Artesian Llangollen Clearwell Repairs

Key Accomplishments

• Rehabilitated the clearwell access systems by removing deteriorated ladders and installing two new approximately 10-foot aluminum ladders at the aerator access hatches. The existing replacement ladder at the interior access hatch was also cleaned of spot laminar corrosion and protected with an approved epoxy coating.
• Restored and recoated major internal steel and cast-iron piping components, including approximately 200 square feet of the 14-inch aerator pipe manifold and approximately 150 square feet of 10-inch pump-intake piping. Rust and laminar corrosion were removed before application of the specified protective epoxy coating system.
• Removed abandoned internal piping and repaired obsolete penetrations through the clearwell structure. The work included removal of two unused 6-inch pipes and sealing unused ceiling-slab and wall openings with reinforcing steel and epoxy concrete to restore the integrity of the reinforced-concrete enclosure.
• Repaired cracking and deterioration around the aerator access-hatch curbing using an injected epoxy-resin sealing system, addressing defects associated with water infiltration, freeze-thaw exposure and deterioration around the hatch perimeter.
• Prepared and coated the clearwell’s reinforced-concrete interior surfaces, including approximately 3,800 square feet of walls and baffle walls, 1,650 square feet of floor and 1,700 square feet of ceiling and beam surfaces—approximately 7,150 square feet total.
• Applied a potable-water-compatible coating system in accordance with specified SSPC and ICRI surface-preparation requirements. Interior concrete received an NSF-approved low-VOC system incorporating Sherwin-Williams Dura-Plate UHS Primer and Dura-Plate UHS finish coating at the specified dry-film thicknesses.
• Performed the work within an enclosed clearwell environment requiring controlled confined-space access and safety procedures. The existing inspection documentation identifies the clearwell as a permit-required confined space and records the use of air monitoring, lockout/tagout and confined-space equipment during entry.
• Completed final cleaning, disinfection, VOC testing and bacteriological testing of the rehabilitated clearwell before returning the facility to service, providing verification that the repaired and coated structure met Artesian’s requirements for potable-water use.
• Johnston Construction Company served as the Prime Contractor for the Llangollen Clearwell Repairs project at Artesian Water Company’s Llangollen Water Treatment Plant in New Castle, Delaware. The clearwell is a reinforced-concrete structure consisting of a floor slab, foundation walls, internal baffle walls, ceiling slab and supporting beams and is used as a water-containment facility within the treatment system.
• Prior to construction, Johnson, Mirmiran & Thompson, Inc. performed a detailed structural inspection of the clearwell for Artesian. The inspection documented the condition of the reinforced-concrete structure, interior piping, coatings, access ladders and associated components and developed recommendations for the repair program subsequently incorporated into the project.
• The inspection found the primary reinforced-concrete structure to be generally in good condition but identified deterioration requiring corrective work. Conditions included accumulated debris over much of the floor, deteriorated pipe coatings, corrosion of steel and cast-iron piping, deteriorated aluminum ladder components, cracks at an aerator hatch curb and numerous abandoned penetrations through the walls and ceiling.
• JCC began the rehabilitation by removing approximately 10 cubic yards of lime, silt and organic material from the clearwell floor and cleaning organic buildup from the pump impeller housings and strainers. The work exposed the underlying reinforced-concrete surfaces and provided the clean working environment necessary for subsequent repairs and coating operations.