Weldon Spring Plant

Site Description

The Missouri Department of Conservation (MDC) approved a plan on June 9, 1995, allowing the U.S. Department of Energy (DOE) at the Weldon Spring Site Remedial Action Project (WSSRAP) to excavate nearly 2 million cubic yards of clay material from land in the Weldon Spring Conservation Area. Clay soil from a borrow area was used to construct the permanent disposal facility at the Weldon Spring site. Clay soil was chosen to construct the disposal facility because it has low permeability when compacted. Extensive tests showed that the proper quality and quantity of material was located in the Conservation Area within 2 miles of the disposal facility and approximately 0.25 mile east of Francis Howell High School across Highway 94. The excavated clay soil was used for foundation backfill, clay liners, clean-fill perimeter dikes, and the radon barrier in the disposal cell.

A cultural resource survey was conducted at the Borrow Area easement to determine that soil removal would not disturb any archeological or historical sites. The land also was assessed from an ecological standpoint to check for threatened or endangered species and wetland areas. DOE signed a separate agreement with MDC to mitigate any loss of wetland area. The agree- ment authorized the creation of a wetlands area in the August A. Busch Conservation Area. This wetlands area provided an aquatic habitat to replace areas that were disturbed during work at the Chemical Plant site.

More than 213 acres, including 150 acres for borrow development and operations, constitute the Borrow Area and dedicated haul road that leads from the borrow source to an entrance at the north side of the Chemical Plant site. The haul road was dedicated to borrow operations to separate project vehicles and equipment from public roadway users. DOE reached an agreement with the Missouri Highway and Transportation Department, Francis Howell School District, and MDC that permitted a portion of Highway 94 to be realigned to allow for a grade separation crossing. The separation routed borrow traffic through an underpass at Highway 94. Construction of the grade separation in 1996 included reduction of two dangerous curves in Highway 94 that had been the scene of numerous accidents.

The hauling operation took place during the construction season from spring to fall each year. Scrapers hauled material from the Borrow Area 10 hours each day during the business week. Nearly 100,000 round trips were made.

Borrow Area operations for the 2001 construction season included the modification of an existing sedimentation basin and the excavation of approximately 100,351 cubic yards of soil to complete the disposal cell. By the time the cell was completed in October 2001, approximately 1.4 million cubic yards of soil from the Borrow Area had been used in cell construction.

In 2002, the continuation of the Hamburg Trail, an extension of the Katy Trail State Park, was constructed. The Hamburg Trail extends the Katy Trail along the Quarry haul road to the Weldon Spring site and then proceeds to the Borrow Area, eventually crossing Highway 94 at Highway D. From there, the trail proceeds along a route parallel to Highway D to the headquarters building of the Missouri Department of Conservation’s August A. Busch Memorial Conservation Area.

When Borrow Area operations were completed, the area was graded to drain in accordance with a final restoration/reclamation plan approved by MDC and the Soil Conservation Service. Phase I Borrow Area restoration was completed in September 2001, and the Borrow Area was turned over to MDC in March 2002. Phase II seeding was completed and turned back to MDC in May 2002. The 6,000-square-foot maintenance building was turned over to MDC in October 2002.