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Home My WebLink AboutCT 2017-0007; TAMARACK BEACH HOMES; HYDROLOGY STUDY; 2018-08-30---.. -.. .. --.. .. .. .. .. -.. -.. -----.. -------------- HYDROLOGY STUDY FOR TAMARACK BEACH HOMES 438 TAMARACK A VENUE SEP 19 20iJ L.r-\1\j[' OE VELO; .. ,' 1 •=N··· .••• I ENGl1\IEERING CT 2017-0007 / CDP 2017-0075 / PUD 2017-0006 CITY OF CARLSBAD, CA PREPARED FOR: TOURMALINE PROPERTIES 2079 GARNET A VENUE SAN DIEGO, CA 92109 PREPARED BY: r ,,,~· -. PASCO LARET SUITER & ASSOCIATES, INC. 535 N. HIGHWAY 101, SUITE A SOLANA BEACH, CA 92075 PH: (858) 259-8212 Prepared: September 20, 2017 Revised: July 31, 2018 Revised: August 30, 2018 G7:AWSON, RCE 80356 DATE -----1 1 RE_C_O_RD-~0~ \ (JG-~ ~ \ \ ~--Oat 1 Imtial . --· · L.----~----- -.. -.. -... -... --------- ---.. -.. -------------- Executive Summary Introduction Existing Conditions Proposed Project Conclusions References Methodology Introduction TABLE OF CONTENTS County of San Diego Criteria City of Carlsbad Standards Runoff Coefficient Determination Hydrology & Hydraulic Model Output Pre-Developed Hydrologic Model Output (JOO-Year Event) Post-Developed Hydrologic Model Output (JOO-Year Event) Detention Analysis ( I 00-Year Event) Appendix Appendix A: Hydrology Support Material PLSA 2760-01 SECTION 1.0 I. I 1.2 1.3 1.4 1.5 2.0 2.1 2.2 2.3 2.4 3.0 3.1 3.2 3.3 4.0 ---.. -.. -... ---.. ---... -.. -.. -.. -.. -.. -.. ---------- PLSA 2760-01 1.0 EXECUTIVE SUMMARY 1.1 Introduction This Hydrology Study for the proposed development at 438 Tamarack Avenue has been prepared to analyze the hydrologic and hydraulic characteristics of the existing and proposed project site. This report intends to present both the methodology and the calculations used for determining the runoff from the project site in both the pre-developed ( existing) conditions and the post-developed (proposed) conditions produced by the 100- year, 6-hour storm. 1.2 Existing Conditions The subject property is located just north of Tamarack Avenue, and is geographically settled between the Coastal Rail Trail and railroad tracks to the west, and Hibiscus Circle, a public street, to the east. The site is bordered by Tamarack Avenue to the south, and Nautical Drive, a private road, to the west and north. A small strip of open space abuts the property to the east, belonging to a parcel that is part of the existing residential development north of the property. The existing site consists of a single-family residence, with a driveway, hardscape, and landscape improvements typical of this type of development. The property is located within the Carlsbad watershed, and, more specifically, the Agua Hedionda Lagoon Hydrologic Area. The existing site is comprised of approximately 0.405 acres. The tributary drainage basin extends beyond the site limits and is approximately 0.45 acres, generally draining in an east to west direction across the property. There does not appear to be any existing storm drain infrastructure located onsite to convey drainage, and runoff sheet flows through the site to the western property line. To the north of the property, existing curb, gutter, and sidewalk improvements prevent offsite runon from entering the site. Drainage does not enter the property from the west, as it is downstream of the subject parcel. Lastly, curb, gutter, and sidewalk improvements in the right-of-way along Tamarack Avenue prevent drainage from entering the site to the south. Runoff leaves the site to the west, where it enters existing public