OF ~ fEEl AWAY ~fJ\ BUtl.OlN6 J WAu...s I proP"R1'{ EoJNDARY, AND TOP a= SL.Of"E:. Us.) DRAIN PI~ WI\.!... F::>6 'nc,f1f' LiNCV"TO A MINIMUM OF IOfEET ~ ----- nu:: !7U1LDINq, (4;) AlL UN51RucnQJ AND MA1ERIALS -SHALL Eo!:': ~ SAN DE"60 CAJNTY ~ICNAL ST.b.'JOARDS. TYPICAL STORAGE! t7J0IPA1H-JCr lRENCH. 6A-/D 11 N.I.S. / ~. ) I . . , ,- I ~ '" ~~' ~ => . \'l, -' ill--i \l ~ ~-- '" L _ ~, -- - N. APt;_ ........- - I I , I: .u I fO.RAGE AREAS ------ ~. I I I '\. CD _ __ -<...!:7- - 0 ~ ;j .t- CD I 2: I I . .::- , I .--- , . , , \ " " \ I " ~4 . , -- .. -, .\ ' * i" --' /(" -~~ -, ~ I ' ...-1 ~ C <.0 '" I. 1 '/ / ~ J I I ; 'J I ,. .. ..L , ,~ ---~ l' --- J: I U\~- ~ ~I~ / --, I Q::~ ' S " ,~.".:' 1'[ I _ ..L...!...- I ..----- -Q I / '~ ..... - ___ 01 o'~il i~L ~ .// --S-1- ~,;- -'- OJ ~ l & --CD_t Z LL . W 0 :::l> '2 .----- 1 ~, , - ~ . " ~~ HJ' . ..)( ,-.- - \\'I ~ c <5> r- -:z. IC/Z ;: .- ~' - , ''i3S);S-JI , /' /' o. )0- d ~I . r 17/1)~j;~( /; 1/ / 1/// 177.:2' j, / ~,l APPROXIMATE DRIVEWAY AREA TO BE STORED , --- ./ D,RAIN , /~ r I 7; / tjf- h :// r \ ,/1751 rL LOT #- 1 - /' -;/~;=-iT- - r -- \\- -', 6A-21 i ',>;JJ /' I-~~I; ~.:..\ :/ \'., .~30' ~ \IIlIQO L__ -, , J/_ l .\ J'.,_ ~ I I I ( ,i '-'--- w o c 8 z w ~ .}} lJ) ,.=- r:l - -- Cl \i\ ~..y- .... -------- O~lN P \1\ - '-,~ , , , , " ---.' \"- --J: u" --( \ \ \ /- ! 'V-" tL"~2./1 , '/ '-- L ~ .J_~ J \ \ \ . . / -o- f / -/~-:.., /! -". I f /' it.. \ ' ---. .--..----.../ DRAIN .-----t-L-.... '\ \ \ STORAGE- AREAS LOT #2 / ~ ~~:llI_::'OI 1~- -- . 1 APPENDIX "A" , , , i ,. I i / . . 6A - 23 JONES RUc;OFF COEHlCIEt>TS (RATIONAL ~IETHOO) . . LAND USE Coefficient. C, Soil Group (J) A B C [j - G Undeveloped .30 .35 .40 .. , Residential: I Rur"l ; 30 .35 . 40 ..:.l:; "I Single Family .40 .45 .50 @ ~lul ti-Uni ts .45 .50 .60 .70 ~lobile Homes (2) .45 .50 .55 .65 Commercial (2) .70 .75 .80 .35 80% Impervious I Industrial (2) .80 .85 .90 q- .." .J 90% Impervious NOTES: (1) Obtain soil group from maps on file ..ith the Department of Sanitat:',Yl and Flood Control. ;,j:,.:,~ "ctu~J condi~ions deviatc significantly from the tabulated i!:;;~~~iouSllCSS values of 80% or 90%, the values given for coefficie~: C, may be r~vised by muJtiplying 80% or 90% by the ratio of ac!uaJ i:::;:C'':",,'iousness to t~H~ tabulated irr.perviousness. Ho~'c\'cr, in I~O (:1:'(> sh:,l: .~:~C final coc:ficicnt be less th:;:1 0.50. For eX.1mp~c: (Ol;~.,.':'~'!' CO:;l~:t:;'C':'::.l propc:-ty on D soil .c.roup. Actual imperviousness = 5D~Cl T3bulateJ imperviousness : SO~ Rcviscd C = 50 X 0 ~5 = " 5' SO .'- u." 1 1 6A-24 AI'PEc;lllX ;\ -. i 1 , ] , -J -'-=-=1 SCCC ~ccc :JCCO .21717C " 117/J/J -" 9 CO BOO 7170 bOO , SCO -100 3~0 200 so - '0 I~~ ,-20 10 H ..:.......~ .. I Ii c." _." \ ....:f: /c. \"fi - ) it:' ;;m~ 01 conc~/7lral/ol7 L. L-=/79Ih '0/ wal<"rsh<"d -/I' t)il/",-r<"/7ce- in ../..val/on a/onfi- d/<"diu SIODt! Ii/?<" rsu Ill''p~nd/x Y.B) ;;. L C M//<"5 rt!t!1 /-/O</rs I M,iwlt!s 4~NO /0 1170 , "- " 'V- ~ ,~ '-<- <<' " " "- " "- "- "- I' 3 180 . . iA-2S s 0.5- NarE r::--"=- .