McGrath & Associates has completed Phase 1 site work on Ameren Missouri’s $8.5 million MLK Switching Station in St. Louis. Phase 2 construction began in April.
The 13.8kV switching station is located at 1901 Martin Luther King Drive in St. Louis. The entire MLK switching project cost is estimated at $42.5 million. The station is part of a larger Ameren Missouri investment to upgrade the electric service in Downtown St. Louis in the coming decades.
The 10-week Phase 1 work, performed during one of the coldest and snowiest winters on record, included mass excavation, soil reclamation and soil remediation. Phase 2 construction includes a perimeter fence, new city sidewalk, and 70 structural piers with eleven concrete pad foundations. The combined estimated cost for site work performed by McGrath in Phases 1 and 2 is $1.4 million.
During the site work phase, McGrath recycled as much existing material as possible rather than haul debris to a landfill and import new rock fill. A Grizzly rock separator was used to remove large chunks of unusable concrete, limestone and debris from the soil. Suitable fill materials were returned to the site, placed and compacted under the direction of a soils engineer to create a stable base for the station structures.
McGrath removed abandoned sewer pipes and three cisterns that were introducing water onto the site, excavating to an average 9′ deep overall and 18′ to 20′ deep around the cisterns. Safety on the relatively small site was a challenge, requiring all workers and heavy equipment operators to be especially aware of their surroundings.
This past winter’s extreme weather conditions created special budget and schedule challenges related to soil remediation. Fill soil was difficult to acquire and high in moisture, requiring a chemical drying process.