East Fork Shoal Creek
Hanson performed a water supply study and supplemental water supply alternatives analysis, including lake-level modeling, for a coal-fired power plant in Illinois. Water requirements had increased because of flue gas desulphurization systems (scrubbers) installed to address promulgated air quality rules, and the changes resulted in a water deficit in the plant's 1,100-acre cooling reservoir.
A pump station and gate structure option was selected to offset the anticipated water volume deficit. Hanson’s services included permitting, design and construction-phase tasks for the gate structure in an adjacent creek; a raw water pump station; and a water pipeline from the proposed pump station to the cooling reservoir. Hanson designed a spillway channel modification to reestablish the original channel profile and shoreline stabilization along the banks of the creek. Hanson also provided architectural services, as well as structural, geotechnical, electrical, mechanical and water resources engineering.
Hanson prepared a permit application package for the Illinois Department of Natural Resources, Illinois Environmental Protection Agency and U.S. Army Corps of Engineers that included the results of stream biological and water quality studies completed by Hanson and a preliminary design report for the proposed pump station and gate structure that was used as part of the Clean Water Act Section 404 permit application package. Additionally, the team performed detailed stream flow modeling to design the gate's size and operating plan, as well as to determine the size of the pump station.
The selected gate structure consists of a 25-foot-wide concrete training structure that contains a 15-foot-tall "torque tube"-style hinge crest bascule gate. he gate will typically sit flush with the streambed, but it will rise when stream flow increases due to a rain event or snowmelt. A single hydraulic cylinder and a hydraulic power unit operate the gate structure, running independently from the pump station using a level sensor.
The team chose a 42-inch-diameter ductile iron main for three of the new 250-horsepower pumps; a 24-inch, welded steel pipe previously installed for initial filling of the lake in the early 1960s was used for two of the new pumps to discharge to the lake. The design included a single-CMU pump station building enclosing all five pumps, as well as the associated switchgear and ancillary equipment. The pump station included all-new electrical drives meeting current electrical standards, climate-controlled spaces and a programmable logic controller system linked to the plant's distributed control system. The pump station also includes new galvanized-steel trash racks for intakes to prevent debris from entering the pump chamber.