=:L,,=---=--=-.:::II =---= ==---:J [FOR :-;';,\JP.;L h'';TERSH::DS/ ~ t.::JO i[N ~.WJUTES TO t COMPUTED TIME OF CON-j CENTRATION. - " 5 SAI~ 01 EGO COUNTY DEPt.RTMENT OF SPECIt.L DISTRICT SERVICES DESIGN MANUAL '-"PROVED -5, II I~~ ~,~5. , 2 120 4 10C 50 B!) 7C 60 .J I 5C .2 ~o .30 " 5tJoa , i{~/J 20 "- III .lOO/J "- IG , N "- 21700 , 12 11300 "- 16tJO 117 I? tJO 9 /20tJ II 1000 7 SOD SOO ~ 1170 6170 5 SOtJ 4- 4tJO 3170 J 200 L Tc NOMOGRAPH FOR DETERMIN:'T10" OF TIME OF CONCENTRt.,IO" (Te) FOR NATURAL WATERSHEDS Dt.TE /2./1/6 <j / APPENDIX X-I. 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I = C> ~ C> M C> <'-' '" OJ ..... ::I c: , , , <r> I' I III 111 .76 C> ~ .., !<;::~ '-~~"f'..V Y'l' --:_-- .r i;." _' ~ t c:. - ... z. - ......~..-. ',' --..... It ~ __ '''' .., .~..... {..','l iI,' "/7 -./ . -, i . t:.. {_I .., { ~... n . . J..ugust 6, 1,,90 Richard Clemons, AlA Clemons/Renvall Architects P.O. Box 710841 San Diego, CA 92171 Re: Case # 88-145DR Revised - Pad Height Elevation of Lot 2 Monaco Subdivision Dear Mr. Clemons: Thank you for providing information related to the height of the sewer lateral at the building pad for Lot 2 (Monaco SUbdivision) in your correspondence dated July 25, 1990. At their Administrative Hearing on July 24, 1990, the Planning commission approved the Design Review Permit for Lot 2 contingent upon lowering the pad height by 4 feet, if at all possible. The approved grading plan for Lot 2 indicates a pad height of elevation 159.6. Therefore, a 4 foot reduction would take the pad height down to elevation 155.6. Since the information you provided estimates the sewer lateral elevation at the building pad to be 153.01, it is staff's determination that the pad height can be reduced to elevation 155.6. Should you \'>'ish to prOV:LOe additional evidence to staff which conflicts with this determination, please do so at your earliest convenlence. C:::l~ .v9~ Craig R. Olson Assistant Planner cc: Planning commission Robert Warren, City Engineer Patrick S. Murphy, Dir. Planning and Community Dev. will Foss, Building Department Supervisor Bill weedman, City Planner "~" CO/mam/CL24-7097wp5 (8/6/90-2) 6A - 2~ / :: .' - I ", '~":." ] ~ ., 1:' ...,:.: I,,,,, 1l;." \.<1 ::, ,~ 11 ;.. ').:.,.: . ,.J."." "....., .",---_.,. H. ":. em' ( I( EI]cil]il({'\ . . August 6, 1990 Rose and Dietmar Rothe 1404 Rubenstein Avenue Cardiff-by-the-Sea, CA 92007 Re: Correspondence dated July 28, 1990 related to pad height: reduction for Lot 2 of the Monaco Subdivision (Case No. 88- H :;DR Revised) . Dear Mr. and Mrs. Rothe: Thank you for your letter regarding the relationship between sewer lateral elevation and the reduction in pad height elevation for Lot: 2 in the Monaco Subdivision. I have discussed the information submitted by Richard Clemons (dated July 25, 1990) with Building Department Supervisor will Foss and with City Engineer Robert Warren. It is staff's determination that a pad elevation of 155.6 feet (as requested by the Planning commission for a 4 foot height reduction) is feasible given the sewer lateral elevation at building pad of 153.01. Since the Commission directed staff to require a 4 foot reduction in pad height, if at all possible, we '.'ill require the property owner to lower the pad to elevation 155.6 and have the pad height: certified, This requirement will be ccntingent upon no substantial evidence being submitted which would prevent a 155.6 elevation pad height. Should such evidence be submitted, I will make it available to you for your review. , 'J CO/dc/CL26-7096wp5 (8-6-90/1) 6A - ?:o / "-:.:- I !