United States

Machado Lake Ecosytem Rehabilitation

Machado Lake, comprised of an upper 40-acre lakeand lower 63-acre marsh separated by a low earthen dam, is located at the Ken Malloy Harbor Regional Park in Los Angeles. Over time, sediment accumulation, toxic pollutants and trash degraded the lake and the surrounding habitat, and the state eventually designated as an “impaired water body.” OHL North America company OHL USA Inc., (OHL USA) integrated ecological and engineering strategies to rehabilitate the area.

The scope of work involved deepening the lake about 3.5 feet via hydraulic dredging to remove 239,000 cubic yards of sediment; capping the lake bottom with an AquaBlok bio-layer that promotes aquatic habitat while preventing contaminant reintroduction; removal of an obsolete aeration/oxygenation system and rehabilitation of the southern dam structure. OHL USA also replaced invasive vegetation with native plants and grasses, while natural resources were conserved using reclaimed water for landscape irrigation.

OHL USA sequenced construction activities in accordance with availability of environmental permits to avoid schedule delays. Its crews adhered to work restrictions imposed by the USACE, USFWS, RWQCB, CDFW and LABOE, including making sure that at least 10% of the
lake water is maintained during dredging to preserve aquatic life. Other challenges included severe rainstorms, which had a potential to affect the planting schedule. In addition, differing soil conditions impacted dredging operations—OHL USA had to haul away 7,000 cubic yards of contaminated material that was not included in the initial scope.

OHL USA constructed four fishing piers and two shoreline fishing platforms, paved pathways, new trails, and three pedestrian bridges, to provide the community safe means to explore and enjoy the recreational amenities of the park. The scope of work also included improvements to the Machado Campground located at the south end of the site.

Main Features:

  • Lake ecosystem rehabilitation
  • Invasive species removal and landscape improvement at a 290-acre city park

Awards:

  • 2018, “Best Project” award in the water/environment category from Engineering News Record California Region