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HomeMy WebLinkAbout15 - Design Report - Baxter Square Ph 3 - Water, Sewer, Stormwater, Pavement CONSTRUCTION PLANS, SPECIFICATIONS, AND DESIGN REPORTS WATER, SEWER, STORMWATER MANAGEMENT, AND PAVEMENT DESIGN BAXTER SQUARE SUBDIVISION, PHASE 3 Prepared for: Baxter Square Partners, LLC 1627 W. Main Ste. #117, Bozeman, MT 59718 Prepared by: E -10 C:I,& I Engineering and Surveying Inc. 1091 Stoneridge Drive • Bozeman, MT 59718 Phone(406) 587-1115 • Fax(406) 587-9768 www.chengineers.com • info@chengineers.com Project Number: 14305.1 JANUARY 2015 TABLE OF CONTENTS 1. Introduction 2. Water,Sewer,Stormwater Management,and Pavement/Street Design Report 3. Appendices a. Water Design Report Supplemental Information b. Stormwater Design Report Supplemental Information c. Soils/Traffic Design Report Supplemental Information d. Project Specifications e. Lighting Cut Sheets INTRODUCTION Baxter Square Subdivision, Phase 3 is a 22-lot major subdivision located on a 2.57-acre parcel located north of Sartain Street and west of Thomas Drive within the City of Bozeman. The property is currently annexed into the City of Bozeman with the zoning designation of R-3. The proposed subdivision layout meets the R-3 zoning criteria. The subdivision will connect to existing City of Bozeman road, water and sanitary sewer networks. The 22 lots proposed with this subdivision will be developed as three and four unit townhouses on individual lots. The proposed lots will have an average size of 3,319 square feet. The development is intended to be of a similar character to the existing homes and lots in the adjoining Phases 1 and 2 of Baxter Square Subdivision. Parkland for the development was provided in Phases 1 and 2. A parkland calculation is included on the plat. Open Space is proposed in the northwest corner of the subdivision. The north/south running trail corridor will be extended from the existing park north through the Open Space. Site stormwater will drain to a stormwater retention pond in the Open Space. ESIGN REPORT WATER & SEWED MANAGEMENT A TER SQUARE SUBDIVISION P ASE 3 Prepared for: Baxter Square Partners, LLC 1627 W. Main Street, #117, Bozeman, MT 59715 Prepared by: C&H Engineering and Surveying, Inc. 1091 Stoneridge Drive, Bozeman, MT 59718 (406) 587-1115 l (r t Project Number: 14305.1 December 2014 INTRODUCTION - The Baxter Square Subdivision, Phase 3 is a proposed 22-lot subdivision located north of Sartain Street and west of Thomas Drive. The 2.57-acre development is situated in the Southeast Quarter of the Southwest Quarter of Section 35, Township 1 South, Range 5 East of P.M.M., Gallatin County, Montana. This project will require connection to existing City of Bozeman water and sanitary sewer systems. WATER SYSTEM LAYOUT The current water main in the area utilized for the Baxter Square Subdivision Phase 3 is the 8-inch ductile iron pipe(DIP)located in Sartain Street. The proposed 8-inch DIP for the subdivision will connect to the existing main in the intersection of Sartain Street and Renee Way. The main will run north under the proposed Renee Way and be terminated at the property line with a cap so that future development will be able to connect to the main. The main will have a tee installed at the intersection of Renee Way and Georgia Marie Lane and this main will run west to the property line for future development. Blow off valves will be installed per City of Bozeman standards at the ends of the mains. A WaterCAD analysis is enclosed (Appendix A) analyzing all mains installed with this project. The connection to the existing system is modeled as a pump with characteristics matching data measured by the City of Bozeman Water Department. WATER DISTRIBUTION SYSTEM SIZING Input Data Average Daily Residential Usage = 170 gallons per capita per day Average Population Density = 2.11 persons/dwelling unit Minimum Fire Hydrant Flow = 1,500 gpm Residual Pressure Required = 20 psi for Fire Flow Design Report-Page 2 of 6 Average Day Demand (Peaking Factor= 1) Maximum Day Demand (Peaking Factor= 2.3) Maximum Hour Demand (Peaking Factor= 3.0) Water Demand (22 dwelling units) Average Day Demand =22 d.u. x 2.11 persons/d.u. x 170 gpcpd=7,891 gpd = 5.48 gpm Maximum Day Demand = 5.48 gpm x 2.3 = 12.60 gpm Peak Hour Demand = 5.48 gpm x 3.0 = 16.40 gpm Available Pressure: 8-inch