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Home My WebLink AboutHydrology(Jan.20,1989) S MARGARITA VILLAGE RETIREMENT VILLAGE HYDROLOGIC ANALYSIS ULTIMATE DEVELOPMENT COUNTY OF RIVERSIDE_,�CAL�FORNIA TRACT NUMBERS 2 3 3 71 ��'37 2-,.=;;AND 2 3 3 7 3 January 20, 1989 J#10583P m��.---�- L� , •„� ��c��a� ` � Q�pr Ea,,lp� , , I ��o • �F� MAY U n 19g7 ' ' �, �' ' Z O` : r �*� s:? N�J. 3Z833 z;� g • o �: ; . sl .�� CIY1�. .� Q .�. ,. ,1� 9lF �f �A�-�� c ---- ! ...._..._.... .� � � � '� i �^ Dennis C. Bowlin M�S.� RCE 32838�; EXP. 6/90 RICK ENGINEERING COMPANY WATER RESOURCES DIVISION 5620 FRIARS ROAD SAN DIEGO, CA 921�10 (619) 291-0707 TABLE OF CONTENTS PAGE INTRODUCTION 1 PURPOSE LOCATION DRAINAGE BASIN DESCRIPTION 2 SUBDIVISION RUNOFF CONTROL 3 DESIGN CALCULATIONS 4 INTRODUCTION RATIONAL METHOD CALCULATIONS SYNTHETIC UNIT HYDROGRAPH METHOD OFF-SITE ANALYSIS ON-SITE ANALYSIS CONCLUSIONS 10 REFERENCES 11 FIGURES 1. Location Map (follows page 1). 2. Offsite Basin Map (follows page 5). APPENDICES l. Rational Method Calculations - Offsite Areas. 2. Rational Method Calculations - Onsite Areas. 3. Synthetic Unit Hydrograph Method Calculations. MAPS (Map Pockets) 1. Rational Method Hydrologic Arialysis Ultimate Development Land Use. 2. Rational Method Hydrologic Analysis Ultimate Development Design Discharges. 3. Offsite Sub-Basin Map INTRODUCTION PURPOSE This report represents a hydrologic analysis report for ultimate development of the Margarita Village Retirement Village (Tentative Tracts 23371, 23372, and 23373) in the County of Riverside, California. The report was engineered following guidelines and regulations within the Riverside County Flood Control and Water Conservation District's (RCFC&WCD) "Hydrology Manual" (1978). The report addresses the conveyance of post-development flood peaks originating within the subdivision. The report also discusses accommodation of flood peaks originating offsite of the Margarita Village project site through the site. Hydrologic design calculations are provided for the storm water conveyance network within the subdivision. Final design of these drainage improvements will be analyzed in the final drainage reports for the individual filings, which will be submitted with the final construction drawings of the subdivisions. LOCATION � Margarita Village Retirement Village is a 473-acre, 2000-unit mixed use residential and golf course development located within Township 7 South, Range 2 West in the Rancho California area of the County of Riverside (Figure 1). The project is bordered by Rancho California Road on the south, Margarita Road on the west, and La Serena Way on the north. Future Kaiser Parkway is proposed on the east border of the project site. 1 Hemet - 74 n I� . _� �� Lake ... .. 74 ��, L2ke� Sk Lak� 15 . N.TS. Efsinore � 79 ,Z"t'� .'. :;. ��'� Fi�it � . � � :�:: � �c a t �o n T e mec - .. �:: � � � ::: � � <::::;: :::;«:<:;>:� �� ... , }�>;>�� R a n c h O ..�.:�.::: ::>: � .< .... . ... California ��:-- .. . - 79 -- �'" '� �. . _. ._� san d�ego c,a 15 � RICK ENGINEERING COMP�ANY FIC�URE 1 CIV�L ENGINEERS: pLANNING CONSULTANTS: SURVE70RS 5920 FRIAqS HOAD SAN DIEQO. CALIFOANIA 921f0 (619) 291�0707 � 7088 GIO GICO ORIVE CML58AD, GALIFORNIA 9YOOE (E19) 7=9'�08� LOCATION MAP � 785 S. RANCHO SANTA FE RD. $AN NARCOS. CA 9208Y (619) 111V800 DRAINAGE BASIN DESCRIPTION Margarita Village Retirement Village is located within two tributary watersheds to Murrieta Creek. Existing runoff is conveyed mostly within natural channels. The southerly portion of the site drains into the Long Canyon channel which traverses the southerly portion of the project. The Long Canyon channel design through the Retirement Village is not addressed in this study. The hydrologic analysis of the watershed for the channel design is shown in "Hydrologic Analysis and Hydraulic Analysis for Interim Condition (Phase One Grading) for Margarita Village Tracts 23371,2,3" prepared by Rick Engineering Company (October 7, 1988). The HEC-2 hydraulic design for the channel is shown in the hydrologic and hydraulic design report prepared for the Phase Two grading of Margarita Village being submitted by Rick Engineering Company concurrently with this report. The Long Canyon watershed is approximately 1,210 acres in size at the east site boundary. The channel flow enters the site in a natural channel at the location of a culvert under Rancho California Road (Map 1). The Long Canyon flow is conveyed through the site in a grass vegetated open channel drainageway through the golf course. Three culvert crossings for onsite roadways are proposed within the Retirement Village. Runoff from the residential areas of the site will drain into the drainageway through several storm drains. Runoff from the golf course will typically drain directly into the channel. Two storm drains under Rancho California Road originating from offsite areas south of the site also drain into the channel. The watershed is approximately 1,690 acres in size at the west project boundary. The channel runoff is collected at the west project limit in an existing triple 5-foot by 12-foot Reinforced Concrete Box (RCB) Culvert under Margarita Road. The northerly portion of the site drains into a natural channel which traverses the site on the south side of La Serena Way. The northerly watershed in approximately 390 acres in size at the east site boundary. The watershed flow enters the site at the location of a future storm drain under Kaiser Parkway. The northerly watershed flow is conveyed through the site in a storm drain system under the streets in the Retirement Village. Offsite areas east of Kaiser Parkway and north of La Serena Way enter the storm drain through existing and proposed pipe systems. The northerly watershed is approximately 620 acres in size at the westerly project boundary. The Retirement Village storm drain connects to an existing 102-inch Reinforced Concrete Pipe (RCP) installed for development of Tract 20881. 2 SUBDIVISION RUNOFF CONTROL Minor and major storm runoff within the Margarita Village Retirement Village is controlled with storm drains, streets and open channels. The RCFC&WCD Hydrology Manual requires that the minor (10-year) storm runoff shall be contained within the street curbs without overtopping and the major (100-year) storm runoff shall be contained within the street right-of-way limits. Interior streets within the Retirement Village are classified as private streets with the right-of-way line placed at the back of curb line. The interior streets have right-of-way widths of either 41.5 feet, 45.5 feet, or 49.5 feet. The interior streets within the Retirement Village have either 6-inch high modified type "C" Rolled Curb and Gutter (See detail on Map 1) or 6-inch Type A-6 Curb (County of Riverside Standard No. 200). The collector streets within the Retirement Village also have the right-of-way line placed at the back of curb line. The collector streets have right-of-way widths of either 53.5 feet, 65.5 feet or 71.5 feet. The collector streets have 6-inch Type A-6 Curb. Streets are used to convey runoff away from individual homes. The depth of water will not exceed 6 inches in the interior and collector streets during the 100-year storm event. This will contain the major storm runoff within the street right-of-way. Storm drain systems are used to convey flow within the subdivision when the flow depth reaches top of curb in the 100-year storm event. The dwelling pad elevations will be established to provide one foot of freeboard above the top of curb elevation at the street adjacent to each lot. Runoff within the golf course is controlled with grass vegetated swales and channels. The minor swales will be placed to collect localized runoff from the golf course in order to protect the adjacent homes from inundation, and to protect the golf course greens and tees. The channels will convey runoff originating offsite downstream. The channels will also be designed to protect adjacent homes from inundation and protect the golf course greens and tees. The swales and channels will be designed for non-erosive velocities. The dwelling pad elevations adjacent to the channels and swales will be selected to provide one foot of freeboard above the 100-year water surface. 