Soil vapor extraction costs

The primary focus of this chapter is to introduce approaches that limit (or prevent) migration of hydrocarbon and organic contaminants from the vadose zone into underlying water-bearing zones. The more conventional strategies, including a brief discussion of the process, relative cost, practical constraints, and limitations, are presented. Also presented are two typical soil vapor extraction case histories. 

The preliminary study identified approximately 2300 yd3 of contaminated soil with a hot zone of approximately 800 yd3, which required the bulk of remediation effort. A pilot air sparge/soil vapor extraction study was made to define remediation costs. The remediation effort was estimated to extend for 3 years. 

Based on data from the U.S. Environmental Protection Agency (EPA) Superfund Innovative Technology Evaluation (SITE) demonstration, the total cost for PF extraction was estimated to be 307/kg of trichloroethene (TCE) removed. This demonstration was conducted over a 4-week period in August and September of 1992 at an industrial site in Somerville, New Jersey. The cost estimate includes expenses associated with both PF and soil vapor extraction. Major cost factors were labor (29%), capital equipment (22%), VOC emission control (19%), site preparation (11%), and residuals management (10%) (D10589F, p. v). 

According to the vendor, MITUs can be half the cost of alternative technologies such as incineration, landfilling, or soil vapor extraction (SVE) (D17269U, p. 8). At a petroleum and gas distribution site in Schuylkill Haven, Pennsylvania, 4200 tons of contaminated soil were treated at a cost of 18.63/ton. (D17269U, p. 30). Additional vendor-supplied cost information is presented in Table 1. 

SPSH has several advantages. It is applicable to sites where contaminants are present as non-aqueous-phase liquids (NAPLs). The technology reduces volatile organic carbon (VOC) removal time to a few weeks for a typical site, whereas soil vapor extraction (SVE) alone requires years for remediation. This reduction in removal time can signrhcantly decrease costs over SVE (from 2 to 10 times). Excavation and ex situ soil treatment is typically much more expensive to implement than SPSH, especially at deep sites. 

TABLE 1 Cost Comparison for Six-Phase Soil Heating and Soil Vapor Extraction... 

In 1993, ex situ soil vapor extraction using nondrilled horizontal wells was used at a contaminated site in Douglasville, Georgia. The U.S. Environmental Protection Agency (EPA) reported that the total cost of the remediation project was 2.2 million. Treatment costs were estimated to be 413/yd of soil treated (D20793M, pp. 20, 21). Treatment costs are summarized in Table 1. 

TABLE 1 Cost Estimate for Ex Situ Soil Vapor Extraction (SVE) Project... 

For another site in Regina in 1995, a total cost for 11 fractured wells, two soil vapor extraction systems, and operation and maintenance for 6 months was approximately 80,000. This figure did not include vapor treatment since none was required. Colder estimated that, had hydraulic... 

TABLE 1 Summary of Soil Vapor Extraction Projects with Fully Defined Costs"... 

Costs for electroremediation were estimated by some researchers to be 90 to 130 per ton of treated waste in 1994, a price range similar to or lower than conventional remediation methods such as soil vapor extraction (D131657, p. 289). 

The primary application of the PSVE technology will likely be to complement active soil vapor extraction efforts. PSVE could also be used on the edge of unsaturated zone contaminant plumes where concentrations of volatile contaminants are low or for enhancement of bioremediation activities. The primary advantages of PSVE application are low capital costs and minimal operating costs. One-way valves may also be incorporated so that the system only takes in or lets out air through wells. 

Based on a cost analysis performed at the U.S. Department of Energy s Hanford site, in Richland, Washington, PSVE was found to be a cost-effective method for remediation of soils containing lower concentrations of volatile contaminants. PSVE used on wells that average 10 standard cubic feet per minute (scfm) airflow rates was found to be more cost-effective than active soil vapor extraction for concentrations below 500 parts per million (ppm) by volume of carbon tetrachloride. For wells that average 5 scfm, PSVE is more cost effective below 100 ppm (D14489S, p. iii). For further details of this analysis, refer to Table 1. 