storm drain infrastructure in Tamarack Avenue, and is conveyed south alongside the railroad tracks before ultimately outletting in the Agua Hedionda Lagoon and the Pacific Ocean. The 0.45-acre drainage basin for the subject property can be broken down into two minor drainage basins in the existing condition with two discharge locations from the site. Basin A consists of the northern half of the existing structure as well as the entire rear yard, and is approximately 0.34 acres in size and 27.7% impervious. Basin B contains the southern half of the existing residence as well as the front yard, and is approximately 0.11 acres in size and 81.3% impervious. Per the Web Soil Survey application available through the United States Department of Agriculture, the area is generally categorized to have group B soils. Based upon soil type and the amount of existing impervious area onsite, a runoff coefficient of0.43 was calculated for Basin A and 0.78 for Basin Busing the methodology described in section 3.1.2 of the San Diego County Hydrology Manual and the formula Page 1 of 10 ---------.. -----------.. -.. -.. .. .. ---------- PLSA 2760-01 provided therein. Using the Rational Method Procedure outlined in the San Diego County Hydrology Manual, a peak flow rate and time of concentration was calculated for each basin for the 100-year, 6-hour storm event. The peak flow rate for the 100-year, 6-hour storm for Basin A was determined to be 0. 73 cfs with a time of concentration of 7. 7 minutes, discharging to Nautical Drive (a Private Road) to the west before entering a storm drain curb inlet just south where it is conveyed west via an existing public storm drain. The peak flow rate for the 100-year, 6-hour storm for Basin B was determined to be 0.57 cfs with a time of concentration of 5.0 minutes that discharges into the Tamarack Avenue curb and gutter to the southwest and travels west offsite. While the two minor drainage basins discharge to two separate storm drain systems in Tamarack Avenue & Nautical Drive, both systems discharge to an existing 84" RCP storm drain approximately 200 feet downstream and are conveyed south to the Agua Hedionda Lagoon. Refer to pre- development hydrology calculations included in Section 3.1 of this report for a detailed analysis and the pre-development hydrology map included in Appendix A of this report for existing drainage basin delineation and discharge locations. 1.3 Proposed Project The proposed project includes the demolition of all onsite structures and the construction of five multi-family, detached condominium units with a shared access driveway, and various hardscape and landscape. Site grading along with drainage and utility improvements typical of this type of residential development will also be constructed. The proposed pad elevations range from elevation 46.7 at the northwesterly end of the property to 48.8 at the southeasterly end of the subdivision. Runoff from the proposed development will primarily drain from east to west to mimic existing drainage conditions and the existing onsite topography. A majority of the site and the entirety of the proposed impervious areas will be routed away from proposed structures to a series of storm drain inlets located in the front, side, and rear yards. Private drain pipes will collect all runoff entering each inlet and will route to a centrally located 8" PVC storm drain in the drive aisle. The 8" PVC line will route all onsite drainage south through the site before connecting to the existing storm drain