Solving a Massive Regional Wastewater Problem: Hybrid solutions employed by small communities for affordable wastewater management in an effort to remediate widespread nutrient contamination

Background
The United States Environmental Protection Agency (USEPA) and Massachusetts Department of Environmental Protection (MassDEP) have recently implemented non-point-source, watershed-based nitrogen Total Maximum Daily Load (TMDL) limits for multiple small coastal estuaries in southeastern Massachusetts. Cape Cod towns have addressed the nitrogen contamination problem – primarily caused by overuse of septic systems as populations grew - in very different ways. These mostly small towns are fiercely independent, often dealing with residents resistant to community-wide sewer systems that some fear might lead to un-controlled growth. Overall the problem has been estimated to cost $4-8 billion dollars to solve, a cost that many fear is unaffordable.
Methodology Although almost all of the towns have explored growth neutral land use controls and solutions such as stormwater management and fertilizer reduction, some towns have taken a primarily traditional approach to solving the problem while others have explored alternative technologies. For example, some towns place an emphasis on traditional solutions such as sewering with a centralized wastewater treatment facility. Others have explored innovative non-traditional technologies such as shellfish aquaculture, permeable reactive barriers, inlet widening to improve tidal flushing, decentrailized treatment facilities, and innovative onsite septic systems. Of late, many communities are favoring a hybrid approach where traditional sewering is reserved for only the most highly contaminated areas densely populated areas while non-traditional approaches are explored wherever practical.
Results
Several of the Cape communities have initiated comprehensive wastewater management plans (CWMP) to develop methodologies to reduce nitrogen impacts. Representative case studies illustrate the unique solutions adopted by two of these communities; these both provide lessons learned to any community facing similar challenges. The communities of Falmouth, MA and Chatham, MA each approached the CWMP process differently and independently. Although the solutions were different, both communities faced a significant backlash - as a result of significant long term project costs - that has to be handled through a very carefully planned public education effort.
Case Study #1 - The Town of Chatham, MA has a severe nitrogen contamination problem. As shown in Figure 1, one third of the watersheds in town require 100% removal of wastewater nitrogen and almost three quarters require more than 50% removal of wastewater nitrogen. The solution to this problem was estimated to cost over $300 million for a community with a year round population of just over 6000. In order to solve this problem, the Town developed a phased implementation approach. This approach primarily consisted of planned implementation of traditional sewering technologies with limited non-traditional technologies for targeted areas. The Town has then implementing projects that account for approximately 15-20% of its TMDL compliance requirements every three years. Now almost 40% complete with its TMDL compliance plan, over 700 properties have been removed to date from septic systems, providing a potential future nitrogen load reduction of about 3,000 kg/y for this initial part of a larger long-term implementation program. In addition, the Town has completed an inlet widening project as well as implemented a fertilizer management plan, the only two non-traditional nitrogen reduction options that were feasible to help address the significant contamination issues in this town. Overall, the Town plans to have its TMDL compliance plan in place within a 20 year timeframe which is slated to be approximately by Year 2030.
Case Study #2 – The Town of Falmouth has a similarly severe nitrogen contamination problem. As shown in Figure 2, one third of the watersheds require 100% removal of wastewater nitrogen and more than three quarters require more than 50% of the wastewater nitrogen to be removed. Traditional solutions to this wastewater nitrogen contamination including sewering and enhanced onsite septic systems were estimated to cost over a half billion dollars to implement. This cost made the project a nonstarter for the community of fewer than 40,000 people. A revised wastewater management plan was developed for Falmouth that included several key factors: 1) the Town would address its needs one watershed at a time and over a thirty year timeframe replacing debt drop off with new wastewater management spending to help control costs and 2) the overall solution included a balance between traditional and non-traditional solutions.
The implementation phase of the project began with the development of a Targeted Watershed Management Plan (TWMP) for one of the watersheds and the initiation of several pilot projects in other areas. The TWMP, which was the first approved TWMP in the state, was developed for a coastal estuary known as the Little Pond Watershed; this TWMP outlined the TMDL compliance strategy for 100 percent removal of controllable nitrogen levels in this watershed. The primary mechanism of compliance was achieved by installing a centralized wastewater collection system in a densely populated, built-out portion of Town, doubling the existing collection system size and capacity. This project is estimated to reduce the concentration of nitrogen in the impacted estuary from 0.837 mg/L to 0.495 mg/L, nearly 90% of the TMDL goal for this watershed. Other strategies to help the Town achieve the balance of the TMDL included: continued use of on-site treatment and disposal; fertilizer management; stormwater management; shellfish aquaculture; and widening the inlet opening to the coastal pond. Demonstration projects for alternative solutions including shellfish aquaculture, composting toilets and permeable reactive barriers yielded unfavorable results for composting toilets with shellfish and permeable reactive barriers still being considered.
With the Little Pond watershed TMDL compliance plan nearly complete, the Town has now initiated its planning for the second watershed – Great Pond. This project planning is expected to be complete in 2022 with implementation expected to begin in that same year. The Town is on its way to achieve TMDL compliance by Year 2045.
Benefits and Concerns
The complex wastewater nitrogen contamination challenges in southeastern Massachusetts have created a $4-8 billion issue. A problem that developed over many decades as growth exploded is being met by the small communities on Cape Cod with innovative solutions that seek to manage high costs by balancing traditional and non-traditional wastewater management solutions. The solutions outlined above are allowing for the recovery of a seriously degraded water environment in an affordable manner. However, as the problem took many years to develop, so will the solutions with many of these comprehensive wastewater management plans having a schedule of 20, 30 and even 40 years to implement, making the results more of a long term goal.