COOL SPRING RESERVOIR RECONFIGURATION
WILMINGTON, DELAWARE
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The City of Wilmington proposed to reconfigure the existing Cool Spring reservoir by replacing the current open pool facility with a below grade, prestressed concrete tank. The proposed 9 million-gallon tank will be founded at the approximate bottom of the existing reservoir. In addition, a new gate house is proposed adjacent to the reservoir, as well as approximately ¾ mile of new water main through the adjacent City streets.

Duffield Associates provided a geotechnical evaluation for the reservoir tank, gate house structure and water main. In order to review the subsurface condition at the proposed tank location, the reservoir was drained and a drill rig was maneuvered into the bottom of the reservoir to perform test borings. Based on the information obtained from the test borings, Duffield Associates provided recommendations to the design team for the design and construction of the proposed tank foundations.

Our team also performed a subsurface evaluation along the proposed water main alignment to assist with construction related issues, such as the reuse of the excavated material for backfill and the presence of rock along the alignment. Challenges associated with this fieldwork included determining the location of many existing utilities in the area of the proposed water main alignment, and coordinating the work effort in the City streets with government agencies and local residents.

Subsequently, Duffield Associates provided engineering consultation regarding the subgrade preparation and installation of groundwater controls during the initial phase of construction, for conformance with the recommendations of the geotechnical report. Duffield Associates also provided full time construction review and testing of the cast-in-place concrete tank structure, during the 14-month construction period.