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PROJECTS:  INFRASTRUCTURE TECHNOLOGIES

Habitat & Wetlands Restoration

Forgen routinely operates in waterfront settings performing complex work in sensitive ecological environments. Our experience includes numerous projects in riparian and intertidal wetlands, stream and river corridors, and ocean front settings. We understand the care and effort required to work in sensitive environments within the constraints of crucial tidal or biological work windows. We are also highly experienced working on and in water and on low strength materials. Our projects have included construction and remediation of wetlands, installation of water diversion and water control structures, dam and levee restoration, channel construction and rock armoring, removal of invasive plant species, and final restoration. Forgen’s wetlands construction and remediation capabilities include design and construction of man-made wetlands; wetlands contouring/shaping; contaminated sediment excavation; stream channel construction and restoration; hazardous waste remediation; water management; and site restoration.

CULLINAN RANCH PHASE 2 WETLAND RESTORATION
Vallejo, California

  • Construction of a 2,200 lf setback levee

  • Excavation of 160,000 cy on-site borrow in soft material

  • Operations in soft subgrade using LGP dozers and tracked haul trucks

  • Sensitive habitat considerations

Forgen performed restoration activities at this wetland site in the San Francisco Bay Area. Scope of work included the construction of an approximate 2,200 lf setback levee along Highway 37 in Vallejo, California. The setback levee was required to protect the highway from flooding after completion of future phases of construction which will include breaching the outer banks of the Cullinan Ranch Wetland along Dutchman Slough, and reintroducing tidal influence to the area. Additional scope elements included excavation of approximately 160,000 cy of on-site borrow material, consisting mostly of bay mud and silt material, for use in the construction of the setback levee. The levee was constructed to a height of approximately 7 ft above the existing ground surface elevation at an average width of 155 ft.

Construction of the setback levee included clearing and grubbing of vegetation along the footprint of the new levee using a low ground pressure dozer and long reach excavator. All debris was disposed at designated on-site locations. Additionally, two existing channels, crossing the alignment of the new setback levee, were over-excavated using a long reach excavator to remove existing vegetation and soft sediment in preparation for placement of suitable backfill material. All backfill material was excavated from designated on-site borrow locations which were excavated using a PC300 excavator which loaded material directly into haul trucks to transport to the fill location.

At the start of the project, a combination of rubber tire articulated trucks, capable of holding approximately 20 cy of soil, and tracked dump trucks, capable of holding 10 cy of soil, were utilized. As the project progressed, site conditions became unsuitable for utilizing the rubber tire articulated trucks in the wet and soft ground conditions, and eventually, all hauling operations were converted to tracked dump trucks with additional trucks added to match production rates and minimize potential schedule impacts.

The backfill material was placed and compacted by track rolling using a low ground pressure dozer using consistent traffic patterns. This phase of work provided temporary stockpiling of material for dewatering, as well as a surcharge along the alignment of the setback levee for a period of approximately one year allowing for any settlement to occur prior to reshaping the setback levee to its final construction profile during a subsequent phase of work.

MONTEZUMA WETLANDS PROJECT
Birds Landing, California

  • Excavation of the borrow area at or below groundwater elevation

  • Segregation of peat, clay, and alluvial soils within the borrow area

  • Installation of over 80 settlement monuments (40 pairs) at the levee hinge

  • Soft peat soils along haul routes and within levee foundation

  • Work on narrow levee crowns; limited access to levees

  • Construction of a peat core within one levee area

The Montezuma Wetlands project included construction of three levees for future use as dredge sediment placement areas on approximately 27 acres of future wildlife habitat. Construction also included a raised embankment for Least Tern habitat and stockpiling alluvial materials for future use. Material for levee and embankment construction was obtained from the on-site borrow source where clay, peat, and alluvial materials were segregated prior to use. Over 137,000 cy of embankment material was placed within the levee prism, Least Tern habitat area, and stockpile location. The foundation soils of the largest levee, as well as most haul routes, consisted of peat which required the installation of over 80 settlement monuments along the levee alignment and additional efforts to stabilize and maintain access for construction equipment.

Scope of work also included construction of a peat core in specified levee sections to prevent failure of foundation soils, and construction of a clay core was performed along a portion of the levees adjacent to a waterway. Construction on the peat foundation soils required regularly scheduled measurement of the settlement monuments which resulted in adjustments to sequencing, production rates, and scheduling during levee construction. The project required continuous coordination with the Owner and Engineer to avoid excessive foundation settlement and allow the on-site maintenance contractor to utilize the levee cells as dredge sediments arrived to the site.

