The first hurdle on the path to building senior housing on the parcel that Hildreth House occupies has been cleared. The Harvard Water and Sewer Commission presented sewer usage numbers at its Feb. 24 meeting and voted unanimously that it would be comfortable calling 3,000 gallons of the excess daily capacity “available for other uses.” The numbers showed that the average private household uses about 140 gallons per day, and based on that, commission member Rick Maiore said that 3,000 gallons a day would support about 20 housing units.
Selectmen ask for number
One of the Board of Selectmen’s goals this year was to investigate the feasibility of senior housing adjacent to Hildreth House. To make progress on that goal, the board sent a letter to the Water and Sewer Commission asking for the number of gallons that could be added comfortably to town sewer usage. The board also made it clear in its letter that “at this time” it was not asking the commission to commit to reserving any sewer capacity for the senior housing project.
CLICK CHART TO ENLARGE (Courtesy)
Senior housing on the 5.66-acre Hildreth House site was first explored by the Harvard Housing Authority and the Municipal Affordable Housing Trust in 2008. A task force came up with a plan for a mix of 60 market-rate and affordable units on the Hildreth House property, but the lack of town sewer at that time was a major contributor to that plan’s demise. The town sewer was completed in 2012, but reliable usage data for the system was not available until last week.
Calculation difficulties
Maiore said that the commission has been attempting to measure the flow into the sewer plant since 2013. But 18 months of data showed wide daily and weekly deviations, making any calculation of average usage difficult. The commission attributes most of those deviations to “batch releases” from the schools. Both Bromfield and the elementary school have effluent holding tanks, and random amounts from those tanks are released at random times to the sewage plant.
Because of the irregular data from the plant, the commission looked instead at water usage, under the assumption that most of the water used by town customers ends up in the sewer system. These daily, weekly, and monthly water numbers appeared to paint a more reliable picture of system usage, and these are the numbers that were used to determine excess capacity. By using water numbers, the commission was able to include usage for the households that have paid the sewer betterment but have not yet connected. Estimates were used for the handful of houses in the sewer district that use private wells and have not yet connected to the town system.
What’s the limit?
The commission calculated the average daily usage number over the past eight quarters to be 14,720 gallons. A little over half of that amount comes from private households, a third comes from the schools, and the remainder comes from other town users, such as the General Store. The wastewater treatment plant can handle 23,000 gallons, but the Department of Environmental Protection (DEP) licensed the plant for only 20,000 gallons per day. If the plant sees that much inflow in one day, the town is required to notify the DEP and stop all new connections. In addition, the commission has its own self-imposed “stop connection” limit of 19,000 gallons.
While the average usage is about 4,300 gallons below the commission’s limit, members agreed that 3,000 gallons was a more comfortable number. They cited empty-nesters selling to families or an increase in school enrollments as events that could cause an increase in system usage. But Maiore pointed out that since the numbers are based on water usage, they are probably about 5 percent higher than the actual sewer usage. He mentioned outdoor watering as an example of water that does not enter the sewer system.
The sewage plant manager has told the commission that the plant needs more flow to operate efficiently. All of the commissioners agreed that they would like to get the maximum use out of the system while still being cautious about its limits. The selectmen plan to share the commission’s response with the Planning Board and the Council on Aging as talks regarding the feasibility of a senior housing project move forward.
