Parametrix Review LetterMay 7, 2008
PMX No. 247-1781-024 (06/01)
Mr. Jim Gibson, P.E.
City of Yelm
105 Yelm Avenue West
Yelm, WA 98597
Re: Wal-Mart STEP Tank Design Review No. 2
Dear Mr. Gibson:
We have completed review of the design submittal by PACLAND for the Wal-Mart Store received in our office April 30, 2008. The submittal has been reviewed for conformance with the City
of Yelm’s Development Guidelines Chapter 7, and the Department of Ecology’s Criteria for Sewage Works Design. We have the following comments based on our review:
COMMENTS
Memorandum
1. Parametrix requested the water meter readings since October to check the average daily flow for the Wal Mart store. Based upon the additional data (enclosed) and excluding the first
month of operation, it appears that the average flows have increased by an additional 16 percent to 4,493 gpd. Additionally it appears that a maximum month average daily flow is approximately
5,670 gpd. Using the maximum month flow and a peaking factor of 1.5, proposed by the designer, the peak day flow would then be approximately 8,500 gpd. Per this peak day flow, the total
liquid volume calculates to approximately 17,000 gallons, with the current design at 12,000 gallons.
2. If the City agrees with our estimate of the peak daily flows, then the peak hour calculation should be revised and resubmitted. We would recommend that daily meter readings be conducted
to confirm the peaking factor.
3. Additionally, the Working Volume calculation should be revised based upon Comments 1 and 2 then resubmitted.
Plan Sheet C-5.2
1. Given the control panel’s current location, please provide additional information on how the direct line of site will be met in accordance with the NEC and the Department of Ecology
Standards.
2. The invert elevation difference between the outlet of the 8,000-gallon and the inlet of the 6,000-gallon tanks could be modified to allow both tanks to be used for surge buffering.
3. It is our understanding that the STEP pumps and controller have not been connected to the standby power system and that electrical modifications would be necessary to make this possible.
Please submit written verification that the electrical modifications have been done or revise storage volume calculations in accordance with DOE standards.
4. Please clarify what “per manufacturer’s recommendations” means regarding the sewer connection between the existing tank and the proposed tank. Will a Core-n-Seal boot work at that
angle or will a fiberglass adaptor be installed with a Fernco coupler?
5. Please submit a copy of the manufacturer’s written recommendations regarding the structural integrity of the existing tank on the domed end with the proposed tank installation in
close proximity.
Plan Sheet C-3.0
1. It is our understanding that in accordance with NEC and DOE requirements, the control panel or a pump lock out must be located within direct line of sight of the pumps but according
to the site plan this does not appear to be possible. Please verify that the design will meet all provisions of NEC and DOE regulations.
If you have any questions or need additional information, please feel free to contact either Mike Ollivant or me at (253) 863-5128. Thank you for the opportunity to review this project
for you.
Very truly yours,
PARAMETRIX
Cole Elliott, P.E.
Senior Engineer, Municipal Services Group
CE:ak
Enclosure
cc: Project File