in Tamarack Avenue. The project site will continue to accept runoff from the parcel to the east, as the limits of the proposed drainage basin remains exactly the same as in the pre-developed condition . Onsite infrastructure has been sized to account for this additional drainage, while improvements along the east property line have been designed to convey the runon. Similar to the existing condition, the analyzed watershed can be broken down into two minor drainage basins with two separate discharge locations from the site. Basin A consists of the majority of the property equal to approximately 0.40 acres in size and 48. 7% impervious. Proposed drainage basin B consists of graded slopes in the front of the property, as well as a portion of the drive aisle and walkways sloping toward Tamarack Avenue, and is approximately 0.05 acres and 14.3% impervious. Based upon soil type and the amount of proposed impervious area onsite, a runoff coefficient of 0.57 was calculated for Basin A and 0.34 for Basin Busing the methodology described in section 3.1.2 of the San Diego County Hydrology Manual and the formula provided therein. Using the Page 2 of 10 -.. -.. .. ----.. ------------,. ---.. ----------- PLSA 2760-01 Rational Method Procedure outlined in the San Diego County Hydrology Manual, a peak flow rate and time of concentration was calculated for the post-development I 00-year, 6- hour storm event. The peak flow rate for the I 00-year, 6-hour storm for Basin A was determined to be 1.10 cfs with a time of concentration of 8.15 minutes discharging to the existing 24" RCP storm drain in Tamarack Avenue. The peak flow rate for the I 00-year, 6-hour storm for Basin B was determined to be 0.12 cfs with a time of concentration of 5.0 minutes, discharging on the surface in the Tamarack Avenue curb and gutter to the southwest and traveling west offsite. While the proposed minor drainage basin A discharges to a separate storm drain system in Tamarack Avenue from existing drainage basin A, it can be considered a local diversion, as both flows enter an existing 84" RCP storm drain approximately 200 feet downstream and are conveyed south to the Agua Hedionda Lagoon. Refer to post-development hydrology calculations included in section 3.2 of this report for detailed analysis and the post-development hydrology map in Appendix A of this hydrology report for proposed drainage basin delineation and discharge locations. In an effort to comply with the City of Carlsbad's storm water standards for Standard Development Projects, the project site will implement source control and site design ~BMP's where feasible and applicable in accordance with the City of Carlsbad's BMP Design Manual, February 2016 edition. All runoff generated from proposed roofs and hardscape areas will be directed to landscaped areas and grassy swales to disperse drainage onto pervious surfaces. A pervious pavement material is proposed for the drive aisle to minimize proposed impervious area, soil compaction, and promote dispersion. Partial infiltration and evapotranspiration in landscaped areas will assist in slowing peak discharges and in reducing total volume generated during storm events. The drive aisle and onsite landscaped areas will remove sediment and particulate-bound pollutants from storm water prior to leaving the project site. 1.4 Conclusions The proposed project is able to decrease the total peak runoff generated by the I 00-year, 6-hour storm event from 1.30 cfs in the pre-developed condition to 1.22 cfs leaving the