3 DESIGN CALCULATIONS INTRODUCTION The hydrologic calculations used for design of the Margarita Village Retirement Village storm water conveyance system are presented in Appendices l, 2, and 3. The drainage sub-basins used in the hydrologic analysis are shown on Map 1(map pocket). The layout and routing of the storm drain systems are shown on Map 2. Offsite sub-basins are shown on Map 3. The RCFC&WCD Hydrology Manual Synthetic Unit-Hydrograph Analysis was used for analysis of the watersheds in excess of 300 acres in size. The Rational Method was used for hydrologic design for drainage facilities with a tributary area of less than 300 acres. The conveyance of flood peaks originating on the Retirement Village and accommodation of flows originating offsite through the site are discussed in this section. The design flows provided are based upon preliminary grading of the site. Final hydrologic and hydraulic calculations will be provided with the Final Drainage Report and construction drawings for the individual filings within the Retirement Village. RATIONAL METHOD CALCULATIONS Rational Method calculations performed for this report are shown in Appendices 1 and 2. The 100-year design storm is used in the design flow calculations for the storm water conveyance system. Soil characteristics were identified using the Soil Conservation Services Soil Survey for Western Riverside Area and Plate C-1.53 from the RCFC&WCD Hydrology Manual. Rainfall information was obtained from Plate D4.1 (Murrieta, Temecula and Rancho California Area) for the site. The Rational Method runoff coefficients used assume developed conditions from the Margarita Village Tentative Map for Tract Numbers 23371, 23372, and 23373. The density of the single family areas of the Retirement Village is greater than 1/4-acre lots. Because of the higher density, the single family areas are modeled using the Condominium Runoff Coefficient Curves from Plates D5.1 - D5.4. The multiple family unit areas are modeled using the Apartment Runoff Coefficient Curves. The golf course area is modeled as Urban Cover-Turf from Plate D5.5. The Runoff Index obtained from Plate D5.5 is used in Table D5.7 to determine the Runoff Coefficient. The RCFC&WCD recommended using 5 percent impervious cover for the golf course. The Rational Method calculations for the 100-year storm were performed using a Rational Method program. This program is a computer aided design program where the user develops a node-link � model of the watershed. The program can estimate the conduit and channel sizes needed to accommodate the design storm discharge. 4 The node-link model is developed by creating independent node-link models of each interior sub-basin and linking these sub-models together at confluence points. The program allows up to five streams to be confluenced at each node. The program has the capability to perform calculations for nine hydrologic processes. These processes are assigned code numbers which appear in the printed results. The code numbers and their significance are as follows: CODE l: Confluence analysis at a node CODE 2: Initial sub-area analysis CODE 3: Pipe flow travel time (computer estimated pipe size) CODE 4: Pipe flow travel time (user specified pipe size) CODE 5: Trapezoidal channel travel time CODE 6: Street flow analysis through a sub-area CODE 7: User specified information at a node CODE 8: Addition of sub-area runoff to main line CODE 9: "V" gutter flow analysis through a sub-area SYNTHETIC UNIT HYDROGRAPH METHOD Synthetic Unit Hydrograph calculations performed for this report are shown in Appendix 3. The 100-year, 3-hour design storm is used in the design calculations to predict the flood peaks in the storm water conveyance system. The precipitation value used was 2.27-inches which was taken from Plate E-5.2 from the RCFC&WCD Hydrology Manual. Soil characteristics were identified using the Soil Conservation Services Soil Survey for Western Riverside Area and Plate C-1.53. The Antecedent Moisture Condition of Two was used as recommended by the RCFC&WCD. The watershed boundaries for the hydrologic analysis were identified using the RCFC&WCD 200 scale orthophoto mapping for the area. The watershed boundaries are shown at 2000 scale on Figure 2. The Synthetic Unit Hydrograph method is used to si2e the storm drain which intercepts the offsite area of the northerly watershed. This watershed is to be intercepted by a storm drain which begins at Kaiser Parkway. The offsite watershed is modeled for developed land use in the offsite watershed assuming 1/4-acre lot single family development for the entire area west of Butterfield Stage Road and 1-acre lot single family development east of Butterfield Stage. This discharge was compared to the 100-year discharge assuming existing land use with a 25 percent bulking factor for debris loading applied as specified by the RCFC&WCD for this watershed (Appendix 3). The 100-year developed discharge is greater and governs the analysis. The trunk storm drain which conveys the offsite discharge through the site also intercepts discharge from the Retirement Village along its course. This storm drain is located in street "00" for approximately 1300 feet and then is located in La Serena Way for its remaining downstream portion. This storm drain is designed for the 100-year developed flood peak. The storm drain will connect to the existing 102-inch RCP storm drain south of La Serena Way. The northerly watershed is divided at two points in 5 . .. �a, ) �.