PRELIMINARY DRAINAGE REPORT NEWCASTLE FIRE STATION OLD STATE HIGHWAY

Transcription

1 PRELIMINARY DRAINAGE REPORT FOR THE NEWCASTLE FIRE STATION OLD STATE HIGHWAY PREPARED FOR THE NEWCASTLE FIRE PROTECTION DISTRICT JULY 2014 BY ROSEVILLE DESIGN GROUP, INC. ROSEVILLE DESIGN GROUP, Inc Established 1979 Planning Surveying Architecture Civil Engineering Structural Engineering Values from the Past, Experience for the Present, Preparing for the Future 8421 Auburn Boulevard Suite 170 Citrus Heights, CA phone: (916) fax: (916)

2 Contents PROJECT DESCRIPTION... 1 PROCEDURE AND DESIGN CRITERIA... 1 HYDROLOGY AND DRAINAGE SYSTEM... 1 PRE-DEVELOPMENT... 1 POST-DEVELOPMENT... 3 CONCLUSSIONS... 5 STORMWATER QUALITY... 5 Attachments Pre-development Calculations Shed Map A Post-Development Calculations Shed Map B Vicinity Map FEMA Map Excerpts from Placer County Flood Control and Water Conservation District Stormwater Management Manual....

3 Newcastle Fire Station Preliminary Drainage Report July, 2014 Page 1 PROJECT DESCRIPTION The proposed Newcastle Fire Station is located within half a mile of the existing station in the downtown area of the Town of Newcastle in Placer County, California. The site is located on Old State Hwy at Newcastle Road. The 0.57± acre project is bound by Old State Hwy to the West, Newcastle Road to the south, an industrial parcel owned by Union Pacific Railroad to the north, and Highway 80 to the East. The property quickly drops off in elevation from Old State Hwy and then gently slopes to the south toward an existing 24 inch diameter culvert on Caltrans property. The highest point of elevation that drains on-site is approximately 928 feet MSL and the lowest point of elevation is approximately 901 feet MSL at the entrance to the culvert. Development of the project area will consist of removing approximately 50 trees, filling a portion of the site with engineered soil, grading, construction of the Newcastle Fire Station, and paving of a new parking lot. Roseville Design Group, Inc. (RDG) has had preliminary discussions with Caltrans regarding draining post-development storm water flow into their existing 24 diameter culvert. According to FEMA flood insurance rate maps 06061C0409F the property is located outside of the 500-year flood plain (unshaded Zone X). PROCEDURE AND DESIGN CRITERIA In accordance with Placer County standards, the Project s proposed drainage facilities will be designed as follows: Response times, peak flows, and detention requirements per the Placer County Flood Control and Water Conservation District s Stormwater management Manual (SWM), version 3, dated February 1990 and October 1994 and 1997 amendments. HYDROLOGY AND DRAINAGE SYSTEM The runoff calculations for both the pre-development and post-development phases and the drainage system design for the post-development phase were performed using the Placer County Stormwater Management Manual dated September 1, 1990 (updated February, 1994). Excerpts of the standards are attached. Return periods have been analyzed for the 10-year and 100-year storm events with Hydrologic Soil Group (HSG) type B soils. PRE-DEVELOPMENT The existing terrain is undeveloped with trees of multiple sizes. Ground cover consists of brush, grasses, and blackberry thickets. The site is depressed approximately 20 feet lower than the surrounding area. Only local runoff drains into the site, then meanders to a 24 inch diameter culvert

