|
Contractor bids were solicited from prospective contractors for the installation, and the project was awarded to Geo Con on January 13, 2003. Site construction began on January 21 with site clearing. Trench installation began on January 30. After excavation of approximately 200 ft of the planned 350-foot trench, a carbonate-cemented sandstone was encountered at the bottom of the trench. In order to maintain the planned trench depth, a larger excavator was moved in and excavation continued. As excavation continued, the sandstone was encountered at progressively shallower depths. Continuous engineering review, supported by revisions to the trench fluid flow model and a series of geotechnical soil borings, resulted in decisions to allow the bottom of the trench to conform to the surface of the sandstone. Excavation was slowed nonetheless and each barrier panel had to be cut individually to conform to the bottom of the trench. Trench excavation was completed on February 20, 2003. Backfilling, recovery well development, spoils disposal, construction fence removal, permanent fence installation, access road construction, and site grading continued through late April 3.
In all, complications from the sandstone caused 11 days delay in the project schedule, required 8 change orders and increased the project cost by approximately $100,000. Total cost for the trench installation is approximately $536,000.The final punch list items for the trench installation were completed on May 28, 2003.
O&M - Oil collection
On February 27, 2003, one week after trench excavation and barrier panel installation was complete, the recovery wells at the east end of the trench had already collected approximately 0.2 ft of crude oil. The first evacuation of the trench on June 12, 2003 resulted in recovery of 150 bbl of oil/water mixture. The collection system will be inspected on a periodic basis and any oil will be retrieved and disposed as necessary.
|