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Home My WebLink About15 - Design Report - South University District Ph 1 & Stadium View Apartments Amended for Ph 1B - Sewer Sewer Main Extension Engineer's Report South University District — Phase 1 , and Stadium View Apartments Amended for Phase 1 B December, 2015 Submitted to: City of Bozeman Engineering Department 20 East Olive Bozeman, MT 59715 Montana Department of Environmental Quality Permitting and Compliance Division Public Water and Subdivisions Bureau PO Box 200901 Helena, MT 59620-0901 Prepared by: Stahly Engineering and Associates 851 Bridger Drive, Suite 1 Bozeman, MT 59715 (406) 522-9526 ��1NEE�f�c STAH LY K-Ail NO. Engineer's Report Contents Note: The Engineer's Report format follows DEQ-2 organization. Additional information required by the City of Bozeman Design Standards is added where required. Report Narrative Chapter 10 — Engineering Reports & Facility Plans 11.1 Engineering Report 11.11 Problem Defined 11.12 Design Conditions 11.13 Impact on Existing Wastewater Facilities 11.14 Project Description 11.15 Design Criteria 11.16 Site Information 11.17 Environmental Impacts Figures and Tables Figure 1. Vicinity Map Figure 2. Sewer Site Plan (included separately) Table 1. Estimated Water Use Data Table 2. Capacity of 8" SDR 35 PVC Sewer Main Sewer Mains 1 12/22/2015 11.1 Engineering Report The South University District - Phase 1 B is a subsequent minor subdivision of Lot 2, SUD Subdivision Phase 1. The subsequent division will provide right of way dedications for South 14th Avenue, State Street and Campus Boulevard and will result in a 3.66-acre lot (Lot 2A), which will be the location of Phase 1 B. Phase 1 B is located within the City of Bozeman west of South 11 th Street and south of Kagy Boulevard. The subdivision is located west of SUD Phase 1 Lot 1 (completed Fall 2015) and south of the existing Stadium Center Subdivision. Phase 1 B is anticipated to be a 208-bed student housing project. The property developer's contact information is: Fountain Residential Partners 2626 Cole Ave, Suite 620 Dallas, TX 75204 Water supply and wastewater treatment will be provided by the City of Bozeman's municipal systems. The system owner's contact information is: City of Bozeman Public Service Department PO Box 1230 Bozeman, MT 59771-1230 The location of the South University District - Phase 1 B is shown on the Vicinity Map in Figure 1. Sewer Mains 2 12/22/2015 w 5 i t 1 Figure 1. Vicinity Map, Bozeman, Montana 11.11 Problem Defined City of Bozeman sewer mains currently extend to the eastern boundary of the property. Connection to the existing sewer infrastructure will take place at this point. The location of the existing mains and proposed extensions to the sewer system are shown on Figure 2 at the end of the report. The proposed student housing project in Lot 2A will be served by 8" sewer mains. These mains will connect to the existing 8" sewer mains on Lot 1, which in turn connect to the existing main on the northern border of Lot 1 at 12i" Avenue (Arianna Way). From this point, an 8" trunk sewer main flows from south to north through the center of the Stadium Center Subdivision and continues north eventually reaching the Bozeman Wastewater Treatment Plant. A sewer capacity analysis of the ability of the existing sewer to convey the additional sewer flow was conducted in November, 2014 and showed the existing infrastructure has capacity to serve SUD Phase 1 B. 11.12 Design Conditions The sewer flow contributed by the proposed student housing project within South University District - Phase 1 B was determined in accordance with Sewer Mains 3 12/22/2015 the City of Bozeman Design Standards. The site for Phase 1 B consists of a gross area of 6.41 acres, with 3.66 acres in Lot 2A. The peaking factor used was based on the total population at the connections to the existing sewer at the east edge of Lot 2A. The sewer flow estimates for the Stadium View Apartments Phase 1 B are shown in Table 1, below. Table 1 Stadium View Apartments Phase 1 B Sewer Flow Estimate Total Site Area acres 3.66 I&I rate d/acre 150 I&I Flow d 549 Student Housing Residents 208 -per capita flow d 89 Student Housing Flow d 18,512 Total Daily Flow d 19,061 Total Daily Flow m 13.2 Peaking Factor 4.14 Peak Flow m 54.8 The proposed 8" SDR 35 PVC sewer mains installed at the minimum slope of 0.4% have a flow capacity of 312.8 gpm using 75% of the flow depth of the pipe as required by the City of Bozeman Design Standards and Specifications Policy. See Table 2 below for the parameters used in the flow calculation. Table 2 Capacity of 8" SDR 35 PVC Sewer Main Status Proposed Location Phase 1 B Pipe Material 8"SDR 35 PVC Pipe Diameter(in) 8 Minimum Pipe Slope (ft/ft) 0.004 Coefficient of Roughness (n) 0.013 Depth in Pipe at 75% Full (in) 6 Depth of Flow(ft) 0.50 Pipe Radius (in) 4 Pipe Radius (ft) 0.33 Wetted Perimeter 1.40 Area of Flow(ft) 0.28 Hydraulic Radius 0.20 Velocity(ft/sec) 2.48 Maximum Pi a Flowrate m 312.8 Avg Flow%of Max Ca acit 4.2% Peak Flow%of Max Capacity 17.5% The minimum allowed slope in the minimum pipe size allowed has sufficient capacity to convey the peak flow from Lot 2A. Sewer Mains 4 12/22/2015 To allow easier maintenance 6" sewer services are provided for the proposed buildings. 