main in Baxter/Buckrake: Hydrant#1960 Static=90 psi Residual = 88 psi Hydrant# 1961 Pitot=75 psi Flow Rate= 1455 gpm HYDRAULIC ANALYSIS A water distribution model was created using WaterCAD Version 6.5 for demand forecasting and describing domestic and fire protection requirements. In order to model the system, each junction node of the water distribution system was assessed a demand based on its service area. The table shown below quantifies the demands placed at the junction nodes and calculates the demands for Average Day,Maximum Day and Peak Hour within the subdivision. The peaking factor for each case is 1, 2.3 and 3.0 respectively. AVG. MAX. JUNCTION DAY DAY PEAK NODE # OF LOTS GPM GPM HOUR GPM J-15 10 2.49 5.73 7.45 J-17 3 0.75 1.72 2.24 J-18 2 0.50 1.15 1.49 J-19 7 1.74 4.01 5.22 Total 22 5.48 12.60 16.40 Design Report-Page 3 of 6 Measurements obtained by the City of Bozeman Water Department indicate a static pressure of 90 psi and a residual pressure of 88 psi at hydrant#1960. Flow rate and pitot pressure were obtained from fire hydrant #1961 located near hydrant #1960. Measurements obtained by the City of Bozeman Water Department indicate a flow rate of 1,455 gpm and a pitot pressure of 75 psi at hydrant#1961. This flow/pressure information was used to develop relationships between static head and flow at the connection point. This relationship was used in the model by simulation of a pump at the connection point. The pump is connected to a reservoir which acts as a source of water. The elevation of the reservoir is fixed at the elevation of the pump, which is also equivalent to the elevation of the connection point. The reservoir does not create any head on the system;the head is generated entirely by the pumps. The input data and the pump curves are included in Appendix A. DISTRIBUTION MAIN The 8-inch DIP water mains do provide capacity with regards to the Peak Hour Demands. The flows and pressures within the system for the Peak Hour Demands were generated with the WaterCAD program and can be found in Appendix A. The capacity of the system to meet fire flow requirements was tested by running a steady state fire flow analysis for all junctions at fire hydrant locations. The model shows that all hydrant junctions satisfy fire flow constraints (residual pressure > 20 psi, flow rate > 1500 gpm), while providing service to lots at peak hour. The results of the analysis at peak hourly flow are given in Appendix A. SEWER SYSTEM In the Baxter Square Subdivision Phase 3, an 8-inch PVC sewer line will be installed in Renee Way and will flow south to connect with the existing 8-inch main located in Sartain Street. An Design Report-Page 4 of 6 additional line will start on the west property boundary in Georgia Marie Lane and run east until it intersects with the line in Renee Way. DESIGN REQUIREMENTS The flow rates used herein are according to the City of Bozeman Design Standards and Specifications Policy (DSSP) dated March, 2004. The peaking factor for the design area is determined by figuring the equivalent population and inserting the population into the Harmon Formula. An 8-inch main is used because that is the minimum diameter allowed within the City of Bozeman. Using the city average of 2.11 persons per household the equivalent is calculated. Connection: Equivalent Population = (2.11 persons/dwelling unit)(22 units)=46 persons Harmon Formula: Peaking Factor=(18 +Pos)/(4 +P°-') where: P =Population in thousands Peaking Factor=(18 +0.046°-5)/(4 + 0.0460-5) Peaking Factor=4.32 Assumed infiltration rate= 150 gallons/acre/day= 150 (2.57 acres)=386 gal/day The peak flow rate is calculated by multiplying the City`s design generation rate of 89 gallons per capita per day by the population,multiplying by the peaking factor,and adding the infiltration rate: Peak Flow Rate = 89 gpcpd (46 persons) (4.32)+ 386 gpd = 18,072 gpd = 12.55 gpm = (0.0280 cfs) The capacity of an 8-inch main is checked using Manning's Equation: Qeuu=(1.486/0.013)AR "S"2 Design Report-Page 5 of 6 For the 8-inch main: Manning's n = 0.013 for PVC Pipe Minimum Slope = 0.004 ft/ft A= area= (3.14/4)d 2= (3.14/4)(8/12)2=0.34907 ft2 P =perimeter=2(3.14)r=2(3.14)(4/12) = 2.0944 ft R=hydraulic radius=A/P = 0.34907/2.0944=0.16667 ft R2'3 =0.30105 ft S = 0.004 ft/ft S 112= 0.0632 ft/ft Qf,,n = (1.486/0.013)(0.34907)(0.30105)(0.0632) =0.7592 cfs