- ` � � � I I _. �{ . 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" 7� / li I � �•1 / i . , <�.... �'� .�1� ,�� Z -\ , `�ryll; 7 � � ` �\�`� � ,/�� 1 �' r �,� � ;�� ,--� 1 � ` �1� \ " � ) � i ,� ; _,,> , > '� ro _ s r ,� ��., .. ,. � i � ��' l � �� , , . , _ �r ( � 1 1 I t I` 1 � / J I � l� l.�'1 \' ��./ ` _� I � / . �, �� , �) 1 � 1 <<—, //�h� r � c � .�1 �--�.��. ` ( ��<�-w-�o/1�� l� — i � Y-� F � , ) � , ->-� ' f_ �� S` �n , d� S�� -- �-l�.t v __ ? I ' ; � -.. � }- �, I I r n — ) � -c- 1 . ,, „ a .� � ` , � �� i�. �! ' _ i� - 11� �� l 4� �`I 11 (� ! � l i � '�� '�? �!.� � I �� ,� �-rl�� -- ' __ ��il i� , � � ,�: i /,J � il'� �� f\ \ \�.� �T 1 � � � �j� 1%1'�\��i\ '�1 I i r l � (; � � ) U �1 � Sl - "��_-�a/J �� i 1 �-,�' �• addition to the offsite area (Figure 2). The storm drain design discharge is determined between the design points by prorating the discharge entering the storm drain by the contributing area. OFF-SITE ANALYSIS Analysis of the remainder of the offsite sub-basin areas which are less than 300 acres in size were analyzed using the Rational Method program. The offsite sub-basins were identified using the RCFC&WCD orthophoto mapping as a basis. This information was supplemented by design plans and tentative maps prepared by other consultants, and field observations. Inlet and catch basin sizing is not addressed as part of this analysis. At points where inlets or catch basins are required to meet the design criteria, the entire flow at the node is conveyed downstream from that point within a pipe. Inlet sizing will be completed at the time of final design and will account for inlet bypass, if applicable. Runoff originating on the offsite areas are conveyed through the Margarita Village Retirement Village within storm drains except for the major drainageway in the golf course north of Rancho California Road. This drainageway is designed in separate reports mentioned previously in this report and is not addressed in this study. The offsite areas south of Rancho California Road are discharged onto the Retirement Village site through two storm drains. These pipes will be extended and discharged onto the golf course. The westerly storm drain has inlet flows from six onsite inlets adding to the pipe flow. In addition to the large offsite watershed analyzed using the Synthetic Unit Hydrograph method, there are two sub-basins east of Kaiser Parkway which discharge onto the site (Map 3). One offsite sub-basin is approximately 14 acres in size and will be intercepted at the intersection of Kaiser Parkway and Street "NN" . (System 1910). This storm drain will run south within Kaiser Parkway and connect to the northerly watershed trunk storm drain. The other offsite sub-basin east of Kaiser Parkway is approximately 49 acres in size and will be intercepted at the intersection with La Serena Way (System 1900). This storm drain will run westerly within La Serena and connect to the trunk storm drain at the intersection with Camino Corto. An additional offsite sub-basin 17 acres in size from the school site north of La Serena will add to the storm drain. The sub-basin runoff will be intercepted with the existing catch basin and 18-inch CMP, and additional street inlets. These inlets will be connected to the storm drain. Three other sub-basins north of La Serena Way will be collected by the trunk storm drain. One sub-basin is approximately 11 acres in size and consists of existing single family land use. The runoff from this sub-basin will be intercepted with street 6 inlets and connected to the trunk storm drain. There is an existing 5-foot inlet and an 18-inch CMP west of Camino Corto which will intercept a portion of this sub-basin runoff and connect to the trunk storm drain. Another sub-basin is approximately 40 acres in size and consists of existing single family land use. This area is serviced by seven large (10-foot to 