Site Preparation

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Site clearing is underway for the River Hill development in Mashpee, Massachusetts, which will feature 11 homes, four of them affordable for families with modest incomes. The preparation of a building site is a step-by-step process that includes analysis of water-table levels and soil make-up, how utilities are run into the home, zoning restrictions, curb-cut location regulations, and environmental concerns. Steps may vary depending on the town, state, or region, but there are some universal site-preparation issues that can always be anticipated. Soil Testing Soil Testing looks at two separate things: the composition of the soil and its ability to support a structure, and the absorption and drainage rate of the soil or how well it will accommodate septic and water. The placement of a property's septic system determines, in part, where the home will be sited, so a soil or "perc test" is usually the first step taken in site preparation—often conducted before the land is purchased. If the property will not be serviced by municipal sewer, the perc test is used to determine if and where a septic system and leach field can be placed on the lot. "Perc" is short for percolation, since this test is used to determine the absorption rate of the soil. Perc tests are conducted by digging multiple pits on the site, a task normally undertaken by a civil engineer, to determine the best location for a septic system. These test pits get a preliminary check to determine the presence of bedrock, the ground-water-table levels, and the nature of the soil. As a general rule, sandy or gravelly soil has good absorption rates, while clay does not. Bedrock found at shallow depths tends to preclude the placement of a conventional septic system because bedrock is considered an impervious soil with no absorption properties. Ground-water-table levels show up as color variations in the soil at certain depths in the pit—mottled or discolored soil is a sign of the seasonal water table level. Local and state regulations will demand that there be a certain distance of separation between the bottom of the septic system and the seasonal-high-water table. If high-water-table marks appear at too shallow a depth, it could prevent the homeowner from using a conventional septic system, and force the crew to dig a new pit elsewhere on the site.

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