Agenda - 09-02-2003-6c1 - Laserfiche WebLink

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s MEMORANDUM TO: John Link, County Manager COPIES: Gwen Harvey, Assistant County Manager Pam Jones, Purchasing/Central Services Director Dave Stancil, ERCD Director Ron Holdway, Environmental Health Director FROM: Paul Thames, PE, County Engineer DATE: August 25, 2003 SUBJECT: Wastewater treatment system for the Northern Human Services Center (NHSC) As per your request, the following information and time projections are provided for expanding the wastewater treatment capacity for the NHSC. As I have indicated in past memoranda, Environmental Health staff and I have previously planned and discussed the expansion of the wastewater treatment system capacity at NHSC (from the current 2700 gallon per day [gpd] system to 6000 gpd system) using the following structural components: • expanded capacity (new) septic tanks, • expanded capacity pumping stations (at a minimum new pumps and controls in the existing pump tank and a new pumping station controlling dosing of new nitrification fields) • expanded capacity (new) nitrification field, • recycling sand filter (or similar proven biological pretreatment technology), • expanded wastewater storage capacity (new storage tanks to enhance flow equalization capacity) Environmental Health staff (Ron Holdway, Tom Konsler and Greg Grimes) and I met recently (August 12th) to begin the preliminary design process for the expanded capacity system. As that date, we still had no information (and none appears forthcoming in the near term) about the availability of grant funding for "Clean Machine" treatment technology and components (and thus the cost viability/effectiveness of using such technology). Accordingly, we assumed that a "Clean Machine" component to the treatment system for the NHSC would essentially replace the "recycling sand filter or other biological pretreatment component" listed above and then moved forward with developing a system layout. We have determined that the expanded capacity system will require the use of septic tank and grease trap components that are much larger than the existing. Accordingly, we have planned to: 1) continue the use of the existing grease traps; 2) provide the necessary additional capacity by converting the existing septic tank to a grease trap; and 3) install a new septic tank with the necessary capacity. As the existing pump station has insufficient storage capacity to provide flow rate control for a new pretreatment unit (regardless of the technology employed), we have determined that it should be used only to convey wastewater to a flow control pump