Connection: Q/Qf„11 = 0.0280/0.7592 =0.0368 or 3.68% Based on these calculations, an 8-inch sewer line is more than adequate to carry the design flows for the subdivision. The 8-inch sewer line will connect to the existing manhole in Sartain Street. Wastewater flows via an 8-inch PVC pipe east to Thomas Drive/future 27"' Avenue then north where it eventually connects to the 27t1'Avenue/Cattail Creek Interceptor at the intersection of 27`t' Avenue and Cattail Street. The 2007 Bozeman Wastewater Facilities Plan indicated that all sanitary sewer lines downstream of the proposed subdivision are operating at less than 50%of pipe capacity for the peak day model. Design Report-Page 6 of 6 DESIGN REPORT STORMWATER MANAGEMENT BAXTER SQUARE SUBDIVISION PHASE 3 Prepared for: Baxter Square Partners, LLC 1627 W. Main Street, #117, Bozeman, MT 59715 Prepared by: C&H Engineering and Surveying, Inc. 1091 Stoneridge Drive, Bozeman, MT 59718 406 587-1115 kA it �if'GS'L.'i'~•�:fti...:,,�'�'� =�yJ Project Number: 14305.1 JANUARY 2015 INTRODUCTION The Baxter Square Subdivision, Phase 3 is a proposed 22-lot subdivision located north of Sartain Street and west of Thomas Drive. The 2.57-acre development is situated in the Southeast Quarter of the Southwest Quarter of Section 35, Township 1 South, Range 5 East of P.M.M., Gallatin County, Montana. This project will require connection to existing City of Bozeman sewer, water and street systems. STORMWATER MANAGEMENT Storm water runoff from the subdivision will be conveyed to one retention facility. A plan view of the site highlighting the drainage areas and the storm water features is included in Appendix 3-B of this construction submittal. DESIGN METHODOLOGY The Rational Method will be used for peak flow determination and design. The storm water retention basin will be sized to handle a 10-year, 2-hour storm intensity event. Storm intensity will be calculated from the tables included in the City of Bozeman Design Standards and Specification Policy (DSSP). DRAINAGE AREA#1 Beginning at the northeast corner of the property, Drainage Area 1 then proceeds southerly along the east property line to the southeast property corner. The said area then proceeds westerly along the south property boundary to the centerline of Renee Way where it then turns northerly along the centerline of Renee Way to the northern property boundary. The boundary then closes back on the northeast property corner. See Drainage Area map in Appendix 3-B. Contributing Areas: Lot Area(C=0.35) =49,060 ft2 Street/ Sidewalk (C=0.95) = 10,161 ft2 Open Space/Blvd. (C=0.2) =4,746 ft2 Total =63,967 ft2 Design Report-Page 2 of 9 = 1.4685 acres The composite runoff coefficient for all of Drainage Area I is calculated as: Q _ [(0.35*49,060 ft2) + (0.95*10,161 ft2) + (0.20*4,746 ft2)] /63,967 ft2= 0.434 DRAINAGE AREA #2 Beginning at the Southwest corner of Open Space 2,Drainage Area 2 then proceeds along the west property line of the subdivision northerly to the centerline of Georgia Marie Lane. The said area then proceeds easterly along the centerline of Georgia Marie Lane until it intersects with the centerline of Renee Way. Then the boundary proceeds southerly along the centerline of Renee Way until it intersects the southern property boundary. The said area then heads westerly along the south property boundary to the southeast corner of Public Park 1.From there the boundary follows the boundary of Public Park 1 northerly to the southeast corner of Lot 5A, Block 2.The boundary then closes back on the southwest corner of Open Space 2 by moving westerly along the property boundary to the corner. See Drainage Area map in Appendix 3-B. Contributing Areas: Lot Area(C=0.35) = 13,447 ft2 Street/ Sidewalk(C=0.95) = 11,380 ft2 Open Space/Blvd. (C=0.2) = 7,782 ft2 Total = 32,609 ft2 =0.7486 acres The composite runoff coefficient for all of Drainage Area 2 is calculated as: C2 = [(0.35*13,447 ft2) +(0.95*11,380 ft2) + (0.20*7,782 ft2)] /32,609 ft2= 0.524 DRAINAGE AREA #3 Beginning at the northwest corner of the property, Drainage Area 3 then proceeds easterly along the northern property line to the centerline of Renee Way. The said area then proceeds southerly along the center line of Renee Way until it intersects Georgia Marie Lane where it turns westerly along the centerline of Georgia Marie Lane until it reaches the west property