It’s been a century since the Bolsa Chica Wetlands were truly a “wetlands”, with an abundance of wildlife and a natural environment. Finally, through the efforts of several environmental groups, the Ports of Los Angeles and Long Beach, Moffatt and Nichol Engineers, Kiewit Pacific Company and Innovative Painting & Waterproofing a 200 acre muted tidal basin is being phased back into life.
Connected to the Pacific Ocean via seven concrete box culvert and weir units that control tidal flow from a renewed 397-acre full tidal basin, the muted basin is the nesting place of several threatened species of wildlife - among them the Western Snowy Plover and California Least Tern. For 100 years the basin has been a relatively dry, below sea level oilfield. When the last real estate development plan was rejected in favor of returning the area to a nature preserve, a huge engineering project developed to smoothly control the tidal flow. Completely phasing out oil pumping will still take years to complete.
One key element of the flow control is the box culvert and weir connectors between the fully-flooded basin and the muted basin, with its nesting islands. Large gates at each end of the 150’-plus long culverts control the flow and containment of water; it is critical that ocean water not flow into the adjoining ground, nor oil-contaminated ground water flow in reverse. When originally constructed, the culverts and weirs used soil-tight design joints that did not maintain control over leakage. The engineering team determined that a combination of concrete repair, grout injection and a critical geotextile-reinforced polyurea membrane was the solution.
Kiewit Pacific Company retained Innovative Painting and Waterproofing Inc. to perform the repair, grout and polyurea installation. Deteriorated sealants, grouts, patching materials and backer rods were removed. The joints and surrounding areas were cleaned and ground to ensure adhesion and integrity of the polyurea repair system. Keyways were cut on each side of each joint for membrane termination. An extensive high-pressure injection of Polycoat’s PCGrout II Polyurethane Foam was performed to fill voids behind the concrete.
After priming, backer installation and sealing of the joints, Polycoat’s Series 21 Epoxy Primer was applied to the specified areas surrounding the joints. With 8 oz. Geotextile fabric cut to specific widths, 150 mils of Polycoat’s Series 5502 Aromatic Polyurea was installed as the final membrane and terminated at the keyways. The culverts are a confined space that required constant air monitoring and specific safety controls. The tight quarters meant unique working conditions, and even with gates in operation tides dictated the working hours, with a short project completion window as well. Innovative deployed two complete Graco EXP-2 Reactor trailer-mounted workshops and two full polyurea crews, plus repair and injection staff, to meet the critical deadlines.
Periodic 24-hour operations were required to perform parts of the operation and to monitor pumps controlling water flow during high tides. Gates were finally opened, tides flowed, and the choice of polyurea as the membrane system proved to be successful. As the oilfields are phased out a natural habitat will be returned to resemble conditions of the early 1900’s. In the case of the Bolsa Chica Wetlands, “this place is for the birds”…in a good way.