\\-I11I:.'" 11":11;",-.11,1 1'1\; 1:1 ..1" 1,_1111,'!11n 'I~!I': I """"'1",,,;11 -, ~=s~ and ~ie:~ar h~~~Je . Pa::!e 2 August 6~ 1990 . . Should you have any questions related to the matter discussed above, please contact me at your convenience. Sincerely, ~{, e .crQ Craig R. Olson Assistant Planner cc: Planning commission Ralph Luedtke Richard Clemonsi AlA Patrick S. Murphy, Community Development Director will Foss, Building Department Supervisor Bill Weedman, City Planner CO/dc/CL26-7096wp5 (8-6-90/1) 6A-31 / - - City of Encinitas Planning Commission 535 Encinitas Blvd. Encinitas, CA 92024 . I ,t ~~IJH 0". I CITY OF ENCINITAS . . Ju ly 28, 1998 SUBJECT: CASE 88-145 DR, MONACO SUBDIVISION, LOT 12 Dear Commi ssioner- Bagg: The Planning Commission in its Appeal Meeting of July 24 tentatively approved the plans for Lot #2, contingent upon lowering the pad by 4 feet if at all possible, but in no event less than 3D inches. The previously approved pad height was 159.5' (not the current pad height). Hence, Mr. Luedtke was requested to lower the pad to the 155.5' level. We would like to bring to your attention the fact that it is easily possible to lower the pad by at least 4 feet. and that I take exception to Mr. Clemons' remarks in his letter of July 25 to the Planning Commission and to Mr. Olson. J.'lr. Clemons maintains that Pad 2 can only be lowered 3D" to meet the existing sewer lateral. We have attached his letter and sketch for reference. First, referring to Mr. Clemons' sketch, there is no law or requirement that there be a 4 foot minimum "structural clearance" between finished floor and top of lateral at the foundation of the structure, especially since the lateral should be in place before the foundation is poured. The 9" clearance between bottom of foundation and top of lateral is not necessary. A 3" clearance should be more than enough. This would allow the pad to be lowered at least 3 full feet and would still allow the present lateral to be used. (Note: If the 4 feet "minimum structural clearance" were to be applied to proposed building for Lot #1, it will be impossible to connect to the lateral for Lot #1). Please refer to the attached copies of city drawings, which show the location of the sewer lines as approved by the Director of Public Works. Mr. Luedtke has several other options to connect to the sewer than through the existing lateral (Alternative A on attached drawings). Lot #2 is an island surrounded on three sides by streets and sewer lines. Besides connecting to the existing lateral (Alternative A). it is possible to make at least three alternative connections with the sewer (Alternatives B. C and D. see red lines on attached drawings). Only Alternative C would require the proposed drainage sump to be relocated. Any of the alternatives (other than A) would allow the pad to be lowered a full 4 feet. Sewer inlet elevations at laterals B, C and D are: Lateral A: Sewer Inlet @ 151.4 (Clemons' Alternative) Lateral B: Sewer Inlet @ 149.7 or lower Lateral C: Sewer Inlet @ 146.4 or lower Lateral D: Sewer Inlet @ 149.7 or lower. j / 6A - 32- Planning Commission, Monaco_Lot #2 Pad Height - Since Mr. Luedtke was instructed to lower the pad by a full possible, he should be made to modify the sewer lateral for additional cost is minimal in comparison to the cost of the building. Estimated cost of new lateral: Materials: $ 400.