line. The boundary then closes back on the northwest property corner. See Drainage Area map in Appendix 3-B. Contributing Areas: Lot Area(C=0.35) = 10,501 ft2 Design Report-Page 3 of 9 Street/ Sidewalk (C=0.95) = 6,323 ft2 Open Space/Blvd. (C=0.2) = 8,379 ft2 Total =25,203 ft2 = 0.5786 acres The composite runoff coefficient for all of Drainage Area 3 is calculated as: C3 = [(0.35*10,501 ft2) + (0.95*6,323 ft) + (0.20*8,379 ft)] /25,203 ft2 = 0.451 The composite runoff coefficient for Drainage Areas 1 and 2 is calculated as: C1&2 = [(0.434*63,967 ft) +( 0.524*32,609 ft2 ) ]/(63,967+32,609) ft2 = 0.464 The total composite runoff coefficient for all three drainage areas is calculated as: Ctotal= [(0.524*32,609 ft) + (0.451*25,203 ft2) + (0.434*63,967 ft2)] / 121,779 ft2 = 0.462 RETENTION VOLUME The retention volume shall be calculated using the following formulas found in DSSP: Q= CIA V = 7,200*Q (ft3) Where: C = Weighted C factor(0.46) I = 0.41 in/hr(per figure 1-2 DSSP) A=Area(acres) Q =runoff(cfs) V= volume (ft) Q = (0.46)(0.41 in/hr)(2.7957 acres) = 0.5291 cfs V= (7,200) (0.5291) = 3,809(ft) RETENTION POND The retention pond has a volume of 3,987 ft3 and will service a drainage area with a total area of 2.79 acres. INLET PIPE SIZING The storm sewer pipes are designed to handle a 25-year storm event. Each of the three runs of Design Report-Page 4 of 9 stormwater pipe are sized according to their contributing areas. Inlet #1 receives runoff from Drainage Area 1. Combination Inlet/Manhole 41 receives runoff from Drainage Area 1 and 2. Combination hllet/Manhole #2 receives runoff from Drainage Areas 1, 2 and 3. Inlet#1, Drainage Area 1 The post-development time of concentration is first calculated to determine the peak discharge: Overland flow: Lot IA (108 ft @ 1.00% slope, C=0.35) = 13.895 min Gutter flow: Renee Way(355 ft @ 1.3% slope, n=0.013) = 1.768 min Total Time of Concentration= 15.663 min (0.261 hrs) For a 25-year storm event, Its = 0.78X"0.64= 0.78 (0.261)-0.64= 1.84 in/hr Q25 = CIA = 0.43 (1.84 in/hr) (1.4685 acres) = 1.16 cfs A 15-inch PVC pipe is proposed for the 149-ft section of storm sewer carrying runoff from Inlet#1 to Combination Inlet/Manhole#1. The capacity of a 15-inch PVC at the proposed slope is checked using Manning's equation: Qs,ii = (1.486/n)AR2i3S v2 Manning's n = 0.013 for PVC Slope = 0.0055 ft/ft A=area= (3.14/4)d 2=(3.14/4)(15/12)2= 1.2272 ft2 P =perimeter=2(3.14)r=2(3.14)(7.5/12) = 3.9270 ft R=hydraulic radius =A/P = 1.3956/4.1867 = 0.3125 ft R2/3 = 0.4605 ft S 1 i2 =0.07416 ft/ft Qr„u = (1.486/0.013)(1.2272)(0.4605)(0.07416)= 4.79 cfs 1.16<4.79 Therefore, a 15-inch PVC pipe will be adequate to handle the storm water discharge rates from Drainage Area 1. Check that minimum velocity of 3 ft/sec is maintained when flowing at design flow rate. Design Report-Page 5 of 9 MANNING'S EQUATION FOR PIPE FLOW Project: Baxter Square Location: Pipe 1 By,Tim Staub Date: 1/2012016 Chk.By: Data__- lClear Data 6 jEntDj Cells INPUT D= 15 inches 7 d= 4,39 inches IvIannings Formula d n= 0.01 mannings D C= 131.0 degrees Q=(1_486in)AR, ­S, S= 0.0055 slope infin R=A,'P A=cross sectional area P=weffed perimeter V=(1.49!n)R�Z 2s,,�2 S=slope of channel Q=VxA n=Manning's roughness coefficient Solution to blannings Ecuation Manning's n-values Vietted Hydraulic Area,ft: Perimeter,ft Radius,ft velocity fUs low cfs Pl..(C 0.01 0.30 1,43 0.21 3.89 1.16 1 PE(,�Vdia) 0.015 PE(>12"dia) 0.02 PE(S-12'dia3 0.017 UP 0.02S ADS 1,112 0.012 HClJP 0.023 Conc 0.013 Combination Inlet/Manhole 41, Drainage Area I and 2 The post-development time of concentration is first calculated to determine the peak discharge: Overland flow: Lot IA (108 ft @ 1.00% slope, C=0.35) = 13.895 min Gutter flow: Renee Way(355 ft @ 1.3% slope, n=0.013) = 1.768 min Pipe flow from Inlet 4 1 to Combo Inlet/Manhole #1=3 8 see (0.63 min) Total Time of Concentration= 16.296 min (0.2716 hrs) For a 25-year storm event, 125 = 0.78X-0-64= 0.78 (0.2716)-0.64= 1.79 in/hr Q25 = CIA = 0.464 (1.79 in/hr) (2.2171 acres) = 1.84 cfs A 15-inch PVC pipe is proposed for the 25-ft section of storm sewer carrying runoff from Combination Inlet/Manhole#1 to Combination Inlet/Manhole#2. The capacity of a 15-inch PVC at the proposed slope is checked using Manning's equation: Qfuii = (1.486/n)AR 2/3SI/2 Manning's n= 0.013 for PVC Slope = 0.0055 ft/ft Design Report-Page 