Georgetown, DL: Site Remediation, MGP Site
Geo-Con completed a site remediation project at a former MGP site in Georgetown, Delaware. The site was small and located within the city limits of Georgetown. Special concern of the client was the close proximity (8 feet) of the proposed excavation area from a cold storage food warehouse where differential settlement could adversely impact the operations. Additionally, a completion date of April 30, 2001 was mandatory as warehouse operations commenced on May 1, 2001. Geo-Con was chosen for its retention wall approach of using a concrete diaphragm wall system which would minimize horizontal deflections and eliminate vibration concerns.
Initial work consisted of several buildings and former gas holder foundation removal, which involved approximately 150 tons of materials. A 2 ft wide, 10 ft deep diaphragm wall was installed which allowed for the successful removal of contaminated subsurface soils. A small offset excavator was used to excavate the trench, while bentonite slurry was simultaneously pumped and maintained in the trench during excavation. A truck-mounted drill rig preceded the excavator and augered 18-inch diameter holes through 22 feet of soil. The 23 holes were used to set the support columns and anchor them into 10 feet of virgin soil. Thereafter, 14 x 73 "H" beams spaced 10-15 ft from centers were placed into the holes. Upon trench completion, 3,000 psi concrete was pumped into the trench, displacing the slurry and creating the retention wall. The subsurface contaminated soils were excavated and directly loaded into trucks for disposal. Upon completion of back filling activities, final restoration was completed.
The project was completed on time with no movement of the cold storage warehouse foundations. Geo-Con managed a confined work area and community concerns successfully in order to execute this project with zero incidents.