San Miguel Electric Cooperative, Inc. and the North American Coal Company met to discuss the mine plan for the Christine, TX, lignite mining operation. The decision was made to develop an area north of the current mine area, enabling extraction of additional lignite reserves. San Miguel Electric Cooperative then contacted Marston Environmental about putting together plans for expanding the mine.
The project was a major expansion to the existing mine and it was imperative that the construction of this new phase did not hinder the existing mining operation. The scope of the project was to include the moving of over 1.8 million cubic yards of fill, the construction of nearly 3 miles of haul roads – in conjunction with several drainage crossings along the new route – and the construction of three separate pond structures.
One particular drainage crossing was analyzed as a major bridge crossing, so Marston Environmental contacted Contech to discuss the available options. After considering a BEBO® Concrete Arch structure, it was decided that a 5-Barrel MULTI-PLATE pipe-arch structure was needed in order to pass the required flows for the specific location.
Due to the permitting and approval process required by the Texas Railroad Commission, the overall project had a very short deadline. The project was bid in late April 2008; awarded the first week of May; construction began the second week of May and the entire project had to be completed by August 1st, 2008. Failure to do so would subject the contractor to liquidated damages of $10,000 per day.
As a result, the San Miguel Electric Cooperative decided to expedite part of the process by ordering the galvanized and asphalt-coated MULTI-PLATE pipe-arch structure direct. Contech provided the design engineer shop drawings, fabricated the material, coated the plates with an additional asphalt coating due to the existing corrosive soil conditions, delivered the material and provided two separate assembly crews to work around the clock in order to meet the required production schedule.
The assembly of all 5 barrels was completed in 23 days which allowed the contractor to backfill the structures, construct the haul road using Tensar BX1200 geogrid and open the first segment of the project by July 1st, 2008 – a month ahead of the deadline.