HomeMy WebLinkAboutSEWER & WATER DESIGN REPORT - 23-00085 - Founders Square Phase 3 - Plat
THE DYER GROUP, LLC • 343 E 4th NORTH, SUITE 108 • REXBURG, ID 83440 - 6001
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M E M O R A N D U M
To: Carlin Feisthamel, PE - DEQ
From: Winston R. Dyer, PE – Project Manager
Date: December 30, 2022
Re: Sewer and Water Design Report for Founder’s Square Subdivision, Phase 3 – Rexburg,
Idaho
The following is submitted as an Engineering Report addressing design capacity and design
flow demands associated with this Phase of the proposed single-family residential subdivision
development.
A previous engineering report dated March 7, 2008 was submitted to DEQ and the City for the
entire Founder’s Square subdivision, which was subsequently approved by both entities. This
report focuses strictly on the Phase 3 area of the subdivision.
Sewer Demand
Demand: equivalent population = 15 homes x 3.4 persons/home = 51 persons
51 persons x 65 gpcd = 3,315 gal/day
Flow Rate: (3,315 gpd / 1440 minutes per day) x 4.0 peaking factor = 9 gpm
Flow Capacity: 8” line @ 0.32% slope = 399 gpm
Flow Capacity Used: 9 gpm / 399 gpm = 2% (maximum) ok
New Treatment Demand: 3,315 gpd
Available Treatment Capacity (Rexburg): 5,500,000 gpd
Treatment Capacity Commitment: 3,315 gpd / 5,500,000 gpd = 0.1% ok
Providing 8” gravity sewer service in the subdivision will be adequate, and generated
wastewater flow will have negligible effect on the existing wastewater collection and treatment
facilities.
Water Demand
Peak Daily Demand: 51 persons x 0.45 gpm / person = 23 gpm
2
Supply Capacity: 3,840 gpm (14” DI from upper reservoir @ 8 fps recommended max
velocity for peak)
Capacity Used: 23 gpm / 3,840 gpm = 0.6 % in peak day ok
Peak Hour Demand: 3 gpm / connection x 15 connections = 45 gpm
Pipeline Capacity: 3,840 gpm (14” DI @ 8 fps recommended max velocity for peak)
Capacity Used: 45 gpm / 3,840 gpm = 1% in peak hour ok
Minimum System Pressure: (5310 wtr surface in elevated reservoir – 10 ft operating
range – 5130 max ground elevation in SE corner) x 0.433 psi/ft wtr = 74 psi > 40 psi ok
(dynamic losses in the 14” and 12” supply lines to this area are negligible).
Fire Flow Demand: 1,125 gpm (IFC B105 for Type V, residential occupancy < 3600 ft.²)
Pipeline Capacity: 8” DI @ 10 fps = 1,575 gpm
Capacity Used: 1,125 gpm / 1,575 gpm = 71% for fire flow ok
Fire Pressure Loss: 12” DI @ 1,125 gpm = 0.0014 psi/ft x 1,260’ = 2 psi
(from 2nd East to Founder’s Square along Sunrise / Washington streets)
8” DI @ 1,125 gpm = 0.0098 psi/ft x 760’ = 8 psi
(from Founder’s Square to NE corner of Phase along Jefferson / Paul Revere streets)
Minimum Fire Pressure: 74 psi min in SE corner – (2 + 8) psi loss = 64 psi > 20 psi ok
Providing water service and required fire flow to this proposed subdivision Phase is within the
capacity of the existing water supply and distribution facilities and exceeds minimum system
requirements for the pipe sizes indicated.
-- End of Design Report --