This fact sheet provides information about the Weldon 

Spring Site. Long-term stewardship responsibilities for 

this site are managed by the U.S. Department of Energy 

Office of Legacy Management under the Comprehensive 

Environmental Response, Compensation, and Liability 

Act and the Resource Conservation and Recovery Act.

Site Information and History Info-square Book-open

The Weldon Spring Site is located in St. Charles County, 

about 30 miles west of St. Louis. The site comprises 

two geographically distinct, U.S. Department of Energy 

(DOE)-owned properties: the former Weldon Spring Chemical 

Plant and Raffinate Pit sites (Chemical Plant) and the former 

Weldon Spring Quarry (Quarry). The former Chemical Plant is 

located about 2 miles southwest of the junction of Missouri 

State Route 94 and Interstate 64. The Quarry is about 4 miles 

southwest of the former Chemical Plant. Both sites are 

accessible from Missouri State Route 94.

During the early 1940s, the U.S. government acquired 

17,232 acres of rural land in St. Charles County to establish 

the Weldon Spring Ordnance Works. In the process, 576 

residents of the towns of Hamburg, Howell, and Toonerville 

were displaced. From 1941 to 1945, the U.S. Army 

manufactured trinitrotoluene (TNT) and dinitrotoluene (DNT) 

at the Ordnance Works site. Four TNT production lines were 

situated on what was to be the Chemical Plant. These 

operations resulted in nitroaromatic contamination of soil, 

sediments, groundwater, and some off-site springs.

Following a considerable amount of explosives 

decontamination of the facility by the U.S. Army, 205 acres 

of the former Ordnance Works property were transferred 

to the U.S. Atomic Energy Commission (AEC) in 1956 for 

construction of the Weldon Spring Uranium Feed Materials 

Plant, now referred to as the Weldon Spring Chemical Plant. 

An additional 14.88 acres were transferred to AEC in 1964. 

Weldon Spring Site, Missouri 

A CERCLA site

Fact Sheet

The plant converted processed uranium ore concentrates to 

pure uranium trioxide, intermediate compounds, and uranium 

metal. A small amount of thorium was also processed. The 

uranium refining process generated waste byproduct called 

raffinate. The raffinate was stored in four raffinate pits located 

on the Chemical Plant property. Uranium-processing 

operations resulted in the radiological contamination of 

the similar locations previously contaminated by former 

U.S. Army operations. 

The Quarry was mined for limestone aggregate used in the 

construction of the Ordnance Works. The U.S. Army also used 

the Quarry for burning wastes from explosives manufacturing 

and disposal of TNT-contaminated rubble during Ordnance 

MISSOURI

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St. Peters

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O’Fallon

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Location of the Weldon Spring Site
Works operations. These activities resulted in the 

nitroaromatic contamination of the soil and groundwater at 

the Quarry. In 1960, the U.S. Army transferred the Quarry to 

AEC, which used it from 1963 to 1969 as a disposal area for 

uranium and thorium residues (both drummed and 

uncontained) from the former Chemical Plant. 

Uranium-processing operations ceased in 1966, and on 

December 31, 1967, AEC returned the facility to the U.S. Army 

for use as a defoliant-production plant. In preparation for the 

defoliant-production process, the U.S. Army removed 

equipment and materials from some of the buildings and 

disposed of them, principally in Raffinate Pit 4. The defoliant 

project was canceled before any defoliant was manufactured, 

and the U.S. Army transferred 50.65 acres of land 

encompassing the raffinate pits back to AEC while retaining 

the Chemical Plant. AEC, and subsequently DOE, managed 

the site, including the U.S. Army-owned Chemical Plant, under 

caretaker status from 1968 through 1985. Caretaker activities 

included site security oversight, fence maintenance, grass 

cutting, and other incidental maintenance. In 1984, the 

U.S. Army repaired several of the buildings at the Chemical 

Plant; decontaminated some of the floors, walls, and ceilings; 

and isolated some equipment. In 1985, the U.S. Army 

transferred full custody of the Chemical Plant to DOE.

The U.S. Environmental Protection Agency (EPA) placed 

the Quarry and former Chemical Plant areas on the 

Comprehensive Environmental Response, Compensation, 

and Liability Act (CERCLA) National Priorities List (NPL) in 1987 

and 1989, respectively. Remediation of the Weldon Spring site 

was administratively divided into four operable units (OU): the 

Chemical Plant OU, the Quarry Bulk Waste OU, the Quarry 

Residuals OU, and the Groundwater OU. The Southeast 

Drainage was remediated under a CERCLA removal action 

and documented through an Engineering Evaluation/Cost 

Analysis process. Remedial activities concluded in 2001 with 

completion of the site’s disposal cell — a 41-acre engineered 

structure designed to contain the site’s waste resulting from 

the cleanup.