project site by increasing the overall flow path and time of concentration for the onsite drainage basin. Implementing various site design BMP's such as a pervious paver drive aisle assist to further reduce the post-developed hydro logic runoff coefficient and volume of discharge. While additional runoff is routed to the 24" RCP storm drain in Tamarack A venue, the existing infrastructure has the capacity to handle the slight increase in demand due to the proposed project. This can also be considered a microdiversion, as runoff leaving the site from both discharge locations comingle several hundred feet downstream. All proposed onsite infrastructure including storm drain piping and area drains have been adequately sized with enough capacity to intercept and convey peak runoff of I. IO cfs generated onsite. Additional calculations and analyses including private storm drain pipe capacity can be found in the Appendix. Based upon the analysis included in this report, the proposed onsite drainage system is adequate to capture and convey runoff from the proposed project and discharge to the appropriate discharge locations. Page 3 oflO -.. ---... -.. --.. --.. -... ----.. .. .. • .. -.. .. .. .. .. .. ---.. -- PLSA 2760-01 1.5 References "San Diego County Hydrology Manual", revised June 2003, County of San Diego, Department of Public Works, Flood Control Section. "San Diego County Hydraulic Design Manual", revised September 2014, County of San Diego, Department of Public Works, Flood Control Section "Engineering Standards, Volume 5: Carlsbad BMP Design Manual", revised February 2016, City of Carlsbad Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov. Page 4 of 10 -... .. --.. .. -.. .. -.. -... ----.. --... .. • -.. .. -.. -------- PLSA 2760-01 2.0 METHODOLOGY 2.1 Introduction The hydrologic model used to perform the hydrologic analysis presented in this report utilizes the Rational Method (RM) equation, Q = CIA. The RM formula estimates the peak rate of runoff based on the variables of area, runoff coefficient, and rainfall intensity. The rainfall intensity (I) is equal to: Where: 1 = 7.44 x P6 x 0·0645 I = Intensity (in/hr) P6 = 6-hour precipitation (inches) D = duration (minutes -use Tc) Using the Time of Concentration (Tc), which is the time required for a given element of water that originates at the most remote point of the basin being analyzed to reach the point at which the runoff from the basin is being analyzed. The RM equation determines the storm water runoff rate (Q) for a given basin in terms of flow (typically in cubic feet per second (cfs) but sometimes as gallons per minute (gpm)). The RM equation is as follows: Where: Q=CIA Q = flow (in cfs) C = runoff coefficient, ratio of rainfall that produces storm water runoff (runoff vs. infiltration/evaporation/absorption/etc) I = average rainfall intensity for a duration equal to the Tc for the area, in inches per hour. A= drainage area contributing to the basin in acres . The RM equation assumes that the storm event being analyzed delivers precipitation to the entire basin uniformly, and therefore the peak discharge rate will occur when a raindrop that falls at the most remote portion of the basin arrives at the point of analysis. The RM also assumes that the fraction of rainfall that becomes runoff or the runoff coefficient C is not affected by the storm intensity, I, or the precipitation zone number. Page 5 of 10 .. .. .. "" .. .. -.. ... .. -.. ----.. -.. -• .. • -.. .. -.. ------- PLSA 2760-01 2.2 County of San