2011 Excellence in Environmental Engineering and Science™ Awards Competition Winner
Grand Prize - Planning
Town of Chatham MA Comprehensive Wastewater Management Planning (CWMP) Project
Entrant: GHD Inc. and Town of Chatham
Engineer in Charge: William R. Hall, Jr., P.E., BCEE
Location: Chatham, Massachusetts
Media Contact: Nathan C. Weeks, P.E., BCEE
The Town of Chatham is a small coastal community of approximately 7,000 year-round residents whose median income is less than the Massachusetts average. The Town is located on the "elbow" of Cape Cod (illustrated on Figure 1) and relies on its fishing and tourist/vacation economies. The Town has experienced large residential growth and environmental impacts due to the use of individual septic systems on small properties. This development has produced water quality problems that need to be solved through the Comprehensive Wastewater Management Planning (CWMP) Project. The following specific problems have been documented:
- Eutrophication of estuarine waters, and USEPA development of stringent nitrogen TMDLs for the four estuaries that surround Chatham. Figure 2 illustrates the percentage of septic system nitrogen load that needs to be removed from the watersheds to meet TMDLs.
- Eutrophication of several freshwater ponds from phosphorus loads to the watersheds.
- Impacts to the Town's drinking water supplies.
GHD Inc. (formerly Stearns & Wheler, LLC) was selected by the Town of Chatham in 1997 to complete the CWMP Project. GHD is an international company with offices around the world and extensive expertise in water resource management and advanced wastewater treatment. The company's nitrogen management experience has been valuable for the CWMP Project. The company's office on Cape Cod (since 1995) has greatly assisted with project delivery.
A map of GHD office locations and a discussion of GHD's US operations are included as Figure 3.
The Town of Chatham Massachusetts (Town) Comprehensive Wastewater Management Planning (CWMP) Project was initiated in 1997 and was completed in July 2009 with the Project Approval Certificate from the Massachusetts EOEEA (regulatory agency).
The project was necessary for the following reasons:
- The Town has relied almost exclusively on individual septic systems for wastewater management, and portions of the Town experienced frequent septic system failures.
- Nitrogen from several sources in the watersheds (mainly from the septic systems) is causing eutrophication of the coastal estuaries.
- Phosphorus (from similar sources) is causing eutrophication of the freshwater ponds.
- The groundwater public drinking water supplies are being impacted by several contaminants originating from septic systems.
- The Town has a small 38 year-old WWTF that serves a small portion of Town.
- MassDEP and USEPA developed nitrogen TMDLs for the four estuaries that surround Chatham. These watershed-based, non-point-source, nitrogen TMDLs are the first in New England.
- The Town initiated a previous CWMP project in the 1980's which did not proceed to implementation due to lack of public support.
- The Town has since received a MassDEP administrative consent order to proceed with wastewater planning.
After twelve years of engineering evaluation and community decision making, the CWMP was approved to include the following components:
- Sewer extension to approximately two-thirds (Phase 1 Area) of the Town (illustrated in Figure 4) to meet nitrogen TMDLs.
- WWTF expansion and upgrade to meet 3 mg/L TN discharge permit (the first in Massachusetts).
- Sewer extension to the remaining one-third (Phase 2 Area) of the Town (illustrated in Figure 4) and WWTF expansion.
- Stormwater management and remediation.
- Fertilizer management.
- Pond treatment.
- Wetland restoration by eliminating undersized culverts.
The timing and capital cost of plan implementation is listed below:
Total capital costs are estimated at $300M to be spent in thirty years by a Town with a year-round population of less than 10,000 people and a median income less than the state's average. In April 2009, Town Meeting appropriated approximately $60M for the initial implementation of Phase 1 as illustrated in Figures 5 and 6. Phase 1 construction is now underway, as illustrated in Figure 7 (aerial photo).
An Integrated Approach was needed, and was provided as follows:
- The Final CWMP Plan was integrated with an Environmental Impact Report to ensure that all environmental media (air, all water resources, and land development) were considered. A key product of this integrated effort was the development of a Growth-Neutral Bylaw that was enacted as a Sewer Use Ordinance to address concerns that sewer extension could promote unwanted growth and sewage flow.
- All water resources were considered and evaluated for the comprehensive plan including drinking water quantity and quality, stormwater discharge quantity and quality, wastewater discharges, pond water quality, and marine water quality.
- All nitrogen sources were considered, modeled, and evaluated to meet the TMDLs including: septic systems, WWTF recharges, fertilizers, stormwater, atmospheric deposition, and estuarine benthic regeneration. Future (2030) watershed nitrogen budgets were developed to demonstrate compliance with the TMDLs.
Project quality and innovation were used to build the needed public and regulatory understanding to gain approval of the plan including:
- Public and regulatory review starting in 1997 and throughout the following steps:
- Project scoping
- Needs assessment
- Alternatives evaluation
- Draft CWMP and EIR
- Final CWMP and EIR
- Town approval of $60M for initial implementation
- Detailed watershed evaluations utilizing:
- GIS nitrogen accounting/budgeting
- Nitrogen attenuation during groundwater transport through riparian ponds and wetlands based on documented attenuation factors
- Particle-track modeling (ModFLo) of the proposed treated water recharge
- Water supply impact evaluation
- Evaluation of decentralized wastewater/nitrogen management as well as centralized wastewater/nitrogen management to indicate that sewers were needed and that individual or cluster systems could not meet the watershed-based TMDLs and were not cost effective.
- Treatment process selection to meet the highly variable flows of this Town (monthly average flows are projected to range from 0.08 to 1.8 mgd) during the Phase 1 period with:
- Oxidation ditch (Orbal® process) followed by denitrification filters
- Planned expansion for Phase 2
- Planned expansion for phosphorus removal if needed in the future
- First discharge permit in Massachusetts to require average effluent TN of 3 mg/L or less
Project completion provides the following social and economic advances in Chatham:
- Remediation and protection of drinking, pond, and estuarine water quality
- Preservation of the Town's fishing economy
- Preservation of the Town's vacation economy
- Land use growth protection (Growth Neutral) to apply to all properties connected to the sewer This was a complex project that required long-term team work to evaluate, educate, respond, and facilitate the plan. Projected costs to implement the plan were unimaginable for a community this size, but they were made affordable by spreading costs to all property owners, and capturing USDA and SRF funds.
Views of the Town scenery and coastal resources are provided in Figures 8 - 10.