One of the many issues facing wastewater utilities is excessive quantities of infiltration of groundwater and inflow of stormwater into the sewer system, thereby consuming capacity, and in some cases, causing overflows. Climate change is likely to make these problems even worse.

The Town of Exeter, NH, facing an EPA Administrative Order to reduce combined sewer overflows (CSO) as well as a mandate to build a new nutrient removal treatment facility to reduce nitrogen to the Great Bay Estuary, decided to tackle not only the infiltration and inflow (I/I) in the public sewer system, but also within the private sewer connections to increase the overall effectiveness of the I/I mitigation measures.

Addressing Private I/I Sources The Town’s CSO master planning work identified that private sources of I/I from residential areas were a major contributor to the I/I problem. Wright-Pierce was hired to assist the Town address the I/I problem, including producing a public-private strategy to maximize the private mitigation results and return on the Town’s investments. The strategy was implemented in the Jady Hill neighborhood of 136 homeowners with high levels of I/I. The partnership with homeowners was essential since the property owners are responsible for operation, repair, maintenance and reconstruction of sewer services from the sewer main to the building foundation, per the Town ordinance.

Increasing Project Efficiency

Following extensive investigations including flow monitoring, smoke testing, manhole evaluations, and inspection by closed circuit television (CCTV), it was estimated that:

  • A 20-25% I/I reduction could be achieved if the infrastructure upgrades addressed just the public sewer mains.
  • A 40-45% I/I reduction could be accomplished if public sewer mains and the sewer services within the public right-of-ways (ROW) were upgraded.
  • A 75-80% I/I reduction could be accomplished, if the 195 sewer services, from the main to the house foundations, were also upgraded.

By choosing the latter, project I/I efficiency increased substantially.

Public Outreach Results in Support

Vetted through a public outreach program facilitated by the Town and Wright-Pierce, the Jady Hill residents provided valuable feedback and embraced the strategy. It required homeowners to:

  1. Use the Town contractor for service line work on their property to ensure schedule compliance and construction quality control.
  2. Grant construction easement on their property.
  3. Agree to hire a licensed plumber to complete and certify all necessary work.

In return, the maximum out-of-pocket expense to each homeowner was limited to $1,000. The Town, through CIP funding, paid 100% of the sewer and utility upgrade work within the ROW (including sewer services within the ROW). The Town also paid for the balance of work beyond the $1,000 per residence on private properties. Long-term financing
options were made available to homeowners. The successful public education program resulted in a 75% homeowner participation rate, many of whom utilized the available Town financing.

Post-construction flow monitoring was conducted in the Jady Hill project area during the spring of 2014. Peak and total volume target I/I reduction rates for both dry and wet weather conditions were achieved and in most circumstances exceeded.

It’s this long-range thinking and citizen buy-in that will result in lower wastewater management costs, a cleaner river for the community, and a healthier Great Bay estuary.