The Weldon Spring Site is open to the public and is an 

excellent example of beneficial reuse of a former World War II 

explosives manufacturing and Cold War uranium metalsprocessing facility. The site’s Interpretive Center opened in 

2002 and communicates site history, cleanup activities, and 

current conditions. The area is frequented by bird watchers, 

native-plant enthusiasts, hikers, mountain bikers, and others. 

A popular public activity is walking the disposal cell stairway 

and taking in the panoramic view overlooking St. Charles and 

St. Louis Counties. The planted, 150-acre, native prairie is rich 

with flowering forbs, grasses, and wildlife. A former haul road 

has been converted to the Hamburg Trail, connecting the site 

to the neighboring Missouri Department of Conservation 

(MDC) public lands, Great Rivers Greenway trail network, 

and Katy Trail State Park. In 2020, The U.S. EPA awarded 

the site with the National Federal Facility Excellence in 

Site Reuse Award.

Regulatory Setting LEAF

Environmental remediation at the site was conducted under 

CERCLA. The EPA and Missouri Department of Natural 

Resources provided oversight for the remediation and 

were involved in various aspects of the cleanup. 

Current Site Conditions tree

The current, 228.16-acre Weldon Spring site (former 219.5-acre 

Chemical Plant property and 8.66-acre Quarry) is open to the 

public. Cleanup and ecological restoration has made the 

Weldon Spring site home to a thriving community of prairie 

plants and wildlife in the planted, 150-acre Howell Prairie.

Weldon Spring Disposal Cell circa 2002
IN CASE OF AN EMERGENCY AT THE SITE, 

CONTACT 911.

Site-specific documents related to the Weldon Spring 

Site are available on the LM website at 

www.energy.gov/lm/weldon-spring-site-missouri

For more information about LM activities 

at the Weldon Spring Site, contact: 

Weldon Spring Site Interpretive Center

7295 Highway 94 South

St. Charles, MO 63304

Phone:

(636) 300-2601

Email:

WSInterpretiveCenter@lm.doe.gov

public.affairs@lm.doe.gov

DOE Office of Legacy Management

(970) 248-6070 (monitored continuously)

(877) 695-5322 (toll-free)

U.S. Department of Energy 

Office of Legacy Management

2597 Legacy Way

Grand Junction, CO 81503

 www.energy.gov/lm

facebook-square www.facebook.com/OfficeofLegacyManagement

 www.linkedin.com/company/legacy-management

Legacy Management Activities Digging

The DOE Office of Legacy Management (LM) manages 

the Weldon Spring Site. LM ensures the continued 

protectiveness of the site’s environmental remediation, 

operates an ongoing groundwater and surface water 

monitoring network, continues ecological restoration 

efforts, and makes information available to the public in 

the site’s Interpretive Center and website. Periodic Five-Year 

Reviews are conducted at the site under CERCLA to ensure 

that the cleanup remedies remain protective of human health 

and the environment. LM also conducts annual inspections of 

the site to ensure compliance and protectiveness of the site. 

Annual reports are prepared, which include the site 

environmental monitoring data, inspection results, and 

other long-term surveillance and maintenance information. 

The annual reports, along with the Five-Year Review reports, 

are available on the website. The native prairie is monitored 

and managed to reduce invasive species populations with 

prescribed burns occasionally used as a best prairie 

management ecological practice.

07/2020

Visitors to the Weldon Spring Site are welcome 

seven days a week at no cost. Trails, outdoor spaces, 

and the disposal cell are available from dawn to dusk. 

The Weldon Spring Site Interpretive Center is open 

during posted hours, excluding federal holidays. 

Meeting room users may use the site afterhours 

with prior approval. 

The Hamburg Trail, in cooperation with MDC, is 

available from 4:00 a.m. to 10:00 p.m.

A full list of prohibited activities and special use 

permission requirements is available on-line: 

www.lm.doe.gov/Weldon/Interpretive_Center/Visitor_

and_Special_Use_Permission_Information.pdf.

Weldon Spring Site Interpretive Center hours 

of operation: 

Monday through Friday: 9:00 a.m. to 5:00 p.m.

Saturday: 10:00 a.m. to 4:00 p.m. (April-October) and 

10:00 a.m. to 2:00 p.m. (November-March)

Sunday: 12:00 noon to 4:00 p.m.

Closed federal holidays 

Weldon Spring Site Interpretive Center Website:

www.energy.gov/lm/weldon-spring-site-interpretivecenter

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