HomeMy WebLinkAbout17 - Design Report - Story Mill Community Park - Water, Sewer ���1NEE1/jyc
STAR LY ESt
www.seaeng.com Engineers and Land Surveyors
851 Bridger Drive,Suite 1,Bozeman, MT 59715 phone:406-522-8594 1 fax:406-522-9528
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Story Mill Community Park
Water and Sewer Engineering Report 0.c�p.,..`',
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August 4, 2017 o', No.11645PE �w
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Prepared for: City of Bozeman Engineering Department '�SS/oNAk. ""'�
Prepared by: Stahly Engineering and Associates
Cordell D. Pool, PE— Project Engineer
Introduction
Story Mill Community Park is a proposed public park located at 600 Bridger Drive, in Bozeman MT,
59715. The park site has been partially improved to enhance the environmental aspects including,
but not limited to, floodplain grading, stream and wetland restoration, planting native vegetation, and
removing existing structures. Existing city water and sewer mains are available to be used on the
west side of the park. The existing mains serve the previously occupied Boys and Girls Club
building, which was incorporated into the park project and is now the Story Mill Community Center.
Major demolition items include removing old trailer park pavement, a few existing buildings, and
abandoning services per city requirements. The proposed improvements to be added to city utilities
include two new fire hydrants, park restroom, children's splash pad play area, and demonstration
garden. Site improvements are displayed on the Civil Plans. This Engineering Report supports the
design of the water and sewer service lines and new fire hydrants. A storm water design report was
submitted separately.
Civil Specifications and Design Standards
The civil specifications for the project will be the Montana Public Works Standard Specifications
(MPWSS) and the City of Bozeman Modifications to MPWSS (COB Mods). Construction plans will
be developed in accordance with the City of Bozeman Design Standards.
Water
City water is provided by an existing 12" main in Bridger Drive via a 12" x 6" tee and existing 6" main
under the community center driveway. The existing 6" main provides services to the community
building, supplies a fire hydrant 100' north of the building, and ends at a blow-off valve at the
southeast end of the existing driveway. This project consists of adding a new 2" water service and
two new hydrants to the existing 6" main.
The new 2" water service will supply the park restroom, future splash pad, and demonstration
garden. The Uniform Plumbing Code was utilized to estimate the peak demand of the restroom. The
restroom has toilets with flush valves, and the mechanical engineer provided a total fixture count of
44 water fixture units, corresponding to a peak flow rate of 44 gpm. The restroom total annual water
use and seasonal daily flow were estimated using existing City of Bozeman East Gallatin Rec Area
restroom meter readings from 2015 and 2016. The proposed restroom is similar to the restroom at
the East Gallatin Recreation Area. That is, both restrooms use toilet flush valves and have
approximately the same number of fixtures. In 2015, the East Gallatin restroom used 0.168 ac-ft and
had a maximum daily use during June-July of 591.2 gpd. In 2016, it used 0.177 ac-ft with a
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Test Number: 15 RESIDUAL HYDRANT FLOW HYDRANT#1 FLOW HYDRANT#2
Test Date: 912912015 Hydrant No. 1861 1863 1862
Hydrant No. Hydrant No.
Start Time: 9:52 AM HPR No. 1240
HPR No. 1241 HPR No. 201250
End Time: 10:08 AM Static: 137.8 psi Flow: 1,441 gpm Flow: 1,426 gpm
Test By: JDH Residual: 86.1 psi
Zone: NORTHEAST Test Hydrants �� Flow Hydrants Other Hydrants
Bozeman Water Distribution
System Model Calibration
Field Test Data Sheet c
maximum daily use in July of 619.4 gpd. Therefore, based on the 2016 data, the new Story Mill
Community Park restroom has an anticipated annual total use of 0.177 ac-ft with a maximum daily
use of 619.4 gpd.
The future splash pad is a water play area for children with button activated play features that create
brief fountains. The splash pad uses a recirculating water supply that is continuously treated.