Diego Criteria As defined by the County Hydrology Manual dated June 2003, the rational method is the preferred equation for determining the hydrologic characteristics of basins up to approximately one square mile in size. The County of San Diego has developed its own tables, nomographs, and methodologies for analyzing storm water runoff for areas within the county. The County has also developed precipitation isopluvial contour maps that show even lines of rainfall anticipated from a given storm event (i.e. I 00-year, 6-hour storm) . One of the variables of the RM equation is the runoff coefficient, C. The runoff coefficient is dependent only upon land use and soil type and the County of San Diego has developed a table of Runoff Coefficients for Urban Areas to be applied to basin located within the County of San Diego. The table categorizes the land use, the associated development density ( dwelling units per acre) and the percentage of impervious area. Each of the categories listed has an associated runoff coefficient, C, for each soil type class. The County has also illustrated in detail the methodology for determining the time of concentration, in particular the initial time of concentration. The County has adopted the Federal Aviation Agency's (FAA) overland time of flow equation. This equation essentially limits the flow path length for the initial time of concentration to lengths under I 00 feet, and is dependent on land use and slope. 2.3 City of Carlsbad Standards The City of Carlsbad requires a Hydrology Study be completed for projects larger than !- acre per Form P-2: Development Permits. The City of Carlsbad has additional requirements for hydrology reports which are outlined in the Grading and Erosion Control Ordinance. Please refer to this manual for further details. 2.4 Runoff Coefficient Determination As stated in section 2.2, the runoff coefficient is dependent only upon land use and soil type and the County of San Diego has developed a table of Runoff Coefficients for Urban Areas to be applied to basin located within the County of San Diego. The table, included at the end of this section, categorizes the land use, the associated development density ( dwelling units per acre) and the percentage of impervious area . Page 6 of 10 .. .. -,.. --- -.. .. --.. ... --.. .. .. ... -.. -.. .. -.. --- -- PLSA 2760-01 3.0 HYDROLOGY MODEL OUTPUT 3.1 Pre-Developed Hydrologic Model Output (100 Year Event) Pre-Development: *Rational Method Equation Q=CIA P100= 2.5 *JOO-Year, 6-Hour Rainfall Precipitation Basin A (Drainage Basin to Storm Drain) Total Area= 14,750 sf-+ 0.34 Acres Impervious Area= 4,088 sf-+ 0.09 Ac Pervious Area= I 0,662 sf-+ 0.25 Ac Cn, Weighted Runoff Coefficient, -0.25, Cn value for natural ground, Type B Soils *Per San Diego Hydrology Design Manual (SDHDM) Section 3.1.2 -0. 90, Cn value for developed/impervious surface *Per SDHDM Section 3.1.2 Cn = 0.9 x 4,088 sf+ 0.25 x 10,662 sf= 0.43 14,750 sf Tc= ti+ tt ti@ 80'= 2.0% => 6.5 min from Table 3-2 of SDCHM for ~14.5 DU/Ac tt => L = 92' 11E = 1.6' tt= [ { I \.9(L/5,280)"3 }/11E]A0.385 tt= [ { 11.9(92/5,280)"3 }/I .6JA0.385 = 0.020 0.020 x 60 = 1.2 Min . Tc= 6.5 + 1.2 = 7.7 Min P6= 2.5 r = 7.44 x P6 x D·0645 I= 7.44 x 2.5 x 7.7·0645 "" 4.98 in/hr Iioo"" 4.98 in/hr Q10o=C*I*A Q100 = 0.43 x 4.98 in/hr x 0.34 Ac= 0.73 cfs Page 7 ofl0 -.. .. ---- .. -.. .. -.. ------.. ... -,. -------------- PLSA 2760-01 Basin B (Southern Drainage Basin to Tamarack Avenue) Total Area= 4,923 sf ➔ 0.11 Acres Impervious Area= 4,002 