Provencher Engineering was contracted by Capital Group Properties and Rosewood Construction of Southborough, Massachusetts to engineer a new wastewater disposal system for a new 46-unit senior housing development.  We conducted a witnessed Soil Evaluation and design of a pressure dosed septic system, which was approved by the Board of Health. We installed vertical 4" PVC monitoring well pipes with perforations and filter cloth at the bottoms of test pits, saving the client money by avoiding costly drilled monitoring wells. We monitored the wells over a few months, and contoured the seasonal high groundwater elevation. We conducted percolation tests, as well as hydraulic conductivity tests, which we used in a groundwater mounding analysis, to estimate the rise in water table due to the recharged effluent, which was required for securing the permit.     

We also designed a complete gravity sewer system, which terminated at a multi-compartment combined septic tank and pump chamber. The effluent was pumped across the site to a 2-level pressure distribution leaching trench soil absorption system. Pressure distribution allowed us to feed unequal length leaching trenches uniformly. This was confirmed by a clear water test, where we adjusted control valves which split the pressurized flow to both levels, while watching the rise of the water inside observation tubes that were connected to the system pressure piping. The liquid inside all of the test tubes were set to the same height, (and therefore pressure), while flowing liquid passed through small equally-spaced perforations facing down into the leaching trench stone.  

The leaching area required a two-tier retaining wall with a geomembrane backing behind the wall to prevant any effluent from weeping through the wall. A putting green and promenade was installed on top of the leach field!