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Chuck Vreeland FDOT Project Manager Project Team
Ardaman and Associates, Inc Jones Wood And Gentry Inc
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SPECIFIC PROJECT OBJECTIVE: CH2M Hill was contracted by FDOT to examine the impacts of replacing the existing S.R. 46 bridge over the St. Johns River in the vicinity of Lake Jesup. The original study, executed in November, 1995, involved the replacement of the existing bridge structure in the location of the existing bridge only. The original study limits began 0.43 miles west of the St. Johns River and ended 0.70 miles east of the St. Johns River. The approximate length of the study was 1.13 miles. The study was later revised to consider replacement of the existing bridge in its existing location, or on a parallel alignment. In March 1996, the FDOT placed the study on hold in an attempt to coordinate the bridge replacement study efforts with a concurrent study of the St. Johns River and Lake Jesup area. A Citizens Advisory Group, the Friends of Lake Jesup, in conjunction with the St. Johns River Water Management District (SJRWMD), was evaluating the impacts of the SR 46 bridge and the SR 46 roadway causeway on the water quality of Lake Jesup. Because that study was going through several iterations, the FDOT put the bridge replacement study on hold pending the outcome of the water quality study. In November, 2000, the FDOT re-initiated the bridge replacement study. The SJRWMD study was nearing completion and some further direction was available. Since that time the study has been completed and a USACOE study was started. The USACOE study is ongoing, but clear direction and a recommendation has been provided to FDOT. The USACOE & SJRWMD studies recommended that in addition to the bridge replacement, evaluation of restoration of existing hydraulic channels should be performed, thereby extending the bridge limits. Further, the studies recommended evaluation of removal of the existing SR 46 causeway fill in order to improve flow into Lake Jesup. These changes lengthened the study area to 1.68 miles. The revised FDOT study included evaluation of the following: accommodation of a future four lane divided rural high speed typical section, bridge length to accommodate any USACOE & SJRWMD study recommendation of restoration of historic channel(s) for hydraulic relief, and allow a bridge replacement that will accommodate removal of the existing SR 46 causeway. Based on these objectives, CH2M HILL evaluated four alternatives that replaced the existing bridge crossing on a parallel alignment. The revised study focused on the limits of bridge replacement; i.e. replace the bridge only over the existing channel, replace the bridge over the existing channel and a historic channel east of the existing channel, or replace the bridge from tree-line to tree-line. Vertical clearance under all the alternatives evaluated ranged from fourteen (14) feet to forty five (45) feet. These alternatives with the various height configurations all allow for implementation of the recommendations of the USACOE & SJRWMD water quality studies.
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