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Home My WebLink AboutSDP 2023-0025; GRAND HOPE MEDICAL OFFICE; HYDROLOGY / HYDRAULICS LETTER; 2023-08-28PL SA Civil Engineering Lond Planroing Surveying + Mapp(r>g August 28, 2023 PLSA 4037 City of Carlsbad Development Services Department -Engineering l 635 Faraday A venue Carlsbad, CA 92008 RE: HYDROLOGY/ HYDRAULICS LETTER FOR 2879 HOPE AVENUE DEVELOPMENT I APN: 203-202-13-00)-CT-2023-00XX & SDP 2023-00XX The purpose of this letter is to address the hydrology and water quality components of the proposed improvements associated with the above referenced property and proposed development. The project will consist of the demolition of the existing dental office building and parking lot, and associated improvements currently located onsite and the construction of two story medical office building at 2879 Hope A venue located northwest of the intersection of Grand Avenue and Hope A venue in Carlsbad, California. The total site area is approximately 7,000 square feet (0.16 acres). The site is bound by private residential apartments to the west and north, Hope Avenue to the east, and Grand A venue to the south. HYDROLOGY The existing condition of the sites consists of approximately 5.4 78 square feet of impervious area on site and has no storm water treatment or detention facilities. The existing site can be categorized into one major drainage basin, with two sub-basins and two primary discharge locations leaving the property. Drainage Basin EX-I consists of most of the project site and primarily drains south to north discharging to Hope A venue right-of-way by surface and sheet flow methods. Once in Hope Avenue right-of-way, runoff leaving the site travels northwest to the Home Avenue intersection. Runoff then travels southwest to the Jefferson Street intersection and then Southeast along Jefferson Street until it is intercepted by a ribbon gutter on Grand A venue where an existing storm drain inlet is located. Drainage Basin Ex-2 is a small portion of the site where excess runoff drains onto Grand Avenue. Once in the Grand Avenue right-of-way, runoff travels southwest entering the same existing storm drain inlet. Surface flows entering the existing storm drain inlet ultimately are conveyed to outlet in the Buena Vista Lagoon prior to entering the Pacific Ocean. The post-developed project will consist of approximately 6.270 square feet of impervious surface, a net difference of 792 square feet when compared to existing condition. There will be one site outfall on Hope Avenue and one site outfall on Grand Avenue. Runoff will maintain the current discharge patterns, and the ultimate outfall for the entire site will remain at the existing inlet on Grand A venue. The total new plus replaced impervious area is 6,270 square feet and is therefore classified as a standard development project. Additionally, the project dispersion and maximized pervious area on-site to mitigate impacts to the off-site stormwater infrastructure. San Diego I Encinitas I Orange County www. plsaeng i neering ,com due to the increase of impervious areas, however this is an insignificant change for the existing infrastructure. Refer to the pre-and post-project hydrology maps attached to this report for more information on site drainage patterns and discharge locations. Please call if you have any questions. Sincerely, Bryan Knapp, PE Project Manager ,.. No. 86542 E,p. 03/31 /25 San Diego I Encinitas I Orange County www.plsaengineering.com PL SA Civil Engineering Lcind Planning surveying+ Mopping ( 0.25 (532 sf}+ 0.90 (1,017 sf}) C,, = 1.549 sf = 0•68 Cn = 0.68 l = 7.44 x P6 X o-OM5 P6 = 2.5 in D =Tc= 5.0 minutes * l 00-Year, 6-Hour Rainfall Precipitation per SOHM *Minimum Time of Concentration for Intensity SOHM I = 7.44 X 2.5 in X s.o-0 645 = 6.59 in/hr I= 6.59 in/hr Q-C IA Q100 = 0.68 * 6.59 in/hr* 0.03 acres Q100 = 0.13 cfs San Diego I Encinitas I Orange County www .plsaengi nee ring .com PL SA CM"""'"'"'"" Land Pkmn!ng survevlng-+-Mapping P6=2.5 in SOHM * I 00-Year, 6-Hour Rainfall Precipitation per D =Tc= 5.0minutes *Minimum Time of Concentration for Intensity SOHM I = 7.44 x 2.5 in x 5.o·0 645 = 6.59 in/hr I = 6.59 in/hr o~c I A Q100 = 0.84 * 6.59 in/hr* 0.7 acres Q100 = 0.38 cfs PRE-VERSUS POST-FLOW ANALYSIS: Q100 EX-I (Pre-Project)= 0.67 cfs Q100 EX-2 (Pre-Project)= 0.13 cfs Q100 Total (Pre-Project)= 0.8 cfs Qioo BASIN I (Post-Project)= 0.49 cfs Q100 BASIN 2 (Post-Project)= 0.38 cfs Q1oo Total (Post-Project)= 0.87 cfs 6. Q ioo == 0. 