- Max. Labor: 8 Man-hours. or Approx. $ 200. Page 2 4 feet if at all Lot #2. The home he is We sincerely hope you will take this under consideration before approving the new pad height and request that Mr. Luedtke take the pad down by 4 feet. We would appreciate hearing from you on your decision. Rose Roth~~~ Dietmar E. Rothe, Ph.D.. P.Eng. Encls cc: C. Olson, R. Warren bA-35 ~. ',. - . .~ ,----- '::.~~ " ~ .~ - ~-;-t;~ ~ ~ ;~_ ~ '~ .~-=:: ~=. .=i ~ :~~-':.~ .~.:~j~;t~~f -~ ~~_:;~~~}L~;~~~:~' ;:~i~~ ,l~~~"~ 1 , I" In" ~\ .-,-.,-"'-.- - .1-- __l . -'- I ~_"c.-'C---. "I, .:,-,.'C '<:~~~~-'" 'I J. : . <01::, ,~~V\':.' c!~. : ?~ '.,' ~::' '.; ~~.,I ~:,-.:::3:~:2:~i ~~_:~2~~~'=-.:0,:~:,~~II'-i ! !_L"'k ._1_ <::;11.1\"-- to ~ .__._ I.: :"..,__~ ll'l~"':---=--=- ~ . Si'~ - --- . :'11...... :.:: --~2:::Jf -.- . - _.. '.",-:;'."=-=== ,C ~~,.S;~:S~~==i=~-j~1~:~~j~:=-~~~1-,~.~"~1 I: 1 . 1 I '>'I~ m '''\K'' ~L I ,._l_, ...., I 1 .'::.:J.::J--.-,.,.I-~;;.;-..-'.,--",,-_.. .",.~".. ..,." -....' 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"-i": .. j'i,i-:;:.-;-l.; R- , h=r-,!1 =:J:-:-i -p,~: i ;-;-'1': i '"I--l,_I_l_i_,,,,,,_, '--F "'i' I" , , '..c'IIi;'oi:: ',' ! ; :_D~'--.::.,:,_", '-j:::i::'i--j:"i- _._' __ 11---1-'.'--"1-' j. 1'1 ',: -1:l:l..........I- 11, ____,_,,,__,__,,,_, 1"""''''__''''1 ,,' _ E!~I[i:ht'l:i~q:r!+1 A~i ~1'~t~li~~L~~LL~rl ~ L'::..j...l..:...L.i.~t--'-~:; , , "', c.r",j --",.... .,~, ~l ..... ~I~ 1" C- SEivER L/,VE " SO' V , ::;z I' \\rl \ ' \ \ , ~'9~.E9~~' Tlj' .t-_, '-;9S09~ Jl I /:;;"" 'j' J',) ." "I ""\ //.// -\ (:,'1 " '; 'I ,/ 11'\ ~ I I; ':/ ~\ ---. 1/ "'/s,',';"'.1 ,/ ' . \ '.'~'" . . :/ ~ \. . ,,,, J.t . - "v I' ----::r, :~" ~' . J.-=, -=1-/ / "',\ ,I, ~ ,t;. , , \ I '0,/ 5 _ '~"'Ii= \, ?_ - " "\;"'{~ J C.~~Z "VC ;"f)'P\tJ 5, ' -::~"-- L'~'( -;;j)l..Ja I .{ .~ =- }';9.7 1-.. LOT .:;- 2 " y v, ':"\ ~...- h,,\..... cD r', 0.,' , \.>~ \o~~\'\-" \\P _/ J In / , !\./ f'\j ~~ ~/J .....,/' /f" '\; f c" " ! I j I , I , ,\ " ,I Ii II f1 " 'I " , , ~ I ~ "'\ .~(...fo ~'/i'-'?' \""\ '1(,. d\' ---c-==- - .", '" ..~ 6/\ - ~'3 ~.tr ~~, '''''.-- . r=~r\/A7 ..:: CONI......::.',l r P C:'f -'r,J) :....[[1] I ___~C~'''':''I' O~ oj.,.. . ? . CU=MO~S RcNVALL ARCHIT t::CTS ~J I JJL 2 5 :::-. , CITY OF EI~C'Il'\iTt.S ' . -- . ~=Sl :)~:::I== =~x "7iO:.c.i s;..~-.: =:=:;:) =":":"'i;==~r-"';l~ :2'";71 277 S2:=j July 25, 19QO :)':;':', S-~e. -: '. _:'-\ City ~f Encinitas Planning ~~ission 535 Encinitas Blvd. Encinitas, Ca. 92024_ ATTN: Craig Olson, Assistant Planner Dear Craig, Pursuant to the Planning Commission meeting of July 24, I acco~anied Ralph Luedke to the Monaco Subdivision to verify the location and depth of the sewer lateral ~ith respect to Lot 2. A meeting ~as held-that afternoon ,..ith Bob \"arren and staff at Engineering, \'nerein our observed data ~as compared to, and confirmed, with "as built" information. As the enclosed sketch