12-foot) inlets north of La Serena in the vicinity of Via Puerta and has a 42-inch CMP outlet pipe. These existing inlets are assumed to be adequate for the majority of the street flows upstream of La Serena. The existing 42-inch CMP will connect to the trunk storm drain. The westerly sub-basin north of La Serena is approximately 4 acres in size and will drain directly onto the north gutter of La Serena Way and be intercepted by street inlets. These inlets will be connected by laterals to the trunk storm drain. Another significant offsite sub-basin is the area covered by the existing trailer park north of General Kearny Road (Map 2). The runoff within the trailer park is conveyed in the asphalt access driveways. A small existing inlet at the intersection of General Kearny will intercept only a minor portion of the 100-year flood peak. The remainder of the 100-year runoff from the trailer park will be intercepted by additional street inlets in General Kearny at this location. The inlets will be connected to a storm drain in General Kearny which will run west to the intersection with Street "Z". This storm drain will intercept two other offsite basins at this point. It will connect to the extension of the existing 30=inch storm drain at La Serena Way and General Kearny from a sub-basin approximately 24 acres in size from existing Tract 20735. The collector storm drain at General Kearny and "Z" street also intercepts runoff from an 11 acre offsite sub-basin from the park north of General Kearny. From the intersection of General Kearny, the storm drain is located within "Z" Street through the Retirement Village site. ON-SITE ANALYSIS Analysis of the onsite sub-basin areas within the Margarita Village Retirement Village site which are less than 300 acres in size were analyzed using the Rational Method program. The onsite sub-basins were identified using the preliminary grading plan for the site prepared for the Tentative Map. The sub-basins used in the onsite analysis are shown on Map l. Inlet and catch basin sizing is not addressed as part of this analysis. At points where inlets or catch basins are required to meet the design criteria, the entire flow at the node is conveyed downstream from that point within a pipe. Inlet sizing will be completed at the time of final design and will account for inlet bypass, if applicable. Runoff originating on the Retirement Village site is conveyed through the site within streets, storm drains channels and swales. Storm drains used in the Retirement Village will be RCP. The street layout and preliminary layout of the storm drains are shown on Map 2. 7 The onsite areas in the south-central portion of the site (systems 1000, 1100, 1600 and 1700) are each collected by a separate storm drain system (Map 2). These storm drains collect runoff entirely from the Retirement Village site and discharge onto the major drainageway on the golf course. System 1000 collects runoff from 51 acres in the easterly portion of the large single family area in the center of the site and discharges onto the golf course channel at Street "B". System 1100 collects runoff from 11 acres in the westerly portion of the same single family area and discharges onto the golf course channel at Street "E". System 1600 consists of two separate small storm drains collecting runoff from the multiple family area in the south portion of the site backing up to Rancho California Road. These storm drains also discharge onto the golf course channel. The six inlets along Street "D" connect to the storm drain from the offsite area south of Rancho California Road. System 1700 collects runoff from a 17-acre area including the south portion of the clubhouse building and parking lot, single family use east of the clubhouse area, and runoff onto Streets "B" and "C". System 1700 discharges into a box culvert on the golf course channel downstream of Street "B". The multiple family and commercial areas in the southeast portion of the site (systems 1200 and 1400) are collected by storm drains which discharge into the Long Canyon channel (Map 2). System 1200 collects runoff from 51 acres which includes the multiple family north of Street "C" and the commercial area at the northwest corner of Rancho California Road and Kaiser Parkway. System 1200 discharges into Long Canyon south of Rancho California Road. System 1400 collects runoff from a 17-acre area from the multiple family