4 Newcastle Fire Station Preliminary Drainage Report July, 2014 Page 2 located at the south end of the site. This culvert directs drainage under the off-ramp in a southerly direction along Caltrans right-of-way. Referring to Shed Map A for pre-development flow, the site has been analyzed by dividing it into sub-sheds as follows: Drainage Path 1 : Sub-shed 1 = 0.08 ac Sub-shed 2 = 0.20 ac Sub-shed 3 = 0.86 ac Sub-shed 4 = 0.35 ac Sub-shed 5 = 0.01 ac Sub-shed 6 = 0.07ac Sub-shed 7 = 0.02 ac Sub-shed 8 = 0.01 ac Sub-total = 1.60 ac Drainage Path 2: Sub-shed 9 = 0.04 ac Sub-shed 10 = 0.03 ac Sub-shed 11 = 0.21 ac Sub-total = 0.28 ac Total = 1.88 ac As noted previously, the methodology specified in the Stormwater Management Manual by the Placer County Flood Control and Water Conservation District was used to calculate the flows. Excerpts of the manual are attached at the end of this report. The following equations and values are used for the predevelopment conditions: Overland flow response time, t ro, as follows: Poor grass cover on moderately rough surface (Table 5-5, Page V-10), n = 0.40 Slope and flow length vary per shed area. Equation 5-3 (page V-10) gives the initial response time. Collector Flow time, t r, as follows: Collector swale length, slope, side slope, and contributing areas vary per shed areas Roughness coefficients: n (table 8-1, page VIII-4) = brush (medium to dense brush, summer) = 0.11 Equation 5-4 (page V-10) give the different responses time within each shed areas Sum of Time of Response The addition of the initial and collector response times. Unit Peak Flow Figures 5-3A (pages V-14) give the Unit peak flows using the sum of response times for a 10 year storm event. Infiltration Factor, F i (cfs/ac) Infiltration rate, table 5-3 (page V-6), class B soil open natural maximum available pervious area, grass, fair to good. I = 0.20

5 Newcastle Fire Station Preliminary Drainage Report July, 2014 Page 3 Equation 5-5 (page V-13) gives: F I = 0.31 cfs/ac (A1-8) F I = 0.31 cfs/ac (A9-11) / Peak Flow Equation 5-6 (page V-13) gives the adjusted infiltration peak flow Pervious area 80.9% Assuming an average elevation of 916± feet MSL, the total Pre-Development runoff for this project using the 10 year storm duration: (Watersheds A1-8) = , See Spreadsheet (Watersheds A9-11) = , See Spreadsheet POST-DEVELOPMENT Development of the site will include importing approximately 13,500 cubic yards of soil to raise a portion of the site even with the adjacent road. Site improvements include an impervious roof, concrete walk, and asphalt pavement. Drainage flows will be directed through landscaped swales around the site, then directed southward toward the culvert. Referring to Shed Map B, the site is again divided into sub-sheds as follows: Drainage Path 1: Sub-shed 1 = 0.10 ac Sub-shed 2 = 0.20 ac Sub-shed 3 = 0.04 ac Sub-shed 4 = 0.27 ac Sub-shed 5 = 0.19 ac Sub-shed 6 = 0.09 ac Sub-shed 7 = 0.07 ac Sub-shed 8 = 0.23 ac Sub-shed 9 = ac Sub-shed 10 = 0.07 ac Sub-shed 11= 0.35 ac Sub-shed 12 = 0.02 ac Sub-shed 13 = 0.01 ac Sub-total = 1.65 ac Drainage Path 2: Sub-shed 14 = 0.04 ac Sub-shed 15 = 0.03 ac Sub-shed 16 = 0.21 ac Sub-total = 0.28 ac Total = 1.93 ac

6 Newcastle Fire Station Preliminary Drainage Report July, 2014 Page 4 Overland flow response time t ro as follows: Short Grasses (Table 5-5, Page V-10), n = 0.15 Slope and flow length vary per shed area. Equation 5-3 (page V-10) gives the initial response time. Collector Flow time t r as follows: Collector swale length, slope, side slope, and contributing areas vary per shed areas. Roughness coefficients: n (table 8-1, page VIII-3) Earth; Minor Irregularity; Minor Obstructions; Medium Vegetation; Minor Meandering = n (table 6-3, page VI-6) Use Interior Plastic Pipe for corrugated metal pipe = n (table 8-1, page VIII-4) = brush (medium to dense brush, summer) = 0.11 Equation 5-4 (page V-10) give the different responses time within each shed areas. Sum of Time of Response The addition of the initial and collector response times. Unit Peak Flow Figures 5-3A (pages V-14) give the Unit peak flows using the sum of response times for a 10 year storm event. Infiltration Factor, Fi (cfs/ac) Infiltration rate, table 5-3 (page V-6), class B soil open natural maximum available pervious area, grass, fair to good. I = 0.20 Equation 5-5 (page V-13) gives: F I = 0.31 cfs/ac (A1-13) F I = 0.31 cfs/ac (A14-16) / Peak Flow Equation 5-6 (page V-13) gives the adjusted infiltration peak flow Pervious area = 56.8% Total Post Development runoff from this project for the 10 year storm duration: (Watersheds A1-13) = (Watersheds A14-16) = , See Spreadsheet, See Spreadsheet

