WorldWide Drilling Resource

25 WorldWide Drilling Resource ® MARCH 2014 Environmental Monitoring by Thomas Kwader, Ph.D., P.G. Exercise Caution Before Drilling Near Abandoned Wells About 20 years ago, a small town on the coast of the panhandle of Florida needed a new supply well. A contract to drill a small-diameter test well was issued to confirm the water quality and quantity would be sufficient to provide the town with at least 1000 gallons per minute. The test well was drilled and the water exceeded all expectations for both quality and quantity. A second bid was let; however, a different drilling contractor was awarded the bid to drill the large supply well on the small fenced area below the town’s water tower. Drilling proceeded smoothly for the 700-foot open-hole-completion, limestone well according to data col- lected from the test hole. When it became time to test the new well, it failed and produced only a frac- tion of the anticipated volume of water. It appears the second crew had drilled right over top of the test hole into the cement-grouted portion of the open hole. The first drilling contractor properly aban- doned the test hole, but no one told and/or the second contractor did not ask exactly where the test hole was drilled. During the grouting of the test hole the grout traveled along all of the cracks and crevices of the limestone, plugging the pore spaces. Approximately three months of time and $250,000 were lost due to lack of knowledge and failure to communicate about where the test well was located. Although in the example above, the test hole was properly abandoned, there are other potential problems when drilling too close to abandoned wells. If an aban- doned well is not properly sealed along the casing, water from above or from different zones could travel to the pro- ducing zone of the new well, potentially impacting the water quality. All abandoned wells should be prop- erly marked at or above land surface to prevent mishaps related to drilling future wells too close to potential problems associated with abandoned wells. Tom Tom Kwader may be contacted via e-mail at admin@ worldwidedrillingresource.com Micropiles Installed in New Jersey Wetland Adapted from Information by CRUX Subsurface, Inc. CRUX recently provided micropile foundation engineering, procurement, and construction services within a Priority Wetland for Public Service Electric and Gas Company’s Susquehanna-Roseland Electric Reliability Project. Due to chal- lenging subsurface conditions and access constraints associated with the protected area, the specialty deep foun- dation was chosen. The power line project includes a line stretching from Berwick, Pennsylvania, to Roseland, New Jersey, with a 1.5-mile segment crossing the Troy Meadows area in Morris County, New Jersey. The new line is required to ensure reliable electric service to the area. Due to standing water and other permit access restrictions, micropile foundations were selected for the seven steel pole structures necessary within the wetland. Prime contractor KH&M (a joint venture between Kiewit and Henkles & McCoy) was permitted to mat a road- way to one structure while the remain- ing six required helicopter support for materials and equipment. To minimize impacts on the wetland without delaying the progress of con- struction, a unique closed-cell coffer- dam was employed at each structure site. The setup provided a stable plat- form for equipment in soft soils and groundwater; contained drill spoils from entering the wetland; and acted as a form for concrete placement. A rotating drill carriage and micropile drill were set on top of the cofferdam to install micropiles which proved to be an efficient choice to dri l l through ex- tremely soft soils and reach underlying bedrock at varying depths between 60- 115 feet below ground level. Two rounds of value engineering were completed prior to foundation con- struction, resulting in fewer micropiles and a smaller area of total impact by the concrete caps. Reducing the amount of concrete poured and piles installed was a significant benefit to a tight proj- ect schedule.