Application Study 0121x Former UST Site – Soil Mixing – Low Level

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Courtesy of EN Rx

SITE OVERVIEW

Former UST Site, St. John’s, Az AZ DEQ Site Number: 0-000772

CONTAMINATION

Gasoline contaminants in clayey soil

HISTORY

Leaking Underground Storage Tank (UST) had contaminated an area at the refueling location for the City maintenance yard. SVE was applied which worked in sandy zone but provided no reduction for clays and sandy clays. Chem Ox was applied to clayey zone but was minimally successfully, making a soil mixing project economical more economical than three ISCO applications.

PRE-CLEAN DATA

  •  Concentrations above the RSRLs in the soil from 10 to 20 ft bls. Sandy clays were stiff from 14 to 20 ft bls.

  •  Two samples were collected from a relatively small foot print 15ft by 20 ft, samples were collected from the vertical center of impact and worst location 15 ft bls. Approximately 100 cy of soil was impacted.

REMEDIATION APPLICATION SPECIFICS

Remediation used a technique of soil inversion where the overburden is removed and placed aside. The

contaminated soil is removed and placed aside. The overburden is replaced in the open excavation to bring it up to a general workable depth. The contaminated soil is reinserted into the excavation in lifts while EN Rx soil conditioner is applied and mixed, then proprietary EN Rx reagents are applied and mixed. This technique, mastered by our staff and consultants, minimized space needed, provided good control of the operation limiting the need for berms or wind control, and keep the soil contamination at the same location of initial impact minimizing possible cross contamination. At this site the treatment took one day to complete.

POST-CLEAN UP DATA

  •  Although exact location of pre sampled soil is unknown after the excavation process, three samples confirm the reduction to very low concentrations far below the RSRL standard for Benzene.

  •  Mass reduced can be calculated as 99.7%. and closed the site.

Case Study 0121X: Treatment Results

Date

Benzene

Toluene

Ethyl benzene

Xylenes

Pre Sample 1

12/15/2009

2.5

7.5

1.4

8.0

Pre Sample 2

12/15/2009

1.1

5.9

3.7

19

3/23/10

EN Rx Treatment

Post Sample 1

4/14/2010

Post Sample 2

4/14/2010

0.24

Post Sample 3

4/14/2010

RSRLs

0.65

650

400

270

All results in mg/L unless otherwise specified RSRL = Residential Soil Remediation Level

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