Septic System Installation in Hopkinton, RI

Why are Hopkinton's villages hard places for septic systems?

Hopkinton's historic mill villages sit on its rivers and brooks, the town plan says. After the March 2010 floods, Ashaway and Hope Valley filed the most requests in town for federal disaster aid. The plan says the village centers have poor soils and typically a high water table. It also notes septic problems already there.

The plan singles out Hope Valley. Most of that village was built under zoning that first called for 20,000-square-foot lots. The plan cites federal soil maps from the Natural Resources Conservation Service (NRCS). They rate the village's soils very severe for septic leach fields, with poor filter characteristics.

Failing systems and well contamination in Hope Valley led to a public water line from Richmond. A wastewater management district for the village came with it in October 1990, as a condition of the line. That line serves part of the village, and homes on it still treat their wastewater on site.

On a small village lot, a replacement system has to fit beside the house and keep its distance from wells. For a repair, RIDEM's rules ask for a design that meets them to the greatest extent possible. RIDEM may relax some requirements at its discretion. The town plan adds that new infill in Hope Valley should wait until a wastewater system is in place.

What do Hopkinton soils and rivers mean for a leach field?

Across the town, NRCS soil maps show a mix of glacial till and sand. Canton and Charlton, well drained soils formed in till, cover about one acre in four. Hinckley, a fast-draining sand and gravel left by glacial meltwater, covers about 6 percent. The town plan says land near the I-95 interchange on Main Street has better soils and a lower water table.

Woodbridge and Paxton soils, formed in dense till, cover about one acre in six. The NRCS says water may sit on the dense layer in Paxton soils from late fall through early spring. Its data put the seasonal high water table about 2 feet down in Paxton and 1.5 feet in Woodbridge. Ridgebury soils, on a little over 5 percent of the town, can have water right at the surface.

State rules need the seasonal high water table at least 2 feet below the original ground at a leach field. The bottom of the leach field stone has to sit at least 3 feet above it. Where native soil falls short of that, the University of Rhode Island says fill or a mound may be approved. When test holes leave the water table unclear, RIDEM calls for wet-season readings from January 1 to April 1.

Hopkinton runs from the Connecticut line east to the Wood River, which forms the border with Richmond. The Wood River flows south through Hope Valley and Woodville to the Pawcatuck River, the town's southern edge. RIDEM's wetland rules reach 200 feet from the edge of a river or stream. A leach field inside that area needs approval from RIDEM's Freshwater Wetlands Program.

Older homes and cesspool replacement in Hopkinton

The Census Bureau estimates Hopkinton has about 3,700 homes, and four in five are detached single-family houses. Nearly one in five was built in 1939 or earlier, and more than half before 1980. The Hope Valley Historic District, listed on the National Register in 2004, has buildings from the 1770s to the 1870s. In Rockville, the Upper Rockville Mill went up between 1863 and 1870.

RIDEM notes that most home septic systems installed after 1970 are not cesspools. Older houses may still have one. Rhode Island's cesspool law requires replacement within 12 months of a sale or transfer. A failed cesspool has to come out of service within a year of discovery.

Renovations can also trigger an upgrade. Under RIDEM's rules, adding a bedroom or a floor makes a cesspool unsuitable, and it must be upgraded. The same goes for a system installed before April 9, 1968. When a newer system fails, septic system repair may fix it, or the house may need a full replacement.

Who approves septic system installation in Hopkinton?

In Hopkinton, as across Rhode Island, RIDEM must approve the plans before a septic system goes in or gets replaced. RIDEM staff inspect key stages of the install, and we build to the approved plan. The town's Building and Zoning Department issues building permits, but only after any approval RIDEM requires is in hand. For a new house, the town grants occupancy only after RIDEM issues its Certificate of Conformance.

The town plan calls for helping owners maintain and rebuild their septic systems, with newer technology where it fits. RIDEM lists Hopkinton in the Community Septic System Loan Program, a state loan program for septic repairs and upgrades.

The town plan says most of Hopkinton is zoned for lots of at least 80,000 square feet, nearly two acres. On a lot with a private well, state rules keep a house-sized leach field 100 feet from the well. The state building code sets the frost line here at 40 inches. A water line from the well to the house has to run at least 6 inches below it.