Water-quality monitoring for a pilot piling removal field evaluation, Coal Creek Slough, Washington, 2008-09

Significant Findings

Water and sediment quality monitoring was conducted before and after the removal of a piling field located in Coal Creek Slough near Longview, Washington. Passive chemical samplers and continuous water-quality monitoring instruments were deployed at the piling removal site, Coal Creek Slough Site 1 (CCS1), and at a comparison site, Coal Creek Slough Site 2 (CCS2), before (2008) and after (2009) piling removal. Surface and subsurface (core) sediment samples were collected before and after piling removal and were analyzed for grain size, organic carbon content, and chemicals of concern. Significant findings from this study include:
* Phenanthrene was the only compound detected in wood piling samples analyzed for a large suite of semivolatile organic compounds and polycyclic aromatic hydrocarbons (PAHs). Metals potentially associated with wood treatment were detected in the wood piling samples at low concentrations.
* Organic carbon was slightly lower in core samples from CCS1 in pre-removal (2008) and post-removal (2009) samples than in surface samples from both sites in both years.
* Grain-size class distributions were relatively uniform between sites and years.
* Thirty-four out of 110 chemicals of concern were detected in sediments. Eight of those detected were anthropogenic waste indicator (AWI) compounds, 18 were PAHs, 4 were sterols, and 4 were metals potentially associated with wood treatment.
* Nearly all reported concentrations of chemicals of concern in sediments are qualified as estimates, primarily due to interferences in extracts resulting from complex sample matrices. Indole, perylene, and fluoranthene are reported without qualification for some of the samples, and the metals are reported without qualification for all samples.
* The highest frequency of detection of chemicals of concern was seen in the pre-removal surface samples at both sites.
* AWI compounds were detected less frequently and at lower concentrations during the post-removal sampling compared to the pre-removal sampling.
* Several PAHs were detected at relatively high concentrations in core samples, likely indicating historical sources.
* Most commonly detected PAHs in sediments were 2,6-dimethylnaphthalene, fluoranthene, perylene, and pyrene.
* Most commonly detected AWIs in sediments were 3-methyl-1h-indole (skatol), acetophenone, indole, phenol, and paracresol.
* Sedimentary concentrations of perylene exceeded available sediment quality guidelines. Perylene is widespread in the environment and has large potential natural sources in addition to its anthropogenic sources.
* Concentrations of metals did not exceed sediment quality guidelines.
* Multiple organochlorine pesticides, both banned and currently used, were detected at each site using passive samplers.
* Commonly detected pesticides included hexachlorobenzene, pentachloroanisole (a degradation product of pentachlorophenol), diazinon, cis-chlordane, endosulfan, DDD, and endosulfan sulfate.
* PBDE concentrations detected in passive sampler extracts were less than the method detection limit at all sites with the exception of PBDE-99, detected at a concentration less than the reporting limit.
* The fragrance galaxolide was detected at a concentration greater than the method detection limit.
* Common PAHs, such as phenanthrene, fluoranthene, and pyrene, were detected in every passive sampler.
* Dissolved oxygen concentration was slightly higher at site CCS1 compared to site CCS2 in both years.
* Overall, there was no systematic increase in chemicals of concern at the restoration site during post-removal monitoring compared to conditions during pre-removal monitoring. Any immediate, short-duration effects of piling removal on water quality could not be determined because monitoring was not conducted during the removal.