indicates, the depth of the main at flow level is 151.43', which \"orks "bacl-..wards" @ 2% to 153.01, thus allo\'.ing the build- ing pad elevation to be lowered 30" from the ele\'ation that ~as subnitted ior review on July 24. This 30" pad reductidn allo\"s sufficient depth for the structure above as well as a small contingency to allow for undisclosed iield conditions. If you have any questions regarding this additional information, or if you need to discuss this matter further; as in the past, please don't hesitate to call. --- .'~_"'.O _I_r "I_~~ ...... e,....."c._.. "'0 C'OlJ:X) tA-36 "O:-_~ "II C-.I....~t. .... r;.,.......c...... ""'0 c.e~. .....r:;:.- ...10 '::1"'0 / . JUNC'::; ENGINEERS,'IIII::;ORPORi- -rED ") CONSUL 1111113-=- ENGIN==RS ,-:.>, / r~ 1.~. ~::-: . . .:~~:-: ? :",-:.. ':" f {_~~_ ;" ~. '". :.r : -. . ~. . ",--.. -;,' .' ':. ";" :'\. -....::;. .' ~:,;' .' .-C'", - :- ",- , -J 3320 Kemper Street, ~204 San Diego, CalMornia 92110 (619) 223.9838-, t -v FOCUSED DRAINAGE STUDY FOR THE MONACO SUBDIVISION TM 4603 LOTS 1 " 2 Prepared By: JONES ENGINEERS INC. 3320 Kemper street suite 204 ,San Diego, CA 92110 Revised July 30, 1990 ,.... ~ -. " ..:.., - - , -!', :" :~ L ~ ,..- ._ . ,.:;-.,0. '. Prepared fer: iU~' IlE 210::"1 I\(!i ........'J ~, \ el\'{ Of ENCiNITAS B'3 - I A6" t:> g.. w~t'1).L6 ," , The city of 'Encini tas Department of Public Works 'or '( -, ." ,L t; -9 CIVIL ENGINEERI"G I Lt-.!\D SURVEYING :>:_-:-'c''';'' ~.~_...--._. - . ',. ., . .1; , ~ : j Ii II II ), 'I I I , ; I , I / JONES ENGINEERS. INCORPORATED CONSULTING ENGINEERS 3255 Wing Street. #107 San Diego. California 92110 /22 c.G- , ---- REVISED DRAINAGE STUDY FOR THE MONACO SUBDIVISION MAP NO. 12049 LOT ONE Prepared by: JONES ENGINEERS, INC. 3255 Wing street #107 San Diego, CA 92110 Revised April 8, 1993 Prepared for: The City of Encinitas Department of Public Works OK ~(b~~ ftG t;s F -- \ \ ~ Cj,? -^ HYDROLOGY EVALUATION FOR THE MONACO SUBDIVISION LOT ONE OP HAP NO. 12049 BACKGROUND: This report presents a hydrology comparison between the existing and proposed conditions of lot 1 of the Monaco Subdivision (Map No. 12049) to determine the impact the proposed development may have on the downstream properties. The study area is a portion of an eleven lot single-family residential subdivision. Presently, ten residences have been constructed. The study area is the remaining lot of this subdivision which is presently under construction. SUMMARY: The site is located within a local hydrologic basin known as the "Summit Sump". The southerly sub-basin of the "Summit Sump" is comprised of 38.0 acres and the subject site makes up an area of .35 acres within the southerly sub-basin. RATES Based on an analysis of a 100 year storm event the southerly sub- basin generates a peak rate flow of 74 cubic feet per second (c.f.s.) and the subject site under existing conditions generates a peak rate of flow of 0.52 c.f.s.,which represents 0.70% of the total. Under developed conditions the peak runoff from the site is calculated to be 0.63 c.f.s.. The incremental increase of peak runoff due to development of the subject site is .11 c.f.s., which represents one sixth of one percent of the total runoff for the southerly