READ MORE: Transformation: Water Infrastructure for a Sustainable Future
READ MORE: View the Full-Length CWERCS Booklet

Executive Summary

Most cities across the globe face a plague of water infrastructure problems, from combined sewer overflows to stormwater pollution to deteriorating pipes and treatment plants. As our climate changes, that infrastructure is proving inadequate to the tasks of building resilience to drought or managing severe flooding. Many wastewater treatment plants situated on the coast are directly threatened by impending sea level rise. 


A flooded treatment facility. Source: New England Interstate Water Pollution Control Commission.

Moreover, 19th Century water systems cause significant damage to our natural world, something that has been accepted as a necessary cost of modern life. Toxic algal blooms, low flow, stormwater pollution, oxygen depletion, are all consequences of existing water management systems. In the 21st century, new technologies and methodologies make these impacts no longer inevitable. Furthermore, many cities are leading the way in climate adaptation and mitigation. Major metropolitan cities are setting aggressive carbon reduction goals but are struggling to establish clear paths toward meeting them. 

Explore this interactive map to see how Boston's coastline could be impacted by sea level rise.  

Due to the inherent damage large centralized water systems visit on the environment, Charles River Watershed Association has for 20 years been pursuing a financially responsible approach to re-engineering them to restore nature, build resilience to drought and flooding, and build flexibility into water infrastructure in anticipation of climate changes. With our partners Natural Systems Utilities (NSU) and Industrial Economics (IEc), we conceptually tested a unique concept for distributed wastewater treatment systems, called Community Water and Energy Resource Centers (CWERCs). Throughout the project, our team met and reviewed our work regularly with a dedicated and knowledgeable Technical Advisory Committee (TAC). Our TAC was comprised of: the Massachusetts Water Resources Authority (MWRA), the Massachusetts Department of Environmental Protection (MassDEP), the Built Environment Coalition, the Boston Water and Sewer Commission (BWSC), the City of Boston Energy, Environment and Open Space Department, City of Cambridge, the Massachusetts Department of Energy Resources (DOER), the Boston Planning and Development Agency (BPDA), NRG Energy, and the U.S. Environmental Protection Agency (US EPA) Region 1 (Ex Officio).


A rendering of a Community Water and Energy Resource Center as proposed by CRWA

CWERCs are distributed energy generating and waste recycling plants. CWERCs mine sewage infrastructure, treating 1 to 5 million gallons daily and recycle organic waste in urban and suburban areas where it is produced. In our conceptual design, the CWERCs combine a membrane bioreactor, thermal energy heat pump, anaerobic digester, combined heat and power (CHP) system, nutrient recapture and composting. Utilities and products produced by each CWERC include electricity, thermal energy for heating and cooling, reclaimed water meeting drinking water standards for non-potable uses, and fertilizer and nutrients. Generating energy from sewage and reducing the distance food waste needs to be trucked significantly reduces green house gas emissions.

How a CWERC Works

In this study, CWERC operations are extensively modeled using real-world conditions. A site selection analysis was conducted to identify two local urban neighborhoods to model CWERC operations using actual site conditions. In a three-phase site selection process two neighborhoods were selected for modeling in the City of Boston. The Innovation (or Seaport) District and the Stony Brook neighborhood encompassing parts of numerous Boston neighborhoods including Mission Hill, Fenway and Roxbury, an environmental justice neighborhood, serve as the two study area neighborhoods.

We ran multiple technical and financial scenarios to assess outputs of the prototype CWERCs and analyze their operational feasibility. CWERC 1, designed to treat 2 million gallons daily (mgd) of sewage, has a capital cost of $46.7 million, and generates over $7 million in income from utility sales, renewable energy credits, and tipping fees. Operations and maintenance costs are estimated at $4.9 million. Income is generated from sales of electric and thermal energy, reclaimed water, renewable energy credits, soil amendment products, and tipping fees for the disposal of organic waste. The model does not include a fee for wastewater treatment. CWERC 2, treating 3 mgd daily, has a capital cost of $53.8 million. Income for CWERC 2, without collecting a fee for wastewater treatment, is estimated at $9.6 million against $7 million in operations and maintenance costs. CWERC 1 is modeled to collect 80 wet tons of food waste daily as the neighborhood contains multiple food and beverage production and processing facilities, while CWERC 2 collects 54 wet tons of food waste per day.

