I have seen alternative septic systems in NH,not the one you described. The ones I have serviced,if they get medications fron household or possibly minerals,discharge from water softeners can get disturbed. A lot of the systems are shared systems with two or more houses on one system. The leachfields in NH can get a 40 to 60 percent in reduction of square footage of field if hooked to an alternative unit. I don't quite agree with that logic if house is at full capacity of people living there. Reason the alternative systems can have little or no mound is the seperation of bed bottom to seasonal high water is decreased because the effluent is pretreated before it gets to the leachfield, if your test pit passes,I don't see why you still need the mound. Mound systems in NH ,if the distribution box or line from septic tank,if near edge of one of the slopes can freeze from windchill blowing against side hill of bed. plowking