Integrated Approaches to Nutrient Management Planning: Southeastern Massachusetts Case Studies

Background The United States Environmental Protection Agency (USEPA) and Massachusetts Department of Environmental Protection (MassDEP) have implemented non-point-source, watershed-based nitrogen Total Maximum Daily Load (TMDL) limits for multiple small coastal estuaries in southeastern Massachusetts. Southeastern Massachusetts towns have approached this nitrogen contamination problem — primarily caused by overuse of septic systems as populations grew - in very different ways. Methodology Although almost all communities in the Study Area 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. Some towns place an emphasis on traditional solutions such as sewering with an enhanced nitrogen removal process centralized wastewater treatment facility. Others have explored innovative non-traditional technologies such as shellfish aquaculture, permeable reactive barriers, inlet widening to improve tidal flushing, decentralized treatment facilities, and nitrogen reducing onsite septic systems. Many communities are developing a hybrid approach where traditional sewering is targeted for the highest density neighborhoods with non-traditional strategies being implemented in more less densely developed areas. Results Communities with TMDLs 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 Oak Bluffs, MA and Chatham, MA each approached the CWMP process differently. Although the solutions were different, both communities faced a significant challenge- as a result of significant long term project costs — which has resulted in a robust public education effort. Case Study #1: Chatham's Septic to Sewer Strategy The Town of Chatham, MA has a severe nitrogen contamination problem. As shown in Figure 1, one third of the watersheds within the Town require 100% removal of wastewater nitrogen and almost three quarters require more than 50% removal of wastewater nitrogen to meet the Town's TMDL goals. 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 consists of planned implementation of traditional sewering technologies with limited non-traditional technologies for targeted areas. In the first phase of the plan the Town's existing Water Pollution Control Facility was upgraded to a limit of technology nitrogen removal process and its flow capacity was increased (Figure 3). The Town has been implementing septic to sewer conversion projects that account for approximately 15-20% of its TMDL compliance requirements every three years (Figure 2). 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 (Figure 4) 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 achieve its nitrogen TMDL goals within a 20-year timeframe. Case Study #2: Oak Bluffs Hybrid Nitrogen Management Approach The Town of Oak Bluffs is a small community with a year-round population of less than 5,000 people. The majority of the Town lies within one of four nitrogen sensitive coastal watersheds (Figure 5). Every summer, the Town sees a substantial population increase from tourism, which has contributed to the nutrient impacts observed in the Town's water resources. The Town has a small centralized wastewater treatment system, with limited options for treated effluent recharge expansion, which drove the Town to evaluate multiple non-traditional nitrogen management technologies as part of its comprehensive wastewater management plan (CWMP). In order to meet its nitrogen Total Maximum Daily Load limit goals, the Town has developed a hybrid Recommended Plan, which integrates multiple nitrogen management strategies for each watershed including centralized sewering, an enhanced nitrogen removal on-site septic system program, and permeable reactive barriers. The Recommended Plan includes the implementation of an adaptive management process to incorporate cost-effective pilot technologies into the plan once they demonstrate feasibility. The adaptive management process will involve ongoing water quality monitoring to monitor and respond to the results of the implementation. This adaptive management approach will enable the Recommended Plan to be adjusted based on the monitoring results of the environmental and economic impacts associated with the construction of sewers and implementation of pilot projects in Oak Bluffs. Benefits and Next Steps The complex wastewater nitrogen contamination challenges in southeastern Massachusetts require significant investments to reverse years of environmental degradation. This problem is being addressed by the small communities in Southeastern Massachusetts 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 degraded coastal waterways using fiscal sustainable approaches. 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.