Guilford Reservoir Improvements Post Award Services

Guilford Reservoir covered an area of approximately 5 acres when originally constructed in 1888 as part of the City of Baltimore’s water system. Starting in 2008, EBA assisted in the evaluation of reservoir cover options to enhance safety. As part of the study, EBA evaluated condition of the existing 40-foot-high dam embankment, classified as a high hazard dam. Of the study’s recommended options, the City selected replacement of the existing reservoir with two 240-foot diameter prestressed concrete tanks.

In 2011, EBA conducted a subsurface investigation that included 26 soil borings. EBA then prepared a geotechnical report that detailed our evaluation of three options to provide support for the new concrete tanks: drilled shafts, pre-loading with shallow foundations, and lightweight fill combined with augered cast-in-place piles. For each option, we considered potential settlement of the tank foundations and the notable downdrag induced by placing up to 40 feet of new fill in the reservoir bottom.  Our analysis led to recommendation of the drilled shaft option due to the associated high capacity and reliability, flexibility in accommodating highly variable depth to rock, reliable quality control, and reduced time versus pre-loading.

EBA served as the geotechnical engineer-of-record during construction, which began in 2016. Construction phase services included evaluation of a value engineering proposal, soil-cement stabilization of the reservoir bottom, rock core borings to map the depth to bedrock prior to drilled shaft installation, shaft load testing, slope stability analysis, and settlement monitoring. EBA also provided quality assurance monitoring during construction and reviewed submittals for geotechnical items.

EBA’s development of an innovative process flow chart to determine bottom termination depth criteria for drilled shafts enabled field decision making and prevented contractor standby time. After construction completion in 2021, the tanks were buried to enable construction of a landscaped park on the site.