The Carlisle Mosquito Online

Friday, March 23, 2007


Carlisle School costs rise for wastewater treatment

High operating costs for the wastewater treatment plant that went online last spring account for $17,000 of the increase in the Carlisle School's budget request for next year.

In the proposed FY08 budget the school allots $81,000 to operate the plant, compared with last year when the school allotted $64,000.

The service maintenance contract for the plant, $57,000 for the next fiscal year, is by far the largest operating expense. Part of the increase is also due to rising energy costs over the last couple of years. The amount of propane and electricity to operate the building is also higher than expected.

The plant is energy-intensive, heating the 800-square-foot building while also ventilating it. The building must be heated to a minimum of 50 to 54 degrees for the wastewater process to work, while a fixed number of air exchanges must also be done each hour to minimize methane gas emissions. "It's essentially heating the whole building, while ventilating it at the same time," said Buildings and Grounds Supervisor David Flannery, likening the operation to heating a house with the windows open.

The wastewater treatment facility is located on the town's Banta-Davis Land off Bedford Road.
Flannery said he and engineer Bill Risso of the School Building Committee have met several times with engineers from Hoyle, Tanner and Associates, the building's designers, and the field manager for Weston & Sampson, the engineering firm that maintains the plant with a service contract.

After examining operations, the temperature was lowered in the control room and the small chemical room in the facility. Engineers designed the rooms to use electric heat, said Flannery, because it reduces the chance of an explosion from a gas flame. The temperature in the large process room was also lowered, where propane is used for heat. Cycling of the ventilation fan in the process room was also modified. It will take another month to see how much of an effect these changes have on utility bills.

Meanwhile, Flannery and members of the School Building Committee, including Risso, Bob Pauplis and Wendell Sykes, continued to evaluate heating and ventilation system operations this week to see if further changes can be made. Engineering issues and adjustments are considered par for the course in the first year of a wastewater plant's operation.


Treatment functions are adjusted from this panel in the control room.

The plant, which began 5operating last May, processes between 3,000 and 4,000 gallons of wastewater a day, with no flow from the school on weekends.

Effluent from the school is treated in five different tanks before it goes into the leaching field across the drive from the plant on the Banta-Davis Land, off Bedford Road.

An engineering contractor from Weston & Sampson visits the plant daily from Monday to Friday. The operator takes samples, runs tests, checks equipment, adds chemicals, if needed, and records flow data in a log book. Weston & Sampson provides the school with a monthly report on plant operations and a copy is sent to the state Department of Environmental Protection (DEP) to comply with its regulations. The company also has sludge and solids removed from the tanks, as needed. The wastewater equipment itself is under a one-year warranty that expires at the end of April.

Current operating bills were used to project expenses for next year's school budget. "Every increase in energy dollars that goes to the wastewater plant is money that doesn't go towards education or programs," said Flannery of the school's motivation to reduce costs. He said the school is considering training a town employee, possibly someone from the school or Department of Public Works, to be a licensed wastewater plant operator to take over daily maintenance of the facility. Though training will take time, a town employee could save the school money compared with the cost of the current maintenance contract.

School heating boiler is efficient

In contrast to the wastewater plant, the school's new heating system is operating efficiently. Installation was completed in February when the second of two boilers was installed in the basement of the Wilkins Building. The new boilers, approved by voters at Town Meeting last year for $350,000, replaced the school's old heating boilers that dated back to the 1960s.

A small piece of asbestos found between gaskets inside one of the school's old boilers required the system to be dismantled by a professional hazardous material contractor during Thanksgiving break. The operation was successful, and safety test results were reported to the state DEP, as required by law.

Boiler 1, the lead boiler installed last November, is a high-efficiency condensing unit estimated at 95 to 97% efficiency. Boiler 2, a conventional hot water boiler installed in February, is designed to turn on and assist the first boiler on the coldest days of winter, but so far it has not gone into service.

Though the heating season is not yet over, the school expects a significant reduction in its gas heating bill. Natural gas is used in the forced hot-water heating system.

School business manager Heidi Zimmerman also looked at different suppliers to reduce natural gas costs for the school this year. Though the cost of natural gas was increasing, she was able to lock in the same rate as last year through a collaborative agreement with Hess Energy. The school has switched from Keyspan as its gas supplier to Hess, the low-bid supplier.

The main process room contains this rotary biological contactor unit.


The final cost for the heating system amounts to about


Chemicals are used to assist bacterial growth.

$290,000. The remaining $60,000 or so left over from the school boiler Warrant Article will return to town funds.

Corey roof leaks

Last summer the school had repairs made to the Corey Building roof to fix leaks over the music rooms at the front of the building, and in the auditorium. After a rainstorm earlier this month, the Corey roof leaked again, but this time the leaks were over the school cafeteria.

Corey was built in 1987, and is now 20 years old. Rubber roofing on the building was installed in sheets, with glued seams and a layer of stones over the top as ballast to hold the sheeting down in the wind.

Treatment tanks are also located in the process room.


Rubber roofs have a life expectancy of about 20 years, and over time the roof seams come apart and need to be resealed, explained Flannery, with repairs lasting about five years. Repairs will be made this summer to the new leaks on the Corey roof and to leaks that occurred this winter on part of the Spalding roof.

2007 The Carlisle Mosquito