Modeling Pollution Load Reductions

Over the course of the next several weeks, the AKRF team will be developing pollution reduction targets for the watershed, and modeling the reduction capabilities of the projects proposed as part of the watershed-based plan. This process will help to focus management actions based on the cost and efficiency of the proposed projects. In addition to pollution reduction values associated with place-based practices, the final plan will also include general percent removal factors typically associated with non-structural activities (land use change, wildlife management, etc).

To determine load reduction targets, we will use WinSLAMM software to establish baseline conditions for each sub-watershed. Baseline conditions will be defined by pollutant loads associated with a watershed comprised of woods in good condition. Our reduction targets for N, P, TSS, and fecal coliform will be the difference in loading between the existing condition models (Phase I) and the baseline condition models.

Once completed, this phase of the project will link the proposed management actions with existing conditions in the watershed. It will also also help us gain a better understanding of the cost/benefit associated with different methods of pollution control, and will help us to develop performance criteria.

Research by Dr. Robert Pitt of the University of Alabama provides the basis for the WinSLAMM modeling approach.

Success Story: A Rain Garden for Vernon park

At Vernon Park in Philadelphia, a group of volunteers has built a functioning rain garden with donated plants and equipment. Lead by the Tookany/Tackony-Frankford Watershed Partnership, the project leveraged support from municipal agencies, community advisers, and a large group of committed volunteers. 


The garden is designed to capture the “first inch” of runoff from the roof of one of the park’s large buildings (seen in the background below). Water from the roof drains is directed into simple swales, which carry water directly into the rain garden. There the water is held back from entering the storm sewer, and can slowly infiltrate into the ground.  

Volunteers graded the rain garden and planted over 400 plugs of fox sedge, bee balm, turtlehead, and ferns, plus small containers of bleeding heart, ironweed, cardinal flower, dogwood, redbud, blueberry, hydrangea, and more. These plants will grow to fill in the rain garden with a lush cluster of flowering native plants that improve habitat and aesthetics in the park. At a fairly low cost to the community, this garden benefits the neighborhood, the city, and the downstream watershed.

Could a project like this happen in the Mianus Watershed? What examples can we share of similar local work?





Before planting





Volunteer gardeners at work (Photos ©AKRF, 2011)



  



Impervious Cover in the Mianus River Watershed

Many of the implementation projects discussed for the watershed-based plan deal with reducing the negative effects associated with impervious cover. This may mean converting the impervious area to a more porous condition (i.e. gravel to meadow, or a traditional parking lot to porous asphalt), or “managing” the runoff from an impervious area by routing storm flows through a BMP specifically sized to handle that quantity of water.  In less developed parts of the watershed, the strategy is simpler: maintain the low levels of imperviousness through conservation zoning and protection of existing open space.

The watershed-based plan uses The Center for Watershed Protection’s 2003 monograph, Impacts of Impervious Cover on Aquatic Systems, as a basis for its approach. But numerous other sources support the idea of impervious threshholds, including several studies by the CT DEEP summarized in this fact sheet. The Impervious Cover TMDL developed for Eagleville Brook near the University of Connecticut campus offers an excellent case study of the impervious cover approach to managing multiple stressors. Of particular relevance to the Mianus River Watershed is the CT DEEP’s Streams of Hope document, which examines conditions in “moderately urbanized” streams where impervious cover is between 6-14% (impervious cover in the Mianus Watershed is approximately 12%).

We are interested in what measures, if any, your town has taken to deal with the impervious cover issue. Conservation zoning, land protection, and LID can be controversial, and there is no single answer that works for every community. If you would like to offer thoughts or feedback on this topic, you may simply leave a message in the “comments” section of this blog post, or write a new post of your own with one of the generic login IDs. For blog support, contact Lia  (lmastropolo “at” akrf.com).

Meeting Recap & Related Resources

On Wednesday November 30th SWRPA, CT DEEP, AKRF, and 18 stakeholder representatives gathered to discuss next steps for implementation of the draft watershed plan. AKRF presented several types of projects that could be implemented to improve water quality and habitat in the watershed. Projects discussed included bioretention cells, retrofits of existing stormwater basins, riparian buffers, and more.

After the presentation, stakeholders offered input on the plan and raised several important questions. Funding was discussed, including regulatory incentives for implementation. Youtube videos, targeted training workshops, and programs for school children were suggested as ways to bring the message of watershed protection to a broader audience. Barriers to implementation were identified, such as limited land use regulation and the difficulty of mobilizing large scale projects.

Common themes that emerged from the meeting were the need for regulatory and financial incentives; funding barriers and the challenges of mobilizing large projects; the importance of innovative outreach and education; and concerns regarding function and aesthetics of structural practices. The following may be useful in continuing this discussion:

• A recent study by American Rivers and the Center for Neighborhood technology begins to quantify the multiple social and economic values associated with low impact development (LID) techniques
• An informative fact sheet on the economic benefits of LID, from the NC Cooperative Extension
• A 2005 study on the economic value of open space in Minnesota
• A detailed discussion of common barriers to implementing green infrastructure, and hidden opportunities
• Project Headwaters, initiated by a Trout Unlimited chapter in southeastern Pennsylvania-- a good example of community-driven implementation of stormwater management projects
• This EPA fact sheet sheds some light on the issue of mosquitoes and stormwater management basins
• A recent zoning debate in Greenwich offers an example of the challenges faced by local land use managers (with commentary from the Mianus Watershed Council’s own jack Stoeker!)