Question 1: Why is ODOT addressing the contaminated soil and groundwater found on the Tillamook Project?
Answer: ODOT must address the contamination to protect the health and safety of construction workers working next to the contamination, and the general public. ODOT is also complying with conditions in the National Pollutant Discharge Elimination System (NPDES) permit which regulates what we can discharge during construction.
The concentrations of soil and groundwater contamination were not high enough to trigger the Department of Environmental Quality (DEQ) clean up rules but they were high enough to trigger waste management rules which require the safe removal and treatment of the contaminated soil and groundwater.
Question 2: Where is the contamination located?
Answer: Most of the contamination is located along Hoquarton Slough in the northeast section of the project. As part of the project, ODOT had to acquire several properties along the Slough which have seen fairly continuous industrial and commercial use for better than 120 years. To date, impacts have only been encountered on the south side of Hoquarton Slough where an old lumber/shake mill, gas stations, vehicle and boat repair, and a laundromat existed in the past, in or adjacent to the current project limits.
As part of ODOT’s project development, several preliminary site investigations (test holes) were preformed to identify areas where past land uses have impacted soil and groundwater within the project limits. ODOT suspected that there might be contamination issues, but did not expect the extent and the quantity of contamination that has impacted the project.
Question 3: How is ODOT addressing the contamination?
Answer: The investigative data gathered during project development along with discoveries during construction excavations has been used to develop a waste management approach. A company that specializes in treatment of contaminated water has provided a treatment system approved by the DEQ. At the construction site, two 20,000 gallon tanks are used to pump out the contaminated water, filter and treat it and discharge it back in to the slough. The system only treats the water. It is not designed to clean up the site.
ODOT’s contractor handles contaminated soil according to special provisions within the project contract. This special provision describes the process of how the contractor should handle, manage and dispose of the contaminated soil. The contaminated soil is taken to a DEQ permitted landfill disposal site.
Question 4: What are the contaminants being encountered in the groundwater?
Answer: A wide range of contaminants exist within ODOT’s project limits. It bears repeating that the concentrations of soil and groundwater contamination are not high enough to trigger the DEQ cleanup rules but they are high enough to trigger waste management rules which require the safe removal and treatment of the contaminated soil and groundwater.
All of the petroleum hydrocarbon ranges (TPH) have been detected suggesting that releases of gasoline, kerosene, diesel, and heavy or used oil have occurred. Volatile Organic Compounds (VOCs) and polynuclear aromatic hydrocarbons (PAHs) associated with petroleum hydrocarbons are present also. Total priority pollutant metals (arsenic, barium, cadmium, chromium, lead, mercury, and silver) are present as well as are low concentrations of PCBs.
Question 5: Why are we treating groundwater and is the treatment system working?
Answer: The wettest winter and spring in decades has resulted in the contractor having to dewater areas adjacent to Hoquarton Slough where excavation activities were necessary for foundation stabilization work and installation of new storm water collection systems. To advance these tasks, ODOT and its contractor found it necessary to deal with large volumes of contaminated groundwater.
The current treatment system filters fine sediments and then treats the impacted groundwater through a combination of carbon filters. Prior to discharge to the current City of Tillamook storm water system, the water is tested for all of the contaminants. These include VOCs, PAHs, priority pollutant metals and TPH. All discharges meet criteria of ODOT’s construction discharge permit. Water is tested before it is discharged to the environment.
Water that still contains contaminants of concern higher than permitted concentrations is treated again after the treatment system has maintenance performed. This retreated water is then tested again before it can be discharged to the environment. Treated water is only discharged to the storm water system when the concentrations meet DEQ Level 2 Ecological Screening concentrations. ODOT’s goal is to have no impact on the adjacent waters of the Hoquarton Slough.
To the extent possible, ODOT’s pumping and treating of contaminated groundwater should reduce the total quantity of historic contamination within ODOT’s project limits, but it is not ODOT’s intention to “clean up the site”.
Question 6: How does the Shell Station property figure into this issue?
Answer: As part of the highway improvement project, it became necessary to significantly impact the former Tillamook Shell and Grocery property. This property has had continuous use of gasoline underground storage tanks since the early 1920’s.
As part of the property acquisition, the property owner was required to remove (decommission by removal) the underground storage tank (UST) system. While the integrity of the UST system appeared to be whole during UST removal, soil and groundwater beneath the tanks was found to be impacted by petroleum hydrocarbons. The property owner and its consultant are actively working with DEQ’s Leaking Underground Tanks Cleanup Program to define the problem and move towards site closure using DEQ’s risk-based corrective action methods. When the property owners have been issued a decision that “No Further Action (NFA) is required at this time”, the property will transfer to the state and the property owner will receive final payment for the property. This will satisfy the current requirements for “cleaned up” under the existing Oregon DEQ cleanup program.
Public Affairs Specialist, ODOT Region 2