07 cfs San Diego I Encinitas I Orange County www.p1saengineering.com HOPE AVENUE ---------------------------- PLSA -PLUI IODII / / / EX 3 ST DRY MUI. n UNIT HOUSING PARCEL t PM32f0 APN: 20:J.202-f!f~ / M l1fW • Ql!SwtG DRAINAGE lfAI' SCAI.E. r• WHOl¥1l:KfN. f / I I I I LEGEND .DISTl'GJ¥IOl'SIJYICUCl,,W' ~MCPflfTY&.IEIIIGHT..o:.wAY ---- ct-Jl1F/I.H.t'IMJNJ .,..,..,_, ADJM:Bffi.OTUNf. --~DN1ffLINE Jlrllt0Po&fDMfe11(WOf-R.f)tl( EJOS1N.DIIWNICiGES&Sl'/IIII/OOICINtr • ---• ..................... f;S::-,",~ AAEA CALCUI.ATIOIIS • TOT/IL BASIN MSINTDTAlAREA , .• SI' ---... ,, ---t,JnY . --, ... "' •• AAEA CAI.CUI.A TIO/IS • BASIN EX• I MSl'H JOTM. ME.A ldl~ BASNAflEPMOtSND Uff# ---"'" • ........... "'" "' on ///!EA CALCUI.ATIONS-BASIN EX-2 MSINJWM.ME.\ , ...... ---1,t1ISF ---"'" • ........... "-"' "' ON GfWIIICtc'.lil!r•W ' ING DRAINAGE MAP GRAND HOPE ~.U.NWIB.«»1 ,a' !t.AI..E·f'•to' I 011n:·tml101J SHEET1 OF2 HOPE AVENUE -------------- Ii'! : ~ ~ 9f2 PLSA -Ra.I I OW t ------ / --------- / / EX 3 STORY 11Ut. TI UMTHOIJSING PARCEL 1 PM3250 APN: 203-202-13/f / PLAN mw · PRreosED PM'tWi€ we SCN.E.1"•WIIQIIZCWl'At / I I I I I I I I _______ J~ .. ',·_. . ,• ••,· """"'-o,-.o,CFS I I I I I I LU I ::::,1 ~I o ' <'. I ~ ~I I 1 I I I I I 1 I I I Em11Gl'ROPflf'fYI/OJHll,IN ADJltt:9(T~TYUIEJIIIGHP'.a:.w.Y <ENn1UE<Y'"""' --NJN;IHf&.Orl.M ---"""' .... ~ORECOOHOFHDW ~~--l!JO.NJN'fr ---■---· ~~ AAEA CALCULATIONS. TOTAL BASIN AAEA CAI.ClllAT70tlS • BASIN 1 M$aH10ToltltlfEA .,.,,,, ----J.flfSF ---''"' • -.... " '" AR.EA CALCU!ATIOHS -BASIN 2 ' "' ,,, '"'"------ 114$1Nll)fAI.MEA ...,, ... ---""" ---'"'' • " """"""" .,,. "' \ OSED DRAINAGE MAP GRAND HOPE ,11(,SAJQIA.IIIER ;,#OJ7 ,er SCM.E·r •W I lM.1'E~"2S1»11 SHEET 2 OF2 3.1" 9'4TN "' i 2 ,.. ::I Hydrologic Soil Group-San Diego County Area, California Map Scale: 1:297 f prttl!ld O'I A pc,17ait {BS x 11 ") sheet. N ----====--------=======,Meiers :a4 0 4 8 16 A ---====------=====::ifett o 10 ~ ~ m Map projedlon: Web MeltzlUlr Caneramlnates: WGS84 fdgellcs: VTM Zaie UN WGS84 Natural RNOUFCN Conservation Service Web Soil Survey National Cooperative Soil Survey "' ~ 2 ,.. ::I 8/23/2023 Page 1 of4 3.l"!l'49"N 3.l"9'4TN Hydrologic Soll Group-San Diego County Area, California MAP LEGEND MAP INFORMATION A,.a of lnte,.at (AOI) D Area of Interest (AOI) Solla Soll Rating Polygon• D A D AID DB 0 B/0 D C D CID D o D Not rated or not avaR•ble Soll Rating Linea -A -AID -8 -BID ~ C -C/0 -0 . . Not rated or not avaHable Soil Rating Polnta a A Iii AID • 8 ■ BID Natural Resources Conservation Service C C C CID Cl 0 □ Not rated or not available Watat-Futurn Streams and Canals Tranaportatlon H-+ Rails -Interstate Highways _,,, US Routes Major Roads Local Roads Background • Aerial Photography Web Soil Survey National Cooperative Soll Survey The soil surveys that comprise your AOI were mapped at 1:.24,000. warning: Soll Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause mlsunder,tandlng of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, 'Milch preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date{s) listed below. Soll Survey Area: San Diego County Area, California Survey Area Data: Version 18, Sep 14, 2022 Soil map units are labeled (as space allows) for map scales 1 :50,000 or larger. Date(s) aerial images were photographed: Mar 14, 2022-Mar 17,2022 The orthophoto or other base map on 'Mlich the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. 8123/2023 Page 2 of 4 Hydrologic Soil Group-San Diego County Area, California Hydrologic Soil Group I Map unit symbol I Map unit name Rating Acres inAOI Per'Cent ofAOI I ~ MIC Marina loamy coarse B 0.2 sand, 2 to 9 percent slopes Totals for Area of Interest 0.2 Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (AID, BID, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (AID, BID, or CID), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 100.0% I 100.0% I 8/23/2023 Page 3 of 4 Hydrologic Soil Group-San Diego County Area, California Component Percent Cutoff: None Specified Tie-break Rule: Higher Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/23/2023 Page 4 of 4