Here we’ll be sharing updates and key details about Green Lawrence–Blue Merrimack, a two-year project focused on reducing flooding, improving stormwater systems, and protecting our rivers. Join us in building a safer, more resilient Lawrence!

Year 1

Data Collection & Review (October-December 2024)

  • Review and summarize available data on the City’s sanitary and combined sewer mains, stormwater sewers, and history of CSO and flood events.

Sewer Flow Monitoring (October 2024-June 2025)

  • To gather data on the city’s sewer system the project will install three rainfall gauges, continuous flow monitors, and five Smart Covers® manhole monitoring systems. The flow monitoring data will be used to create a computer model for the sewer system’s baseline condition. Observed results are then compared to simulated results to calibrate and validate the computer model.

Combined Sewer and Separated Storm Sewer Modeling (October 2024-June 2025)

  • Prepare a hydrologic and hydraulic model (H&H Model) to create a detailed computer representation of the city’s sewer network and simulate how these elements respond to local rain events.
  • H&H models investigate hydrology (Where does rainwater go? How much will flow into the sewer network?) and hydraulics (What will be the volume and velocity of the flow in the sewer network? How will the infrastructure manage and treat the flows?).
  • Once the computer model is built and tested with existing conditions, the team will run the model and add in different types of infrastructure throughout the city. The model will estimate how the system will perform and measure possible benefits like a reduction in sewage discharges to the river and reducing nonpoint source water pollution.

Green Stormwater Infrastructure Evaluation (October 2024-June 2025)

  • Green stormwater infrastructure (GSI) is a nature-based way to manage stormwater runoff. It uses plants, soil, and permeable surfaces to reduce the amount of stormwater that flows into sewer systems.
  • Conduct a comprehensive evaluation of GSI solutions by reviewing 150 City-owned properties to identify opportunities that include tree planting/canopy increase, rain barrel/storage, buffer creation/restoration, and impervious area reduction to control peak flow during storm events, mitigate flooding and reduce non-point source water pollution.

Stormwater Utility Feasibility and Organizational Assessment (July 2024-June 2025)

  • Conduct preliminary work to determine the feasibility of establishing a stormwater utility to ensure the city has the financial resources to maintain and upgrade the city’s sewers.
  • This task also includes an organizational assessment of the Department of Public Works to ensure the human resources are in place to implement the recommended stormwater management and combined sewer overflow mitigation opportunities.

Final Stormwater Resilience Master Plan Report (April 2024-June 2025)

  • Prepare a report that summarizes work completed in Fiscal Year 2025 incorporating information learned in the previous tasks.

Year 2

Continued Sewer Flow Monitoring & Model Calibration

  • To improve the computer model of the city’s sewer system the project will complete a second year of flow monitoring to increase the range of precipitation intensity to improve model calibration.

Green Stormwater Infrastructure Model Integration

  • With the computer model is built and tested with existing conditions, the team will run the model and add in Green Stormwater Infrastructure (GSI) opportunities identified in year 1. The model will estimate how the system will perform and measure possible benefits like a reduction in sewage discharges to the river and reducing nonpoint source water pollution.

Real Time Modelling

  • With the computer model calibration is complete for baseline flow and rainy weather flow, real time prediction of targeted combined sewer and storm sewer response to incoming precipitation events will be analyzed. Real time modeling will be developed for a pilot area within the combined and/or separated storm sewer system.

Rain Barrel Promotion Pilot Program

  • Conduct targeted outreach to offer free rain barrels for up to 25 properties. This includes assistance to landowners with setup and installation of rain barrels.