SFWMD RS-G341 CONVEYANCE IMPROVEMENTS
SEGMENT 1&2
Belle Glade, Florida

  • Dewatering of canal and farm ditches to elevation 0.0 using 24 in hydraulic pumps to construct adjacent farm roads

  • Blasting of 12,700 lf of 40 ft wide canal

  • Excavation of 12,700 lf of canal to elevation -2.0

  • Construction of 4 separate cofferdams

  • Placement of muck on rock core spoil pile embankment to minimum elevation of 15.5

  • Installation of drainage culverts

Forgen was contracted to provide services for the RS-G341 Conveyance Improvements project for the South Florida Water Management District (SFWMD) in Belle Glade, Florida. Dewatering of the project area was completed after the installation of cofferdams to block off water from the existing Bolles Canal to the east and west of the project. Four cofferdams were constructed and dewatering was completed in three sections using 12 to 24 inch diameter hydraulic pumps. Following dewatering of each section, muck within the proposed excavation and spoil pile embankment footprint was removed and stockpiled outside the proposed embankment footprint. Muck was removed to expose a limestone rock layer beneath the muck. Once muck was removed, the proposed canal excavation cross section was drilled and blasted to break up the limestone rock layer within the proposed footprint of the new canal.

Following blasting, the canal was excavated using a Caterpillar 374 excavator to an elevation -2.0 (depth of approximately 8 ft from surface of rock layer). Excavated material was used to construct the rock core for the spoil pile embankment adjacent to the canal for flood control, and rock material was placed in lifts using a Caterpillar D6 bulldozer.

Dewatering during the excavation of the canal was maintained at an elevation 0.0. Using smaller Caterpillar 330 size excavators and D6 dozers, stockpiled muck was placed and compacted atop the rock core to increase the spoil pile embankment elevation. The minimum elevation of the completed spoil pile embankment was elevation 15.5. Farm ditches were blasted and excavated in a similar manner, with rock excavated from the farm ditches used to construct adjacent farm roads. Drainage culverts were installed at the ends of the farm ditches to facilitate the movement of irrigation water to and from fields adjacent to the project.

TEN MILE CREEK REHABILITATION
Fort Pierce, Florida

  • Nearly four miles of collection canal filled

  • Over 7,000 tons of bentonite blended with soils on site

  • Project required continuous dewatering

  • Additional work requested/required was completed within the original project schedule

The Ten Mile Creek Reservoir is a stormwater control unit located in Fort Pierce, Florida and managed by the local water district. It was originally constructed with a collection canal inside the levee which required filling for proper operation of the structure. The existing reservoir was unable to store the volume of water required due to seepage once the water level reached a specific elevation inside the reservoir. The seepage was due to a “fish collector ditch” that was excavated at the base of the interior wall of the dike that removed a two to three foot layer of natural clay. The adjoining stormwater treatment area also required regrading to allow for proper distribution and retention of water introduced into the area.

Forgen dewatered, cleared, and grubbed approximately 300 acres of the interior of the reservoir, borrowed sand and sandy clay from the interior of the reservoir, and backfilled approximately 26,000 ft of the “fish collector ditch” in lifts. A two foot section of the backfill materials were mixed with bentonite to replace the impervious clay layer removed from the “fish collector ditch”. Other work included approximately 7,000 tons of riprap installed at Pump Stations 382 and 383, clearing and grading of an adjoining 136 acre stormwater treatment area, installation of geocomposite clay liner in selected areas, installation of coir logs, and planting of bulrush around the entire interior perimeter of the reservoir.

ANAHAUC NATIONAL WILDLIFE REFUGE
MIDDLETON UNIT
Winnie, Texas

  • Moat excavation of 24,032 cy
  • Construction of 42,593 cy of perimeter levees
  • Installation of seven water control structures
  • Limited access to the site
  • Working in an environmentally sensitive area
  • Project team overcame extreme rainfall to complete the work

Forgen was contracted by Ducks Unlimited, Inc. to create a duck habitat in the coastal plains of Texas. The project was located within the Anahuac National Wildlife Refuge just south of Winnie, Texas. The 34,000 acre refuge was created in 1963 and is home to an abundance of wildlife, from migratory birds, to alligators, ducks, bobcats, and more. The scope of work consisted of moat excavation totaling 24,032 cy, construction of 42,593 cy of perimeter levees, and installation of seven water control structures within the levee system to control water levels in the habitat.

Although Forgen was faced with extreme challenges and delays caused by excessive rainfall the project was completed. Ducks Unlimited, Inc. was appreciative of our team efforts, determination, and professionalism to complete the project.

The project photo on this page was the 2016 winner of ENR’s Year in Construction photo contest.