http://www.nwk.usace.army.mil/Geology/htrw.html

OverviewOverview

Site AssessmentPotential sitesSoil Gas SurveysField Analysis

Site Assessment

Contaminated soil, a global problem Difficult to assess subsurface contamination

can’t see it3-d problem even with lots of monitoring wells can

miss important subsurface features.

Expensive to decontaminate sites competing national prioritieshighest priority needs to be prevention

Hazardous Waste Site Surveys

loading zoneshydraulically operated lifts accidental spills

storage tanks vegetative distress

herbicide applicationhazardous materials

stained soil

fill materialused to hide evidence of

spillmay contain hazardous

substanceswater and sewer lines

provide pathways for migration of subsurface contaminants

Soil Gas Survey

Effective screening technique for mapping the extent of VOCs

Indicates location of contaminant sources

Advantagesrapidlow costminimal disturbance to siteno waste generatedadaptable to site conditions

Disadvantagesdetection limits may be too highsome compounds may not be detectedfield results are semi-quantitative

Sampling Matrix

Soil Gas Survey

Soil Gas Survey: Methods

Place hollow, small diameter probe in soil Apply vacuum to probe Extract soil pore gas Take a sample of soil pore gas using:

syringe - on-site gas chromatograph analysisTedlar bag - on-site or off-site analysis

unaffected by most compounds impermeable to gas exchange

stainless steel adsorption tube - quantitative laboratory analysis

Soil Gas SamplingSoil Gas Sampling

Static sampling can be done two ways: An in-situ adsorbent (usually an activated charcoal rod) is buried in

the soil for a period of days to weeks. The adsorbent is retrieved and analyzed at a laboratory for VOCs.

Samples are collected from containers placed in the surface soil and analyzed using portable analytical instruments.

Concentrations in soil gas are affected by dissolution, adsorption, and partitioning. Partitioning refers to the ratio of component found in a saturated

vapor above an aqueous solution to the amount in the solution.

Contaminants can also be adsorbed onto inorganic soil components

or "dissolved" in organic soil components.

Field Analysis Field Analysis

Less accurate and less sensitive than laboratory analysis!

Immediate resultsExamples

Portable Gas chromatographPhotoionization Air MonitorFlame Ionization DetectorTest kits

Analysis Matrix

http://www.perkin-elmer.com/photo/pvac.html#VOyager

Portable Gas ChromatographPortable Gas Chromatograph

Portable GC containsa built-in 3-column configuration with

isothermal oven which provides optimized fast GC analysis for up to 40 volatile organic compounds (VOC).

a miniaturized PID/ECD dual detection system which allows monitoring at 1-10 PPB levels of a wide range of aromatic, chloroalkene, and chloroalkane solvents.

Photoionization Air MonitorPhotoionization Air Monitor

The 2020 hand-held Total VOC air analyzer weighs just 1.75 lb. (0.79 kg).

Sample is drawn via the internal pump

Results are displayed on the built-in LCD.

The operating concentration range is 0.5 - 2000 PPM.

Flame Ionization DetectorFlame Ionization Detector

The Micro FID weighs 8.1 lb. (3.7 kg.),

the smallest and lightest datalogging Flame Ionization Detector (FID) available.

The concentration range is 0.1 - 50,000 PPM with a response time of less than 3 seconds.

Potential Sites

Underground fuel storage tankshome owner beware!gasoline stations

Waste management facilities Chemical storage facilities Liquid waste lagoons Injection wells Chemical transfer facilities

http://www.cha-llp.com/tankmgt.htm

Underground Storage TanksUnderground Storage Tanks

Leaking underground storage tanks are a significant source of soil and water contamination in the United States.

New regulations went into effect in 1998Many facilities removed underground tanks and

replaced them with double walled tanks or above ground tanks for petroleum product and chemical storage.