6 of 9 A =area= (3.14/4)d _ (3.14/4)(15/12)2= 1.2272 ft2 P =perimeter=2(3.14)r= 2(3.14)(7.5/12) = 3.9270 ft R=hydraulic radius = A/P = 1.3956/4.1867 = 0.3125 ft R211 = 0.4605 ft S v2 = 0.07416 ft/ft Qfuil = (1.486/0.013)(1.2272)(0.4605)(0.07416) =4.79 cfs 1.84<4.79 Therefore, a 15-inch PVC pipe will be adequate to handle the storm water discharge rates from Drainage Area 2. Check that minimum velocity of 3 ft/sec is maintained when flowing at design flow rate. MANNING'S EQUATION FOR PIPE FLOW Project: Baxter Square Location: Pipe 2 By:Tim Staub Date: V2012015 Chk.B Date. Clear Data Entry Cells r INPUT D= 15 inches ' d= 5.59 inches Polannings Formula d r' n= 0.01 mannings 6= 150.5 degrees Q=(1.48Gfn)AR`"S"` S= 0.0055 slope Win R=A1P A=cross sectional area P=wetted perimeter V=(1A9fn)R"'S'" S=slope of channel Q=V x A n=tlanning's roughness coefficient Solution to Mannings Ecuation Planning's n-values 'Aletted Hydraulic Area,ft' Perimeter,ft Radius,ft •.�ebcdy fVs flow,cfs PVC 0.01 0.42 1.84 0.25 �2 1.85 PE(<9"dia) 0.015 PE(>12"Cia) 0.02 PE(9-12"dia) 0.017 CLIP 0.025 ADS N12 0.012 HCP,1P 0.023 Ccnc 0.013 Combination Inlet/Manhole #2, Drainage Areas 1, 2 and 3 The post-development time of concentration is first calculated to determine the peak discharge: Overland flow: Lot IA (108 ft @ 1.00% slope, C=0.35) = 13.895 min Gutter flow: Renee Way(355 ft @ 1.3% slope, n=0.013) = 1.768 min Pipe flow from Inlet 1 to Combo Inlet/Manhole#1=38 sec (0.63 min) Pipe flow from Combo Inlet/Manhole #1 to #2=7 sec (0.12 min) Total Time of Concentration= 16.413min (0.2736 hrs) Design Report-Page 7 of 9 For a 25-year storm event, I25 = 0.78X-0-"= 0.78 (0.2736)"0 64= 1.79 in/hr Q25 = CIA = 0.462 (1.79 in/hr) (2.796 acres) = 2.31 cfs A 15-inch PVC pipe is proposed for the 45-ft section of storm sewer carrying runoff from Combination Inlet/Manhole #2 to the retention pond. The capacity of a 15-inch PVC at the proposed slope is checked using Manning's equation: Qmi = (1.486/n)AR2i3Sv2 Manning's n= 0.013 for PVC Slope = 0.0052 ft/ft A = area= (3.14/4)d 2=(3.14/4)(15/12)2= 1.2272 ft2 P =perimeter=2(3.14)r= 2(3.14)(7.5/12) = 3.9270 ft R=hydraulic radius =A/P = 1.3956/4.1867 = 0.3125 ft R2/3 = 0.4605 ft S v2 =0.07211 ft/ft Qfuii =(1.486/0.013)(1.2272)(0.4605)(0.07211) =4.66 cfs 2.31<4.66 Therefore, a 15-inch PVC pipe will be adequate to handle the stone water discharge rates from Drainage Area 1, 2 and 3. Check that minimum velocity of 3 ft/sec is maintained when flowing at design flow rate. F,IANNING`S EQUATION FOR PIPE FLOW Project: Baxter-Square Location: Pipe 3 By:Tim Staub Date: 1120i2015 Chk-BV: Date: Clear Data 8 Entry Cells f INPUT D= 15 inches \ d= 9.87 inches Mannings Formula d n= 0A1 mannings `\D 6= 143.2 degrees Q=(1.486,1n)AR,2,`S'" S= 0.0052 slope in/in R=AIP A=cross sectional area P-wetled perimeter V=(1.491n)R;2'2S"2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to 6lanniings Equation Manning's n-values Wetted Hydraulic .Area,ft' Perimeter.It Radius,tt valocdy tt/s fbr�,cfs PVC 0.01 0.86 2.37 0.3E 5:44 4.E£ PE(<9"dia) 0.01E PE(�12'dia) 0,02 PE(9-12"dis) 0.017 C14P 0.025 ADS nit 0.012 HUM 0,023 Conc 0.013 Design Report-Page 8 of 9 GUTTER CAPACITY CHECK The longest run of water flowing in a gutter on-site is from the high point at the south end of Renee Way, flowing north in the west gutter around the curb return and onto Georgia Marie Lane, where it flows to Inlet 2. This stretch of gutter has a distance of 440 feet, the same distance that was used in calculating the time of concentration for sizing Inlet 2. The flow from Drainage Area 2 was calculated previously to be 2.7 cfs. The gutter capacity of this section of curb is calculated as follows. Qfuu = (1.486/n)AR213Sii2 Manning's n= 0.013 for concrete Slope = 0.015 ft/ft A = area= 1.24 ft2 P =perimeter= 9.23 ft R= hydraulic radius = 0.13 ft R2/3 =0.2623 ft S v2 =0.1225 ft/ft Qf«u = (1.486/0.013)(1.24)(0.2623)(0.1225) =4.55 cfs 2.7<4.55 Therefore, the longest section of curb is able to adequately handle the runoff and maintain a depth of at least 0.15 feet below the top of curb. Design Report-Page 9 of 9 PAVEMENT DESIGN REPORT BAXTER SQUARE SUBDIVISION PHASE 3 Prepared for: Baxter Square Partners, LLC 1627 W. Main Street Ste. #117, Bozeman MT 59718 Prepared by: C&H Engineering and Surveying, Inc. 1091 Stoneridge Drive, Bozeman, MT 59718 (406)5 7. 