Blog - Charles River Watershed Association

Water Transformation Part 13: Blue Cities Exchange

Posted by Robert Zimmerman

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8/6/15 10:34 AM

PREVIOUS POST: Water Transformation Part 12 - Paying for Green Infrastructure  and Restored Streams

In Part 12, I introduced one of the tools CRWA has been developing to help drive down costs for the installation of blue/green infrastructure, while potentially providing income to help restore streams and rivers. This tool is an interactive website called Blue Cities Exchange.




Sandy soil (left), loamy soil (middle), clay soil (right)

Blue Cities Exchange

CRWA will provide limited access to our stormwater trading website,, for interested parties. Click here to receive the username and password. The website and software, as well as the concepts leading to website development, remain the Intellectual Property of Charles River Watershed Association. The website remains under construction. Its completion is dependent on CRWA acquiring necessary funding.

It is important to understand that soils, when it comes to infiltrating rainwater, are not created equal. Sandy soils do a much better job, at least-cost, infiltrating water than do clays, glacial tills, and rock ledge. CRWA’s stormwater trading tool seeks to exploit the cost differentials to allow property owners located on soils that do not infiltrate water well to “trade,” or buy credits from property owners who can install stormwater controls that remove phosphorus much more cheaply. 


Our website, still under construction, can be found at Our desire is to make Exchange a one-stop site for all things green infrastructure. The site is being designed to assist property owners in designs for onsite green infrastructure and as a marketplace for trades. Presently, the site is loaded with data to support property owners in three pilot upper Charles watershed towns, Bellingham, Franklin, and Milford. The algorithms we put together for the pilot website, and the costs associated, are real for that region. They may not translate well for urban Boston or other parts of the watershed, where complications around what is already in the ground could increase costs. In other words, we have a lot of work left to do, not only mapping soils, but completing the financial and legal effort to make phosphorus trading work.


 Try Blue Cities Exchange


In its current state, the website is a technological proof of concept. Bellingham, Franklin, and Milford, three headwaters towns, were selected for the pilot site because six years ago U.S. EPA designated these areas as a pilot region to implement new stormwater regulations.


The website is pre-loaded with soils data. Selections among 10 different stormwater controls can be investigated for cost of installation for specific properties, and recommendations are made based on cost options. The trading pages themselves, however, are not currently operational. Working through the legal, environmental, and market aspects of trades remains.


One of the significant benefits of our approach is that our website is designed to promote trades between regulated and unregulated properties. We believe that as unregulated property owners recognize the opportunity to make money by selling credits for building rain gardens on their properties to mine passing stormdrains and infiltrate equivalent stormwater, options for stormwater control will increase and costs will diminish.

As the Charles flows downhill and the idea is to clean the river over its entire length, we intend to introduce scientifically-based geographic control, so that trades generally occur at or upstream of regulated properties, i.e., in areas where the systems will have a similar or greater impact on improving river quality. Eventually, we would like to include engineering tools on the website, allowing for design of green infrastructure installations and the filing of “as-built” plans with municipal agencies.

I believe there is a major benefit for property owners in Boston if our approach is implemented. If the City of Boston were to build green infrastructure and restore the buried streams in its midst at some cost, the City could then sell stormwater credits beyond those it needs for permit compliance to regulated private property owners within each restored stream subwatershed. For their investments, the property owners would get two benefits: 1) compliance with stormwater requirements, and 2) new flood storage and greenspace within the city.


I envision a hybrid regulatory framework for stormwater control in Boston, meaning a city-wide stormwater utility employing trading as a tool to seek and promote use of “best sites.” With a grant from Surdna Foundation, we are examining the application of Exchange in the city. There are myriad possibilities for the application of Exchange, particularly in promoting solutions on both public and private properties by creating incentives for discovering and using best sites. The outcome we seek is one where stormwater controls are distributed on both public and private land, where the riparian corridors in restored city streams are used to store and treat stormwater, and the result is a city far more resilient to both drought and flooding. Many uncertainties remain, however.

I know those whose properties would be regulated are not enthused about costs associated with removing phosphorus from stormwater runoff on their properties. But I wonder whether concomitant flood protection for their properties would sweeten the deal. The cliché is that an ounce of prevention is worth a pound of cure. I believe that mutual interest might provide Boston with a real opportunity to address major citywide climate change concerns, while restoring nature.


As a side note, CRWA is also interested in standardizing stormwater treatment systems. With standardization, a host of opportunities for non-traditional stormwater contractors would open.  In conversations with two universities, the notion of creating installation and maintenance certification courses was well received. Our hope is that by increasing the number of qualified contractors, we could further drive costs down, while providing a wealth of opportunities on the blue/green jobs front.


In other regions of the country, Exchange may allow for a different approach to nutrients in water bodies affected by agricultural runoff. The website could be adapted to promote trades between cities and farms to provide funds to reduce farm runoff. Perhaps, for example, by creating berms along the waterside of fields that drain runoff to collect in vegetated retention areas and then released, farmers could dramatically reduce runoff and collect silt for spreading back on their fields, all without losing much in the way of planted acreage. The notion would revolve around balancing nutrient loads by source, reducing costs to cities while increasing funds available to farmers. We have yet to look at the complexities of such an approach, but it is at least worth considering.

 NEXT POST: Water Transformation Part 14 -Reality Assessment



Topics: Charles River, Stormwater, Stormwater Management, Green Infrastructure, Pollution, Blue Cities, Water Transformation Series, Stormwater Runoff, Blue Cities Exchange

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About Charles River Watershed Association:

One of the country's oldest watershed organizations, Charles River Watershed Association (CRWA) was formed in 1965 in response to public concern about the declining condition of the Charles. Since its earliest days of advocacy, CRWA has figured prominently in major clean-up and watershed protection efforts, working with government officials and citizen groups from 35 Massachusetts watershed towns from Hopkinton to Boston. Initiatives over the last fifty years have dramatically improved the quality of water in the watershed and fundamentally changed approaches to water resource management.