PEABODY SQUARE GREEN STREET PILOT
Project Background
In July, 2007, the City of Boston was awarded a grant from the Massachusetts Department of Environmental Protection (MassDEP) to undertake an innovative pilot project to assess the potential stormwater management and recharge benefits of a so-called Green Street. Green Streets are streets designed to incorporate innovative stormwater management techniques, including Low Impact Development (LID) stormwater Best Management Practices (BMPs), into the street right-of-way to collect and treat stormwater runoff that is generated from sidewalks, roadways and other impervious surfaces.
Green Streets have been constructed in cities including Seattle, Washington, Portland, Oregon, and Atlanta, Georgia, where they have proven successful at reducing both pollutant loads and stormwater runoff volumes from public streets. The City of Boston is interested in determining whether Green Streets are feasible in Boston, particularly given our cold climate, and understanding more about their costs and benefits. Since there are currently no Green Streets in Massachusetts, the City of Boston Environment Department (BED) and CRWA began working together to identify an appropriate pilot project in 2006. A proposal was submitted to MassDEP in December of 2006 seeking funds to support the pilot project. In the spring of 2007, BED and CRWA selected Peabody Square as a potential site for a pilot project, and upon receipt of the 604(b) grant from MassDEP, began work to assess the feasibility of including Green Street designs into an existing plan to redevelop the streetscape.
Existing Conditions Analysis
Peabody Square is situated in Dorchester, MA at the intersection of Dorchester Avenue, Talbot Avenue, and Ashmont Street (Figure 1).
Figure 1: Project Location and Area
The area is "mixed-use" in that it is comprised primarily of commercial and high-density residential land uses (MassGIS, 1999).
Figure 2: Peabody Square - Mixed-Use Environment
The study area drains to the Neponset River, which is on the Massachusetts list of impaired waters (http://www.mass.gov/dep/water/resources/2006il4.pdf) and is identified as impaired for organics, pathogens and turbidity, all common pollutants in stormwater runoff. The Neponset TMDL, which is available at http://www.mass.gov/dep/water/resources/neponset.pdf requires reductions in bacteria loading.
Figure 3: Peabody Square - Stormwater System
In addition to document research, CRWA conducted site visits to study the existing physical conditions at Peabody Square and analyzed how the 25% design studies will change the existing landscape characterization of the study area.
Figure 4: Peabody Square - 25% Design
Figure 5: Peabody Square - Land Cover under 25% Design
Given the dearth of green spaces and street trees in the area, a need for replacing paved areas with vegetative and soil based best management practices was immediately identified. A summary of the project background along with existing and 25% designed conditions for the site is included in this presentation (PDF).
WinSLAMM Model Runoff Volume and Loading Estimates
CRWA used a stormwater runoff model, WinSLAMM (Source Loading and Management Model for Windows), to estimate stormwater runoff flows and loads in the study area. Development of the model for the study area included inputs of land use, building footprints, and drainage area delineation, as well as calibration of rainfall data sets and analyses of pollutant loading estimates as detailed in the QAPP. Runoff volume and pollutant loads were calculated for several design storms, as well as average annual pollutant loads for several pollutants.
The study area or "analysis extent" was determined using a combination of the extent of proposed work and analysis of a MassGIS-developed light detection and ranging (LIDAR) digital elevation model (DEM). Using ArcGIS Watershed Analysis tools, drainage paths or channels were developed from the DEM (Figure 6). This process aids in defining drainage areas and sheet flow direction and accumulation during a hypothetical storm.
Figure 6: Modeled Stormwater Runoff Drainage Channels (grey - white grid cells) Using the DEM
Low Impact Development (LID) Best Management Practice (BMP) Opportunities
Based on the existing conditions, the planned redesign of Peabody Square, and the needs and interests of the various departments in the City of Boston as well as the neighborhood groups, CRWA selected a suite of LID BMPs to consider for application in the pilot project. CRWA
has begun to develop fact sheets (links below) for each of these BMPs,
and a matrix to help evaluate and select potential BMPs for use in the Peabody Square pilot project.
Fact Sheets for Low Impact Development BMPs
|
WATERSHED INFO