In previous posts, I’ve laid out CRWA’s vision of green infrastructure and restored urban streams to obtain a host of benefits, perhaps chief among them flood control. Flood control was not, however, what led us to investigate green infrastructure; phosphorus was.
|Land cover distribution in the Charles River Watershed|
|Distribution of phosphorus pollution to the Charles River by source|
The Charles suffers from more than twice the phosphorus pollution it can handle and still function as a healthy ecosystem. In a natural system a limited supply of phosphorus would control growth of aquatic fauna; it’s a case of “too much of a good thing.”
To determine the sources of phosphorus, CRWA, MassDEP, and EPA and their consultant Tetra Tech completed “total maximum daily load” (TMDL) analyses for the river. EPA concentrated on the sources to the Charles River Lower Basin, the last 10 miles of the river, while CRWA with MassDEP concentrated on the sources for the 70 miles of the river upstream of the Watertown Dam. EPA completed its analysis in 2007, and we completed the Upper Middle Charles TMDL in 2011. These analyses confirm that fully 50 percent of the phosphorus pollution in the river comes from industrial, commercial, and high density residential properties with high impervious cover (i.e., parking lots and buildings).
It turns out phosphorus accumulates on pavement from atmospheric deposition, auto exhaust, and grease and oil, to be picked up by rainfall running off to storm drains. From the storm drains, phosphorus-laden stormwater is dumped directly into Charles tributaries and the river.
There was immediate pushback from some among the pilot area towns and property owners. A new requirement associated with new compliance expenses is seldom greeted with enthusiasm. Based on the science, and with Conservation Law Foundation (CLF), our legal partner in this endeavor, we had lengthy discussions with EPA New England to convince them to exercise their residual designation authority pursuant to section 404(p)(2)(E) and (6) of the Clean Water Act to extend their water discharge permits to include stormwater runoff from such currently unregulated properties. In 2010, EPA released a draft general permit requiring such property owners with two acres or greater impervious area to remove 65 percent of the phosphorus in runoff from their properties, first in a pilot area of the towns of Milford, Bellingham, and Franklin in the Upper Charles.
Anticipating the reaction, we had begun work in 2006 on a stormwater trading program/website to help drive down the cost of compliance. Though among the most difficult projects to find funding for in my experience at CRWA, we nevertheless were able to find enough funding to put together a proof-of-concept website based on real data for the pilot towns.
Currently, with funding from Surdna Foundation, we are investigating the applicability of our trading approach for Boston in addition to the upper watershed area.
Briefly, what we have built is based on the fact that when it comes to infiltration of water--the best method of phosphorus reduction, all soils are not created equal. Rainwater does not easily percolate through clay and bedrock, and property owners in these areas required to capture stormwater runoff and infiltrate it could face costly retrofits to comply with the draft regulation. Sandy soils, however, do work well with water, and installation of stormwater infiltration systems on such soils is much cheaper, hence the concept of trades to achieve compliance more efficiently.
Rain gardens filter and absorbs stormwater runoff
The other thing CRWA based our trading website work on was the option for non-regulated property owners to trade with regulated property owners. An unregulated property with good soils could infiltrate stormwater at a lower cost than a regulated property with poor soils, offering the regulated property owner relief at a lower compliance price, while making a profit for the unregulated property owner. By mining stormdrains, and by distributing stormwater remediation, unregulated property owners could significantly enhance both compliance and remediation effectiveness.
Our software and website, called Blue Cities Exchange, are based on two observations. First, encouraging the control of phosphorus across the landscape is better for the Charles. Second, giving property owners a “one stop” website explaining the problem and the regulation, allowing them to investigate their soils and compare the costs of different stormwater control installations, and allowing them to explore trading as an option to meet much of their the regulatory requirement would drive down costs, and increase compliance.
In my next post I will describe what it is we have built, and give readers an opportunity to take a look at the website in its current state.