sf ➔ 1.68 Ac Pervious Area= 921 sf ➔ 1.39 Ac Cn, Weighted Runoff Coefficient, -0.25, Cn value for natural ground, Type B Soils *Per San Diego Hydrology Design Manual (SDHDM) Section 3.1.2 -0.90, Cn value for developed/impervious surface *Per SDHDM Section 3.1.2 Cn = 0.9 x 4,002 sf+ 0.25 x 921 sf= 0.78 4,923 sf Tc= 5.0 Min *Minimum Tc per SDCHM r = 7.44 x P6 x D-0645 I = 7.44 X 2.5 X 5.o-0 645 "' 6.59 in/hr 1100"' 6.59 in/hr Q10o=C*I*A Q100 = 0.78 x 6.59 in/hr x 0.11 Ac= 0.57 cfs Page 8 of 10 .. .. -... -------.. -... --- -- .. --.. .. ------------ PLSA 2760-01 3.2 Post-Developed Hydrologic Model Output (100-Year Event) Post-Development: *Rational Method Equation Q=CIA P100 = 2.5 *JOO-Year, 6-Hour Rainfall Precipitation Basin A (Drainage Basin to Storm Drain in Tamarack) Total Area= 17,293 sf+ 0.40 Acres Impervious Area= 8,423 sf+ 0.20 Ac Pervious Area= 8,870 sf+ 0.20 Ac Cn, Weighted Runoff Coefficient, -0.25, Cn value for natural ground, Type B Soils *Per San Diego Hydrology Design Manual (SDHDM) Section 3.1.2 -0.90, Cn value for developed/impervious surface *Per SDHDM Section 3.1.2 Cn = 0. 9 x 8,423 sf+ 0.25 x 8,870 sf= 0.57 17,293 sf Tc=Ti+Tt Ti= 6.5 min *Per SDCHM Table 3-2 for -14.5 DU/Ac Tt = ITtt + Tt2 + Tti -11.9 (siso ft) (1.49(R2/351/2)1 ( 7 5 ft 3) 0 · 385 Tt -1.2 ft + 110.0ft/ 0.013 ( 1.49(R2/3 51/2)1 + 48.0ft/ 0.013 Th= I 10 ft/ (*4.21 ft/s) = 0.435 min Tti = 48 ft/ (*4.21 ft/s) = 0.190 min *Velocity/ travel time though 6" PVC pipe *Velocity/ travel time though 6" PVC pipe Tt = (0.017 hrs+ 0.007 hrs+ 0.003 hrs) x 60 min= 1.65 min Tc= Ti+ Tt = 6.5 min+ 1.65 min= 8.15 min P6= 2.5 1 = 7.44 x P6 x D·0645 I= 7.44 X 2.5 X 8.15·0645 z 4.81 in/hr Q100= C*l*A Q100 = 0.57 x 4.81 in/hr x 0.40 Ac= 1.10 cfs Page 9 oflO -.. ---------.. -... ----... -.. • .. -.. ---.. ---... ----.. Basin B (Drainage Basin to Tamarack Avenue) Total Area= 2,379 sf-+ 0.055 Acres Impervious Area= 341 sf-+ 0.0 I Ac Pervious Area= 2,038 sf-+ 0.045 Ac Cn, Weighted Runoff Coefficient, -0.25, Cn value for natural ground, Type B Soils PLSA 2760-01 *Per San Diego Hydrology Design Manual (SDHDM) Section 3.1.2 -0. 90, Cn value for developed/impervious surface *Per SDHDM Section 3.1.2 Cn = 0.9 x 341 sf+ 0.25 x 2,038 sf= 0.34 2,379 sf Tc= 5.0 Min *Minimum Tc per SDCHM 1 = 7.44 x P6 x D-0645 1 = 7.44 x 2.5 x 5.o-0645 cc 6.59 in/hr I IOO cc 6.59 in/hr Q100 = C*l*A Q100 = 0.34 x 6.59 in/hr x 0.055 Ac= 0.12 cfs Pre-Development vs. Post-Development (Undetained-Total Site Runoff) Pre-Development (Basin A) Q100 = 0. 73 cfs Pre-Development (Basin B) _Q100 = 0.57 cfs Pre-Development {Total Site) Q 100 = 1.30 cfs Post-Development (Basin A) Q100 = 1.10 cfs Post-Development (Basin B) Q100 = 0.12 cfs Post-Development {Total Site) Q100 = 1.22 cfs Delta 0.37 cfs Delta -0.45 cfs Delta *-0.08 cfs *Total overall site runoff reduced in proposed condition from pre-development Page 10 of 10 3: Hydrologic Soil Group-San Diego County Area, California 3: ~ ~ r.i r.i ~ ~ 4681:Il 46814) 46813) 468100 <68110 46818) 468100 4fE!X) 468210 468220 46BZJ) 4€824) E82S) -4E8210 -4E82g) 33"9':J'N I I 33" 9':J'N I I I I i i I I 0 I i i i I I I I I I 33" 8'99"N I I 33" 8'99"N 4681:Il 46814) 46818'.l 46818'.l 468110 46818) 468100 45l!a:XI 468210 468220 46BZJ) 4E824l 4E823) -4E8210 -3: 3: !;\ Map Scale: 1: 74 lf Jmb:d on A landscape ( 11" X 8.5") sheet ~ r.i Meiers r.i ~ N 0 10 20 40 8) ~ ~ Feet 0 35 70 140 210 Map~: W!b Mercator Comeraxmnates: WGS84 Edge tics: U11'1 Zooe 1 lN WGS84 USDA Natural Resources Web Soil Survey 9/6/2017 --Conservation Service National Cooperative Soil Survey Page 1 of 4 Hydrologic Soil Group-San Diego County Area, California MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons D A D AID DB 0 BID □c □ CID D D D Not rated or not available Soil Rating Lines -A -AID -B -BID C -CID -D .. ; Not rated or not available Soil Rating Points ■ A ■ AID ■ B ■ BID !,!SDA Natural Resources ..