Modeling Results CWERC 1 Scenario (output volume and value will differ with different locations and scenarios)

Parameter Volume Value ($/year)
Mined wastewater 2 mgd $0
Renewable Energy Credit (accounting for 90% utilization) 6,732 MWhr/yr $439,400
Thermal Energy  (includes energy input to heat pump) 273,181 MMBtu/yr $2,326,000
Thermal Energy from CHP  26,145 MMBtu/yr $223,000
Total Electricity Generation (for demand with excess to grid) 7,480 MWh/yr $665,720
Sludge compost (Class A biosolids) 770 cu yd/yr $19,200
Food Waste Tipping Fees 29,200 tons/yr $2,336,000
Reuse Water Sales 1.5 mgd $1,201,000
Food Waste Digestate Soil Amendment 12,650 cu yds/yr $151,800
Food Waste Digestate Nitrogen Recapture (Ammonium Sulfate) 85,100 lbs-N/yr $59,600
Income Total   $7,421,720
Operating and Maintenance (O&M) Expenses    
Electricity Demand 3,870 Mwh/yr $432,600
Natural Gas Demand (Heat pump and CHP) 188,466 MMBtu/yr $1,840,100
Labor, Chemicals, Maintenance   $2,602,800
O&M Total   $4,875,500


Through modeling, our team determined scenarios in which plants are financially viable without charging a fee for wastewater treatment. Under existing site and regulatory conditions, if CWERCs receive favorable public financing of 0% to 2% interest and require no capital investment for the property they are built on, CWERCs will “break even.” Break even conditions are defined as a scenario in which the net present value of the infrastructure is equal to zero over a twenty year life span (including capital replacement reserves) with no additional revenue or capital investment required (i.e., the CWERC is self sustaining). Collecting a small wastewater treatment fee, a third or less of Boston’s current rate, would make the CWERCs viable in every public and private financing scenario investigated. The modeling further revealed that site specific conditions such as organic waste availability, sewage availability, and markets for reclaimed water and thermal energy influence financial conditions. Therefore consideration of these conditions, neighborhood input, and local water management impacts should drive site selection. 

In the study area neighborhoods, CRWA also examines historic natural hydrology. CWERCs are introduced to restore natural hydrology using a portion of the water reclaimed. With such restoration, neighborhoods gain improvements in flood control and drought resilience, heat island mitigation, reductions in polluted stormwater runoff, enhanced groundwater recharge, and an increase in open space amenities. In Neighborhood 1, we propose 44 new acres of green infrastructure across the district, enough to filter runoff from a 1 inch rain storm. Multiple opportunities to create new or restore historic water features using CWERC effluent are also presented including reestablishing buried canals by daylighting two large stormwater culverts.


Greening plan for Neighborhood 1



Rendering of proposed stream for Neighborhood 1

An ambitious design for a 300 acre floodable wetland is also presented. This large wetland area recreates flood storage for what was once an historic open water bay. Allowing this area to flood would protect the neighborhood against fresh water flooding, and modest storm surge and sea level rise, while also providing new, unique recreational opportunities in an urban setting.


Existing View of Future Open Space Identified in 100 Acre Plan


Rendering of 100 Acre Wetland

Neighborhood 2, the Mission Hill/Stony Brook neighborhood, is a densely developed area that overlays the historic confluence of the Stony Brook, Muddy River, and Charles River tidal estuary. Currently the Stony Brook is completely buried in culverts, the dammed Charles River is no longer tidal, and nearly all the rivers natural flood plain wetlands have been filled and developed. Our greening plan for the neighborhood identifies 14 new acres of green infrastructure, enough to filter or infiltrate runoff from a half-inch rainfall event. A site identified within the neighborhood hosts CWERC 2, and the design includes a constructed urban stream for treated water to flow to the Muddy River, mimicking the historic confluence of the Muddy River and Stony Brook. Base flow to the restored tributary would come from CWERC reclaimed water. 