11.13 Impact on Existing Wastewater Facilities As previously described, Phase 1 B consists of an additional 208-beds on lot 2A adjacent to Phase 1. The proposed Phase 1 B sewer mains connect to existing mains installed during Phase 1. An existing city sewer main is stubbed to the north property line of Lot 1 at South 12th Avenue. The capacity of this line to serve Phase 1 and Phase 1 B was evaluated. The existing service area of this line was determined and peak flows estimated based on existing land use. An initial review of pipe capacity showed the limiting section of this sewer to be located in the alley between 19th and 20th between Olive and Babcock streets. The flows were monitored for 33 days between August and September of 2011 and correlated to wet weather peak flows measured at the treatment plant in early summer. Sewer flow contributions were determined for the proposed development using the City's design standards. The existing pipe's capacity was evaluated with the existing wastewater flows adjusted to wet weather conditions and the addition of SUD Phase 1 and Phase 1 B contributions. The existing pipe is at approximately 66% of its 75% flow depth capacity under wet weather peak flows. SUD Phase 1 and Phase 1 B will contribute flows equivalent to an additional 21% of the existing pipe's 75% flow depth capacity, for a total pipe utilized capacity of 87% of the 75% flow depth. This evaluation shows the existing pipe has capacity to serve the Stadium View Apartments within its 75% flow depth at peak flow conditions. 11.14 Project Description The Phase 1 B Stadium View Apartments project is the second development phase within the Master Planned SUD Residential Emphasis Mixed Use (REMU) zoning district. Six student residential buildings are proposed within the Stadium View Apartment project. Altogether, the six buildings provide 56 living units and 208 student bedrooms. 11.15 Design Criteria The South University District— Stadium View Apartments Phase 1 B sewer main extensions were designed in accordance with Montana Department Sewer Mains 5 12/22/2015 of Environmental Quality Circular 2, Montana Public Works Standards and Specifications, City of Bozeman Modifications to Montana Public Works Standards and Specifications, the Uniform Plumbing Code, and the City of Bozeman Wastewater Facility Plan. 11.16 Site Information The site is typical of Bozeman with fine grained soils overlying gravel deposits. Geotechnical borings have determined the depth to gravel ranges from 7 to 10 feet. Estimated depth to groundwater obtained from the geotechnical borings is 6-13 feet. If mains are installed during high groundwater times dewatering may be required. 11.17 Environmental Impacts Continued use and new extensions of City of Bozeman municipal sewer mains has the least environmental impact. No new environmental impacts will be caused by these sewer main extensions. Sewer Mains 6 12/22/2015 STAH LY - STADIUM CENTER SUBDIVISION I d f I �AT EXISTING SEWER - _ STAHLY PHASE: 1 BOUNDARY ENGINEERING STATE STREET & ASSOCIATES PROFESSIONAL ENGINEERS b www.seaeng.cotom .Ii-� 404 W. BROADWAY UILDING 9 !- - I �11 LEWISTOWN, MT 59457 + / r Phona(406)S35-8594 O s uNlrs/za BDRMS. BLDG 7 BUILDINGS t. BUILDING 3 �� IJ I`1 R. 12 UNITS 12 UNITS/48 BDRMS, ,y' ,(I 33 UNITS/105 BDRMS. � 35EL CENTENNIAL 1 Ph—(406)41 2-859 01 N � _ __.JI� -_, � I` _.__. _....... ._.- --�,.i !, � Fox(406)442-6557 f' ,' ,`♦ 1 `., _. _ - -. -- ,-1 w 851 BRIDGER DR. STE. 1 6 ry - ff pr U BOZEMAN. MT 59715 O SEWER SIZE TYP XIST NG SEWER n JCS ( ) p I i Phone:4D6 522-9528 N z m Fox:(406)522-952s N _ 1 � - ' �� _). I�._ ISSUE/REVISION No. DATE BY 1 1s ISSUE DESCRIPTION SUED m 73SPACES I� PAC S Ll 1 ISSUESDESCROPTION SP�CES I �l ~ teInn _ BUILDING SERVICE lii CONNECT TO --'' No. DATE BY z z (TYP) EXISTING SEWER { — I I, 2 mm N _ HA j— � DESCRIPTION - -- LOT 2A l' LOT 1 F , �` I! I! -- 3.66 act. N 9.82 ac. .,i N3. DATE BY v - - r u i DESCRIPTION 1 - c __ t .•....T,. No. DATE BY i s CONNECT TO ' 1 4 ILU DESCRIPTION EXISTING SEWER :.•`. c. (_ '.-71 ! ICI �'�,"t. Q J G 89 SPACES' ^1U / - T No LLI 0 t 7 I J I I( l I I p DATE CES PHASE 1 N �' _ ! �— 5 P BY = I - DESCRIPTION STORMWATER PARK m . -� ;, �_ DETENTION 1+ o II s II EXISTING SEWER y � ' co a E � N BLDG 8 BUILDING 6 �I 1- BUILDING 4 LDING 1 BUIL=1O' - 1z uNITs/ !I 1 � I 12 UNITS/48 aDRMS.6UNIT 4B BDRMS. 33 UNITS/105 BDRMS. 1 ! 1 1 J - , - 1.. .. 3 -...-._ -.....— —_- ....... - _. __— SEWER SITE --jam-- ___ I v _ I CAMPUS BLVD CAMPUS BLVD, PLAN UCKY ROAD) I fi - -_ ST — -- LOT S (FUTURE PHASE I PHASE 1eAND ` ) I ;I EW AT SOUSTATH UNIVERSITYNIVIE SIITY a DISTRICT 7 a I I N II I. I BOZEMAN,MONTANA tt) ! JDS DESIGNED: 0 25 50 100 I� I, I DRAN: PD/JDS i I_I I CHECKED: CDP DATE 7/27/2015 SCALE IN FEET I I SHEET fi II FIGURE 2