Ridgefield National Wildlife Refuge Cleanup Investigation
Peregrine falcon. Photo: USFWS region 6The Ridgefield National Wildlife Refuge (NWR) is located in Ridgefield, Washington, along the lower Columbia River.  The refuge provides important wintering habitat for waterfowl and is used extensively by migratory shorebirds, wading birds, and passerines during fall and spring migrations.  The refuge is also used as a roosting area for lesser sandhill cranes (Grus canadensis) and a roosting and foraging area for tundra swans (Cygnus columbianus).  Federally threatened and endangered species such as bald eagles (Haliaeetus leucocephalus) use the refuge as foraging and nesting habitat, and peregrine falcons (Falco peregrinus) are also known to forage on the refuge.  Due to its proximity to the Columbia River, anadromous fish use nearshore habitats along the refuge boundaries. The northern unit of the refuge is bordered by the Pacific Wood Treatment facility (PWT) contaminated with wood-treating related chemicals including pentachlorophenol (PCP), creosote, chromated copper arsenate, and copper napthenate.  This site is located immediately south of Carty Lake, which is part of the refuge located at the southern end of the Carty Unit and east of Lake River. Until the 1980s, chemicals were allowed to drain directly onto the open ground.  Preliminary investigations on this site began in 1986 when potential contaminants were identified as petroleum hydrocarbons; volatile and semi-volatile organics; chlorinated phenols and related compounds; trace elements such as arsenic, chromium, and copper; and dioxins and furans. The objective of this study was to document environmental contaminants which may have entered the refuge from the PWT site through the groundwater or surface water.  The investigation included chemical analysis of sediment and fish collected adjacent to the PWT site and on Ridgefield NWR.  The main contaminants looked at in this study were PCP and trace elements but it also looked at organochlorine pesticides, total PCBs, and chlorphenoxy herbicides.

Map: Ridgefield, WAMethods: Sediment and fish samples were collected in June and July, 1999 from areas adjacent to the PWT site, on the refuge, and from Bachelor Island Slough, a reference area near the refuge.  The sites for sediment collection were Bachelor Island Slough, Lake River North, Lake River South, Carty Lake North and Carty Lake South.  Large-scale sucker were collected with a gill net from Carty Lake on June 15, 1999 and by electroshocking at Bachelor Island Slough and Lake River on July 2, 1999.  Three fish of similar size were collected and composited at each of the Lake River and Bachelor Island Slough sites and two fish were composited at the Carty Lake site.

Results and Discussion: Sediment samples from all sites did not contain detectable concentrations of organochlorine compounds with the exception of one sample at Carty Lake South which contained hexachlorobenzene at the detection limit.  Most organochlorine compounds were also below detection limits in samples of large-scale sucker. PCP and dichlorprop were detected in sediment at the two locations adjacent to the PWT facility whereas concentrations were at or below detection limits in sediment from the reference area.  The highest concentration of PCP was found in sediment in Carty Lake that was adjacent to the PWT site at the south end.  The next highest concentrations were found at the Lake River South and Lake River North sites. These amounts indicate a potential exists for impacts to aquatic organisms, such as benthic invertebrates, in sediment from the south end of Carty Lake and parts of Lake River.  PCP and chlorophenoxy acid herbicides were not detected in sucker samples from any location so it appears that higher organisms are not accumulating PCP at these sites.

The highest concentrations for every trace element evaluated occurred in sediment from the two Carty Lake sites.  They were highest at Carty Lake South, Carty Lake North was more similar to the reference samples for most elements except nickel, vanadium, and lead.  In Lake River, sediment concentrations of trace elements were generally similar to or within one order of magnitude of the reference area.  Previous investigations stated that the trace elements were not found in sediment from Carty Lake or Lake River.  This suggests that the trace elements arsenic, copper, chromium, and possible lead and zinc originated from the PWT site. The trace elements aluminum, arsenic, cadmium, chromium, copper, lead, nickel, and zinc approached or exceeded the Threshold Effects Level (TEL) at the Carty Lake South site, and arsenic exceeded the Probable Effects Level (PEL).  Cadmium, nickel , and zinc also exceeded the TEL at other sites.  The data indicate that PCP and the trace elements arsenic, chromium, copper, and possibly lead and zinc are elevated on the refuge as a result of contaminant migrations from the PWT site.  The contaminants were found at the highest concentrations on the refuge site adjacent the PWT site compared to reference or Lake River sites and previous investigations documented PCPs, arsenic, copper, chromium, and zinc in water samples from Carty Lake near the PWT site.  PCP and some trace elements in sediment at the south end of Carty Lake could be impacting or limiting the occurrence of some benthic fauna in the area adjacent to the PWT facility.  PCP concentrations, based on sediment levels from this study and water concentrations from previous investigations, could also impact fish eggs, developing embryos, or sensitive fish species such as trout and other salmonids.


  1. Additional sampling should be conducted around the Carty Lake South location to determine the extent and depth of PCP and trace element contamination.  Once the depth and extent of contamination are characterized, sediment should be removed or evaluated in toxicity assessments to ensure the contaminants are not available to aquatic organisms.  Contaminated sediment at Carty Lake should be remedied to a level that would be protective of salmonids, since they could use the site following restoration activities.
  2. Sediment in Lake River should be further characterized to determine if cleanup is necessary.  Additional sampling should be conducted near the outfalls to better evaluate if cleanup is warranted.
  3. Sediment should be evaluated in Carty Lake and Lake River for dioxins and furans or overall dioxin-like activity.
  4. Polyaromatic hydrocarbons (PAHs) should be evaluated in sediment and groundwater wells in Carty Lake and associated wetlands.
  5. Additional groundwater wells should be installed in Carty Lake, adjacent to the wood-treating facility.  These wells should be sampled periodically for contaminants during the cleanup phase to evaluate the success of groundwater treatment, and to ensure that pressure created during the groundwater treatment does not force contaminants back onto the refuge.
  6. Restoration efforts should occur in or near the Carty Lake site.

Learn more by reading the full report:
Buck, J. Preliminary Assessment to Determine Superfund Site Impacts on the Ridgefield National Wildlife Refuge.    USFWS.  June 27, 2000.

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