Water: Nonpoint Source Success Stories
Hoopa Valley Tribe
The Hoopa Valley Tribe Is Making Plans -
A Soil Remediation Project to Remove Leaking Diesel Fuel
For the Hoopa Valley Tribe of northern California, 1997 is a potential turning point: it is the first year the tribe is formally participating in the section 319 grant program.
A watershed assessment financed through a 1991 Section 305(b) grant has identified both point and nonpoint pollution problems on tribal lands. Four major industrial areas and approximately 20 minor sites contaminated with petroleum hydrocarbons (total petroleum hydrocarbons [TPH]) remain in residential areas of the reservation. Many are contaminated with diesel fuel (D), and some threaten the tribe's domestic water supplies. Among these 24 sites, a single site has been selected to demonstrate and evaluate a soil remediation technique and whether an air contact and wood-chip composting program can reduce the TPH-D levels in soils. The treatment should be sufficient to protect both surface and groundwater.
The Masonite Mill Creek site is an abandoned sawmill with two large underground storage tanks. A leak from the tanks has contaminated the surrounding soil with diesel fuel. Investigators suspect that the leak may have been as much as 10,000 gallons. Initial site investigations show that petroleum hydrocarbons had already contaminated the site's groundwater. Project managers had the tanks removed and disposed of in an approved manner by a licensed contractor. Contaminated soils were likewise excavated and transported off-site. Postexcavation testing of both the residual soil and the groundwater show no traces of TPH-D.
The tribe considered various alternative methods for cleaning the contaminated soil and eventually selected bioremediation. This technology appears to be the appropriate method; it is within the scope of the tribe's available technological skills and appears to be cost-effective. Bioremediation uses microbacteria to break down and digest volatile organics (such as diesel fuel). The warm summer months will aid this process. The tribe plans to conduct bioremediation on approximately 1,700 cubic yards of soil contaminated with diesel fuel. The process will include windrowing the soil on an impervious surface, working wood chips into the soil, and turning the soil monthly to encourage complete aeration. The soil will be monitored for TPH-D during the treatment period.
The tribe's Environmental Protection Agency believes that two summer seasons will be required to remediate the soil. Windrows will be covered during the rainy season between the first and second years. When remediation is complete, the open pit will be refilled, and the site will be cleaned and revegetated. During the remediation period, the site can also be used for educational field trips.
|CONTACT: Larry P. Oetker
Hoopa Valley Tribal Environmental Protection Agency