However, water is lost by evaporation and on swimsuits. After the initial fill, make-up water is
required to keep the recirculation system full. A splash pad designer provided a typical make-up
water use rate of 0.65 gpd/sf derived from previous splash pad projects. The Story Mill splash pad is
1,215 sf, equating to a daily use of 792 gpd during the operating season. The make-up water is
supplied by an automatic valve periodically opening. Assuming a daily make-up time of 1 hour for
the splash pad yields a peak demand of 13.2 gpm (792gal/60 min). The total annual volume for the
splash pad was calculated assuming that the pad is re-filled at 762 gallons per day for an operating
season of June 1 to August 31, or 92 days. This equates to a total annual volume of 0.224 ac-ft and
a maximum daily use of 792 gpd.
Park landscape irrigation water will be supplied by new irrigation wells. However, a 2,415 sf
demonstration garden will be irrigated by city water. Typical annual water irrigation use for gardens
is 29 inches per year. Thus, the total annual use is estimated at 0.134 ac-ft, or 43,655 gallons. It is
anticipated that this volume will be applied from June to September, approximately 120 days of the
year, for a daily use of 364 gpd. A typical watering rate is assumed to be 10 gpm (one hose bib at a
time). At a flow rate of 10 gpm, the daily watering time required is 36.4 minutes (364gal/10gpm).
The estimated water use data for the new 2" service is summarized in Table 1.
Table 1 —Water service use summary
Annual volume Annual Volume Daily Flow(gpd) Peak flow
Description al Ac*ft (gpm)
Restroom(4wash closets) 57,596 0.177 619.4 44.0
1215 sf splash pad 72,900 0.224 792.4 13.2
2415 sf demonstration garden (29 in/year) 43,655 0.134 363.8 10.0
Total= 174,151 0.534 1,775.6 67.2
Based on a maximum velocity of 10 ft/sec in the water meter, this flow rate will require a 2" service
line and water meter.
Two new fire hydrants are proposed at the park. A nearby hydrant flow test conducted by city
representatives indicated that more than 2,000 gpm is available for fire flow in the area. The flow
test was performed on two existing fire hydrants about 600' north of the community center driveway,
the static water pressure was 138 psi, and the flow rate wa 2,867 gp with a residual pressure of
86 psi. This test indicates that the water system network in this area can rvivide the anticipated fire
flows and peak domestic demand with very little1�'mpact on the system pressures
Sewer
An 8" sewer main exists in the community center driveway. An existing 6" sewer service was
installed with this main to the park property. This service will be re-routed from the existing wye at
the main to the restroom building. The sewer will provide service to the park restroom and splash
pad. The restroom flow will be the same as the water use. The splash pad typically does not
Page 2
discharge to the sewer system except for large rainfall events that overfill the recirculation system
and filter backwashing. The filter backwash rate is typically in the range of 100 gpm for a very brief
time. However, this flow rate, in conjunction with the restroom rate, requires a 6" sewer. The sewer
service is 138' long with cleanouts provided at about 50' spacing. The sewer is proposed to be at a
1% slope to provide sufficient depth for the splash pad drainage. The sewer will be about 7' deep at
the restroom building. The capacity of a 6" sewer at 1% slope is 230 gpm at three quarters full,
sufficient to accommodate the restroom flow and splash pad filter backwashing.
Page 13
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Test Number: 15 RESIDUAL HYDRANT FLOW HYDRANT#1 FLOW HYDRANT#2
Test Date: 912912015 Hydrant No. 1861 1863 1862
Y Hydrant No. Hydrant No.
Start Time: 9:52 AM HPR No. 1240
HPR No. 1241 HPR No. 201250
End Time: 10:08 AM Static: 137.8 psi Flow: 1,441 gpm Flow: 1,426 gpm
Test By: JDH Residual: 86.1 psi
zone: NORTHEAST Test Hydrants 171 Flow Hydrants Other Hydrants
Bozeman Water Distribution
System Model Calibration
Field Test Data Sheet 15