Wastewater Information

The Town of Eastham is dedicated to protecting its waters - both drinking and scenic. That is why Eastham places such importance on wastewater planning. Wastewater, if unchecked, has the possibility of contaminating our drinking water and upsetting the delicate ecosystems of our ponds and beaches.

Eastham wastewater area

Wastewater Needs

Wastewater needs were evaluated and separated into two groups; human health needs or the need to have safe drinking water. Access to safe drinking water is the town's number one wastewater planning priority. Currently, the town is serviced by a mix of private wells and the municipal water system. In some areas, wells are showing high nitrate levels. High nitrate levels are an indication that wells are being contaminated with septic effluent and runoff from activities (fertilizer, car washing, auto storage, pesticides).

Environmental health needs include high levels of nitrogen and phosphate in the groundwater act as fertilizers in estuaries and ponds. This causes algae growth affecting the water quality and disturbing the ecosystem.

Wastewater Planning

The three priority areas determined under environmental health needs are the Nauset-Town Cove Estuary, Rock Harbor Estuary, and Fresh Water Ponds.

map of eastham showing watersheds

The town is looking into ways to address the wastewater needs. The installation of municipal water will provide safe drinking water to those that choose to hook up to it (more information on the Eastham Water page). Traditional methods, such as on-site wastewater treatment, are being implemented on a case-by-case basis. Non-traditional methods are being tested to see if they will be feasible.

Read an overview of Eastham's wastewater projects.

Permeable Reactive Barrier at Salt Pond 

PRB diagram

A permeable reactive barrier (PRB) is a permeable treatment area that runs perpendicular to groundwater flow. The treatment zone intercepts and removes contaminants before they can travel further down-gradient. The Eastham PRB is designed to remove nitrate from groundwater flowing into Salt Pond.

Depending on the reactive material, contaminants are removed through different processes:

  • Contaminants sorb (stick) to the surface of the reactive material. For example, carbon particles have a surface onto which contaminants, such as petroleum products, sorb as groundwater passes through.
  • Metals dissolved in groundwater precipitate, which means they settle out of the groundwater by forming solid particles that get trapped in the wall. For example, limestone and shell fragments can cause dissolved lead and copper to precipitate in a PRB.
  • Contaminants react with the reactive material to form less harmful ones. For example, reactions between iron particles and certain industrial cleaning solvents can convert the solvents to less toxic or even harmless chemicals.
  • Contaminants are biodegraded by microbes in the PRB. Microbes are very small organisms that live in soil and groundwater and eat certain contaminants. When microbes digest the contaminants, they change them into water and gases, such as carbon dioxide

Eastham PRB

The Eastham PRB was constructed by injecting a food source (emulsified vegetable oil) into the groundwater for particular types of naturally-occurring microbes to eat. When these microbes process the food, they create conditions favorable for a different type of denitrifying bacteria. These bacteria are what ultimately intercept nitrate in the groundwater and make it inert, all without changing the natural groundwater flow. PRBs are considered to be sustainable, unobtrusive, low energy and low maintenance nitrogen removal methods.

Eastham permeable barrier location

PRB Installation

Before installing the PRB, a conceptual site model was developed of the Salt Pond sub-embayment to characterize its hydrogeologic and environmental conditions. A multi-organization project team collected exhaustive data before selecting the most effective PRB location. After three years of site characterization, the PRB was finally installed in April 2020 at the Salt Pond Visitor Center. Please find a video of the installation here.