-Conservation Service Cl C ■ CID ■ D □ Not rated or not available Water Features Streams and Canals Transportation +++ Rails -Interstate Highways -US Routes MaJor Roads Local Roads Background • Aerial Photography Web Soil Survey National Cooperative Soil Survey The soil surveys that comprise your AOI were mapped at 1 :24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil I 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, which 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. Soil Survey Area: San Diego County Area, California Survey Area Data: Version 10, Sep 12, 2016 Soil map units are labeled (as space allows) for map scales 1 :50,000 or larger. Date(s) aerial images were photographed: Nov 3, 2014-Nov 22, 2014 The orthophoto or other base map on which 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. 9/6/2017 Page 2 of 4 Hydrologic Soil Group-San Diego County Area, California Hydrologic Soil Group Hydrologic Soll Group-Summary by Map Unit -San Diego County Area, California (CA638) Map unit symbol I Map unit name I Rating I Acres In AOI I Percent of AOI MIC Marina loamy coarse B sand, 2 to 9 percent slopes 1.0 Totals for Area of Interest 1.0 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 CID). 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 C/D), 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% 100.0% 9/6/2017 Page 3 of 4 Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 30® by Autodesk, Inc. Monday, Feb 12 2018 8-in PVC Pipe Capacity Circular Diameter (ft) Invert Elev (ft) Slope(%) N-Value Calculations Compute by: Known Depth (ft) Elev (ft) 0 = 0.67 = 40.00 = 1.00 = 0.013 Known Depth = 0.66 Highlighted Depth (ft) = 0.66 Q (cfs) = 1.224 Area (sqft) = 0.35 Velocity (ft/s) = 3.47 Wetted Perim (ft) = 2.10 Crit Depth, Ye (ft) = 0.53 Top Width (ft) = 0.00 EGL (ft) = 0.85 8" PVC pipe at 1.0% has capacity (1 .22 cfs) to convey peak runoff generated onsite of 1.1 cfs. Section Reach (ft) 1"'?,;~ i,c: \,\:I_\ ~?1--------r-4 s ··--- 1 \ I <J) I <J) I \ <J) \ <J) ~ ' / , / / \/ / V i I /,,2 / / f / / \ \/ I t, I I r\ I (fJ lJ_,_· (j) \~_A ,I I ,_,, I ', ! I I I \ I ' \ ' <J) \ \ <J) I \ <J) \ ' I \ i (j) z / POR. 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TP ·1-P '·) \.:5.8 / \ NODE'A.3 /45.TFG) .-. _.-, /. 46 0\ :c 460 -,-45.9 Q10()'~ Q.73 CFS ' • • /7 \ ~~----1 ':'. 45.8 .---- I I ,,,-, ____ .~,.-,. • NAUTICAL DRIVE s (PRIVA fE ~; 45."S .,.i ,,.-/ ·--".-· 75·· TP.· ', "· \ 46 · : .f,G-,; -~ifl· .:,..;__;,, s,••oJ ~-iC, ...,_, -- 438 TAMARACK AVENUE s --· --s ·----· s -------s s s "1 P, iLlt· ·) ·-· . -· :{ 45.3 --y----- 71,--; r:9 l!.•i (!!:ct, -=~,=--~--, .. -.. -.. ·--· ·-··-..... , ....... ----·--------- X 4o.G ---------·----I, ·---•---,'\ ;_-. '",•. " _,,,----~ X 4f!7 ... ,,, • / BAS/NA ;; 45 8 AREA = 14,750 SF (0.34AC) Cri.'.."/J43 \ 47-: 146.8 NODEA2 47.3 FG s --···-·-s :'J :-so C·,:r, <~ "1'":,a;J· 2.0 ,---. :--l_u.. : --"='•;:::'-~·:·· .. , ' '-v:: -~:......;,-_4'!--:~-. _-, __ _ ' _ _, 47.0 ----s "\47 2 i\ ... ----------A -----------A .,...._ __ ._ A _____ ,,,_ .. , •.•. 7._: ------· X. X -'70 -3' TC :: 47.3 ,: 4? 3 ;< 47 8 12-i-e,-p <: 48.6 /478 >'. 