North Yarmouth school site study supports septic system

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NORTH YARMOUTH — A hydrogeological study at the site of the former North Yarmouth Memorial School has determined that the existing sewer system there could operate at a greater capacity – something needed to support the municipal sewer system that goes to referendum in November.

The Board of Selectmen has recommended that the school at 120 Memorial Highway, which was closed in June 2014, be redeveloped as a municipal and community campus. The existing Town Hall would be sold for housing or commercial development, and a municipal sewer system would be created to help create new development.

Meanwhile, an opposing referendum question, the result of a successful citizen petition opposing the selectmen’s plan, in part calls for the town to stop all spending and work concerning the study or development of a sewer system.

The municipal sewer system question has dominated town politics in recent months, particularly at a Board of Selectmen candidates forum last month.

A public hearing on the selectmen’s question will be held at North Yarmouth Memorial School at 7 p.m. Oct. 14, followed by one on the petition question the next day at the same time and place. An informational presentation on the development recommendation will be held Oct. 21, also at the same place and time.

Sevee and Maher Engineers of Cumberland Center stated in its Aug. 26 report that the firm’s study was meant “to estimate the maximum hydraulic capacity for subsurface wastewater disposal at the Site using leachfields, and to identify the optimum location(s) for leachfields that avoid adverse impacts to off-Site water quality.”

The firm mentioned five key findings:

  • The hydraulic capacity at the site for treated wastewater is about 45,000 gallons daily
  • The untreated wastewater capacity is about 7,000 gallons daily
  • In both cases, added wastewater can be disposed of at the site “without having adverse impacts to off-Site groundwater, residential water supply wells, or the Yarmouth Water District’s water supply well.”
  • Usage of wastewater is better developed in phases, as necessary, to keep project costs at a minimum
  • Maintenance of the leachfields in the long run “will likely be limited based on the soils present but any field that does fail can be replaced within the same footprint.”

The Water District’s well is about 1,200 feet east of the closest property boundary of the site, according to Sevee & Maher.

John Sevee, president of the firm, noted that the water table was found to be 40-60 feet below the surface, “a positive finding” because when a lot of water accumulates in one location, the groundwater rises a little, creating a mound; if the water table is too close to the ground surface, that mound can rise into the base of the wastewater disposal system, he explained.

The firm also studied nitrate levels in surrounding wells, finding them to be 1 milligram per liter, as compared with the drinking water standard of 10, Sevee said. Natural sites in Maine with little development typically show less than half a milligram per liter, he added.

“You’re getting a fairly high level of efficient treatment of the wastewater as it migrates down through that 40-50 feet of unsaturated soil before it hits the groundwater table,” Sevee said. “That’s a good finding, because that says that there is some intrinsic treatment within the soils” at the site.

The soil conditions, relative to the groundwater depth and level of treatment from the existing system, are “excellent,” he said.

Since there are similar wells used by the Water District adjacent to the flow of groundwater, the system must be monitored in order to assure that the groundwater supply will never be contaminated, Sevee noted, adding, “By having a monitoring system in place, you can determine what the conditions are, and you have plenty of time to react.”

Monitoring through water sampling could occur two to four times a year, according to Dan Diffin, project engineer with Sevee & Maher. The cost could range from $2,000 to $20,000 a year, depending on magnitude of the system, Sevee said.

Should the project move forward, the next step will be to present the firm’s findings to, and obtain input from, the state Environmental Protection and Health and Human Services departments, according to Diffin.

Alex Lear can be reached at 781-3661 or alear@theforecaster.net. Follow him on Twitter: @learics.

Dan Diffin, project manager with Sevee & Mahar Engineers, on Sept. 24 explains the results of a hydrogeological study the firm conducted on the sewer system at North Yarmouth Memorial School. The town votes in November whether to create a municipal sewer system, built from that at the school.

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A Maine native and Colby College graduate, Alex has been covering coastal communities since 2001, and currently handles Bath, Topsham, Cumberland, and North Yarmouth. He and his wife, Lauren, live in the Portland area, and Alex recently released his third album of original music.