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PROJECTS:  INFRASTRUCTURE TECHNOLOGIES

Dam & Levee Rehabilitation

Forgen is highly experienced with dam and levee rehabilitation projects. These projects typically involve repair of damaged or eroded levee embankments, slope drainage modifications, and shoreline restoration. Construction methods include excavation of slump areas or unsuitable embankment materials, installation of stabilization or drainage fabrics, and placement of rock slope protection material, such as riprap. Forgen’s experience in this area includes projects for public sector agencies such as the USACE, Bureau of Reclamation, and local flood control agencies.

FEATHER RIVER WEST LEVEE PROJECT
AREAS A-D
Sutter County, California

  • Completion of 4.6M+ sf of soil-bentonite open trench cutoff wall
  • Construction of 500,000 sf soil-bentonite cutoff wall to depths of approximately 100 ft using Deep Soil Mixing (DSM)
  • Construction of 450,000 sf soil-cement-bentonite cutoff wall to depths of ≈ 120 ft using DSM
  • Partial levee deconstruction, reconstruction, and restoration
  • 2.3M cy of earthwork
  • Coordination of 90 utility crossings (sewer force mains, overhead power lines, and pressurized irrigation pipes)
  • Seepage berm construction
  • Relief well installation

Forgen and joint venture partners constructed a soil-bentonite cutoff wall for Area A along 7,500 lf of the Feather River Levee in Yuba City, California. The cutoff wall consisted of 500,000 sf using single pass Deep Soil Mixing (DSM) technology and 150,000 sf of conventional open trench. Preparatory work included demolition; clearing and grubbing; top soil stripping; utility removal/relocation; and levee degrade to facilitate cutoff wall construction. Once the wall was installed, the levee embankment was rebuilt from suitable levee fill. Additional work included a cement-bentonite slurry wall constructed to close a gap around a PG&E utility.

Scope of work for Area B and Area D included the construction of a soil-bentonite cutoff wall along 16.5 miles of the Feather River Levee in Sutter and Butte County, California. The cutoff wall consisted of 4.5M sf using conventional open trench method and 450,000 sf using single pass DSM. Preparatory work included demolition; clearing and grubbing; topsoil stripping; utility removal/relocation; and levee degrade to facilitate cutoff wall construction. Once the wall was installed, the levee embankment was rebuilt from suitable levee fill.

PRADO DAM DIKE PROJECT
CALIFORNIA INSTITUTION for WOMEN
PHASE 2
Corona, California

  • 250,000 CY of subgrade and ponding area excavation
  • 500,000 CY of embankment fill
  • 25,000 TN of riprap slope protection and spillway
  • Two concrete box culverts and concrete V-ditch
  • Hydroseeding and 1 year maintenance of 80 acres

The Phase 2, Prado Dam California Institution for Women (CIW) Dike project is a portion of a larger Prado Dam Project in the City of Chino, San Bernardino County, California, approximately 45 miles southeast of downtown Los Angeles. The dike is located within and along the northern boundary of the Prado Dam Reservoir Basin, approximately 4 miles north of Prado Dam. The planned raising of the Prado Dam Spillway will increase the inundation elevation of Prado Basin to 566 feet and result in an expanded inundation area. Note that while the CIW facility is not within the inundation boundary under existing conditions, it will be within the inundation boundary after the planned spillway raising is constructed. The purpose of the CIW Dike project was to provide the California Institute for Women with flood protection from the Prado Dam Reservoir up to elevation 566 feet.

The plan for the CIW Dike project was to construct a compacted earth fill embankment along the southern and western borders of the CIW property. The dike is divided into two segments by a knoll located just southwest of the CIW property. Each dike segment had unique foundation conditions and design approaches. Accordingly, for purposes of analysis, design, and construction, the CIW Dikes were segmented into CIW North Dike and CIW South Dike.

The CIW South Dike was constructed on top of an old dairy farm property. The foundation of the CIW South Dike was excavated in order to remove all unsatisfactory materials. The start of the earthen fill was constructed on satisfactory native ground. The earthen fill consisted of a native decomposed granite material, mined from a borrow pit, located approximately 1 mile south of the CIW South Dike. The outer shell of the CIW South Dike was comprised of a 15 foot wide sandy material and a 3.87 foot wide 15” minus riprap material, both of which were imported from a local rock quarry. The top crest of the South Dike was constructed to an elevation of 571 feet, and tied into an existing knoll located at the west end of the CIW South Dike. The last 400 feet of the east end of the CIW South Dike transitioned to an elevation of 566 feet and tied into the existing ground. The 2,700 foot CIW South Dike was constructed using approximately 70,000 cy of earthen materials. Located through the center of the CIW South Dike, 650 feet from the west end, is a double 4 foot wide by 6 foot tall concrete box culvert, with double 4’x6’ steel flap gates. The box culvert was designed to allow the flow of storm water from the landside to the reservoir side of the dike.

The CIW North Dike was constructed adjacent to an existing storm water channel. The foundation of the North Dike was highly saturated and was comprised of highly organic native material. Two 70 foot deep dewatering wells were constructed in order to lower the ground water table prior to construction activities. The CIW North Dike Foundation was excavated down to a competent native material. Approximately 200,000 cy of foundation material was removed, in order to reach satisfactory native soils. The unsatisfactory material was hauled onsite and placed in an owner designated area, 1.5 miles from the CIW North Dike. The earthen fill consisted of a native decomposed granite material, mined from a borrow pit, located approximately 1.5 miles South of the CIW North Dike. The outer shell of the CIW North Dike is comprised of a 3.87 foot wide 15” minus riprap material, which was imported from a local rock quarry.

Stretching the entire centerline length of the dike is a 3 foot wide chimney comprised of sandy material, which was also imported from a local rock quarry. The CIW North Dike is 3,380 feet long, and ties into the same knoll as the CIW South Dike. The CIW North Dike was constructed using approximately 430,000 cy of earthen materials. Located through the center of the CIW North Dike, 1,400 feet from the south knoll, is a single 4 foot wide by 6 foot tall concrete box culvert, with a 4-foot x 6-foot steel flap gate. The box culvert was designed to allow the flow of storm water from the landslide to the reservoir side of the dike.

Both the dikes were constructed using a combination of off highway bottom dump and articulating dump trucks. The material was loaded into the trucks using several large excavators. The dikes were shaped and compacted using large sheeps-foot compactors and bull dozers, equipped with automatic Trimble GLONASS positioning systems. The dike construction crew size ranged from 25-30 operators and laborers.

Also, included in this contract was the installation of two piezometers, the abandonment of several existing monitoring wells, the construction of 3.5 miles of aggregate base maintenance roads, the construction of a 12 acre aggregate base parking lot, the construction of 38 settlement monuments, the construction of 4,500 feet of concrete lined v-ditch, the construction of 5,000 feet of cable rail fence, the construction of 8,000 feet of chain link fence, and the complete site restoration and yearlong maintenance of new landscaping.

This entire project was constructed per plans and specifications for $17M and took approximately 16 months to complete.