In addition to our analysis of the financial viability of CWERCs, we also looked at the social welfare benefits of CWERCs and associated greening plans. Social welfare benefits include the value of both resource recovery (renewable energy generation, emissions reduction, reclaimed water) and environmental restoration (wetland services, ecosystem services, carbon sequestration, recreation potential, property value enhancement).

For Neighborhood 1, the assessment of potential benefits including annualized energy production and savings, reduced carbon emissions, air quality improvements, greening enhancements, and property value enhancements produce a range of economic benefits from $7 million to $14 million annually. If the 300 acre proposed wetland is included in the analysis, the social welfare economic benefits increase the range to $9 million to $20.5 million annually. For Neighborhood 2, the estimated potential benefits range from $11.75 million to $24 million annually. If groundwater recharge to preserve wooden building supports are included in the analysis, the range jumps to between $20 million to $47 million due to the avoided cost of replacing rotted wooden pilings.

Benefit Estimated Annual Benefits Comments
  Lower Estimate Upper Estimate  
Annual Welfare Benefits, Excluding Fort Point Channel Wetland
Energy Production and Savings $1,150,058 $1,338,025  
Reduced Carbon Emissions $94,957 $455,056  
Reduced Criteria Pollutant Emissions $177,852 $443,419  
Green Infrastructure Carbon Sequestration  $1,690 $3,390  
Air Quality Improvements from Green Infrastructure $13,932 $47,232  
Avoided Stormwater BMP Costs $4,997,222 $9,994,444 Partial overlap with wetland services estimate
Total $6,435,711 $12,281,565  
Quantified Welfare Benefits that Overlap with Other Categories
Annual Wetland Services $6,858 $21,439 Reflects only the wetland services associated with the two medium-scale wetlands; overlaps with avoided BMP costs.
Annual Property Value Enhancements from Greening $6,992,375 $13,984,751 Reflects broad set of amenities and therefore overlaps with other benefits (e.g., energy savings, recreational benefits); Annualized assuming 7% discount rate and 50-year useful life.
Total $6,999,233 $14,006,190  
Annual Welfare Benefits Associated with Fort Point Channel Wetland
Fort Point Channel Recreation $1,237,500 $3,888,000  
Fort Point Channel Wetland Services $122,810 $774,203  
Avoided Stormwater BMP Costs for Fort Point Channel Wetland $7,914,013 $15,828,025  
Total $9,274,323 $20,490,228  


Site specific social welfare benefits are an important aspect of managing water, energy, and waste more holistically. Benefits are significant, and will alter the quality of life in the affected districts. Further, property value enhancement and associated increases in property taxes as a direct consequence of the greening can help provide the revenue necessary to fully implement and maintain new green spaces.

There are a number of creative ways progressive cities across the nation have used to pay for the broadcast introduction of “green infrastructure.” In “Opportunity: Stormwater Trading”, we introduce Blue Cities Exchange, CRWA’s stormwater trading website based on trading pounds of phosphorus. Cost differentials between introducing green infrastructure to dense, impervious urban sites compared to less dense and more permeable sites support a market for trading stormwater treatment credits.

Finally, extrapolating from the financial and economic analyses of the two CWERC and neighborhood greening plans, we investigate expanding CWERCs to all 43 communities in the Massachusetts Water Resources Authority wastewater system. Recognizing the limitations in such an extrapolation, particularly given the site-specific nature of expenses and income, and that the two sites modeled for this study are located in two of the most dense and therefore most expensive areas in Massachusetts, the analysis remains useful. In the analysis, we introduce additional storage to each CWERC at 3 and 5 times the daily volume treated, and introduce collection of residential food waste to increase power generation. We estimate that a system of CWERCs could be operated at costs very similar to the cost of operating and maintaining the existing system. For a fee covering the operations and debt for its existing centralized system, regional authorities operating those systems could over time shift treatment responsibilities to a mix of their own CWERCS and others operated by city departments, neighborhood organizations, and private entities. Given the social welfare benefits, the enormous environmental benefits, and the climate change preparedness gained, CWERCs and the greening and restoration of natural hydrology presented here make for a compelling argument to transform our wastewater and stormwater systems over time. 

