The Society for the Protection of New Hampshire Forests (SPNHF) renovated its headquarters to include an 11,400-square-foot green addition to house 23 private offices and a 391-square-foot conference room. The expansion called for a 1,600 gallon-per-day conventional septic system but the SPNHF wanted to protect the environmentally sensitive hilltop area that is adjacent to the Merrimack River and minimize excavation. Architects and engineers specified a Clivus compositing system and greywater filtering system. All solid waste