Chris Hirsch, environmental scientist

putting it back. Most of our towns are dependent on groundwater and they use the sewer system. So water is pulled from the ground and then sent to Deer Island. That water does not come back. We’re pumping water out and then sending it away without recharging our own land. In summer there is little regulation on private wells. There are regulations but very little enforcement. Add to this that summer also has the highest rates of evapotranspiration.

In your wildest dreams, with all the funding and political support you needed, do you think there would be a way to redo the sewer system?

Yes, there is. Through septic. Most of the Town of Sharon is septic and it infiltrates water back into the ground but most of the towns don’t do it. But septic has its own drawbacks. The easier fix would be to hook up to the mwra for seasonal uses where they’d receive Quabbin water. The problem is that Quabbin water is ten times the price of local water which isn’t really feasible and, so, it’s hard to sell. Quincy is very concerned with their groundwater levels and sewer infrastructure because they get a lot of infiltration and inflow. If the gw level is higher than the sewer infrastructure then they get a lot of seepage and then they pay a lot for the inflow they send to Deer Island. It was really interesting- I was talking to the town engineer of Quincy and he said how they had a big flood in January and because they had lined the sewers since the last big flood, the flooding was markedly decreased. When they were unlined, the stormwater overwhelmed the ssos that emptied into water bodies that were flooding the streets.

Even with data on how many private and public wells?

We can point out how much is beyond our control - all the private wells that are not monitored versus the public wells. There’s also the a high development rate, sudden growth in the last 5-10 years. Every time a wetland is filled for development you lose infiltration. It’s more of a past thing where they did a lot of legacy filling, before there was a lot of regulation.

Have you seen any increase in salinity in the Neponset River or other areas where the groundwater table has dropped?

We do not monitor groundwater quality. Many towns who are impacted by saltwater intrusion like Quincy and Boston are already using mwra water. We do have a concern for salinity from road salt. We see that increasing here and statewide though there’s not a lot ofdata locally.

Do you have water quality concerns regarding the many oil and gas tanks along the Neponset?

I assume they are being monitored very heavily. We have esuen (sediment monitoring program) where we look at stream and river pollution over a twenty year timespan. We have forty different sites in the watershed. mwra does the monitoring though. A lot of our focus is on stormwater and making the river safe for recreation at all times. 75% of the river is fine during dry weather. During rain, however, e-coli levels increase 10% because the stormwater coming from off the land has picked up pet and wildlife waste. At that time only 5% of the river is safe. We don’t have an exact idea of what’s happening with septic waste.

How do wetlands buffer communities from the impacts of flooding?

In 1920 there was a plan to fill Fowl Meadow and industrialize it. They also filled a lot of the river downstream for the potential project. Once they filled the wetland, they realized the quantity of water that came through the area was going to flood Boston and so they would need to channelize it. The money fell through for filling the section and thank god we still have the wetland which protects Boston. It slows velocity and allows for some infiltration. Looking at Turner Pond, the development around there is highly septic. The pond has high phosphorous and occasionally high bacteria counts. I’m wondering if there’s a lot of communication between the septic systems and the pond.

Do you have issues with arsenic contamination?

We do have some arsenic-impaired water. This is more related to what railways did back in the day. Before RoundUp was invented, the railroad would just go through and spray arsenic on the land to kill all the plants. It’s still present in the soil. Our main concern is pollution from PCBs- in terms of legacy stuff.

Is the town and your organization looking to add on to the Neponset River Greenway? Do you think the “green” buffer works to filter stormwater runoff?

The goal of the Greenway wasn’t to create a buffer. It was a co-benefit. The goal was to bring people to the river for recreaion. But Finnigan Park in Dorchester, which opened last summer, made a conscious effort of trying to make it wildlife friendly. __ They have a prairie-like grassland in the middle and a restored saltmarsh on one side but I don’t know if flooding was a major driver as to why it was done.

Anonmyous

Geotechnical engineer specializing in groundwater

In what ways do you have to consider groundwater when building?

Well, we have to decide if we can build below grade, obtain a permit for groundwater pumping and understand treatment requirements. Once they get a permit to de-water there is no limit to it generally.

What are you typically involved with?

I conduct risk analysis on prospective properties and recommend whether or not to buy the land e.g. are there too many risks or considerations that are cost prohibitive like pollutants? My main concern is how buildings are impacted by contaminated groundwater - how the impurity can make people sick and not so much about what the buildings put into the ground. Construction materials are so heavily regulated that it’s not really an issue.