Deer  Island Treatment Plant


Deer Island Treatment Plant Service Area Communities

CRWA started this investigation 20 years ago as we systematically studied the Charles River and its myriad issues. The analysis in Transformation represents our take on what is necessary to fully restore the Charles River, prepare eastern Massachusetts for many of the vagaries of climate change, and achieve those ends in a financially responsible and economically desirable way. 


The key to constructive restorative change lies in managing water, carbon, and nutrients in a way that replicates their natural cycles. Our team applied the principles of nature to develop a plan for a new generation of water infrastructure that effectively provides for human demand and restores nature while building resilience to drought, flooding, and warming. CRWA rejects the concept of “waste” and proposes generating significant energy from organics currently being thrown away. We restore the natural water cycle by breaking up centralized systems into distributed networks of interconnected water and energy facilities which mine sewer pipes to reuse the water, reducing potable demand, and producing local, renewable energy. We recreate natural hydrology through stream and wetland restoration and the introduction of green infrastructure. By reconnecting stormwater and reclaimed water to restored urban water resources, our landscapes flourish and we build natural and social resilience. We accomplish all this while capturing new revenue streams and in the process both adapt to and mitigate global climate change.

CWERCs are replicable and adaptable. Through integration of water, energy and waste management, CWERCs integrate the function of multiple facilities that individually are resource and capital intensive. This dramatically reduces system wide costs and environmental externalities inherent to the current single-function, linear, take-make-waste infrastructure model.

CRWA’s case studies reveal that CWERCs are self-sustaining while charging users only a fraction of current water rates for non-potable reuse water and wastewater treatment. In our Boston case studies, based on local input factors for commodity costs and sales, CWERCs are sustainable at roughly 30% of the current potable water charge and $0 wastewater treatment fees. A single CWERC, treating 2 to 3 million gallons per day (mgd) of wastewater reduces annual CO2 emissions by as much as 30 million pounds. Finally, our economic models show that we can construct a distributed network of CWERCs to replace existing centralized systems while remaining cost neutral in the near term and likely profitable in the medium and long terms.

Based on the results of this study, CRWA is actively seeking partners to work with on a CWERC implementation project. Through our robust advocacy program we are also seeking regulatory and policy changes necessary to encourage and incentivize our holistic approach. In many ways, cities are leading the way on climate change adaptation planning, and the City of Boston is one of the leaders in this movement. Cities are recognizing the benefits of district scale energy generation both for resiliency and to improve efficiency and help achieve greenhouse gas reduction targets. Green infrastructure is also being identified as a method of achieving multiple goals such as flood mitigation, CO2 sequestration, cooling, energy reduction, CSO compliance, improving air and water quality, and more.

It is essential that the infrastructure we invest in today is ready to face the challenges climate change will bring. It is imperative that we transition away from a fossil fuel based economy as soon as we possibly can. This will require significant investment in renewable sources and employing all renewable energy generation opportunities at hand. Nature’s remarkable endurance and self-healing abilities must be guiding forces as we chart our course forward. We can no longer just live on the Earth, we must instead, using Nature’s own principles, learn to live with the Earth.  

Afterword by former CRWA Executive Director Bob Zimmerman

The antiquated water systems on which we depend are incompatible with nature and represent significant risks to society as they age and as our climate changes. They throw away water and organic resources, are inflexible, expensive, and most are in need of repair and replacement. Nevertheless, as better approaches are identified, these systems are extraordinarily difficult to replace. Existing water infrastructure is generational because water authorities have multi-year budgets, five year capital plans, 10 to 20 year planning horizons, and 30-plus year funding and structural debt. Combined with historic precedent, risk aversion leading to a strong preference for “standard practices,” political pressure and political realities, regulations, permits, expectations, and perhaps most importantly, the lack of a sense of urgency around the future realities of our changing climate, any transformational change to these systems becomes nearly impossible. Consequently, as we continue to do what we have always done simply because it is what we have always done, this deeply rooted Inertia kills all but the most incremental of changes.