sub-basin. VOLUMES During a 100 year storm event, the total volume of runoff from the southerly sub-basin is 8.3 acre feet. Based on the dimensionless hydrogragh under buildout conditions the incremental increase in volume of runoff from the subject site is 1,818 cubic feet which equals 0.04 acre feet. This incremental increase in runoff volume represents one half of one percent of the total runoff for the southerly sub-basin. STORAGE The developer proposes to retain 75% of the total incremental increase of storm water runoff during a 100 year twenty-four hour storm, (1,370 cubic feet). An analysis of the roof area of the proposed home indicates a total area of 2,673 square feet. Assuming a 100 year storm yields 4 JONES / inches of rainfall, the total volume of runoff collected by the roof is 891 cubic feet which represents 49% of the incremental increase in runoff which would occur under buildout. An additional 479 cubic feet of runoff from the patio, driveway and parking areas will be collected by placing inlets at collection points on the yard area, the driveway and parking area routing the runoff into the retention system. A system of perforated pipe in trenches with gravel bed is proposed to store the storm water collected from the roof and driveway. Enclosed is a lot layout illustrating the area for a trench system to be installed. A detail of the trench is also included. The remainder of the incremental increase in runoff, attributable to construction of the home is equal to 1/8 of 1% of the overall volume of runoff generated by the southerly sub-basin. This relative increase should be considered negligible. CRITERIA: The design standards, basic criteria and procedures will be based upon the San Diego Flood Control District Hydrology Design and Procedure manual. The existing and proposed conditions will be evaluated for the worst-case scenario (100 year storm) to analyze the most severe impact the development will have on downstream properties. COMPUTATIONS: (100 YEAR STORM, 24 HOUR DURATION) RUNOFF FOR NATURAL CONDITIONS Q = CIA C = 0.45 (Appendix "A"IX "0" SOIL GROUP A = 0.35 ACRES P6 = 2.5 in./100 yr. (Appendix "A" XI-E) P24 = 4.0 in./100 yr. (Appendix "A" XI-H) tc = 15.0 min. (Appendix "A" X-A) I = 3.3 in./hr. (Appendix "A" XI-A) Q(NAT.) = (0.45) (3.3 in./hr.) (0.35 ac.) Q(NAT.) = 0.52 c.f.s. JONES / RUNOFF FOR DEVELOPED CONDITION Q = CIA C = 0.55 (Appendix "A" XI-A) "D" SOIL GROUP A = 0.35 ac. tc = 15 min. (Appendix "A" X-C) i = 3.3/hr. (Appendix "A" XI-A Q(DEV) = (0.55) (3.3) (0.35 ac.) Q(DEV) = 0.63 c.f.s. INCREASE IN RUNOFF RATE BY PROPOSED DEVELOPMENT Q(DEV) - Q(NAT) = INCREASE RUNOFF BY DEVELOPMENT (0.63) - (0.52) = 0.11 c.f.s. For 100 year storm SOUTH SUB-BASIN PEAK FLOW. = Q100 = 74 c.f.s.. INCREASE IN PEAK FLOW BY SITE DEVELOPMENT = Q100 = 0.11 c.f.s. = 0.15% OF TOTAL SUB-BASIN PEAK FLOW OR 1/6 OF 1% . Per Hydrology study for proposed 11 Lot Subdivision TM 4603, 7/31/86 by Conway & Associates (with no ground infiltration.) JONES VOLUME OF SOUTHERLY SUB-BASIN V = 8.3 ac-ft * VOLUME INCREASE OF SITE BY DEVELOPMENT V = (1,818 c.f.) (1 ac./4,3560 s.f.) V = 0.04 aC-ft = .5% OF TOTAL SUB-BASIN VOLUME * Per ASL Consulting Engineers Master Drainage Plan City