1115 "J r Project Number: 14305.1 January 2015 LOCAL STREETS WITHIN SUBDIVISION PUBLIC RIGHT-OF-WAY SOIL CONDITIONS Test pits were excavated across the proposed subdivision on March 23, 2003. The 11 test pits revealed very similar soil profiles. The subsurface conditions were generally observed to consist of 2 to 2.5 feet of an Organic Soil of Low Plasticity (OL) followed by a layer of Silty Clay (ML- CL)to depths ranging from 2 feet below grounds surface (bgs) to 6.5 feet bgs, after which Poorly Graded Gravel with Sand and Cobbles was encountered to the end of each excavation at approximate depths of 6.5 feet bgs to 9.3 feet bgs. Groundwater was encountered at the end of each excavation, with the seasonal high groundwater elevation estimated to be 4 to 8 feet bgs. The Standard Test Method for California Bearing Ratio (CBR) of Soils in Place, based on ASTM Designation D 4429, which requires complex and specialized equipment, was used by HKM Engineering Inc. to determine a CBR value for the overall subdivision. Their CBR result of 7.1 was used in the design report for Georgia Lane and Renee Way, and is also used for this report. STREET DESIGN Criteria for design: Bozeman Municipal Code, Section 38.24.060 and City of Bozeman Design Standards and Specifications Policy, Addendum No. 4, Section IV.G: pavement thickness design will be based on the current AASHTO Guide for Design of Pavement Structures, or the current Asphalt Institute Manual Series No.I (MS-1). The design shall be based on a minimum 20 year performance period traffic volume, with the minimum design lane based on a minimum of 50,000 ESAL. According to minimum traffic design standards each single family lot will generate 10 vehicle trips per day. The estimated traffic after all 22 subdivision lots are built-out is expected to be approximately 220 vehicle trips per day within the subdivision during the average weekday. All of the roads in the proposed subdivision contain two driving lanes (one in each direction) so the number of trips per day is divided in half to calculate the ESAL value for each lane. Average daily traffic per lane equates to 220/2 = 110 vehicles per lane per day (vplpd), which equates to 110 vplpd x 365 days/year=40150 vehicles per lane per year. The following assumptions were made while calculating the Total ESAL: 2% of the AYT will consist of heavy trucks or buses Growth rate = 4% over 20 years 2000 lb axle load for cars, and 10,000 lb axle load for trucks. 2 axles per vehicle Based on 2% of the traffic being trucks/buses, this yields 39,347 cars per lane per year, and 803 trucks/buses per lane per year at full build out. Traffic Estimate for Local Streets within Subdivision Vehicle Type Vehicles Growth Design Vehicles ESAL Factor Design per year Factor (20 years) ESAL (4%,20yrs) Passenger Car 39,347 29.78 1,171,754 0.0003*2=0.0006 703 2 axle/6 tire 803 29.78 23,913.34 0.118*2=0.236 5,644 truck/bus Total ESAL 6,347 The calculated estimate of the equivalent 18,000 lb Single Axle Load(ESAL) = 6,347 The calculated ESAL is less than the minimum 50,000 ESAL design requirement. Therefore, ESAL=50,000 shall be used for all calculations. According to the California Bearing Ratio (CBR) Test (ASTM-D 1883/AASHTO T193) performed by HKM Engineering Inc., the CBR used for the subgrade soil is 7.1. CBR can be related to the subgrade Resilient Modulus MR by the following: (Sec. 3.5.4, Highway Engineering Handbook, McGraw Hill, 1996) Subgrade Resilient Modulus MR (psi): MR= 1,500 CBR (Shell Oil Co.) This value used by Asphalt Institute. Ma = 5,409 CBR0-711 (United States Army Waterway Experiment Station) MR = 2,550 CBR0-14 (Transport & Research Laboratory, England) With CBR= 7.1 MR = 1,500 CBR = 1,500 (7.1) = 10,650 psi MR = 5,409 CBR'-"' = 5,409 (7.1)0.71 1 = 21,795 psi MR=2,550 CBR0.64 =2,550 (7.1)0-64 = 8,940 psi Use most conservative value= 8,940 psi USING THE AASHTO METHOD OF FLEXIBLE PAVEMENT DESIGN The AASHTO method utilizes a value known as the Structural Number (SN) which relates the below variables to the wear surface, base, and sub-base depths. Structural Number Equation(EQ 1): I o OPSI log W18 = ZRSo + 9.36[log(SN + 1)] - 0.20 + g T.T + 2.32 log MR 0.40 + 1094 5.19 Variables: 1. ESAL(W 18) = 50,000 2. Level of Reliability (ZR) _ -1.282 for Local Streets used for Local Streets based on 90% reliability from Part I, Table 4.1, and Part II, Table 2.2, AASHTO Guide. Level of reliability is based on the cumulative percent of probability of reliability with a standard normal distribution. 