Constructed Stormwater Wetland Information

Project Summary

The Maillet, Sommes & Morgan Constructed Stormwater Wetland System is the result of a regional watershed wide effort to reduce flooding in the downstream communities by creating offline storage and treatment areas upstream within the Mystic River Watershed. The Mystic River Watershed totals 76 square miles of land that drains towards the Mystic River. Its headwaters begin in Reading, MA with the Aberjona River (which runs through the Maillet, Sommes & Morgan land) and flows through a number of municipalities before draining into Boston Harbor. With 21 municipalities and more than 600,000 peoples within the watershed area it is a vital resource to the state of Massachusetts and is the most densely populated watershed in the state. As with many others across the state this resource is vulnerable to climate change impacts including flooding, extreme rainfall and/or drought, and urban heat island effects. Climate change driven extreme rainfall is already causing smaller tributaries such as the Aberjona River to overtop their banks, leading to local and downstream flooding of residential areas. 

The project proposes to capture and attenuate stormwater impacting the Aberjona River by creating adjacent offline storage areas. The overall objective is to reduce climate related in-land flooding upstream by increasing stormwater storage capacity through the construction of a series of stormwater wetlands that will also provide co-benefits of: stormwater treatment/water quality; improved ecological and stream stability; invasive species removal; and, additional open space and trail development (including ADA access).

Stormwater would be diverted from the local roadways and existing culverts, as well as overland from the River, during high flow events. The wetland system would be designed to maintain a consistent water level by utilizing overflows and set elevations with an eventual discharge back into the Aberjona River.

Improving Resiliency

Climate change is linked to heavier and more frequent rainfall, leading to more destructive in-land flooding. Reading’s MVP Report (2020) indicated that the Town currently experiences 1-2 days of intense rainfall (greater than 2”) per year, although recent years have shown this estimate to be conservative. An 8% increase is projected by mid-century and a 13% increase in extreme precipitation events is projected by 2100. 

By incorporating climate change considerations into the design this project and site will improve in-land flooding resiliency and water quality. Not only will local in-land flooding be reduced but downstream communities of the Mystic River would benefit as stormwater flows and velocity will be reduced, in turn reducing flooding and erosion, in downstream communities.  

Upland and/or constructed wetlands have shown to have a positive and valuable impact on flood protection. As impervious areas increase the rate and volume of runoff the risk of flood damage also increases. When rain storms and snow melt occur, volume is increased and flooding may result. Wetlands, and especially those in floodplains (which near the Maillet, Sommes & Morgan land), have the capacity to store flood water during high runoff events. By slowing the rate at which flood water is released downstream climate induced flooding and erosion can be mitigated.

The plan design utilizes the most up to date and recent climate data As part of the MVP Grant application (see more info on the grant program below) a Resilient MA Action Team (RMAT) Climate Resilience Design Tool Report was developed. You may access the findings of the RMAT Tool Report here. To learn more about RMAT and Resilient MA please visit their site here. 

Additional Co-Benefits of the Project

Community co-benefits of the project are numerous as it improves: ecological stability through invasive species removal and native plant replacement; stream bank stabilization; water quality; accessibility through the creation of ADA accessible entries and paths; public access and parking by improving an area previously inaccessible/hard to access; and, open space and recreation development through the creation/improvement of its path/trail network, which in turn can lead to improved public and social health of community members.

Project Schedule

The remaining project timeline would see completion of the project by June 30, 2024. 

The Plan Design is currently at 75% Completion and the 100% Construction Ready design is expected to be completed before January 2023. Upon completion of the plan set the project will be released for bid between January and February 2023. Construction is expected to ensue in March 2023. Site grading, earthworks and utility install are proposed to be completed by July 1, 2023 (FY24). FY24 will see the construction of the wetland system, paving and curbing, trail development and the installation of site elements and landscaping. While elements may be subject to future change the proposed schedule is as follows: