JLW Associates Inc.
Walker Diving completed modifications to the intakes of the Perryville, MD Water Treatment Plant. The intakes are located approximately five hundred feet from the shore in the Susquehanna River. The water intakes had to remain in operation through the project. To perform the work Walker used three barges - one crane barge with a 70 ton P+H crane and two deck barges. First a sheet pile cofferdam was constructed downstream of the existing intakes. The cofferdam was de-watered, then excavated to sub-grade. The bottom was covered with bedding stone. The pre-cast concrete vaults were loaded on a barge and transported to the site. After assembling both vaults the internal screens, valves and piping were installed. To prevent flotation, a sixty cubic yard concrete collar was poured around the vaults to provide ballast. After backfilling, the sheet pile cofferdam was removed. To provide the plant with an uninterrupted supply of water a back-up pump system was assembled. The back-up system utilized two six inch diesel pump sets. The most challenging part of the job came next. The new vaults had to be connected to the existing intakes underwater. Divers removed one existing intake screen and installed the new piping while the second intake remained in operation. After the new intake vault was placed in operation the remaining intake line was connected to the second vault. The entire area was then covered in rip-rap and wood piles were driven to protect the intake structure. (2007)