7 Newcastle Fire Station Preliminary Drainage Report July, 2014 Page 5 CONCLUSSIONS The following is a summary comparison of the pre- and post-development flows: 10-Year Return Period Pre-Development Area Response Time Peak Flow Drainage Path acres 7.14 min 3.45 cfs Drainage Path acres 3.18 min 0.64 cfs 4.09 cfs Post-Development Area Response Time Peak Flow Drainage Path acres 9.17 min 3.37 cfs Drainage Path acres 3.18 min 0.64 cfs 4.01 cfs 100-Year Return Period Pre-Development Area Response Time Peak Flow Drainage Path acres 7.14 min 6.65 cfs Drainage Path acres 3.18 min 1.29 cfs 7.94 cfs Post-Development Area Response Time Peak Flow Drainage Path acres 9.17 min 6.34 cfs Drainage Path acres 3.18 min 1.29 cfs 7.63 cfs The post-development flows do not increase compared to the pre-development flows, and actually decrease slightly due to the longer times of concentrations. This indicates that the project will not adversely affect the site s existing hydrology. Although site drainage will be predominantly overland flow, drainage inlets and 8 diameter pipes will be utilized to prevent erosion due to washout at the tops of slope. These pipes will direct water down the slopes to the grassy swale located between the fire station and the freeway off-ramp. Drainage will then meander to the south to the culvert similar to existing conditions. STORMWATER QUALITY In relation to stormwater quality, the project site will be more than adequately protected from potential storrmwater impacts. Best Management Practices (BMPs) will be utilized thoroughly throughout the site to mitigate potential impacts from land disturbance activities. A Storm Water Pollution Prevention Plan (SWPPP) will be developed and implemented on-site. Five minimum control measures (employee training, scheduling & maintenance, good housekeeping, erosion & sediment controls, and inspection & maintenance), as outlined by the State Water Resources Control Board, will be implemented during construction activities, as required. CASQA BMP specifications shall be strictly adhered to for the duration of construction activities.

8 Newcastle Fire Station Preliminary Drainage Report July, 2014 Page 6 During grading, the primary potential pollutant of concern is anticipated to be wind erosion, particularly during grading activities. Areas of exposed soil have a potential to contribute sediment to stormwater discharges if a rain event occurs. Furthermore, during dry periods, dust control measures involve applying water to the exposed area, which can also produce sediment-laden runoff if not applied properly. Runoff control measures such as fiber rolls and inlet protection will be utilized on-site to avoid an unauthorized discharge due to grading disturbances. Cut and fill activities also have the potential to contribute to erosion and sedimentation if proper techniques are not employed. Disturbed areas will be stabilized through a variety of methods including hydroseeding and fiber rolls. Material storage and equipment staging areas will be protected from potential run-on and covered and secured prior to predicted rain events. Post-development pollutants are anticipated to consist primarily of oily stormwater runoff during the first substantial rain event following the completion of paving activities. Paving activities will add asphalt and concrete materials to the site, which will require additional BMPs to be implemented in order to protect the site from a potential unauthorized stormwater discharge. Runoff control measures including, but not limited to, drain inlet protection and fiber rolls will be utilized to prevent any oils or pollutants from exiting the work area. Steep slopes on the site will also require the use of erosion and sediment control measures such as hydroseeding. Runoff will discharge as sheet flow and channelize into swales leading to existing vegetated areas simulating pre-development condition). At a minimum the following CASQA BMPs shall be implemented on-site. Please refer to the SWPPP for an all-inclusive list of BMPs that will be utilized on-site: EC-4 Hydroseeding; NS-10 Vehicle & Equipment Maintenance; SE-5 Fiber Rolls; TC-1 Stabilized Construction Entrance; WE-1 Wind Erosion Control; and WM-1 Material Delivery and Storage The BMP s listed above are included in the CASQA Stormwater Best Management Practice Handbook for New Development and Re-Development, November Also refer to the SWPPP and the Erosion Control plans for more detail location and description of the BMPs. See the Water Quality appendix for the sizing calculations of the facilities.