Many applications for this technology utilize wells that already exist from previous soil vapor extraction operations. In these cases, costs are further reduced because the need to drill additional wells is negated. 

According to the vendor, cost for a 400 x 30 x 3-ft aeration curtain with soil vapor extraction of off-gases is approximately 1.2 million. In general, costs are very site specific (personal communication Paul Bitter, Radian International, L.L.C., 1997). 

In 1999, HRC was used with other treatment technologies at a brownfield site in Aurora, Colorado. An in situ air sparge/soil vapor extraction system was first used at the site to treat TCE contamination however, additional measures were needed to prevent the migration of PCE off-site. After an unsuccessful application of zero-valent iron injection, 240 lb of HRC were injected at five locations by direct-push methods. Total project costs were 110,000, which... 

A cost comparison between ORC, pump and treat, and air sparging with soil vapor extraction (SVE) is presented in Table 1. The costs given are for a site in Oklahoma with a plume width of 60 ft, a treatment area of 9146 ft and a treatment thickness of 11 ft. The peak BTEX (benzene, toluene, ethylbenzene, and xylenes) load was 25 parts per million (D13823I D14008Z). 

An example of S.A.V.E. system costs comes from a remediation project conducted in Silver Springs, Nevada, between 1994 and 1995. Installation of the S.A.V.E. system at the site, including eight monitoring and soil vapor extraction wells, cost 35,000. A S.A.V.E. 11 unit was purchased for 72,000, and its direct operating costs over 10,182 hours of operation were 29,000. 

Cost effective compared to current remediation technologies such as steam injection, bioventing, soil vapor extraction (SVE), and pump-and-treat methods. 

The Barometrically Enhanced Remediation Technology (BERT ) removes and recovers volatile organic contaminants from soil by enhancing the natural air exchange that occurs in soil as a response to changes in atmospheric pressure. This process is sometimes referred to as barometric pumping or passive soil vapor extraction. The process is a low-cost complement to conventional active-extraction methods because investment and maintenance costs are low and no power is needed. The passive process is better suited than conventional methods for certain problems. 

DOE also compared cleanup costs and times for DUS and conventional groundwater pump and treat with soil vapor extraction and soil excavation (D168698, p.l2). Table 1 summarizes the results of this comparison. 

A soil vapor extraction (SVE) system, which included the Terra Vac DVE technology, was used to clean up the Tyson s Dump Superfund site in Upper Merion Township, Pennsylvania. Total remediation costs at this site were 39.9 million to treat 30,000 yd of soil, or l,330/yd of soil treated. These costs included construction, operation, and maintenance expenses. The U.S. Environmental Protection Agency (EPA) notes that technology costs at this site may be high when compared to other SVE applications because of enhancements made to the system during operation (D18517V, p. 255). 

A DDC system was nsed to treat petrolenm hydrocarbons at Keesler Air Force Base in Biloxi, Mississippi. One DDC well and 1 soil vapor extraction (SVE) well were installed for the pilot stndy at the site, and 32 DDC weUs and 6 SVE wells were installed for the fnll-scale application. Total costs were 360,000, inclnding 100,000 for the pilot stndy (D22635H, p. 5). 

In situ thermal treatment — In situ thermal treatment allows pollutants to be treated without being excavated and transported. Thermal treatment requires a shorter clean-up time however, high costs are usually associated with the amount of energy and equipment required. For example, enhanced soil vapor extraction is usually an energy-intensive process. 

The physical and chemical removal of oil spills can often be successful, but mostly expensive. We can mention soil incineration, soil vapor extraction and thermal desorption methods, all of which are very expensive and destructive (Hyman, 1999). Besides that the primary goal of remediation is the preservation of public health and safety, it is necessary to carry out the remediation in a cost-effective manner to keep the owner/operator of the site in business and out of bankruptcy court. In this case, biodegradation by natural population of microorganisms or bioremediation, is often considered as the primary mechanism because of its low cost and effectiveness in ambient conditions. The scientific basis is biochemical conversion of organic chemicals by bacteria and fungus in natural processes. 

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