20110161 STEP Sizing Calcs 03182011SEWER STEP TANK SIZING
PROJECT: Yelm Professional Center
PROJECT: NO.: 1412.01
DATE: 2/23/2011
The sizing calculations below have been based on the following information:
• The Washington State DOE Criteria of Sewer Works Design
• City of Yelm Development Guidelines
• Current Water Use Records from Yelm Professional Center
The medical bldg has 3 water meters. Total water usage is +/ -2,296 CF a month
5 day work week.
Average Water Use for a day is: 115 Cubic Feet
• Daily Water Use based on 20 days a month is: 859 Gallons per day
Using the above information the calculations from the DOE manual can be solved.
Detention Volume from Pg C1 -32
V = (2.0) Q
V= Liquid Volume 1718 Gallons
Q =Daily Volume 859 Gallons
Non Resid. Strength = 2.0 2
Working Volume from Pg C1 -32
Working Volume is defined as the difference between the peak inflow and
pumps ability to keep up with the flow.
1 - O.S. 20 GPM pump will be installed in this tank. It has the ability to
convey 600 GPH. The pump will be capable of conveying the whole daily
flow in less than 2 minutes. This pumps flow is substantially higher than the
actual. All commercial systems are required to have OSI 20 pumps
• The standard City of Yelm float settings should be used (4.5 ")
Power Outage Storage Volume from Pg C1 -32 HE z, e W ,„
1
BY: ........ ................
24 hours of additional storage volume is required and has been
included. (859 gallons)
Tank Sizing Summary
Based on standard concrete 3,000 gallon step tank (11.50'x6.08'x6.25')
• Required Detention Volume
• Required Working Volume (4.5 ")
Total Tank Depth 75"
• Pump on level is 43" from tank bottom
Total Vol Necessary for Detention
Total Working Volume
Total Tank Volume
Extra Tank Vol for Power Outage
1718 Gallons
172 Gallons
43 Inches Required
1,890 Gallons
1718 Gallons
172 Gallons
3000 Gallons
1110 Gallons
Extra tank volume exceeds Power Outage Volume
2