Navy Adds Wetlands, Grasslands to Point
The Navy’s cleanup program has not only removed toxic substances from below ground, it has dramatically improved some of the above-ground environment by creating new native grassland and wetlands. January rains filled the Navy’s new seasonal wetland on the northwest shoreline corner of Alameda Point and fostered growth of newly planted native grass seed on the surrounding soil.
The 2.25-acre wetland lies within an approximately 37-acre shoreline cleanup area known as Site 1 at the confluence of the Oakland Estuary and San Francisco Bay. It is where the Navy buried its waste between 1943 and 1956. Most of the waste pits were covered by pavement in the mid-1950s when a new runway was added.
The approved plan for leaving the waste in place was completed in 2015 after 17 years of study by state and federal regulatory agencies. None of the studies showed any toxic leaching from the waste material into Bay waters after sitting below the water table for more than 50 years. Hence, the plan to further isolate the waste with a soil cover mirrors the remedy used at other underground dumps.
The Navy will be responsible in perpetuity if anything fails, just as with other Superfund cleanup sites at Alameda Point. The Navy was required to create the new wetland as a mitigation measure for covering existing wetland with some of the soil cover. The secondary objective was to provide increased native plant and wildlife habitat along San Francisco Bay.
This mitigation requirement means that marginal wetlands that appeared by happenstance from runway drainage have now been replaced by a high quality engineered wetland. The new wetland holds a much larger volume of water and is situated to capture runoff from the soil cover.
It is also engineered at a lower elevation than the wetlands it replaces, thereby increasing water retention and allowing for recharging as sea level rises. There is no waste material located below the new wetland.
After removing old pavement and sculpting the site, the wetland substrate was created using imported clean fill material and topsoil. The soil was then amended with gypsum and potassium sulfate to facilitate growth of wetland plant species.
Learning a bitter lesson from a failed attempt in 2014 to grow native grasses by blowing seeds from a truck onto the soil at the nearby Site 2 cleanup area, the Navy used a different method at both sites. Known as drill seeding, the method involves cutting into the soil with a disc machine and simultaneously depositing seeds. It is followed up with a mulch cover.
Thirteen grass species were planted on the lower zone of the new wetland; another seven on the upper zone. The seeded area was then covered with mulch. The soil-cover over the former dump received another eight species of native grass seed with grasses like chairmaker’s bulrush, seaside heliotrope, Baltic rush, white yarrow and coyote brush, all of which produce flowers.
The Site 1 grassland and wetland is on land slated to be transferred to the city at no cost and to become part of a 147-acre regional park. Plans call for additional wild grassland and wetlands.
The Navy’s new wetland sits directly atop the original narrow landmass extending into the Bay that carried train cars to a ferry terminal at the site.
The Navy’s grassland and wetland work at Site 1 and Site 2 on the old airfield is the only ecological habitat creation, other than the placement of sand on the 9.6-acre least tern nesting site, since military operations ended in April of 1997.