of Encinitas July, 1989. / JONES TRIANGULAR DIMENSIONLESS HYDRO GRAPH ..., o. k.; (j '-' ~ J?EAj( FLDW 'JOl-UME I~G OF t7~V!:Uf'e'O CONDIT/ON - -VS. GXl=rnNCI ~Nli'ITIO"-l JE:X 151111Jt( c..O~I7IT1CN ___-0W~LO~O COlJl7111DfJ I.L. 1L- C> :z ::J c.:: ; : Tp Tb TIME (hrs_) Tp = Time to Peak, (hrs.) D = Duration, (6 hrs.) L = Lag Time, 0.6 (Te); (hrs.) EMPIRICAL EOUATIONS FOR HYOROGRAGH CONSTRUCTION- Tp = 0/2 + L Tb = 2.67 (Tp) RUNOFF FLOWS Q 100 (OEV) = 0.63 Q 100 (NAT) = 0.52 e.f.s. Te = 15 min. (0.25 hr.) Te =0 15 min. (0.25 hr.) TIME TO PEAK Tp (OEV) = 6/2 + 0.6(0.25) = 3.15 hr. Tp (NAT) = 6/2 + 0.6(0.25) =0 3.15 hr. TIME BASE Tb (OEV) = 2.67 (3.15) = 8.4 hr. Tb (NAT) = 2.67 (3.15) = 8.4 hr. -JONES / . e .:i <:r- ~ph~ ~rC ~ U) .~I~: ~'" :z~! -\.I .. . C+. ~~~ , - ~ <:$) o - b..~- -:.c(\ u. ~ II \\ ~~~ i I Q') f' 0", ,. :z , '2 Ul d) ; ::J J: 0 'IJ} }-- ~ t- ~- E if1~1I , . ~. ' . me-. ~ ~ l \0 :Id :z cl~ <::> 7- c;.) H ::>t & ~ ~I .~ \U ~ Q \U I .~ .!!l ""' ~ r. ~ ~ ' , lll';;' . I ; ~ ~ U ~ I u () -" !1 Z~ ";j:1: ~ \t\ --...I w~ Q~ I v , '-' ; 0 . ; ~~ I ~ W ~ e ~ 2 0 I- ~'" 3'2i ...l~ ~lP l! ~~; ~ Z "" , ' o o ~ ~ Q ~ Q o ? METHOD OF ELIMINATING INCREASED RUNOFF: The increase in runoff is due mainly to the building and driveway. Collecting and storing the rainfall from the roof of the building will significantly reduce potential increases in runoff. This can be accomplished with roof drains connected to perforated pipe/french drains that will allow the runoff to seep into the ground in the lower yard area. The driveway area also contributes to the increase in runoff. The developer proposes to collect and store a portion of these areas where feasible. To minimize the increase in runoff from this project the proposed retention system will collect and store all of the roof area and a portion of the driveway area so that a minimum of 75% of the incremental increase of runoff will be stored on site. RUNOFF STORAGE Volume of Incremental Increase in Runoff V = 1,818 c.f. = 0.04 ac-ft 75% x 1,818 c.f. = 1,370 c.f. = 0.03 ac-ft Total Reauired Storaae Volume Lot 1 Storage Volume = 1,370 c.f. Lot 1 Storaae 1370 c.f. Roof Area = 2,750 s.f. x 0.33 ft. of precipitation = 891 c.f. = 0.02 ac-ft Remaining Volume to be stored = 462 c.f. = 0.01 ac-ft 462 c.f. 0.33 ft. = 1400 s.f. of driveway area to be collected, (See Drainage Plan.) STORAGE CALCULATIONS FOR PERFORATED PIPE I FRENCH DRAIN: VOLUME OF PIPE PER LINEAR FOOT: A =1r r2 A = (3.14) (0.25) 6" P.V.C. R= 0.25 ft. A = 0.19 c.!. AT 1/2 Full = A = 0.10 c.f. JONES ~ VOLUME OF VOIDS = Ve (l+e) e = void ratio e 0.5 (pea gravel) VOLUME OF VOID PER CUBIC FOOT: = (1 c.f.l (0.5) 1 + 0.5 = 0.33 c.f./c.f. VOLUME OF TRENCH: H = 4.0 (See typical detail.) h = 2.5' = storage area w = 4' V = HWL V = hw V = (2.5 s.f.) (4 s.f.) V = 10 c.f. TOTAL VOLUME OF TRENCH & DRAIN PIPE PER LINEAR FOOT: VOLUME = (VOLUME OF TRENCH) (VOLUME OF VOID) + VOLUME OF PIPE V = (10 c.f.) (0.33 c.f. Ic.f. ) + 0.10 c.f. V = 3.40 c.f. I 1. f. LOT 1: REQUIRED STORAGE = 1,370 c.f. LENGTH OF STORAGE TRENCH REQUIRED: L = 1370 C.F. 3.40 c.f. I 1.f. L = 403 1.f. JONES " MONACO SUBDIVISION I LOT HYDROLOGY STUDY COST ESTIMATE FOR STORAGE I DISSIPATION TRENCH 1. 