HomeMy WebLinkAbout16 - Design Report - Sacajawea Middle School Expansion - Water, Sewer SANDERSON t�ir
STEWART
May 19, 2016
Project No. 15074.01
UTILITIES DESIGN REPORT
FOR
SACAJAWEA MIDDLE SCHOOL EXPANSION PROJECT
WATER MAIN RELOCATION
SITE NARRATIVE
The Sacajawea Middle School is located on a tract of land in the SW 1/4 of the SE 1/a of Section 24,
Township 25, Range 5E, P.M.M., City of Bozeman, Gallatin County, Montana. The school is
planning five expansions to the existing building which are to be constructed over the next two
years.
WATER
There is an existing 8-inch City of Bozeman water main which loops around the west side of the
school facility which provides fire protection, domestic and fire services to the facility. Several of the
planned expansions to the facility will land on top of the current water main, therefore as part of the
project the water main will be cut and abandoned in-place and a new water main loop installed
around the perimeter of the new expansions. Water Plan and Profile Sheet C5.2 attached shows the
alignment of the proposed water main. Two new fire hydrants will be installed in order to replace
two existing hydrants affected by the building expansions. Connections to the existing 4-inch
domestic and 6-inch fire service lines into the building will be extended from the new main.
The existing main being abandoned is an 8-inch diameter main and will be replaced by an 8-inch
PVC main. The existing pressures in the system near the school are approximately 50 psi static with
42 psi residual when flowing at 1090 psi (information supplied by the City of Bozeman per flow test
conducted on March 11, 2016). The school currently utilizes a domestic pump and a fire pump
within the building in order to facilitate pressure requirements. According to information from the
mechanical engineer on the project, the existing fire pump within the building is rated for 300 GPM
and is tested at a maximum flow rate of 450 GPM (150% of rated capacity). The existing water
system has a negligible drop in pressure at over 1,000 GPM. When the fire pump is running at a
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maximum flow rate during a pump test, the water system pressure won't even drop from the 50 PSI
static pressure. Only minor additional losses are expected within the main itself as part of the
relocation/expansion and should not affect the pressures at the fire hydrants compared to what
currently exists.
SANITARY SEWER
Sanitary service from the building is a 6-inch gravity service and exits from the east side of the
building. The service then connects to the City of Bozeman gravity system at the corner of S. 3rd
Avenue and Cambridge Drive to the northeast. One of the proposed expansions to the facility will
fall on top of the existing manhole located to the east. The existing manhole will be removed and a
new manhole installed on the existing 8-inch service line approximately 53 feet to the northeast. A
new service line will be extended from the proposed expansion to the new manhole.
The expansion of the school will facilitate an additional 220 students and faculty. Using Circular
DEQ 4, Table 5-1, the expected increase in sewage flows from the facility is 25 GPD/student, for a
total of 5,500 GPD, or 3.82 GMP average flow. The facility will contain 569 Total Water Supply
Fixture Units and 471.5 Total Sanitary Fixture Units upon full build-out. Using the Hunter's Curve
this translates to approximately 140 GPM or 8400 gallons per hour peak demand per the Uniform
Plumbing Code. The proposed expansions will contain 112 Total Sanitary Fixture Units. This
translates to approximately 20 GPM or 1,200 gallons per hour additional peak demand from the
proposed expansions. Calculations show that the 6-inch service line and existing 8-inch service line
will handle the flows adequately during the peak flow periods.
P:15074.0'1_Design_Memo_051916_SC 2 (05/19/'16)WRS/jil
Channel Report
Hydraflow Express Extension for AUtodesk®AutoCAD®Civil 3D®by Autodesk, Inc. Thursday, May 19 2016
New 6-inch Service Line
Circular Highlighted
Diameter (ft) = 0.50 Depth (ft) = 0.05
Q (cfs) = 0.015
Area (sqft) = 0.01
Invert Elev (ft) = 100.00 Velocity (ft/s) = 1.49
Slope (%) = 1.00 Wetted Perim (ft) = 0.32
N-Value = 0.010 Crit Depth, Yc (ft) = 0.06
Top Width (ft) = 0.30
Calculations EGL (ft) = 0.08
Compute by: Q vs Depth
No. Increments = 10
Elev (ft)
Section
101.00
100.75
100.50
100.25
v
100.00
99.75
0 1
Reach (ft)
Depth Q Area Veloo Wp
{ftj (cfs) (SGft) <(f#!s) (ft)
0.05 0.015 0.010 1.49 0.32
0.10 0.065 0.028 2.29 0.46
0.15 0.143 0.050 2.88 0.58
0.20 0.246 0.073 3.35 0.68
0.25 0.367 0.099 3.72 0.79
0.30 0.491 0.123 3.98 0.89
0.35 0.612 0.147 4.16 0.99
0.40 0.713 0.168 4.23 1.11
0.45 0.777 0.186 4.17 1.25
0.50 0.729 0.196 3.71 1.57
Hydraflow Express - New 6-inch Service Line- 05/19/16 1
t
Channel Report
Hydraflow Express Extension for AutodeskO AutoCADO Civil 3D0 by Autodesk, Inc. Thursday, May 19 2016
Existing 8-inch Service Line
Circular Highlighted
Diameter (ft) = 0.67 Depth (ft) = 0.07
Q (cfs) = 0.021
Area (sqft) = 0.02
Invert Elev (ft) = 100.00 Velocity (ft/s) = 1.15
Slope (%) = 0.40 Wetted Perim (ft) = 0.43
N-Value = 0.010 Crit Depth, Yc (ft) = 0.07
Top Width (ft) = 0.40
Calculations EGL (ft) = 0.09
Compute by: Q vs Depth
No. Increments = 10
Elev (ft) Section
101.00
100.75
100.50
100.25
100.00
99.75
0 1
Reach (ft)
Q8ptt1' Q At'efl V@JOG wP
0.07 0.021 0.018 1.15 0.43
0.13 0.089 0.051 1.76 0.62
0.20 0.197 0.089 2.22 0.78
0.27 0.340 0.132 2.58 0.92
0.34 0.507 0.177 2.86 1.06
0.40 0.678 0.221 3.06 1.19
0.47 0.844 0.264 3.20 1.33
0.54 0.984 0.302 3.25 1.48
0.60 1.073 0.334 3.21 1.68
0.67 1.006 0.353 2.85 2.10
Hydraflow Express - Existing 8-inch Service Line - 05/19/16 1