Concord Naval Weapons Station Creek Tour Report

Mount Diablo Creek Watershed Planning Group

September 10, 2005

Jessica Hamburger, Watershed Coordinator

Speakers: Jim Hale, Contra Costa Fish and Wildlife Committee; Phillip Torres, Rancher/Property Owner; Phillip Ramsey, U.S. Environmental Protection Agency; Phillip Woods, Concord Planning Department; Rich Walkling, Natural Heritage Institute.

Other Participants: Polly Boissevain, Friends of Mount Diablo Creek; Sylvia Chatagnier, Diablo View Middle School; Bill and Helene Feil, Land for Urban Wildlife; Brian Holt, East Bay Regional Parks District; Hsun Hsueh, watershed resident; Arlene Kikkawa-Nielsen, Clayton Library; Jessie Levine, Natural Heritage Institute; Mary Malko, Friends of Mount Diablo Creek; Diane and Bob Malucelli, watershed residents; Sharon and Garry Seidlitz, watershed residents; Cindy Welles, watershed resident.

Speakers presented information on different aspects of the creek and the watershed: wildlife habitat, grazing issues, toxic contamination, land use planning and geomorphology.

Jim Hale, Contra Costa Fish and Game Committee: Wildlife Habitat

Jim Hale took the group to see riparian habitat at four sites along the creek.  The first site was under Highway 4 and the BART tracks. The dominant riparian species there were red willow, arroyo willow and cottonwood. There were some standing pools of water. The second site was further upstream. Hale noted that native fish such as western roach, hitch and stickleback can be found in the remnant pools in this reach of the creek, as well as introduced mosquitofish. Watercress was growing along the edge of the bank, and Hale said that he had seen tree frogs emerging earlier this month. We saw a red-shouldered hawk using the habitat along the creek and saw burrows of one of its prey species, California vole or meadow mouse, in the adjacent grassland. At the third site, we saw the mud nests of cliff swallows stuck to the bottom of an overpass. Cliff swallow nests and black phoebe nests can also be found in culverts, Hale said. At the fourth site, where a road crossed the creek, Hale pointed out the scat of coyote, gray fox and black-tailed hare. He noted that many species used the creek as a migration corridor, even when it is dry, because the riparian vegetation provides shade and a place to hide from predators. We saw an elderberry bush, which was used by Native Americans for food and to make dye. It is the host for the threatened valley elderberry longhorned beetle.

Phillip Torres, Rancher/Property Owner: Grazing Issues

Since Arthur Anderson, the rancher who grazes cattle on the base was not able to make the field trip, Phil Torres agreed to say a few words about grazing issues. Torres said that this has been a good year for cattle because of the rains. The ponds have been full and the reservoirs are topped off.  The bumper crop of grass has meant that ranchers did not have to supplement their feed with as much hay as in other years. The main problem they face is yellow star thistle. Hale commented that East Bay Regional Parks District has been using sheep to control yellow star thistle and has found them to be effective at regenerating native grasses. Controlled grazing can be good for habitat, Hale said.

Phillip Ramsey, U.S. Environmental Protection Agency: Toxic Contamination

Phillip Ramsey is EPA's Remedial Project Manager overseeing the Navy's cleanup of the Concord Naval Weapons Station Superfund site. Ramsey explained that the Concord Naval Weapons Station was listed as a Superfund site in the 1990s because of high levels of heavy metals in the Tidal Area on land formerly owned by General Chemical corporation. The Superfund site designation covers the whole base, from fenceline to fenceline, including both the Tidal and Inland Areas.

Initially, the Inland Area was considered clean, but more recently, extensive arsenic contamination has been discovered. Arsenic-based herbicide was used to reduce fire risk throughout the bunker area and it has remained in the soil, making the land unfit for residential development in its current state. Ramsey told the group that there is very little uptake of arsenic to the grass on the base, and it poses an extremely limited risk to the cattle and elk that graze there. There are very low levels of arsenic dissolved in water in the creek, but EPA is concerned that arsenic-contaminated sediments may have washed into the creek, where they might pose a risk to benthic macroinvertebrates at the base of the food chain.

EPA is now overseeing the Navy's development of a sampling plan to test this hypothesis. The draft plan is available for public review at the Concord library. In addition, members of the public can get provide ongoing input on the cleanup by joining the Navy's Restoration Advisory Board, which meets monthly at the Concord Police Station.

Phillip Woods, Concord Planning Department: Land Use Planning

Phillip Woods told the group that the City of Concord is currently updating its General Plan, which contains policies on how city land will be used. The draft environmental impact report on the General Plan Update will be released soon and will be available for public review and comment. Woods emphasized that the information released by the City regarding the number of houses and jobs to be created in the NWS  are maximum numbers for a 25 year buildout and may be refined through a Reuse Plan and a Community Plan.  He did not have accurate information about open space and hillside protection with him at the time of the field trip and submitted the following correction by email:

“The General Plan Policies do not prohibit development based on an elevation or a slope percentage.  Instead the General Plan provides an Overall Land Use Allocation for the Naval Weapons Station (NWS) that gives a range of 32 to 50 percent to dedicate to "other public open spaces" that includes hillside areas. It should be noted that almost 30% of the land (1,540 acres) in the NWS is over 15 percent slope. The City's Hillside Ordinance, which requires all parcels that have an average slope of 15 percent or more to have a Hillside Development Plan, would be applicable to the NWS.  Also there are many policies that support open space preservation.”

Rich Walking, Natural Heritage Institute: Geomorphology

The Natural Heritage Institute (NHI) is studying the geomorphic stability of the creek channel as part of the Mount Diablo Creek Watershed Inventory they are conducting for the Contra Costa Resource Conservation District. Studying the creek can help determine how much of a setback is needed to protect creek ecology, habitat, water quality, and infrastructure in case the creek were to move laterally in the future.

Maps show that there has not been much change in the course of the creek for the last 60 years. However, an 1871 map shows Mount Diablo Creek flowing west, away from its current course through the base, before heading north into Pacheco Slough. It is possible that the diversion of Mount Diablo into Seal Creek, which was once a small stream flowing out of Clayton Ridge, resulted in the deep incision that can be seen in parts of the creek on the base.

The creek has also cut down into its bed in urban areas upstream, and grade control structures have been installed to keep it from incising any further. Such incision is typical of urbanizing areas, where the increase in impervious surfaces increases runoff and the volume of water flowing in the creek.

NHI's watershed inventory also will describe factors to consider in determining how much of a riparian buffer is needed for wildlife on the base and identify barriers to fish migration along the entire creek, including a pipeline on the Tesoro property downstream of the base, and the Bailey Road culvert.