|Overnourished by phosphorus and nitrogen carried into the Charles by nonpoint sources, Blue-green Algae thrive at the expense of other aquatic organisms
Perhaps you have heard WGBH's recent series Water Pressure discussing nonpoint source water pollution and are curious about CRWA's strategies to address this threat to the Charles River. Nonpoint source pollution (NPS) occurs when rainfall, snowmelt, or irrigation moves over the ground, picks up man-made and natural pollutants and deposits them, untreated, into our rivers, lakes and coastal water bodies. Imagine a drop of rain slapping onto an oily and grimy street, or a pesticide-rich lawn, picking up speed and contaminants in equal measure, then flowing through drains and unloading directly into a waterway. Because of its diffuse nature, NPS pollution is a challenge to address. The sheer variety and scale of nonpoint sources is staggering: sediments eroding from riverbanks or construction sites; fuels, grease and heavy metals leaking from cars and running off roads; car exhaust and power plant emissions; fertilizers and herbicides washing off agricultural lands and lawns. CRWA has long been working to reduce nonpoint source pollution, and has developed a multi-disciplinary strategy combining our strengths in science, advocacy and design to reduce nonpoint source pollution to the Charles River
1. Monitoring and Investigating Nonpoint Source Pollution
Reducing nonpoint source pollution begins with monitoring water quality and understanding the sources of pollution. For over twenty years, CRWA has collected water quality monitoring data across the 80-mile Charles River through our volunteer monthly monitoring program. We have found that the Charles, like other urban rivers, is polluted by many contaminants. In particular, it suffers from about twice as much pollution than it can handle while still remaining a healthy, functional river system. Though all living things need phosphorus to survive, too much phosphorus in the river causes algae and invasive aquatic plants to grow explosively, smothering and shading all other aquatic organisms. Our science team, together with Massachusetts Department of Environmental Protection, investigated the sources of phosphorus runoff in the Charles. These analyses showed that fully half of the phosphorus pollution in the river came from industrial, commercial, and dense residential properties with high impervious cover (i.e., roads, parking lots and buildings).This investigation also included a plan to reduce phosphorus in the Charles.
2. Replacing Impervious Surfaces with Green Infrastructure
|Green infrastructure installed at Mace Apartments
Over half of the land in Boston is paved, including streets, buildings, and parking lots. In some parts of the city, like Allston, that number is as much as 70%. Instead of nature's slow and steady absorption and purification of rain water, hard, impervious surfaces short-circuit the natural water cycle preventing the infiltration of water into the ground, and increasing runoff of contaminated water into storm drains and ultimately the Charles River.
Green infrastructure makes use of soil and vegetation to slow, capture and filter stormwater and provides an alternative to the overburdened, traditional gray infrastructure (sewers, pipes and water treatment plants). As part of our Blue Cities Initiative, CRWA has implemented and advocated for many green infrastructure projects including porous pavement, stormwater tree-pits, and rain gardens.
For example, our Porous Alley Project in Boston's South End involved covering an alley with porous asphalt so that any polluted runoff from the area would filter through the pavement into a large gravel-filled storage space and then infiltrate into the ground. This process captures and treats polluted runoff locally while also reducing flooding problems and replenishing groundwater levels. After the porous alley was completed last fall, CRWA and the Boston Groundwater Trust have been monitoring groundwater levels and evaluating the reduction of pollutants from the site including phosphorus, nitrogen and heavy metals.
On a larger scale, CRWA aims to restore natural hydrology in our cities. We have pushed for the preservation and creation of large interconnected natural areas such as wetlands and parklands that can act as both a flood barrier and a living filter: removing excess nutrients, sediments and other contaminants from stormwater runoff.
3. Advocating for Good Stormwater Management
Tackling the diffuse sources of nonpoint source pollution requires a cohesive regulatory and policy effort. CRWA advocates for stronger stormwater permits which will clean the Charles River, add green space to our cities and towns and protect drinking water supplies. We ensure that new redevelopment projects comply with the plan developed to reduce phosphorus concentrations in the Charles. CRWA reviews plans for new developments in the Charles River Watershed and advocates for the incorporation of low impact development and green infrustructure. We also work with municipalities to promote the installation of green infrastructure. For example, CRWA worked with the City of Boston to develop Boston Complete Streets Guidelines to incorporate green infrastructure firmly into Boston city planning.
What You Can Do to Help Prevent Nonpoint Source Pollution:
- Minimize your use of fertilizers
- Pick up and compost leaves in the fall
- Maintain your car to reduce oil leaks and minimize corrosion
- Visit a car wash, where water is treated and recycled, instead of washing your car in your driveway
- Pick up after your dog
- Build a rain garden to capture runoff from your roof