3. Standard Deviation (SO) = 0.49 for flexible pavements. See Part I, Sec. 4.3, AASHTO Guide. The standard deviation is the statistical error in the estimates for future values within the formula. Typical values range from 0.40-0.50 for flexible pavements, with a value of 0.49 used to ensure a conservative solution. 4. Serviceability Loss (OPSI) =2.2 for Local Streets. The designed allowable deterioration of the roadway is represented by the serviceability loss. A new road is usually assigned a serviceability index of 4.2 and the final index is based on the type of roadway. Local streets are normally allowed to deteriorate to 2.0. The resulting difference in the initial to final indexes is the total serviceability loss. 5. Soil Resistance Modulus (MR) = 8,940 psi Solution: using (EQ 1), the SN for Local Streets= 1.99 Pavement Design Equation (EQ2): SN = a1D1 + a2D2M2 + a3D3M3] 1. Layer Coefficients: a, = 0.44 (IIot-mix asphalt concrete) a2 = 0.14 (Base Course - 1 '/2" minus crushed gravel) a3 = 0.11 (Sub-base Course - 6" minus crushed stone) 2. Drainage Coefficients: m2 = 1.00 (good drainage 5-25%) m3 = 1.00 (good drainage> 25%) % of time base & sub-base will approach saturation 3. Layer Depth Assumptions: DI = 3" for Local Streets D2 = 6" for Local Streets Solution: using the values given for D1 and D2, and solving (EQ2), D3 = -1.55" for Local Streets Based on soil profile in the area of the proposed subdivision, top soil extends to a depth of 24 to 30 inches. Top soil will have to be removed prior to road construction. Based on top soil removal use a street sub-base section of 18" on the Local Streets. This results in an asphalt section of 3", a base course of 6", and sub-base course of 18" for the Local Streets. SPECIAL CONSIDERATIONS Field data we have obtained shows groundwater depths across the site vary between 2 to 6 feet below the grounds surface. Past experience with road construction in the Gallatin Valley has shown us that the clay loam encountered is highly moisture sensitive. All subgrade material should be proof rolled prior to placement of pit-run to check for structural competence. Where saturated materials or soft spots are encountered one of three alternatives should be pursued. 1. The first alternative is to allow the subgrade to dry out. For fine-grained soils, this is best accomplished by frequently scarifying them during warm climactic conditions. This is the least expensive method but can cause delays to the project with even minimal precipitation. Prior to stopping work for the day it is recommended that all scarified soils be re-rolled with a smooth drum roller to seal them against moisture infiltration. 2. Option 2 is the over-excavation of the subgrade soils and replacement with compacted engineered fill. When this option is exercised we recommend that the over-excavation occur down to native sandy gravels. This option is most effective when native sandy gravels are found within a reasonable depth from bottom of sub-base. 3. Option 3 includes over-excavation of subgrade soils and installation of a geotextile fabric and approved geogrid. This option should be utilized whenever there isn't time for the subgrade to dry out and when native sandy gravels are located at excessive depths. If this option is chosen, the engineer will need to be involved for geotextile and geogrid design, and inspection and compaction testing during construction. Project# 14305.1 Title: Baxter Square Subdivision Phase 3 To solve for minimum required Sub-Base depth,we first need to calculate the Structural Number(SN). Calculating SN can be accomplished by formula or graphically(AASHTO Guide for Design of Pavement Structures) Required Values For SN Calc W16 (ESAL) Equivalent Single Axle Load R(%) Probability serviceability will be maintained over the design life(R is used for graphical solution) ZR Probability serviceability used in numerical solutions(Equated to R by table below) So Standard Deviation in estimates for ESAL,typically 0.30-0.50 APSI Serviceability loss over design life MR Soil Resistence Modulus of subgrade soil EQ 1: log APSI log W18= ZRSo+ 9.36[log(SN+ 1)]— 0.20+ 1094 2.7 + 2.32logMR— 8.07 0.404 SN+ 1)5.19 Equivalent Single Axle Load ADT 220 Peak