City of Lenoir, NC

The Challenge

The City of Lenoir owns and operates a water treatment plant with a permitted capacity of 12 MGD, serving the majority of Caldwell County. The facility was constructed in the 1950s, with many of the original structures and processes still in service. McGill helped the City replace its original high-service pump station in 2009 and then to secure its raw water source with new intake screens / pipes and an off-shore pump station in 2011.

Through the CIP planning process during the next five years, it was apparent that other treatment processes were vulnerable to failure and some insufficient in capacity. The City of Lenoir needed to secure the long-term viability and reliability of its water system and to produce drinking water up to the rated capacity of 12 MGD.

Further, although the City’s raw water is supplied by Lake Rhodhiss, the settling basins were susceptible to major turbidity spikes from wet weather impacts on the upstream stretch of the Catawba River. Hydraulic limitations also impacted settling performance at higher flow rates.

The Solution

Beginning in 2017, our team initiated the critical, multi-phased water treatment upgrades to restore the reliability and capacity of the plant. McGill helped the City obtain a $6 million Drinking Water SRF loan at zero interest to replace failing equipment and to rehabilitate aging processes. Phase 1 focused on the filtration system, chemical tanks and pumps, and high-service pumps in the 1970s-era high-service pump station.

As a result of those updates, the recently rehabilitated filters were in good shape for the next few decades; however, filtration capacity was still limited. Phase 2 focused on ensuring a firm filtration capacity of 12 MGD by adding filters 5 and 6. McGill also designed a dual-train, high-rate settling system ahead of the conventional process to reduce high amounts of raw water turbidity. This system also enables expansion of the raw water supply without the need for expensive and land-intensive off-stream storage.

The Results

The rehabilitated filters and new chemical feed facility have been extremely important to the reliability of the City’s treatment plant. The high-service pump upgrades restored the pumping redundancy and provided standby power backup during power outages. This project, which had an anticipated cost of $6.5 million, ended with a total project cost under $5.5 million.

The 2 filters added in Phase 2 have provided redundancy and filtration capacity to 12 MGD. With the new mechanical pre-treatment system in service, the plant staff is realizing the benefits of improved raw water quality before water enters the settling basins and filters, particularly during the recent wet weather events. This project ended with a total project cost of $10 million, nearly $2 million under budget.