The Carlisle Mosquito Online

Friday, May 18, 2007


Carlisle School seeks to lower wastewater treatment costs

The Carlisle School continues to monitor operations at the year-old wastewater plant to try to cut down electricity and propane costs.

During its first winter of operation the facility turned out to be much more energy-intensive than the school expected. The 800 square-foot building must be heated with propane to a minimum temperature for the biological system to work. At the same time ventilating fans run to exchange outside and inside air to minimize methane gas in the plant.

State Department of Environmental Protection regulations specified up to 12 air exchanges per hour for the wastewater plant. Hoyle, Tanner and Associates of Manchester, New Hampshire, engineers for the system, designed the system to make the maximum 12 exchanges per hour. Designing to the maximum ventilation setting may be the result of ambiguous wording in the DEP specifications, according to Bill Risso of the School Building Committee. Plant operation settings were recently modified to reduce the number of air exchanges from 12, down to three an hour.

School Business Manager Heidi Zimmerman sent a letter to Hoyle, Tanner and Associates in April requesting a solution to the ventilation design issues. HTA disputed the design problem in a letter sent by Vice President, Paul Clinghan. "The heating and ventilation system is designed correctly per the (state) regulation for 12 fresh air changes per hour." Clinghan pointed out that both the school's hired project manager and the state DEP approved the plans.

The school was required by the state to hire an Owner's Project Manager (OPM) for the wastewater project to provide professional oversight. Mark Thompson of SEA consultants of Cambridge was the OPM. He approved the physical design of the plant but the contract did not specify SEA consider later operating expenses for the facility, according to Zimmerman. With the proposed new school building project, she said the school must ensure that ongoing operating and maintenance costs are addressed in the design phase.

Members of the school building committee will meet with HTA engineers and with Thompson, the project manager, in June to try to work out a resolution to the outstanding issues. The school is considering requesting HTA pay for the excess in electricity and propane costs over the last year. Buildings and Grounds Supervisor David Flannery maintains records of electricity and propane use per month to track energy usage.

The plant processes wastewater effluent from the school, treating it in five different tanks before it goes into the leaching field across the drive from the plant on the Banta-Davis town land, off Bedford Road.

In its FY'08 budget, the school allocated $81,400 to operate the plant, compared with last year when the school budgeted $64,000. The $57,000 annual maintenance contract with Weston & Sampson is by far the largest operating expense. The engineering contractor sends a technician to perform daily maintenance on the plant from Monday to Friday.

The school is considering training a town employee to be a licensed wastewater plant operator to take over maintenance of the facility, or sharing costs for an operator with another school in the area. Compared with the annual cost of an outside maintenance contract, a local employee could save the school considerable amounts of money over time.

2007 The Carlisle Mosquito