A.M. Peak P.M. Total 220 AYT 40150�(per lane) Assumptions: 2 %of AYT Consisting of Heavy Trucks 4 %over 20 Years Growth Rate Lb/Axle 2000 for cars Lb/Axle 10000 for trucks Initial SN 3 AASHTO tables for ESAL Factor are based on SN and above listed axle loads Vehicle Type Vehicles Per Year Growth Factor Design Vehicles ESAL Factor Design ESAL (4%,20 years) (20 years) Passenger Car 39347.00 29.78 1171754 0.0006 703 2 Axle/6 Tire Truck 803.00 29.78 23913.34 0.236 5644 Total ESAL l_ 6347 or Use Minimum Value of _ 50,000 Level of Reliability(R and ZR) R to ZR Conversion Chart R ZR 90 -1.2820 95 -1.6450 97.5 -1.9675 99 -3.0800 R(%)= 90 (Conservative estimate) ZR= -1.282 Standard Deviation(So) So=' 0.49 Serviceability Loss(APSI) Road Type vs.T_SI Present Serviceability Index(PSI)= 4.2 Highways 3.0 Terminal Serviceability Index(TSI)= 2.0 Arterials 2.5-3.0 Local Roads 2.0 APSI= 2.2 �sistance Modulus(MR) CBR 7.1 Determined on basis of soil analysis MR= 10650 Shell Oil Co. (Should not be used for CBR>10) MR= 21795.24 U.S.Army Waterway Experimentation Station MR= 8940.16 Transport&Research Laboratory,England Use most conservative value of the three methods to calculate MR 8940.16 Structural Number(SN) SN 1.9895„ 058211Calculated by EQ 1 - ._ Once SN is determined,the thickness of the wearing surface,base,and subbase layers can be determined by EQ 2. EQ 2: SN= a,D,+ a2D2M2+ a3D3M3� a,,a2,a3 structural layer coefficients of wearing surface,base,and subbase Mr M3 drainage coefficients of base and subbase D,,D2,D3 thickness of wear surface,base,and subbase in inches Structural Layer Coefficients(a) Pavement Component Coeffiecient Wearing Surface Sand-mix asphaltic concrete 0.35 Hot-mix asphaltic concrete 0.44 Base Crushed Stone 0.14 Dense-graded crushed stone 0.18 Soil cement 0.2 Emulsion/aggregate-bituminous 0.3 Portland cement/aggregate 0.4 Lime-pozzolan/aggregate 0.4 Hot-mix asphaltic concrete 0.4 Subbase Crushed Stone 0.11 a,= 0.44 (Hot-mix asphaltic concrete) 0.14 (1 1/2"Minus crushed gravel) a3= 0.11 (6"Minus crushed stone) Drainage coefficients(M) M2= 1.00 Good Drainage M3= 1.00 Good Drainage Layer Thickness D,= 3 Assumed(in inches) D2= 6 lAssumed(in inches) Solve for D3 _1_55 Solver set Objective= 4,698969 To a value of= 4.69897 7 N 0 10 �- Ul in '- m � 0) = N 16 (a � > � o mU m c m rn W c ?S w u m "o N a` r m tL In h Cl) a � N �� C + VJ c0 O r l0 � o 0 c _ AeM aaUaZtJ oo =z T lid na lCl LL 3 m � N N a �+ o a0 LO d C + rn m c v --� - x Y M (0 U /W C co o J t d a) I� ' N ca {V P 0 C� M N CL d a c .N o m m v m U a m a `m r M a ah U a) mc N N V m m �- � n m �- N �- Calculation Results Summary Scenario:Peak Hour [Analysis Started] Wed Jun 18 16:01:32 2014 (Fire Flow) Failed to Converge.......0 Satisfied Constraints....6 Failed Constraints.......0 Total Nodes Computed.....6 [Steady State] 0:00:00 Balanced after 2 trials;relative flow change=0.000221 Flow Summary 0:00:00 Reservoir R-2 is emptying (Analysis Ended] Wed Jun 18 16:01:32 2014 Title:Baxter Square Subdivision,Phase 3 Project Engineer:Matt Hausauer zA...\design reports\baxterwatercad.wcd C&H Engineering&Surveying,Inc. 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N N O aa� � y M d mxz O m m m d' t() to t- c0 O) m II ti t- N .- \ \( / \\ = aCL ] / % < ` f \ c / z S cu e ]ƒ OM m G � to % § j ƒ \\ \ . ( // o § ® 2 c my ) E / \ \K � § m _ § \ § § J c @ C ¢ 5- @ &] 2 a) k 2 $ fg2 2 R e 8 } / � {k F / I � O � k) } 3« / n B ° ) d mR ƒ /k E @ � > m / \ } \ / � /{§ } 1 mee ( $ c — / . . m ® c o10 F-N ( Detailed Report for Pump Definition: Baxter Pump Head Characteristics Pump Type Multiple Point Discharge Head (gpm) (ft) 0.00 207.69 2,386.44 196.15 3,469.82 184.62 4,319.13 173.08 5,045.02 161.54 5,691.08 150.00 6,279.89 138.46 6,825.01 126.92 7,335.32 115.38 7,817.03 103.85 8,274.67 92.31 8,711.69 80.77 9,130.79 69.23 9,534.11 57,69 9,923.38 46.15 10,300.06 34.62 10,665.36 23.08 11,020.29 11.54 11,365.74 0.00 Pump Efficiency Characteristics Efficiency Type Constant Efficiency Pump Efficiency 100.0 % Motor and Drive Characteristics Motor Efficiency 100.0 % Variable Speed Drive? false 250.0 200.0 150.0 - 100.0 - 50.0 0.0 0.0 2000.0 4000.0 6000.0 8000.0 10000.0 12000.0 Title:Baxter Square Subdivision,Phase 3 Project Engineer:Matt Hausauer z:\...\design reports\baxterwatercad.wcd C&H Engineering&Surveying,Inc. 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