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• <br /> Thomas E. Wohlleber <br /> July 22, 1992 <br /> Page 4 <br /> use of a mound which requires installation of the subsurface infiltration area <br /> in sand fill placed on top of native soil . Infiltrative surface area of a <br /> mound will be sized using a 1.0 gpd/ft2 hydraulic loading rate. <br /> System costs will be determined by system type and the design flow. As <br /> previously indicated, system type will be determined by siting choice. Both <br /> conventional and mound systems will require multiple cells for long-term <br /> operation. However, use of a conventional system will require that a <br /> replacement area equal to 100 percent of the constructed infiltration area be <br /> identified and reserved for future use, should the need arise. This area <br /> cannot be used for other purposes which might compact or otherwise impact the <br /> native soil . This requirement will significantly increase land area <br /> requirements. A mound system can be replaced in position so no additional <br /> land area need be reserved. <br /> ILHR 83 code requires a design flow of 750 gpd per classroom for a school <br /> which serves meals and has shower facilities. For a 20 classroom school , a <br /> design flow of 15,000 gpd is required. A design flow of greater than 8,000 <br /> gpd must comply with the "Large System Guidelines" developed by the Wisconsin <br /> Department of Industry, Labor and Human Relations (DILHR) , the regulatory <br /> agency for on-site wastewater systems. These guidelines require more <br /> stringent site evaluation and operational monitoring which will result in <br /> additional system costs. Activities included in the more stringent <br /> requirements are installation of groundwater monitoring wells to determine <br /> system impacts on the groundwater, a mounding analysis to evaluate long term <br /> system operation and semi-annual submittal of groundwater sample analyses and <br /> operational reports to DILHR. <br /> Based on past experience, actual wastewater volume generation for such a <br /> facility is much less (i .e. 3,500 gpd at West Middleton Elementary School ) . <br /> DILHR currently allows variance requests to reduce design flows for new <br /> arptrdir.wp <br /> 4153.00 <br />