9 EXHIBITS AND ATTACHMENTS

10 PRE-DEVELOPMENT CALCULATIONS, 10 Year Period

11 Placer County Flood Control and Water Conservation District Small Watershed Peak Flow Worksheet, Pre-Development Date July, 2014 Engineer Roseville Design Group, Inc. Project Newcastle Fire Station Watershed A1-8 Area, acres 1.60 Elevation 916 Return Period, Years 100 Feet Contributing Side Slope Response Length Slope Mannings Area (ft H per Time (feet) (V/H) n (acres) 1 ft V) (minutes) Overland Flow, A Swale 1, A Swale 2, A Swale 3, A4-A5-A Swale 4, A7-A Total Response Time (minutes) 7.14 Unit Peak Flow (cfs/acre) 4.40 Infiltration Rate (inches/hour) 0.2 Infiltration Factor (cfs/acre) 0.31 Percent Impervious Watershed Peak Flow 6.65 Area x Unit Peak Flow - (1-Percent Impervious) * Area x Infiltration Factor

12 Placer County Flood Control and Water Conservation District Small Watershed Peak Flow Worksheet, Pre-Development Date July, 2014 Engineer Roseville Design Group, Inc. Project Newcastle Fire Station Watershed A9-11 Area, acres 0.28 Elevation 916 Return Period, Years 100 Feet Contributing Side Slope Response Length Slope Mannings Area (ft H per Time (feet) (V/H) n (acres) 1 ft V) (minutes) Overland Flow, A Swale 1, A Swale 2, A Total Response Time (minutes) 3.18 Unit Peak Flow (cfs/acre) 4.90 Infiltration Rate (inches/hour) 0.2 Infiltration Factor (cfs/acre) 0.31 Percent Impervious 4.91 Watershed Peak Flow 1.29 Area x Unit Peak Flow - (1-Percent Impervious) * Area x Infiltration Factor

13 PRE-DEVELOPMENT CALCULATIONS, 100 Year Period

14 Placer County Flood Control and Water Conservation District Small Watershed Peak Flow Worksheet, Pre-Development Date July, 2014 Engineer Roseville Design Group, Inc. Project Newcastle Fire Station Watershed A1-8 Area, acres 1.60 Elevation 916 Return Period, Years 10 Feet Contributing Side Slope Response Length Slope Mannings Area (ft H per Time (feet) (V/H) n (acres) 1 ft V) (minutes) Overland Flow, A Swale 1, A Swale 2, A Swale 3, A4-A5-A Swale 4, A7-A Total Response Time (minutes) 7.14 Unit Peak Flow (cfs/acre) 2.40 Infiltration Rate (inches/hour) 0.2 Infiltration Factor (cfs/acre) 0.31 Percent Impervious Watershed Peak Flow 3.45 Area x Unit Peak Flow - (1-Percent Impervious) * Area x Infiltration Factor

15 Placer County Flood Control and Water Conservation District Small Watershed Peak Flow Worksheet, Pre-Development Date July, 2014 Engineer Roseville Design Group, Inc. Project Newcastle Fire Station Watershed A9-11 Area, acres 0.28 Elevation 916 Return Period, Years 10 Feet Contributing Side Slope Response Length Slope Mannings Area (ft H per Time (feet) (V/H) n (acres) 1 ft V) (minutes) Overland Flow, A Swale 1, A Swale 2, A Total Response Time (minutes) 3.18 Unit Peak Flow (cfs/acre) 2.60 Infiltration Rate (inches/hour) 0.2 Infiltration Factor (cfs/acre) 0.31 Percent Impervious 4.91 Watershed Peak Flow 0.64 Area x Unit Peak Flow - (1-Percent Impervious) * Area x Infiltration Factor

16 PRE-DEVELOPMENT Map

17 HWY OLD STATE SHED MAP "A" TAYLOR RD UNION PACIFIC R.R. NEWCASTLE RD NEWCASTLE FIRE STATION Swale Swale 3 Swale INDIAN HILL RD VICINITY MAP Pre-Development Shed Map Newcastle Fire Station County of Placer, California Swale "D Swale " = 50' JULY, of BD PH

