Infrastructure Services Project

Oxbow Road Drainage Study and Design

Town of Lexington Lexington, MA

Solution Overview

Client:

Town of Lexington

Business Challenge:

  • Severe street and overland flooding
  • Drainage surcharging

Solution:

  • Field investigations
  • A detailed stormwater model
  • Outfall and stream restoration
  • Install a relief drain
  • Road drainage Improvements

Results:

  • Drainage system hydrologic/hydraulic model for detailed watershed and drainage analysis
  • Reduced occurrence of future flooding events

Challenge

Environmental Partners (EP), Apex’s Infrastructure Solutions platform, was engaged by the Town of Lexington in 2017 and continues to support the Oxbow Road neighborhood, which has a history of severe street and overland flooding during periodic rain events. The Oxbow Road neighborhood is a residential area in Lexington made up of Oxbow Road, Constitution Road, and Freemont Street, and is bordered by Route 128/95. This major highway system contributes substantial stormwater runoff into the municipal drainage system with a discharge to Kiln Brook.

Solution

Field investigations were carried out with the critical objective of providing data to develop a detailed stormwater model. The work delineated the boundary of the watershed that contributes stormwater to the Kiln Brook outfall and identified drainage connectivity and maintenance issues through CCTV inspection.

EP provided the following phased plan to the town to mitigate the impacts of flooding in the neighborhood.

PHASE 1 - Kiln Brook Outfall & Stream Restoration

Phase 1 allows for the later upstream enhancements of Phases 2 and 3 to increase hydraulic capacity of the existing drainage system and mitigate flooding of the roadways and residential areas.

The design of Phase 1 improvements included daylighting approximately 175 linear feet of existing drainage pipe, wetland restoration, and increasing the size of upstream drainage structures within Constitution Road. EP supported the town in procurement of the box culvert and custom drainage structures to allow for 2021 construction. Final completion will conclude in Spring 2022 with wetland plantings and site restoration.

PHASE 2 - Oxbow Road Relief Drain

The goal of Phase 2 is to mitigate the flooding associated with existing hydraulic limitations along the Oxbow Road/Constitution Road drainage network. The improvements include installation of a 36-inch relief drain to improve hydraulic capacity of the drainage system. And improvements to the inlet drainage piping and headwall. Permitting and final design is expected to be completed Winter 2022 with construction beginning Spring 2022.

PHASE 3 - Freemont Street & Constitution Road Drainage Improvements

Following completion of Phase 2, the drainage system will be evaluated using in-situ flow meters to assess the need for additional improvements along Freemont Street and Constitution Road upstream of the Phase 1 and Phase 2 drainage improvements.

Results

Using results from field investigations, EP updated the town’s drainage system GIS data and incorporated this information into a drainage system hydrologic/hydraulic model. Additionally, advanced GIS-based stormwater modeling software, PCSWMM, was used for this study to allow for a more detailed watershed and drainage analysis.

After the 2018 completion of the Oxbow Road Drainage Study, EP recommended a series of phased drainage improvements to address the problematic flooding conditions along Constitution Road, Oxbow Road, and Freemont Street. These improvements are currently being conducted, with positive results achieved from Phase 1 and a commitment to see the project through all phases.

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