HomeMy WebLinkAboutWater Design Compliance ReportBleyl & Associates
Project Engineering & Management
March 18, 2007
Carol Cotter, EIT
Planning & Development Department
City of College Station
P.O. Box 9960
College Station, TX 77842
Re: Wolf Creek Condos
Water Design Compliance Report
Dear Carol,
The following should provide the requested additional information for this project.
It should be obvious that the dead end assumption for this water line is the worst case
scenario when evaluating fire flow pressures and velocities, therefore the information
below is based on that condition.
It will be up to the Stewart Property to establish that they will be able to provide the
flows for their project with available water lines, including the line for this project if
approved in time.
The Domestic Water section of the UDM stipulates that for high density residential uses,
the Fire Marshall shall be contacted to obtain fire flow demand information. The Fire
Marshall has (like in most other cases) referred to the International Fire Code.
Based on the worst allowable construction type (Type V), and the largest single building
area (5080sf), IFC Table BIOS.I requires 2000gpm. IFC table C105.l then translates this
flow into a requirement for 2 hydrants.
This same table also describes the maximum allowable spacing between multiple
hydrants (450 feet) and the maximum distance from any hydrant to point on a fire lane
(250 feet). The submitted design meets both of these requirements.
Because the fire flow is divided between two hydrants, we can asslline that 1 OOOgpm
should be provided from each hydrant for the evaluation of fire flow velocities and
residual pressures. Therefore we have three sections to evaluate for fue flow velocities
and two hydrants for residual pressures.
Bryan
(979)-268-1125
(979)-260-3849
Austin
(512)-328-7878
(512)-328-7884 Fax
Conroe
(936)-441-7833
(936)-760-3833 Fax
The first section to test for excessive velocity is the existing line in George Bush Drive
East. Because the line is fed from two directions, there is the equivalent of 2-12" lines to
pass a total of 2000gpm. Based on simple cross sectional area, the fire flow velocity in
this line would equal 2. 7 fps, well below the maximum allowed.
The second section to test is the 8 inch line connecting the existing 12 inch line to the
first hydrant tee. Again using 2000 gpm for both hydrants, the 8 inch line should
experience 11.4 fps in flow, just below the maximum allowed.
The last section is the 6 inch line running eastward to the second hydrant. Using the
lOOOgpm being applied to this one hydrant, the 6 inch line should see a velocity of9.7
fps, again below the 12 fps maximum.
For residual pressures, we obtained the fire flow information at the hydrant located at the
intersection of George Bush East and Holleman Drive. At this location, the static
pressure was 101 psi and the test flow was 1455 gpm at 100 psi residual pressure.
Accounting for elevation differences and head loss via the Hazen-Williams Equation,
while applying a 1 OOOgpm demand from each hydrant, we obtained predicted residual
pressures at the western hydrant of 106 psi and at the eastern hydrant of 83 psi.
Obviously the design exceeds the 20 psi residual requirement.
Based on these calculations, we confirm that the design of the water distribution system
meets the Uniform Design Guidelines as requested.
Sincerely, l!~
Sr. Engineer I Branch Manager
College Station Utilities
Reliable, Affordable, Community Owned
WATER SERVICES DEPARTMENT
P.O. BOX 9960
COLLEGE STATION TEXAS 77842
BUTCH WILLIS, FIELD SERVICES DIVISION
PHONE 979-764-3435 FAX: 979-764-3452
FLOW TEST REPORT
Date 1-Feb-07
Nozzle size 2.5
Location HOLLEMAN AND GEORGE BUSH EAST
Flow Hydrant Number E-139
Pitot Reading 75
GPM 1455
Static Hydrant Number E-147
Static PSI 101
Residual PSI 100
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