area along Rancho California Road west of the commercial area. System 1400 discharges into the Long Canyon.box culvert crossing under Rancho California Road. The central and westerly.portions of the site (system 1500) are collected by a storm drain which discharges into the north cell of the existing triple 5-foot by 12-foot RCB Culvert under Margarita Road (Map 2). System 1500 collects runoff from a 227-acre watershed including some offsite areas north of General Kearny Road and La Serena Way. The beginning of the system 1500 storm drain collects runoff from the single family and golf course areas east and north of the clubhouse. This storm drain connects to a storm drain across the golf course downstream of Street "B". The runoff is conveyed through the golf course in the storm drain along the south side of the M.W.D. right-of-way and intercepts runoff from the north portion of the clubhouse area, and the golf course along its path. The golf course storm drain connects to a storm drain in Street "Z" which intercepts runoff from the north. The storm drain in Street "Z" collects runoff from offsite areas (see the "Off-Site Analysis" section of this report) and from the multiple family area in the northwest corner of the Retirement Village site. After the two systems combine, the storm drain traverses west and south from Street "Z" along the right-of-way line of Margarita Road. The storm drain 8 also collects runoff from the single family area in the west portion of the site before discharging into the triple RCB Culvert. The northerly portion of the Retirement Village is collected by the trunk storm drain from the offsite area east of Kaiser Parkway. The design discharge for this trunk storm drain is discussed in the "Synthetic Unit Hydrograph Method" section of this report. The lateral storm drains from the north portion of the site (systems 1300, 2000, 2021, 2028, 2035, 2200, and 2300) connect to this trunk storm drain and are designed using the Rational Method. System 1300 collects runoff from the northerly portion of the multiple family area along Kaiser Parkway and the adjacent golf course. System 1300 connects to the trunk storm drain at Kaiser Parkway near the trunk storm drain starting point. Systems 2000, 2021, 2028, and 2035 collect runoff from the northeast single family portion of the site and connect to the trunk storm drain along Street "00". Systems 2200 and 2300 collect runoff from the north central single family and multiple family portions of the site and connect to the trunk storm drain along its reach in La Serena Way. The trunk storm drain also collects runoff from offsite areas as discussed in the "Off-site Analysis" section of this report and from street inlets along La Serena Way before connecting to the existing 102-inch storm drain near the west boundary of the Retirement Village. 9 CONCLUSIONS The storm water conveyance system for the Margarita Village Retirement Village includes a storm drain network, a open channel system and a street system. Design calculations in this report show required systems to provide protection for the dwelling pads within the project during the major (100-year) storm. Provisions are made to accommodate developed runoff originating offsite through the site. Final hydraulic calculations for the individual filings within Margarita Village Retirement Village following the design presented in this study will be provided in the Final Drainage Reports submitted with the construction drawings of the filings. 10 REFERENCES l. Riverside County Flood Control and Water Conservation District, 1978; Hydrology Manual. 2. Riverside County, California, 1982; County Road Improvement Standards and Specifications. 3. Rick Engineering Company, 1988; Hydrologic Analysis and Hydraulic Analysis for Interim Condition (�Phase One Grading) for Margarita Village Tracts 23371,2,3. 4. County of Riverside Flood Control and Water Conservation District Orthophoto Mapping; various dates. 5. San Diego County Regional Standards Committee, 1986; Regional Standard Drawings. 6. Rick Engineering Company, 1988; Hydrologic Analysis and Hydraulic Analysis for Phase Two Grading for Margarita Village Tracts 23371,2,3. 7. Robert Bein, William Frost and Associates, 1987; On Hydrology and Hydraulics Report, Margarita Village, Tract 20881. 8. U.S. Department of Agriculture Soil Conservation Service, 1971; Soil Survey for Western Riverside Area. 11