Brandywine Hundred Sewer Rehabilitation

Reason for Rehabilitation

The New Castle County Department of Special Services is responsible for the engineering, operation, and maintenance of the New Castle County sanitary sewer system, a significant portion of which is located in that part of New Castle County commonly known as Brandywine Hundred.

The Brandywine Hundred system is also the oldest sanitary sewer system for which New Castle County is responsible. As this system has aged groundwater and surface water flows have entered and exceeded the capacity of the pipe conveyance system causing repeated overflows into the basements of some homes as well as discharges into local watercourses during significant storm events. Extensive observations have been performed on the sewer pipe system throughout the area leading New Castle County to conclude that rainwater and groundwater are entering the pipe system through:

• Clearwater connections – including sump pumps, roof drains, punctured floor drains, and foundation drains from buildings unlawfully connected to the sanitary sewer system
• Cross connection to storm sewer pipes
• Leaking collector sewer pipes
• Leaking sewer manholes
• Streams flooding over sewer manholes

Phases of the Project

In 2002, New Castle County, with approval from the State of Delaware Department of Natural Resources and Environmental Control, developed a program to address the sewer flow problems entitled CSO Elimination Plan: Brandywine Hundred Sewer Rehabilitation Plan.

The program prioritizes the areas requiring sewer rehabilitation by addressing the problems that are most critical for flow conveyance as well as those that have been determined to contribute the most rainwater and groundwater flows to the pipe system by volume in phase one, which began in 2002 and will continue until 2014.

Phase two will take place from 2015 to 2018 and will continue the effort in areas where the sewer pipes have not deteriorated to the same critical stage as the pipes identified in phase one, but are still a measurable source of rainwater and groundwater intrusion. For phasing information, view the Project Phasing Map. The phases have been divided into project areas for design, construction, and scheduling purposes.

New Castle County’s goal is to reduce peak flow rates in the sewer system by 35% in order to minimize the burden for future costs to county property owners which would be associated with upgrades to the Wilmington Wastewater Treatment Plant, sewage pump stations, and interceptor systems, to create capacity for the continually increasing flows from the deteriorating pipe system. The projects feature some of the innovative technologies available to rehabilitate the sewer pipe system as economically and with as little intrusion into the activities and properties of residents and business owners as possible.