Significant Project Features:
- Geo-Trencher
- High concentration of boulders in alignment
Background:
The J&L Steel Site is a former iron ore processing plant located in Star Lake, New York. The property was purchased in 1946 and operated until 1976, during which a substantial amount of fuel oil had leaked into the ground and adjacent Little River. The site has had previous mitigation efforts installed which had previously collected an estimated 300,000 gallons of fuel oil.
Project Objectives:
Geo-Solutions was contracted to install an interceptor trench that would collect the fuel oil contaminated groundwater prior to reaching the Little River. Geo-Solutions also installed 25 wells in the trench for use by the EPA to install vents to volatilize collected fuel oil.
Description of Work:
Due to the nature of the soils, the trench alignment had been pre-trenched and the soils screened prior to Geo-Solutions’ mobilization. Geo-Solutions used our Geo-Trencher to complete the installation which excavates the soil and backfills the trench in one pass. The Geo-Trencher excavated soils to a calculated design depth, and with the use of the backfill hopper and boot, filled the void created with NYSDOT #1 Stone. 25 vertical wells were then installed by Geo-Solutions’ subcontractor using hollow stem augers, along the complete length of the trench at 50 foot increments. A woven geo-textile fabric was placed across the entire foot print of the trench and capped with 3 feet of clean soil from the trenching process. Each well received a protective steel cover and a concrete pad.
Project Challenges
- Inadequate pre-trenching by others resulted in numerous issues which resulted in additional costs, delays, and damages:
- Design depth was not cleared to, as a result trench depth had to be decreased.
- Backfill soils were not screened properly and countless boulders were still in the alignment. This resulted in over one hundred broken cutting teeth and link pins.
- Geo-Solutions was asked to perform our own pre-trenching effort at an OP Rate. Geo-Solutions cleared dozens of boulders and obstructions from the alignment. The boulders reached as large as 6 feet in diameter, and obstruction included steel ingots and old railroad rail.
- The alignment was also surveyed incorrectly by the owner. The exact location of the pre-trench centerline was not properly marked. As a result the Geo-Trencher was excavating native soils in certain locations. Geo-Solutions used our support excavator to expose the pre-trench centerline, and adjusted the alignment as needed.
- Coarse soils coupled with high groundwater and saturated soils led to increased caving of the sidewalls. Geo-Solutions consumed a higher amount of stone backfill as a result.
Location
Star Lake, NY
