The World's Largest Wastewater Treatment Facility

The Enhanced Nitrogen Removal Expansion is part of the $3.2 billion ten-year Capital Improvement Program (CIP). This $270+ million and 6-year DC Water facility expansion will reduce the amount of nitrogen in effluent to meet the new U.S. EPA and Chesapeake Bay Program goals of 4.7 million pounds per year or less in 2016.

The project included the construction of slurry walls and tankage; anoxic reactors, including mixers; construction of large channels to convey process water, including a 250-foot-length, 12–foot-diameter tunnel under the existing nitrification equipment gallery; a new 890 mgd lift station; improvements to the existing nitrification/denitrification tanks and aeration system; a new alternative carbon receiving, storage, and feed system; demolition of existing buildings, addition of a protective sea wall and modifications to the existing facilities to enhance performance.

As part of the Construction Management team, The Robert B. Balter Company (Balter) provided full-time Special Inspections (per DCRA and IBC requirements); QA Inspections and Field Testing; and Materials Laboratory Testing. In addition, Geotechnical and Materials Engineering Consulting were provided on an as-needed basis.

The scope of the project has required maintaining a full-time on-site inspection staff up to five inspectors, with intensive supervision by our NICET Level IV QA Manager, as well as regular review and oversight by our Professional Engineers, also acting as the Third-Party Inspector and Special Inspections Engineer of Record, in accordance with DCRA regulations. These services included shallow and deep foundations; steel reinforcement; cast-in-place structural concrete; earthwork with undercutting, stabilization, fill placement and compaction; application of geo-synthetic fabrics and membranes; roof insulation and built-up roofing; pavements; temporary earth-support with soldier piles, lagging and tie-backs; jet grouting and shotcrete with soil-nailing; open-face shield tunneling; review of construction plans and documents; pre-construction and progress meetings; daily review and submittal of technician reports and testing forms; and Special Inspection certifications to DCRA.

In addition to our contracted role of Special Inspections, QA Inspections and Field Testing, and Materials Laboratory Testing, Balter assisted the owner (DC Water) and construction manager with supplemental Geotechnical and Materials Consulting to expedite the resolution of construction quality issues, as they arose. These issues included unsuitable fills and backfills, wet and unstable roadway subgrade, poor footing bearing, defective Partial Displacement Piles, miss-located steel reinforcement, weak or otherwise defective concrete, poor shotcrete conditions, poor soil nail practices, deep shaft dewatering issues, and raveling clays in deep shafts.

The Blue Plains Advanced Wastewater Treatment Plant is the world’s largest facility of its kind processing an average of 370 million gallons of wastewater per day.