Stormwater Drainage Design and Construction

  • Client

    Town of Norwell

  • EP’s Role


The Town of Norwell reached out to Environmental Partners (EP) to evaluate and seek solutions to localized flooding concerns along Route 123 which is approximately 3.5 miles in length and runs from the town line to Hanover’s town center.

From 2015 through 2016, EP executed an aggressive 20-month project with the Town, which involved the Design, Permitting, and Construction Oversight of over 3.5 miles of roadway paving and 20 new infiltration/drainage system installations along Route 123 to address localized flooding concerns. Additional work tasks included making recommendations for intersection reconfigurations and upgrades, and a conceptual sidewalk alignment along this busy stretch of road.

Prior to design and construction, EP evaluated the condition of each roadway and examined drainage issues during stormwater events, and within six weeks a series of test pits and in-situ hydraulic conductivity testing of the underlying soils to simulate groundwater recharge into the ground at pre-determined locations were conducted. Based on the field data, EP compiled a series of calculations for multiple storm events including 1, 2, 5, 10, 25, 50, and 100-year storms in order to understand the volumes of stormwater that must be accommodated at each site via a series of subsurface recharge systems. EP submitted a report to the Town that summarized recommendations for improvements along with cost estimates for repairs.

Based on this report, the Town immediately enlisted EP to address 15 drainage areas within 3 of the 5 streets that required repair. EP advanced test pits in the drainage areas to identify the groundwater table elevation and soil types. A topographic survey was then conducted which augmented the Town’s aerial topographic maps in order to determine catchment areas and volume of stormwater runoff to manage.

During the design period, EP worked in partnership with the Town’s Highway Department and Conservation Commission agent to ensure their concerns were met. Stormwater BMP’s included grass/rip rap swales and deep sump catch basins tied to large in-ground leaching structures which recharged the groundwater versus discharging directly to wetland resources. EP’s Notice of Intent submittal to the Conservation Commission resulted in one hearing where all proposed improvements were approved enthusiastically. The NOI included a stormwater and drainage report demonstrating compliance with the Massachusetts DEP stormwater standards and MassDOT environmental requirements. EP provided all construction administration and resident engineering services.

Construction phase services spanned over two seasons and included a major traffic management plan with detours along Route 123. EP conducted numerous public sessions with the Town and local abutters during construction to ensure that traffic impacts were minimized to residents and local business. The total project cost including roadway restoration and resurfacing was $3.2M with less than half of a percent in change order work.

Key Team Members