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JERREY ROBERTS

Peter Shanahan, an environmental engineer and MIT professor, speaks during Tuesday's forum on the Northampton landfill at JFK Middle School.

NORTHAMPTON - They explained complicated hydrological models and used technical jargon about water flow, but in the end the two environmental scientists who were the centerpiece of a landfill expansion forum Tuesday night reached dramatically different conclusions about what might happen should the city move ahead with plans to add on to its Glendale Road facility.

Peter Shanahan, a professor at the Massachusetts Institute of Technology and a consulting engineer for Northampton, used his 30-minute presentation to explain a "containment transport model" designed to test the impact the proposed expansion would have on the Maloney Well, a backup drinking water supply for Easthampton.

The model found that the flow of several chemicals, including biochemical oxygen chemicals, manganese, zinc, methylene chloride and a theoretical contaminant, would be below dangerous detection levels.

"The results show that essentially nothing will reach the Maloney Well," he said.

On the other hand, Robert M. Newton, a geologist and professor at Smith College who is also a member of the Barnes Aquifer Protection Advisory Committee, found in his models that the concentration of similar chemicals at individual wells in and around the landfill was increased significantly. He said that taking steps to protect the drinking water should be the city's top priority, and that the cost of the landfill will be borne by future generations.

"The landfill represents a liability. It is a large liability," he said. "Clean water is our most precious natural resource and we can no longer take it for granted."

Fit to drink

The scientists were brought together for what is the first of a hoped-for series of public forums sponsored by the Board of Public Works and Citizens United for a Healthy Future. In addition to the groundwater hydrology presentations, many of the 100 residents present weighed in with their thoughts before the BPW quizzed the panelists.

The board must decide if it will submit a special permit application to the City Council for the landfill expansion. If the nearly 20-acre expansion moves forward as planned, it would add another 21 years to the lifespan of the nearly full solid-waste facility.

About two years ago, the Department of Public Works received a special waiver from the state Department of Environmental Protection for the expansion. The city sought the waiver because the area of expansion lies over a drinking water recharge area of the Barnes Aquifer, which feeds the Maloney Well.

The well became the focus of Tuesday's forum - specifically, whether the landfill expansion would have a negative impact on the municipal drinking water supplies in Easthampton, on private residential wells and on nearby brooks and streams.

Shanahan, working in collaboration with Stantec Engineering, said Tuesday that the transport model took into consideration several worst-case scenarios. Among those were overestimating leakage and a catastrophic leachate release. The model assumed a single composite liner would be constructed for the expansion, when in reality regulations call for a double-composite liner with a leak detection zone.

Even with these adverse scenarios, the model showed a small percentage of leakage, Shanahan said.

"There was no impact on the Maloney Well with near total dilution occurring by the time water from the landfill would reach the well," according to a Department of Public Works study from last year.

Several audience members asked what assurances Shanahan could give that the liners would stand the test of time. He said the liners currently in use are approved by the EPA.

"It's the material of choice ... there is a track record to the material and scientific history behind it," he said.

Rising concentrations

City resident Lisa DePiano pointed out, as did others, that "eventually the contaminants will happen." She urged city officials to closely examine other alternatives to expanding the landfill, noting that 70 percent of trash could be composted.

"Northampton could be different," she said.

Newton has maintained that existing studies of the impact of the landfill on water resources are flawed. He showed charts from tests taken at monitoring wells at the landfill that showed the chemical concentration of iron and manganese increasing through time. He noted that concentrations dropped significantly in 1994, after a portion of the unlined landfill was capped, but since then they have gradually crept back up.

"Why? Where are they coming from?" he asked.

Just as alarmingly, he said, were tests from a separate, private well located about 1,000 feet from the landfill that showed a dramatic spike in the levels of zinc, lead and calcium. His tests revealed a 200 percent increase.

Arsenic is another concern. The chemical occurs naturally in the aquifer and is not caused by the landfill; however, landfills have been shown to cause arsenic to mobilize, he said.

Newton also cautioned that scientific models should only be used as a tool in the planning process and should not be key documents in decision-making.

"People can make different models using the same basic input and come up with different results," he said.