Thomas & Hutton provided high service pump station design, water treatment facility design, permitting, and bidding for the 1.5 mgd Bogue Banks Reverse Osmosis Water Treatment Plant, including pre-treatment, post-treatment, and a cleaning system. The project included a new high service pump station with three 550 gpm VFD high service pumps, a degasifier to remove hydrogen sulfide in the raw well water, transfer pumps, and modification of the existing ground storage tank.
The Reverse Osmosis Skids were designed to fit within an existing building that formerly housed an EDR treatment process. The EDR system was abandoned because it could not treat increasing chloride from the local aquifer. The water treatment plant includes an anti-scalant pre-treatment system and a calcium chloride post-treatment system; a calcium chloride bulk storage tank; instrumentation and controls with fully integrated programmable logic controller; an auxiliary generator; a HSP station; three raw water supply wells; and concentrate disposal to Bogue Sound. Harn Reverse Osmosis Systems provided the reverse osmosis equipment subsequent to proving lower life cycle costs than competitors.
The water supply for Emerald Isle comes from the Castle Hayne Aquifer that underlies the western end of the island. This is within the Paleo River channel and contains high salt concentration that declines as it moves east. The goal of the project was to protect the eastern wells from salt migration by pumping the western wells more to affect a western flow of fresh groundwater. This “sink” created by the reverse osmosis raw water supply wells mitigates lateral movement of salt toward the east and protects the overall salinity of the entire island’s well field.
GMA and Dr. Richard Sprull provided the design of three new raw water supply wells, which also are to create the sink to mitigate the salt water movement. Thomas & Hutton worked with Harn Reverse Osmosis Systems on the design and construction of two 0.75 mgd trains, which have provisions to meet future projected increases in chloride concentrations.
Thomas & Hutton worked with suppliers and Bogue Banks to pre-purchase select equipment, thereby allowing the project to be constructed in less than 11 months. Equipment pre-purchased also saved Bogue Banks more than $350,000 or 8.25-percent of the construction cost. Thomas & Hutton had to competitively bid the select equipment and finalize the design using the products Bogue Banks selected while permitting was underway.