How can pollutants enter the building?

If you build let’s say five feet below the groundwater level, the basement has slab joints through which water can seep in and contaminate the building. You might get these from adjacent land uses like gas stations or laundromats.

What are the particular impurities to be considered?

There are many of them. For example, gasoline plumes, dry cleaners/laundromats, and industrial cleaning all carry risky chemicals.

With climate change, has there been much talk about soil salinity?

Salinity is a layman’s term. Saline concentration is what you’re talking about, but there’s a gradient. You look at saline concentrations based on where you are relative to the coast and the hydrological connectivity to consider corrosion risks- especially in the av and ae zones. How salt will react with infrastructure is important so you may use pvc instead of steel.

Do you consider future conditions in projects now?

Mainly we look at sea level rise and how that will impact our projects. If you have to raise a building half a floor then you have additional parking and ada concerns. We also look at 2030 groundwater levels.

Do you have pollution concerns when de-watering? The potential to mobilize groundwater by pulling pollutants along the water gradient?

Contamination and pollution are problematic words. They are very general terms we tend not to use. They are relative terms. The question you should ask is: are they above or below a certain threshold?

I generally don’t deal or think about drinking or discharge of water.

Do you believe construction of these new development impacts groundwater positively or at all?

Before we develop any project we have to get permission from the Boston Groundwater Trust and demonstrate that our plan won’t impact the groundwater flow. Our project is well water-proofed. And this answer is complex to answer as it cannot be generalized. It has to be understood on a site-by-site basis. Due to the glacial deposits, conditions can be very inconsistent from one point to another a hundred feet away. Other places like Cape Code can count on consistency of its groundwater levels. Glaciation makes things more complex.

I just think of built projects. Environmental projects are different. For example, if a gas station has caused a plume in the groundwater and is next to residential project we would place a subsurface seepage barrier wall. Thus we have to mitigate the plume. We work with our neighbors if and when necessary.

Tom Palmer

Willet Pond Manager| Neponset River Watershed Association

Who has septic around here?

You’ll see most septic fields at the edges of the watershed.

Nitrate pollution by septic systems has been cropping up over the course of our research as a major issue in water quality. Is there a fundamental problem with household septics?

The best a septic system can do is remove pathogens and break materials into nitrates and phosphates but there’s no getting rid of the nutrients. Take Willet Pond for example. It was built in 1914 for a tannery in Norwood and has experienced very little sedimentation over its hundred years. The southern end of it is high in peat, a very anoxic environment, and raises suspicions of septic leakage from bordering homes. Cape Cod also has to be careful because it’s a sole source aquifer, with relatively uniform sand, and high water table. Nitrates and other pollutants move quickly and easily through the ground there. Now, they’re having troubles with eutrophication and shellfish loss (loss or ban on harvesting?) from nitrates and other pollutants.

Do towns in the Neponset River Watershed use mostly groundwater?

Weymouth has tapped out its groundwater resources. They want to get Quabbin water and so the Massachusetts Water Resource Authority (mwra) estimated that to extend from the nearest point in Willet to Weymouth it would cost $50 million. This kind of expense has shelved redevelopment plans for a military base and I can see it affecting property values in the future.

What are the major sources of pollutants around here? Any notable instances of water pollution?

A well in Canton near Neponset Street failed because it was pulling trichloroethylene (tce) or other solvents used to wash cars at the Cumberland Farms. It turn out that the pollutants were traveling from the ground near the store, underneath the river channel and up into the well. The well owners went on to dig a deeper well 500 feet away, further into Fowl Meadow.

Most of the old landfills in the watershed are unlined and the area — have you seen pollution as a result of this?

Postwar (wwii) towns were scrambling to find space for trash. Southeast Mass was a major player and there were ash heaps near the cranberry bog region. All the garbage used to be incinerate at a Rochester facility but then towns shifted to landfilling. When the Big Dig was going on they’d test the fill coming out of the ground so that they’d go to the appropriate facilities. Often, the clean fill was previously undisturbed earth and the contaminated fill was from old land that had been tainted by tanneries including lead and arsenic. These factors determined the level of protection required of their end destination. They struggled to find sites for all of the material that was removed from the site and situated some of it in the Blue Hill.