Bolsa Chica Lowlands Restoration Project

Project Description

The Bolsa Chica Lowlands Restoration Project is located in Orange County, California adjacent to the City of Huntington Beach. The purpose of the project is to restore portions of the wetland ecosystem of the Bolsa Chica lowlands. The project area covers about 1,247 acres and will restore tidal influence from the Pacific Ocean to about half of this area to reinvigorate the wetland ecosystem. To achieve the biological benefits of tidal restoration, a direct connection to the Pacific Ocean must be reestablished through the creation of a new tidal inlet that will cut through Bolsa Chica State Beach and cross the Pacific Coast Highway near the Huntington Mesa. Construction is anticipated to start in October, 2004 and span 2.5 to 3 years, in order to avoid or minimize impacts to fish and wildlife resources, coastal traffic, and beach recreation. The Pacific Coast Highway and adjacent Oil field facilities will remain in operation during the entire construction period.

Project Features

Full Tidal Basin:

A 366 acre tidal basin will be constructed that will receive full tidal action from the new ocean inlet. Approximately 2,700,000 cy of material will be removed from 175 acres within the basin to support depths varying between 6.0-6.8 feet below mean sea level (MSL). Excavated material will be dredged and dry excavated for project construction features. Material will be used to pre-fill an ebb bar (1,300,000 cy of > 80% sand), build levees for the full tidal basin (456,000 cy), three nesting areas (366,000 cy), beach nourishment fills (190,000 cy), an inter-tidal shelf for cordgrass (98,300 cy) and as much as 253,000 cy of material may be hauled off site.

Muted Tidal Basin:

A 200 acre muted tidal basin will be created through three box culvert and weir connections between the full tidal basin and the proposed muted tidal basin. The boxed culverts will include water control structures to regulate the tidal influence. Additional site modifications include site improvements for tidal channels and overflow structures.

Pocket Muted Tidal Basin:

The pocket muted tidal basin is an isolated pocket of land on the north side of the East Garden Grove Wintersburg Flood Control Channel that forms the northern boundary of the project. In order to gain access to a suitable tidal water source, hydraulic connections must be made to the Outer Bolsa Bay adjacent to the tide gates of the adjacent flood control channel.

Nesting Habitat Islands:

Three nesting areas will be created on twenty acres within the site for federally-listed endangered species. Nesting areas will be constructed using 366,000 cy of material excavated from the full tidal basin at elevations from existing ground to 4-10 feet.

Ocean Inlet:

An ocean inlet will be constructed to the full tidal basin that will be 360 feet in width between the levy crests and encompass an area of approximately 3.7 acres when completed. As the inlet is excavated, approximately 190,000 cy of sand will be placed for on the adjacent state beach for beach nourishment purposes.

Entrance Jetty:

To stabilize the inlet, two jetties will be constructed to prevent the entrance channel from closing. Each jetty will be approximately 450 feet in length from Pacific Coast Highway to the jetty tips. Each jetty will be about 100 feet at their base. The area of beach that will be excavated to construct the jetties and the inlet totals is about five acres. The amount of rock in the inlet jetty and under the bridge is about 72,000 tons.

Shoreline and Bridge Revetments:

Approximately 750 feet of shoreline revetment will be constructed on each side of the jetties on the west side of the PCH bridge. Following construction, they will be buried under beach sand. The total amount of rock in these is 31,000 tons. In addition, a revetment would be placed east of the bridge for erosion protection in the flood shoal management area of the full tidal basin. The total amount of rock in these is about 138,000 tons.

Ebb Shoal:

To stabilize the down-coast region near Huntington Cliffs from the loss of the existing beach, assure sand movement along the beach and maintain beach stability, an ebb shoal will be constructed just outside the inlet mouth. The equilibrium volume of the ebb shoal will be approximately 620,000 cy of sandy material. To provide additional safety, it is proposed to place as much as 1,300,000 cy of sandy material (> 80% sand) in the proposed ebb shoal location over approximately 45 acres of soft bottom substrate.

Pacific Coast Highway Bridge and Retaining Walls:

A bridge will be placed along the existing alignment with Bosla Chica State Beach immediately to the west of the road right-of-way and Bolsa Chica Wetlands immediately to the east. The bridge will accommodate four traffic lanes and a separate safety vehicle/bike path for the local beach traffic along Bolsa Chica State Beach. Roadway drainage improvements will be constructed in the inlet/PCH bridge vicinity. Retaining walls are utilized to minimize land requirements along the west side of the bridge. The recommended bridge structure is a ten span cast-in-place deck slab structure 420 feet long supported on driven pre-stressed concrete piles, about 18-24 inch in diameter, with a desired capacity of 70 tons each. PCH bridge construction will include maintaining four lanes of traffic during construction via a detour along the inland edge of the existing right-of-way.

Oil Service Bridge:

In order to maintain existing oil field operations on a parcel isolated by the new ocean inlet, a two lane oil service bridge will be constructed parallel to the PCH bridge. The bridge structure will include a ten span cast in place deck slab structure 420 feet long supported on driven concrete piles with the same standards as the PCH bridge. The two lane structure will also include a three meter wide utility platform that will accommodate production lines for oil field operations including oil, gas and water lines in casings.

Groundwater Barrier

Approximately 10,000 feet of groundwater barrier will be constructed to prevent groundwater and salinity intrusion under the adjacent neighborhoods. The salinity intrusion barrier will be up to 30 feet deep. A French Drain to control shallow groundwater levels will be up to 10 feet deep and will include several pump stations that will discharge into the muted tidal basin.