DEQ has drafted proposed beneficial use approvals for two city projects: the reuse of soil with certain chemicals above the clean fill screening levels on the city's property where the water filtration system is to be constructed and the reuse of slightly contaminated soil that is disturbed when constructing the water pipeline to the water treatment facility. DEQ is requesting public comment on the proposed beneficial use approvals and will attend a community-sponsored public meeting on June 11, 2024 to answer questions about the proposed beneficial use determinations. Information is published on DEQ's
Public Notices page.
Both applications and associated analytical data indicate that the proposed beneficial uses do meet DEQ's
beneficial use requirements. The proposed reuse of soil is productive, and the contaminant concentrations can be managed to acceptable human health and ecological risk levels if the soil is managed according to the proposed conditions of beneficial use approval.
The requirements for reuse include using best management practices for handling the soil during excavation, loading, transporting and stockpiling to minimize all potential risks to human health and animals. The requirements also include that the soil is placed below a clean soil cap, so the surface soil, where humans and animals are in direct contact with the soil, meets DEQ's clean fill requirements.
Learn more about DEQ's clean fill guidance.
The Portland Water Bureau proposes to reuse soil with certain chemicals above the clean fill screening levels mixed with clean fill soil at the filtration facility location. Soil with certain chemicals above the clean fill screening levels that is not reused within the pipeline trench will also be stored and reused at the filtration facility location.
A portion of the pipeline trench will be built within a right-of-way, or land owned by another entity or entities. As a request of a right-of-way landowner, the surface soil excavated in the portion of the pipeline footprint that will be built on their property will be reused onsite and not transported to the water filtration location. The City has requested that DEQ approve beneficial use of the soil generated from the pipeline construction project for four reuse options: (1) use of the soil as nonstructural construction fill within the excavated pipeline trench, (2) use of the soil as nonstructural construction fill on the shoulder surfaces immediately adjacent to the roadway, (3) use as topsoil as part of trench restoration of a farm field as specified by landowner, or (4) use of the soil as nonstructural construction fill at the water filtration facility.
Contaminants in the soil that exceed DEQ's clean fill criteria are: 4,4-dichlorodiphenyldichloroethylene (DDE), 4,4-dichlorodiphenyltrichloroethane (DDT), dieldrin and lead. The maximum lead concentration in the surface soils at the pipeline are measured at 28.3 mg/kg are slightly elevated above clean fill criteria or background concentrations at 28 mg/kg. Background concentrations refer to the chemical concentrations that exist in soils naturally. The concentrations of pesticides exceed ecological risks but are below risk levels for human health. The pesticide concentrations are similar to the concentrations found on neighboring agricultural properties.
Download the data tables comparing contaminant concentrations to risk screening values.
From DEQ's evaluation of the sampling data and comparison to risk screening values, the concentration of contaminants are below risk values for construction and occupational workers. The city has proposed and DEQ proposes to approve through the beneficial use determinations specific conditions to ensure that the soils will be properly managed to protect human health and the environment by requiring that the soils be stored under cover until reuseds .
When the soil is placed for reuse, it will be covered with three feet of clean fill or a foot of clean fill and a textile barrier at the filtration facility location. For pipeline construction, soil removed for the pipeline will be reused to fill trenches or stored until reused at the filtration facility property. DEQ considers that reuse of this soil has the following public benefits.