As part of a Florida Department of Transportation (FDOT) Interstate I-75 Improvement project, an existing bridge on Fowler Av. over the Hillsborough River was to be replaced. The Hillsborough River is an Outstanding Florida Waterway and a very sensitive environmental area. The City of Temple Terrace had an existing 12 inch force main (FM) attached to the bridge that required replacement. Cardno TBE was retained to provide design, permitting and construction administration services for the City to relocate their utilities for the project. The utility relocation design included a subaqueous relocation of 1,000 feet of 12-inch sanitary sewer FM beneath the Hillsborough River by horizontal directional drilling (HDD). The geotechnical investigation revealed that the soils encountered were sandy soils underlain by weathered limestone/calcareous clay and chert. The chert material had a relative Moh's hardness of 7. The boring logs also noted a loss of circulation. The HDD operations presented its own unique challenges due to the chert and maintaining circulation. However, after the FM was constructed and in order to construct the new bridge over the Hillsborough River, FDOT allowed the contractor to construct temporary piles to enhance crane activities, adjacent to the FM. Due to the subsurface conditions and the close proximity to the FM special requirements were initiated to maintain the integrity of the FM.
展开▼