6" P.V.C. PERFORATED DRAIN PIPE @ $15.00/1.f. LOT 1 = 371 L.F. @ $15.00/1.f. = 6,045.00 2. GRAVEL TRENCH.@ $0.50 s.f. with filter fabric (4' x 4' TRENCH TYPICAL) = 16 s.f./1.f. = $8.00/1.f. LOT 1 = 371 1.f. @ $8.00/ 1.f. = 3,224.00 LOT 1 TOTAL $ 9,269.00 JONES ? , FINISH G;l(OUNO O::i ~~ -c,'~PVc <>.. .:> ~ 4: ~lEP 'acfo 11 0 0 f'lFt:< <> <;) 6 FI ClEl( 10 6' 0 , 0 ~ ~eRIC - Cl + d ~ 0 X d 6 Q II o D 0 :: <:> 10 0 0 D 0 f'lS\o. \IJ 0 G~"a '1 0 .J:; (. , w= 4-0 t I.) TOP OF 1l<a\CH WILL e,e. A MINIMuM OF Z Fl:ET 6IaOW ~ Fl::bT1NGi. (Z.JT\l~ ~CR Cf"/H€. 7RENC..H WILL f%: A MINIMUM OF 5 FEET AWAY FF:DM 15U11.01NC:. l WALL.S I Pl<OPIOR1'{ ecuNOARY) AND TOP a= S~. (::5.} ~IN PIF'E WIlL.. ee rl(iHT' UNEl;1 TO A MINIMUM OF IOfEET ~ m:; l'UILDIN6,. (4;) ALL. ~1R.Uc.nOJ AND MA1ER\ALS SHALL ~e:: ~ SAN [A~O CCUNTY ~ICNAL ~T~DAI<:DS. TYPICAL :;rOIZAQf/ t/J"JPATI~~ 1RENC.~. N.T. S. JONES ~ , , APPENDIX "A" JONES ~ RUNOFF COEFFICIENTS (RATIONAL METHOD) LAND USE Coefficient, C Soil Group 0) , A 8 C D Undeveloped .30 .35 .40 e Residential: Rural .30 .35 .40 .45 Single Family .40 .45 ,SO @ Multi-Units .45 .50 .60 .70 Mobile Homes (2) .45 .50 .55 .65 Commercial (2) .70 .75 .80 .85 80% Impervious Industrial (2) .80 .85 .90 .95 90% Impervious NOTES: (1) Obtain soil group from maps on file with the Department of Sanitat:on and Flood Control. (2) \~'~~e actual conditions deviate significantly from the tabulated ir.J!Je~viousness values of 80% or 90%, the values given for coefficier:: C, may be revised by multiplying 80% or 90% by the ratio of ac:ual ir.lp~rviousness to the tabulated imperviousness. Howe"er. in no (:l:,e sh.111 ::.e final coefficient be less than 0.50. For example: Cons."::::' comr.lercial property on D soil group. Actual imperviousness = 50% Tabulated imperviousness = 80%' Revised C = 50 X 0.85 = 0.53 80 JONES H ( F""d Sooo ~ooo 3000 2000 , 100d -, 900 BOO 700 GOO -lop $"0 2tJO ( /00 .so ~o EGLI/?TION Tc' el;L ..T1.J85 lC. J;m~ 0/ t:onc=Inv'/on L. L~/79/;' 0/ waI~r.s,h~d If. LJ///~~/7C'" i/7 ~/~va..ho/7 a./C/79' dl'<"Cl/y~ 510_ li/7~ (S~~ ~"",n&x 1'-B) ;;. L " M//~$ r~er Nov/-.3 M//7u/~S <I NO 10 as 30 NOTE r.oR~TURALw;.TERS~~ ZO B ADD TEN MINUTES TO COMPUTED TIME OF coj CENTRATION_ =~ . , "- S 00 "- '0- = ,,~ Y,<" '\. "- "- '\. '\. '\. "- / /0 5 \ h' SAN 01 EGO COUNTY DEPARTMENT OF SPECIAL DISTRICT SERVICES DESIGN MANUAL APPROVED .i./.I'. ~/ ,< <J..J..X;:Z, " .3 ISO 2 120 .5 100 '0 eo 70 GO 4 J I !i"tJ z 40 30 , StJOtJ '~~O 20 "- /8 JOOo '\. 1& , I~ 2000 "- "- 1.2 11100 "- /GOO 10 /.roo 9 l.2tJO 8 1000 7 900 800 b 700 btJO 5' 5'00 4- 100 300 .1 1'00 L ~- NOMOGRAPH FOR DETERMINATION OF TIME OF CONCENTRATION (Te) FOR NATURAL WATERSHEDS DATE /2/1/6 9 APPENDIX X-A V-A-IO Rev. 5/El ~ C.3 - I- ~ !- - r....._ - ~ I.l.J @: a.. -C:: ~ ...,.; o :!: I c.o l::::: ~ I.r..J >- I o o - ... 5 - I- 0;:: '" - .., - -- Q~ :z....-l ":00 '" '" ....1-1- OZ=:: ..,0 >-~u t:"'Q ::;:<0 _"-0 Q..,-l uc.... c::: ::l o - -- , (0 c:::: cz: LI..l >- , c:::l Q ...- Ll.. o en ....I c:: - :> ::l . - 0... o en - c~_ - \ = ...... l . :i /' _0 /g /, ,- u z . ~ " - '^ -7 - o "" '^ - '^ -7 . "" "" Revised 1/8S . , I '" '^ o "" . .... '^ w U S' '" w " '" w zi: 0< -w ~a ,"oJ -laJ ... .. 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