48.4 -~, ·ro·· .. ,, ·--,-- W TP) X I ---{··~--I -~-v I I ~I POR. LOTS , 48 ,MAP ~825 .,,// ' ! ' ' , ' ' \ \t'\ \\ \ XL81 X .::.8.3 • • • X i7.1 • ?< 46.6 :<: 46.8 L -i , , 17k 3 ·,, 46.7 -----····--··-r·-~---· ,, I ' TAMAR~CK AVENUE ,, PLAN VIEW -EXISTING HYDROLOGY SCALE: 1" = 10' • • ;< 47.3 \4I.8 / I X47 6 " .,. ' / l .:i'Cr TP " • 12" TP, " / 12' TP ("'; X X 1.- 'I X ""'>··--/-/ \. ' " "' ' \ e:· TP n ·,...,_ \-:,✓,'' ·-· ¼--c_: __ •• --::,.___ ___ ~ -·-..,_ __ ;'. .,j"j' s ; I ' '· '·" X 48.9 L ·. X 4-8 2 • X4b./ ;,: 49 2 ---~- :.,,~~~~~-: __ "'' : 1-=c. !:,.(4---I'-.L I , -.,--.. -...1.00 • < / , ' ',[ 48.5 / ( • • X 48.S '/ 49.3 X4fL3 1.45.6 NODEA1 ~ )( 48 8 X 49-. l / ' / ( ;, 1')" ~- \ i \ I I X 48.7 •·,: I ,: i J-;4E}l X 48. i i/ ;·--~-/.. 49.2 ; --~,--/ / /. ·! -)~ 49.2 I j ; !, -,, I{:' // LEGEND EXISTING PROPERTY BOUNDARY ADJACENT LOT LINE I RIGHT-OF-WAY CENTERLINE OF STREET DRAINAGE BASIN BOUNDARY EXISTING CONTOUR LINE EXISTING FLOW PATH EXISTING DRAINAGE DIRECTION EXISTING IMPERVIOUS AREA BASIN A -AREA CALCULATIONS BASIN A TOTAL AREA BASIN A IMPERVIOUS AREA BASIN A PERVIOUS AREA % IMPERVIOUS Cn BASIN B-AREA CALCULATIONS BASIN B TOTAL AREA BASIN B IMPERVIOUS AREA BASIN B PERVIOUS AREA % IMPERVIOUS en 10 0 -- • .. __ _,_ ... ----- 14,750 SF (0.34AC) 4,088SF 10,662 SF 27.7% 0.43 4,923 SF /0.11 AC) 4,002SF 921 SF 81.3% 0.78 GRAPHIC SCALE 10 1"=10' 20 • 30 PASCO LAREY SUITER & ASSOCIATES CML ENGINEERING + LAND PLANNING + LAND SURVEYING 535 North lltp1nlf 101, Ste A. Solen• Beach, CA 113875 ph 858.259.8212 I fz 858.259.4812 I plMenglneerlng com PLSA 2760-01 i \ \ (J) \ \ \ (J) \ u (J) \ \ I I U) \ I I Ul I I \ :a, \ \ m \ 11 ~ POR. LOTS MAP9825 I C \ -+-- (J)_-t-- \ (J) \ <ii \ I I 'Ul \ \ \ j .,~ ,.44 . .., .,.-, X 44.7" . ---"---'-----. \ \ \ ---- / \ ) I / I I r l 'T/W: ~ ~:-v=-.,...,. "' ·-·-J:!l;::j i~"--<EL-··---~-------··· ·-·--~--~-----t;w:;;mi·f(i'1,s ftt1ti:ii,, '""';;,,,,:;;J<.,;fi, ,ii:;_;;-m"J;;;::i;;;;;,mi::i;;~ ~!~ /_,, Cf) ·"-'"'· WJ,,¥'/2:#:ws-'lii! ;'% -.j!N ~y \ U) -s EXISTING 24' RCP \\ S STORM DRAt . J:IActive Jobsl2760 TOURMALINE 438 TAMARACKICIVILIREPORTSIHYDROLOGYIDISCRETIONARYIAPPENDIX\2760-CV-PROP-HYDRO.dwg PROPOSED HYDROLOGY EXHIBIT ./ ,:Y ./ X X ~ -=r \ X 438 TAMARACK AVENUE s -----·· -·.-X 47 1 ----0 ,.,. 1·~ >~~~-~~:::--=-~~:lg ,,;r :-;,<---·c PLAN VIEW -PROPOSED HYDROLOGY SCALE: 1" • 10' 1/ 0 I () / I X 48.6 ) POR. L'qT5 X 48_,MAP 9,825 -·-/ i / ;{ 48.3 X48.3 X 48 2 X4S.3 i /. 48.3 I • \ • • ~- X 48.7 '--,\ X 48:9 I ---/·· 49---- \ X48.3 • X48.5 X 4'l.B NODEA.1 48.9HP X 48.1 X 48 • X48.9 ( X49.2 ( X49.3 X 4,S.3 s s X 49.3 \ / -(')" -- s \ \ I \. • \ " t'<i ,,. ! • --~-~ xoo . \' , ~-I .. <I. •; I s LEGEND EXISTING PROPERTY BOUNDARY ADJACENT LOT LINE I RIGHT-OF-WAY CENTERLINE OF STREET DRAINAGE BASIN BOUNDARY EXISTING CONTOUR LINE PROPOSED CONTOUR PROPOSED FLOW PATH PROPOSED DRAINAGE DIRECTION PROPOSED IMPERVIOUS AREA PROPOSED PERVIOUS PAVEMENT BASIN A -AREA CAL GULA TIONS TOTAL BASIN AREA BASIN IMPERVIOUS AREA BASIN PERVIOUS AREA IMPERVIOUS AREA % Cn BASIN B -AREA CAL GULA TIONS TOTAL BASIN AREA BASIN IMPERVIOUS AREA BASIN PERVIOUS AREA IMPERVIOUS AREA % Cn 10 0 -- -------46------ • ··---···--- ~/21/1//¼l I : : : : : : : : : : : : : : I 17,293 SF 8,423 SF 8,870 SF 481% 0.57 2,379SF 341 SF 2,038 SF 14.3% 0.34 GRAPHIC SCALE 10 1" :,-: 10' 20 • 30 PASCO LARET SUITER & ASSOCIATES CML ENGINEERING + LAND PLANNING + LAND SURVEYING 535 North llfglnny 101, Ste A, Solua Beach. CA !l2075 ph 858.25!1.8212 I fl: 858.25!1.'812 I plwen11■eer1-..com PLSA 2760-01