Alternative and Nonstructural Solutions to Phosphorus Control in Stormwater

The 2016 Massachusetts Small Municipal Separate Storm Sewer System General Permit (MS4) goes into effect in 2018—setting off a timetable for municipalities in the Charles River watershed to initiate controls for phosphorus in stormwater run-off. These types of stormwater regulations are not unique to Massachusetts—while regulated MS4 areas represent only 4% of the United States, they include over 80% of the country’s population, with many areas along rivers and coasts increasingly coming under pressure to reduce nutrient discharges in all NPDES permits.

Over 20 years ago, the EPA launched the Clean Charles Initiative with the hopes of making the Lower Charles River fishable and swimmable again. While the effort successfully reduced bacterial contamination in the river, nutrient discharges, continue to impair water quality. The EPA and the MassDEP outlined aggressive targets to reduce phosphorus levels in the watershed and are using the MS4 permit to spur action within watershed municipalities. The new permit defines a relatively finite suite of strategies and built solutions to control nutrient loading. However, we’re increasingly understanding how nonstructural and alternative structural control strategies can reduce nutrient loads in other parts of the country and, perhaps more importantly, provide numerous community co-benefits.

In 2010, the East of Hudson Watershed of New York City was faced with a similar nutrient control requirement. After five years of planning and implementing stormwater projects, the coalition of municipalities that make up the area—the East of Hudson Watershed Corporation (EOHWC)—hired Woodard & Curran to develop their stormwater retrofit plan for the next five years. As a part of this work, we conducted a cost-benefit analysis of hundreds of projects implemented in the watershed over the past several years to see which strategies were most efficient and cost-effective in reducing phosphorus loads. Through this evaluation, we uncovered some useful and surprising insights that can help municipalities across the country reduce the high price tag that tends to come with phosphorus reduction projects heavily reliant on stormwater treatment technologies.

Collaborate for better results

Just like in the case of the Charles River, the benefits of nutrient control apply to the entire watershed, not to specific municipalities. But municipal-based permits require nutrient load reductions for individual communities. This has the potential to make some, already largely developed, communities take on much costlier retrofit scenarios with limited watershed benefit. In New York, we found that communities vary greatly in opportunity areas for stormwater treatment. By working across municipal boundaries, more cost-effective projects can be identified regardless of where in the watershed they occur. To cost-effectively manage stormwater transported nutrients then, we must work across municipal boundaries.

Plan more thoroughly

Many projects there were implemented during the first five years didn’t fit into the built environment and didn’t consider variables like permitting, field conditions, ownership, and operations in the planning process, resulting in unnecessary EOHWC administration and consultant expenditures. By more thoroughly planning for retrofits (and hopefully across municipal boundaries), individual municipalities can see significant savings during implementation. Where hundreds of millions of dollars of stormwater retrofits are potentially required—don’t scrimp on the planning.

Advocate for the best strategies to receive appropriate credit

The projected cost-per-pound of phosphorus removal varied significantly for several stormwater retrofit practices. These values are largely defined by the regulatory agencies, as is the case in the Charles River. A limited range of “creditable” stormwater treatment options, which do not necessarily coincide with current MassDEP stormwater management standards, limit creativity and do not take advantage of the latest science. In New York, channel stabilization proved to be one of the most cost-effective retrofit practices, but this technique is not even an option in Massachusetts. The Chesapeake Bay total maximum daily load (TMDL) program and expert efforts there have adopted and allowed channel stabilization and erosion control as viable nutrient control projects. Additionally, the co-benefits of channel stabilization and erosion control go well beyond stormwater treatment to protecting infrastructure, enhancing wildlife habitat, and improving public spaces. By narrowly defining stormwater treatment without considering insights from other regions of the country, we have done ourselves a potentially costly disservice. Given the costs and challenges of long-term nutrient control, communities will need the flexibility to implement more cost-effective strategies with multiple co-benefits to justify expenditures.

Look beyond the structural control

In 2016, William Selbig of the U.S. Geological Survey published an article in which he presents research findings that demonstrate municipal leaf collection programs have the ability to reduce loads of total and dissolved phosphorus in a given drainage area by 84 and 83%, respectively, and total and dissolved nitrogen by 74 and 71%. This is massive! His research indicates that nearly 60% of the annual phosphorus yield in urban and suburban environments comes from leaf litter in the fall, making it a huge contributor of nutrients to urban receiving waters. Not only is developing a leaf litter collection program a potentially less-expensive option than a widespread installation of stormwater treatment systems, there are several co-benefits of removing leaf litter from roads and drain systems: cleaner streets, safety, and a reduced likelihood of clogged storm drain inlets. This is something that citizens already demand as a municipal service and that many communities already do, so if municipal managers can assess the appropriate timing and frequency of leaf removal and street cleaning, they have the opportunity to make a substantial impact on nutrient loading in stormwater runoff. But the implementation of these programs must be creditable at a level that reflects the current state of the science. In Massachusetts, they currently are not.

By implementing the lessons learned in New York, and through other regional and national initiatives for nutrient reduction, Massachusetts can reduce overly costly investments and improve water quality more effectively and more quickly with multiple community co-benefits.


Zach Henderson Practice Leader Stormwater

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