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.
Project scope
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
(916) 625-5515 |
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