18 POST-DEVELOPMENT CALCULATIONS, 10 Year Period

19 Placer County Flood Control and Water Conservation District Small Watershed Peak Flow Worksheet, Post Development Date July, 2014 Engineer Roseville Design Group, Inc. Project Newcastle Fire Station Watershed A1-13 Area, acres 1.65 Elevation 916 Return Period, Years 10 Feet Contributing Side Slope Response Length Slope Mannings Area (ft H per Time (feet) (V/H) n (acres) 1 ft V) (minutes) Overland Flow, A Swale 1, A Swale 2, A Pipe, A Swale 4, A Swale 5, A Swale 6, A5-A Swale 7, A Swale 8, A9-A10-A Swale 9, A12-A Total Response Time (minutes) 9.17 Unit Peak Flow (cfs/acre) 2.20 Infiltration Rate (inches/hour) 0.2 Infiltration Factor (cfs/acre) 0.31 Percent Impervious Watershed Peak Flow 3.37 Area x Unit Peak Flow - (1-Percent Impervious) * Area x Infiltration Factor

20 Placer County Flood Control and Water Conservation District Small Watershed Peak Flow Worksheet, Post Development Date July, 2014 Engineer Roseville Design Group, Inc. Project Newcastle Fire Station Watershed A14-16 Area, acres 0.28 Elevation 916 Return Period, Years 10 Feet Contributing Side Slope Response Length Slope Mannings Area (ft H per Time (feet) (V/H) n (acres) 1 ft V) (minutes) Overland Flow, A Swale 1, A Swale 2, A Total Response Time (minutes) 3.18 Unit Peak Flow (cfs/acre) 2.60 Infiltration Rate (inches/hour) 0.2 Infiltration Factor (cfs/acre) 0.31 Percent Impervious 4.91 Watershed Peak Flow 0.64 Area x Unit Peak Flow - (1-Percent Impervious) * Area x Infiltration Factor

21 Placer County Flood Control and Water Conservation District Small Watershed Peak Flow Worksheet, Post Development Date July, 2014 Engineer Roseville Design Group, Inc. Project Newcastle Fire Station Watershed A1-3 (Flow at Proposed 8" Culvert, North Side) Area, acres 0.34 Elevation 916 Return Period, Years 10 Feet Contributing Side Slope Response Length Slope Mannings Area (ft H per Time (feet) (V/H) n (acres) 1 ft V) (minutes) Overland Flow, A Swale 1, A Swale 2, A Total Response Time (minutes) 6.59 Unit Peak Flow (cfs/acre) 2.50 Infiltration Rate (inches/hour) 0.2 Infiltration Factor (cfs/acre) 0.31 Percent Impervious Watershed Peak Flow 0.80 Area x Unit Peak Flow - (1-Percent Impervious) * Area x Infiltration Factor

22 Placer County Flood Control and Water Conservation District Small Watershed Peak Flow Worksheet, Post Development Date July, 2014 Engineer Roseville Design Group, Inc. Project Newcastle Fire Station Watershed A5 (Flow at Proposed 8" Culvert, South Side) Area, acres 0.19 Elevation 916 Return Period, Years 10 Feet Contributing Side Slope Response Length Slope Mannings Area (ft H per Time (feet) (V/H) n (acres) 1 ft V) (minutes) Overland Flow, Street Swale 1, Parking Lot Swale 2, Parking Lot Total Response Time (minutes) 1.83 Unit Peak Flow (cfs/acre) 2.60 Infiltration Rate (inches/hour) 0.2 Infiltration Factor (cfs/acre) 0.31 Percent Impervious Watershed Peak Flow 0.49 Area x Unit Peak Flow - (1-Percent Impervious) * Area x Infiltration Factor

23 POST-DEVELOPMENT CALCULATIONS, 100 Year Period

24 Placer County Flood Control and Water Conservation District Small Watershed Peak Flow Worksheet, Post Development Date July, 2014 Engineer Roseville Design Group, Inc. Project Newcastle Fire Station Watershed A1-13 Area, acres 1.65 Elevation 916 Return Period, Years 100 Feet Contributing Side Slope Response Length Slope Mannings Area (ft H per Time (feet) (V/H) n (acres) 1 ft V) (minutes) Overland Flow, A Swale 1, A Swale 2, A Pipe, A Swale 4, A Swale 5, A Swale 6, A5-A Swale 7, A Swale 8, A9-A10-A Swale 9, A12-A Total Response Time (minutes) 9.17 Unit Peak Flow (cfs/acre) 4.00 Infiltration Rate (inches/hour) 0.2 Infiltration Factor (cfs/acre) 0.31 Percent Impervious Watershed Peak Flow 6.34 Area x Unit Peak Flow - (1-Percent Impervious) * Area x Infiltration Factor

