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a. initial vertical separation siting criteria or vertical separation distances for trench bottoms <br /> specified in Rules.1955(m), .1956 or.1957 have not been reduced, <br /> b. sandy clay loam saprolite is not proposed to be used, <br /> t. horizontal separation distances specified in Rule.1950 haven(L been reduced,and <br /> d. for systems to be installed in fill,a pressure dosed drainfield(LPP or DRIP distribution)is to be <br /> used. <br /> e. for systems to be installed on sites with Group III or IV soils within three feet of the trench <br /> bottom or on sites requiring drainage of Group It or III soils,the site has been evaluated by a <br /> Licensed Soil Scientist(see Section 1,below). <br /> 3. For ground absorption systems utilizing modified,graveless or other types of nitrification trenches <br /> separately approved in accordance with Rules.1956 or.1969,no reductions in linear footage of nitrification trench <br /> or system area shall be applied when the LTAR has been increased in accordance with section E.2,above. <br /> F. DESIGN CRITERIA <br /> 1. Pretreatment: <br /> a. A septic tank as required in Rule.1952 shall be provided. An access riser extending <br /> above finished grade shall be provided over the outlet. <br /> b. An effluent filter shall be provided instead of or in addition to the sanitary tee.Alternately,a <br /> screened pump vault may be provided in the pump tank. <br /> 2. Common Components of Type A,13,and C Pressure-Dosed Sand Filters <br /> a. Sand Filter Containment Structures <br /> (1) Lined built-in-place sand filters: <br /> i.The containment structure shall consist at a minimum of a reinforced plywood support <br /> structure made from 1/2-314-inch plywood placed in an excavated hole with a 30-mil <br /> PVC liner along the bottom and sides and appropriate welded seams at any liner seams. <br /> ii.The finer shall be large enough to cover the bottom and extend up the sides of the <br /> support structure with enough excess to allow the liner to be firmly anchored (e.g., <br /> clamped or weighted). <br /> iii. actory fabricated boots shall be used at the supply line and underdrain penetration <br /> points of the liner. All fittings shall extend into the liner and be watertight. Alternately, <br /> the supply line may be directed into the filter over the tap edge of the liner, with <br /> adequate cover and freeze protection provided <br /> (2) Prefabricated and built-in-place concrete tank filters. <br /> i.The containment structure for systems using precons€rutted concrete boxes shall <br /> consist of a watertight,precast,top-seam septic tank(without baffle wall)or pump tank <br /> constructed without a top,or the bottom half of a watertight,precast mid-seam <br /> septic tank(without baffle wall)or pump tank. <br /> H.The containment structure for built-in-place concrete filters shall be a cast-in- <br /> place concrete,block or brick masonry tank constructed without a top in <br /> accordance with Rule.1954(d). <br /> 5 <br /> 132 <br />