Soil: High Risk

PAHs and metals are evident in samples. The potential for workers and firefighter exists for contact with contaminated soil.

Contaminants: Lead 200.0 mg/kg Naphthalene 253.0 mg/kg

Soil: High Risk

Significant risk to aquatic inertebnrates, fish and black rails from metal contamination in soil, sediment and surface water

Contaminants: Selenium 5.8 mg/kg Cadmium and compounds 38.6 mg/kg Arsenic 528.0 mg/kg Copper Cyanide 894.0 mg/kg Lead 6060.0 mg/kg Zinc Cyanide 10800.0 mg/kg

Surface Water (Marine): High Risk

Contaminants: Phenylethane 0.3 ug/L Arsenic (III) 51.0 ug/L Cadmium 60.0 ug/L Selenium 66.0 ug/L Copper 160.0 ug/L Lead 1000.0 ug/L Zinc 22000.0 ug/L

Sediment (Human): Medium Risk

Contaminants: Cadmium and compounds 38.6 mg/kg Lead 6060.0 mg/kg

Groundwater: High Risk

Groundwater daylighting into surface water. Human contact with surface water in a recreational setting.

Contaminants: Arsenic 9900.0 ug/L

Surface Water (Fresh): High Risk

Contaminated goundwater migating into surface water. Aquatic plants and animals using or living in surface water that has been impacted by arsenic contaminated groundwater.

Contaminants: Arsenic (III) 9900.0 ug/L

Groundwater: High Risk

Adjacent properties downgradient to IR Site 31 detected high level of metals partyicularly arsenic in groundwater. Although the site has no drinking water wells in the vicinity, groundwater elevation at the site is at depth. In addition, Suisun Bay is located down gradient and approximately 200-300 feet away.

Contaminants: Mercury (Methyl) 0.07 ug/L Benzo(a)Pyrene 1.6 ug/L Benzo(j)Fluoranthene 2.5 ug/L Selenium 19.1 ug/L Arsenic 1230.0 ug/L

Soil: High Risk

Contaminated surface waste and soils are present at point of exposure. Access to the site is restricted. Visitors limited to occassional maintenance, field sampling, and surveillance crews.

Contaminants: Chromium 86.0 mg/kg Mercury (Inorganic) 113.0 mg/kg Arsenic 239.0 mg/kg Lead 11400.0 mg/kg

Soil: High Risk

High concentration of metals were detected at surface and subsurface soil in along the mosquito ditchess located within the RASS 1 Area. Due to the high concentration of metals in the sediment and the proximity of the surface water such as Sloughs and Nichols Creek, there are evident that ecological receptors has been impacted. Unacceptable risk to fish and aquatic invertebrates.

Contaminants: Mercury (Methyl) 0.87 mg/kg Selenium 9.6 mg/kg Cadmium and compounds 832.0 mg/kg Lead 872.0 mg/kg Copper Cyanide 1560.0 mg/kg Zinc Cyanide 2990.0 mg/kg Arsenic 3260.0 mg/kg

Sediment (Marine): High Risk

High concentration of metals were detected in the sediment. Because the area is conidered habitat to known endangered species, ecologiocal receptors is potentially impacted by the high concentrations of metals.

Contaminants: Mercury 0.87 mg/kg Cadmium 832.0 mg/kg Copper 1560.0 mg/kg Zinc 89300.0 mg/kg

Surface Water (Marine): High Risk

The Mosquito Ditches is transporting sediment and groundwater contamination to the sloughs where it discharges the water to Suisun Bay. Unacceptable risk to fish and aquatic invertebrates, black rail and Salt Harvest Mouse.

Contaminants: Mercury 1.7 ug/L Selenium 14.1 ug/L Cadmium 207.0 ug/L Lead 1330.0 ug/L Arsenic (III) 2970.0 ug/L Copper 7240.0 ug/L

Soil: Medium Risk

Primary pathway either injestion for biological receptors.

Contaminants: Lead 6940.0 mg/kg Copper and compounds 9060.0 mg/kg

Groundwater: Low Risk

The groundwater is shallow. Metals have been detected in the groundwater monitoring wells at this site greater than the PRG. GW has evident of interaction with the surface water. No water supply wells are down gradient of the site. Groundwater, due to high total dissolved solids and saltwater intrusion, is not used as a water source. Water from the tidal area is unlikely to have any potential beneficial water supply use.

Contaminants: Antimony and compounds 60.9 ug/L Arsenic 126.8 ug/L