25 Placer County Flood Control and Water Conservation District Small Watershed Peak Flow Worksheet, Post Development Date July, 2014 Engineer Roseville Design Group, Inc. Project Newcastle Fire Station Watershed A14-16 Area, acres 0.28 Elevation 916 Return Period, Years 100 Feet Contributing Side Slope Response Length Slope Mannings Area (ft H per Time (feet) (V/H) n (acres) 1 ft V) (minutes) Overland Flow, A Swale 1, A Swale 2, A Total Response Time (minutes) 3.18 Unit Peak Flow (cfs/acre) 4.90 Infiltration Rate (inches/hour) 0.2 Infiltration Factor (cfs/acre) 0.31 Percent Impervious 4.91 Watershed Peak Flow 1.29 Area x Unit Peak Flow - (1-Percent Impervious) * Area x Infiltration Factor

26 Placer County Flood Control and Water Conservation District Small Watershed Peak Flow Worksheet, Post Development Date July, 2014 Engineer Roseville Design Group, Inc. Project Newcastle Fire Station Watershed A1-3 (Flow at Proposed 8" Culvert, North Side) Area, acres 0.34 Elevation 916 Return Period, Years 100 Feet Contributing Side Slope Response Length Slope Mannings Area (ft H per Time (feet) (V/H) n (acres) 1 ft V) (minutes) Overland Flow, A Swale 1, A Swale 2, A Total Response Time (minutes) 6.59 Unit Peak Flow (cfs/acre) 4.50 Infiltration Rate (inches/hour) 0.2 Infiltration Factor (cfs/acre) 0.31 Percent Impervious Watershed Peak Flow 1.48 Area x Unit Peak Flow - (1-Percent Impervious) * Area x Infiltration Factor

27 Placer County Flood Control and Water Conservation District Small Watershed Peak Flow Worksheet, Post Development Date July, 2014 Engineer Roseville Design Group, Inc. Project Newcastle Fire Station Watershed A5 (Flow at Proposed 8" Culvert, South Side) Area, acres 0.19 Elevation 916 Return Period, Years 100 Feet Contributing Side Slope Response Length Slope Mannings Area (ft H per Time (feet) (V/H) n (acres) 1 ft V) (minutes) Overland Flow, Street Swale 1, Parking Lot Swale 2, Parking Lot Total Response Time (minutes) 1.83 Unit Peak Flow (cfs/acre) 4.90 Infiltration Rate (inches/hour) 0.2 Infiltration Factor (cfs/acre) 0.31 Percent Impervious Watershed Peak Flow 0.93 Area x Unit Peak Flow - (1-Percent Impervious) * Area x Infiltration Factor

28 POST-DEVELOPMENT MAP

29 HWY OLD STATE SHED MAP "B" TAYLOR RD UNION PACIFIC R.R. NEWCASTLE RD NEWCASTLE FIRE STATION INDIAN HILL RD VICINITY MAP Post-Development Shed Map Newcastle Fire Station County of Placer, California BD PH " = 50' JULY, of 2

30 FEMA MAP

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33 VICINITY MAP

34 TAYLOR RD I-80 UNION PACIFIC R.R. OLD STATE HWY NEWCASTLE RD I-80 NEWCASTLE FIRE STATION INDIAN HILL RD DRAWN: CHECKED: JOB NO: Roseville Design Group Inc Auburn Blvd, Suite 170 Citrus Heights, California Phone: (916) Fax: (916) SCALE: DATE: SHEET: Comprehensive Services PLANNING SURVEYING BUILDING DESIGN CIVIL ENGINEERING STRUCTURAL ENGINEERING DRAINAGE REPORT VICINITY MAP PLACER COUNTY, CA

35 EXCERPTS FROM PLACER COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT STORMWATER MANAGEMENT MANUAL

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