PROJECT

Horizontal Collector Well Addition

Our team provided design and construction services for a new horizontal collector well (HCW) for the Jefferson County Water Authority (JCWA). Delivered via a progressive design-build approach, the new well is now the primary water source, with a production rate of 3.5 million gallons per day (MGD) even during low river flow periods.

JCWA is the water provider for two communities in the southern St. Louis metropolitan area, Festus and Herculaneum. The well serves the Cathy Jokerst Water Treatment Plant, drawing its raw water supply from the Mississippi River. The region’s economy is growing, with a siding manufacturing facility opening in 2025.

JCWA’s existing collector well, completed in 2003, never achieved the desired yield of 4 MGD because of fluctuating river levels. The additional well was further necessitated by the need for redundancy and increased capacity related to regional economic growth. The original HCW now serves as redundant backup supply.

The use of a progressive design-build approach allowed the team to develop project costs quickly and created more cost certainty. The new well is connected to a 250-kW backup generator that will operate either collector well in the event of a power failure.

The project was delivered on time, within budget and with zero safety incidents.

Client

Jefferson County Water Authority

Location

Crystal City, Missouri

Region

Midwest

Services

Municipal Water & Wastewater

Construction

Design-Build for Water & Wastewater Infrastructure

Water Supply & Distribution

Source Development & Groundwater Supply

Industry

Water

Case Study

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Collector Well Construction

The collector well consists of a 13-foot inner diameter caisson to bedrock approximately 70 feet below grade, with a pump house approximately 20 feet above grade for flood protection. The well has five 200-foot-long laterals projected in a fan orientation along the Mississippi riverbed.

Construction adjacent to the river requires consideration of excavation, hydraulic uplift and potential flooding during critical sequences. Our team successfully sank over 70 feet of caisson collector well and built the pump house without encountering unanticipated conditions, mitigating risks with best practices for subsurface investigation, monitoring hydrological conditions and optimizing the design.

Our team worked with a specialty contractor, Ranney Collector Wells, to facilitate the protocols and methods necessary for pouring and sinking sections of the caissons. Sump pumps pulled water from the bottom of the wet well as the new well was built.

Source Water Development

Water is extracted from beneath the Mississippi by laterals that protrude horizontally from the bottom of the caisson to fresh water. The water is clean due to river bed filtration, and the supply is resilient to drought because it is extracted from beneath the river instead of through a surface intake. The laterals do not interfere with fish or wildlife along the river.