Agenda - 06-02-2004-9d - Laserfiche WebLink

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subsequent emails and project development schedule) the consultant outlined three potential wastewater system design alternatives (or Steps as per the report format) based on the following findings of fact related to the existing and projected wastewater flow conditions at NHSC: • the permitted capacity of the existing wastewater treatment (and its components) is 2400 gpd; and • wastewater system flow records of March 1999 through January 2004 indicate an average daily wastewater flow of 1324 gpd; and • peak wastewater flows have reached approximately 3800 gpd; and • installation of water efficient plumbing fixtures should reduce average daily flow rates by approximately 30%; and • proposed additional uses of the facility should generate a total (new plus existing) average daily wastewater flow of approximately 2062 gpd (after the installation of the efficient plumbing fixtures); and • the probable maximum average daily flow that could be generated by maximum use of the facility (after retrofitting the facility with low flow plumbing fixtures) should not exceed 3000 gpd; and • the probable maximum daily peak flow associated with the projected expansion of facility use (after retrofitting the facility with low flow plumbing fixtures) is estimated at approximately 5980 gpd Step 1, with an estimated price of approximately $70,000 and completion time of approximately 42 weeks, outlines a system design that is basically a modification to the existing treatment system by incorporating a new flow equalization component (Flow equalization allows the system to balance surges in flow from peak uses or plumbing infiltration from rain events. Excess flows are stored in a large holding tank and metered to the drainfield in regular doses over several days of lighter (below capacity) flows). The proposed flow equalization component would essentially address peak flow conditions of up to 6000 gpd for up to four consecutive days or lesser peak flows conditions for a proportionally longer period of time. While flow equalization would address some of the shortcomings/problem areas of the existing system, it would not provide any higher level of treatment (or protection to the environment) than that provided by the existing system. Step 2, with an estimated price of approximately $162,000 and completion time of approximately 42 weeks, outlines a system design consisting of the flow equalization component outlined in Step 1 above with the addition of a 3000 gpd capacity secondary treatment system component. This component, using tidal vertical flaw wetland or wetland plant-type treatment technology, provides the natural ecological wastewater treatment technology of the "Living Machine" and similar systems of interest to the BOCC as a means of providing an enhanced level of wastewater treatment/effluent discharge quality and the associated higher level of environmental protection. Step 3, with an estimated price of approximately $324,000 and completion time of approximately 104 weeks/24 months, outlines a system design consisting of larger capacity versions of flow equalization (12,000 gpd) and wetlands-type secondary treatment components (6000 gpd) outlined in Steps 1 and 2 above with the addition of a 6000 gpd capacity subsurface nitrification field component located on the Vincent tract (both the Step 1 and 2 alternatives envision the use of the existing nitrification field, perhaps with fewer nitrification lines should any have to be removed with the development of a new front circular drive layout).