Right now we are confronting water infrastructure repair and replacement we cannot afford. The American Society of Civil Engineers has estimated that existing infrastructure needs $3.6 trillion in repairs and replacement by 2020, while infrastructure spending levels are unclear under the new administration, this gap is likely too large to close. Add the drought and flooding of climate change, and the stark inadequacies of our 19th Century water systems are clear. From sea level rise to flooding and drought, from loss of groundwater to harmful algae blooms, rising temperatures, and carbon dioxide and methane emissions, we cannot continue to accept the status quo for water infrastructure. If all we do is rebuild and extend our existing inflexible centralized systems, promoting them by adding modest bells and whistles to generate some energy at end-of-system treatment plants, we will witness their spectacular failure in the face of climate change.

CRWA has identified an approach that is both restorative of natural systems and financially and economically responsible, even desirable. Additionally, the Community Water and Energy Resource Centers (CWERCs) we analyzed provide us the opportunity to leverage value in existing centralized infrastructure as we move away from it over time. Our existing infrastructure is not a “sunk cost;” it provides us a means of starting the transition to a more resilient system. Additionally, as elements of our existing systems are phased out, they can be repurposed for things like flood storage and conveyance. CWERCs allow us to think about pipes and capacities in very different and far more flexible ways.

There is also a very important social side to the creation of CWERC districts. There are opportunities for new ownership and utility models as energy generation becomes more distributed. Not every CWERC needs to be owned and operated by a central water authority. Neighborhood-owned CWERCs, providing treatment and energy and water utilities to neighborhood desired development could give neighborhoods greater control of their destiny. Further, our work has shown that due to the resource generating potential of wastewater, there is significant opportunity to stabilize water and wastewater rates, which have risen inexorably over recent decades, a trend that will certainly continue if we elect to rebuild existing infrastructure. Price increases unduly burden those at the lowest income levels. Contrast that reality with rates subsidized by wastewater-generated utility sales. Together with the introduction of restored streams and green infrastructure as both neighborhood amenities and resilience to climate change, CWERCs will contribute to a sense of place while enhancing affordability.

The transformation of centralized water systems to CWERC districts will take years. During that transformation, we must use the opportunity to restore natural hydrology, flexibility and adaptability, and urban surface waters. We must integrate management of all “types” of water: drinking, reclaimed, surface, ground, waste, a concept becoming known as “One Water.” Green infrastructure is a necessary companion to CWERC implementation that completes the fully integrated water management and restoration objectives. The move to CWERCs gives us a one-time opportunity to address most all the failings of the water infrastructure we have inherited, an opportunity we must not squander. CRWA’s approach to restored streams and green infrastructure using our “Blue Cities Exchange” trading system for stormwater will drive down costs as it provides the necessary financing.

With the construction of CWERCs in several locations across the country we can continue to add to the knowledge base we have established with this publication. There are myriad regulatory and ownership questions we look forward to addressing, as well as many questions related to siting, construction, and operations. There are additional social impact questions such as costs and equity, community utility ownership models, climate adaptation, Blue Cities trading, even simple concepts like the separate collection of household food waste for use in CWERC energy generation.

As CWERCs are constructed, their cost and nature will begin to change. We acknowledge it is important to get implementation costs down over time to enhance financial viability. Innovation around this new investment opportunity will lead to CWERCs becoming cheaper to build while increasing their ability to handle more waste on less land, generating more energy more efficiently, and engaging new partners to provide new opportunities we have not yet identified or investigated.

CRWA is actively pursuing CWERC pilot projects in Massachusetts and cities across the country. The environmental benefits are compelling: restoration of flow and water quality to urban rivers, restoration of flow to water supply watersheds, renewable energy, reduced greenhouse gas emissions, increased flood control, resilience to drought, reduced heat island effect, improved air quality, and improved public health. The need is real, the opportunities are real, and the time to start is now.

CWERC economics are so compelling, I believe, that the construction and operation of just a few will result in their replication everywhere.

Bob Zimmerman, former Executive Director
Charles River Watershed Association
February, 2017