TRENT AVENUE SR290 REALIGNMENT
SPOKANE, SPOKANE COUNTY, WASHINGTON
The proposed realignment of Trent Avenue (SR 290) would place the roadway through the current BBM property and along a portion of Riverside Avenue. BBM is located on property formerly occupied by the Spokane Gas and American Tar companies. Significant sub-surface soil contamination related to byproducts from the past coal gasification, has been found in this area. The area along Riverside Avenue that would also be occupied by the new road was formerly used as a rail yard. Elevated levels of lead and TPH have been found in both surface and sub-surface soil in this area. The remaining areas investigated in the preliminary assessment of the area performed for DOT did not reveal significant contamination.
The following discussion addresses the potential exposure of persons who might come into contact with soil, sediment, and surface water at or near the BBM property.
Current exposures to contaminants in soil are limited to transient persons exposed via accidental ingestion and dermal contact to surface soil in the vicinity of the former rail yard. Contaminants of concern in surface soil in the vicinity of the former rail yard include TPH and lead detected at a maximum of 1804 and 568 ppm, respectively. No adverse health effects are anticipated to result from exposure of transient persons living near the site to contaminants in soil. Although surface soil sampling is limited to the former rail yard area along Riverside Avenue, extensive soil borings taken throughout the other areas of concern indicate visible contamination only at depth. This fact is supported by evidence that fill had been placed on-site at various times, including efforts to cover visible tar with approximately 4 feet of fill. Therefore, no completed exposure pathway exists for customers and workers at the BBM property.
The proposed realignment of Trent Avenue represents a potential exposure pathway for road workers to contaminants in surface and sub-surface soil. However, the nature of any such exposure would be limited by the duration of the project. As noted above, contaminants detected on the BBM property are below ground surface, but could present an opportunity for exposure depending upon the extent of excavation necessary for the road construction. While most of the significant contamination appears to be greater than 7.5 feet below ground surface, some borings were described as hydrocarbon stained in the 0-5 foot range. No adverse health effects are anticipated to result from a 6-month exposure of road workers to the maximum levels of TPH and lead detected in surface or sub-surface soil in any areas of the proposed Trent Avenue realignment. It is important to note that road workers who directly manipulate hot tar can be exposed to PAH via inhalation and dermal contact, depending upon labor practices and personal protective equipment.
Surface water and sediment
A maximum of 4.4 ppb lead was detected in surface water and 53 ppm in sediment taken from the Spokane River. TPH was not analyzed in sediment or surface water samples. PAH was found at a maximum of 1.6 ppb in surface water and 0.42 ppm in sediment samples taken from the river. The area of the Spokane River, adjacent to the site, is well covered with brush. Some clearings provide access via foot paths. There are no residences in the area and no evidence that trespassers may be using the BBM property for recreational access to the river. Although there is evidence that transient persons live in this area, it is unlikely that they use the river for bathing or drinking water.
The Trent Avenue realignment is not anticipated to increase access to the river as the area is zoned heavy industrial, and the new road will leave little room for development in this area. It is important to note, however, that only one sediment and two surface water samples have been taken adjacent to the site. Although the potential for significant human health exposure is limited, available data is not sufficient to determine the extent of sediment and surface water contamination along the south bank of the river that is adjacent to the site. Any future land use that involves increased access to the river, should be preceded by further evaluation of river surface water and sediment.
Groundwater samples taken from soil borings using temporary well casings and screens indicate very high, but localized contamination with maximum concentrations of TPH and PAH at 206,000 and 9866 ppb, respectively. The actual levels of dissolved contaminants may be considerably lower since these samples are suspect for suspended solid contamination. PAH was detected at a maximum of 272 ppb in only one of eight monitoring wells (MW-2d) installed around the periphery of the high contamination zone defined by the previous soil borings. TPH was not analyzed in these samples. Only one well (private) exists within a one-mile radius of the BBM property. Three (3) public water supply wells (Nevada, Grace and Ray), operated by the City of Spokane, are within a 2 mile radius (see Figure 3). (7,8) These wells have tested below detection levels for PAH as recently as August or October 1997, but have not been analyzed for TPH . (9) No data was located on the single private well.
The BBM property appears to be located at the edge of the Spokane Valley-Rathdrum Prairie Aquifer. Water level measurements indicate that groundwater in the shallow zone moves along a very slight gradient away from the river in a northeast direction. The deeper monitoring wells are approximately 40 feet below ground surface and indicate very little horizontal movement, but do show a downward gradient. None of the soil borings or monitoring wells reached bedrock, but bedrock outcroppings are visible to the south of the site. It is unclear how this shallow zone of groundwater relates to the Spokane Valley-Rathdrum Prairie Aquifer which supplies drinking water to the city via many public supply wells. This aquifer is designated by EPA as a sole source aquifer. Groundwater in this aquifer moves generally to the west until it hits a basalt rock formation at Five Mile Prairie where it then turns north. Although the shallow flow around the BBM property appears to be opposite to that of the larger aquifer, it is likely that this shallow groundwater eventually moves vertically into this unconfined aquifer.
Phase 1 of a recent study completed for the City of Spokane Wellhead Protection Program shows that the BBM property is not in the capture zones of existing supply wells operated by the city. However, the site appears to be within or very near to the capture zone of one of two new wells (West) proposed by the city. The exact location of these new wells has not been yet been determined and could differ from the locations used to model the capture zones. (8) A wellhead protection study is currently being prepared for the Spokane Aquifer Joint Board that will predict capture zones for public supply wells not owned by the city. Initial results from this study indicate that the BBM property is not within the capture zones of any of these public supply wells. (10)
Preliminary investigations at the BBM property indicate that groundwater movement in the area is slow. Three public supply wells are located within 2 miles of the BBM property. The lack of PAH in these wells, along with their predicted capture zones, indicate that residents supplied by these wells are not being exposed to contaminants related to BBM. However, since PAH and TPH contamination is extensive in BBM soil and groundwater, further characterization of groundwater is necessary to determine the extent of contamination and the potential threat to future wells in the area.
Exposure Pathways and Children
The potential for exposure and subsequent adverse health effects are often increased for young children as opposed to older children or adults. For example, children are far more likely to engage in activities that involve "getting dirty". Playing in dirt, combined with frequent hand to mouth activity, provides toddlers with an increased chance of exposure to soil contaminants by way of ingestion and skin contact. In addition to the potential for higher exposures of young children, the risk of adverse health effects is also increased. ATSDR and DOH recognize that children are susceptible to developmental toxicity that can occur at levels much lower than those causing other types of toxicity. These effects can be subtle as is the case with lead poisoning which has been linked to behavioral changes including poor performance in the classroom.
The potential for exposure of children at the BBM property was examined with the above considerations in mind. Since the area is industrialized, exposure is limited and is not expected to involve children.