Pierre VOC Ground Water Investigation and MTBE Remediation Pilot Study

Transcription

1 Pierre VOC Ground Water Investigation and MTBE Remediation Pilot Study Joint Meeting of 2007 Eastern South Dakota Water Conference and the 52 nd Annual Midwest Ground Water Conference October 30, 2007

2 Why is DENR Conducting a Groundwater VOC Investigation in Pierre? Impacted City Wells (Data Provided by the City) Known PCE and TCE impacts at City Well #8 since February 1999 PCE Range 2/99 3/05. ND 0.82 ppb TCE Range 2/99 3/05. ND ppb Know PCE and TCE impacts at City Well #4 since March 2005 (note: six year sampling waiver) PCE 3.49 ppb TCE ppb In June 2005 the City removed this well from service.

3 DENR Responds to the March 2005 City Well Data DENR DENR in conjunction with the City of Pierre decides to conduct a VOC investigation in the vicinity of City wells #4 and #8. American American Engineering Testing, Inc. (AET) retained to conduct the investigation.

4 Study Area

5 Pierre VOC Investigation Phase I Review Review area for potential VOC sources. Collect Collect and review City of Pierre well construction information. Choose Choose well locations and begin well installation and sampling.

6 Potential Source Areas Current or Former Gas Station, Fuel Storage Facility, or Known VOC Impacts Auto Repair Dry Cleaner Newspaper

7 Phase I Monitor Well Locations

8 Phase I Monitoring Well Information All wells constructed to approximately 60 feet deep and screened in the bottom 20 feet of the well. This was done to mimic City of Pierre well design. During installation contaminated soil detected in MW-3 3 at the foot range. Samples sent to the lab for confirmation. Wells were sampled for the VOC short list method First sample round conducted on May 26, 2005

9 Phase I Sampling Results Nine Wells Sample 7 MW and 2 City wells Lab analysis confirms a detection of PCE in the soil in MW mg/kg. PCE detected in 4 wells (2 MW and 2 City Wells). Range 0.14 ppb 35 ppb TCE detected in 3 wells (1 MW and 2 City Wells). Range 0.39 ppb 0.92 ppb Cis-1,2 Dichloroethene detected in 2 wells (1 MW and 1 City Well). Range 0.39 ppb 1.3 ppb MTBE detected in 8 wells (6 MW and 2 City Wells). Range 0.37 ppb to 36 ppb. 1,2-Dichloroethane detected in 5 wells (4 MW and 1 City Well). Range 0.31 ppb to 4.1 ppb

10 Phase I PCE Concentrations and GW Elevations

11 Phase I MTBE Concentrations and GW Elevations

12 Pierre VOC Investigation Phase II Using Using phase I data re-evaluate evaluate plume and close data gaps with additional wells. Include Include well locations chosen specifically to narrow down the potential PCE source area. Eight Eight additional deep monitoring wells installed.

13 Phase II Monitor Well Locations

14 Phase II Monitoring Well Information All wells constructed to approximately 60 feet deep and screened in the bottom 20 feet of the well. This was done to mimic City of Pierre well design. During installation contaminated soil detected in MW-13 at the foot range. Samples sent to the lab for confirmation. Wells were sampled for the VOC short list method Second sample round collected on August 18, 2005.

15 Phase II Sampling Results Nineteen Wells Sample 15 MW and 4 City wells Lab analysis confirms a detection of PCE in the soil in MW mg/kg. PCE detected in 6 wells (4 MW and 2 City Wells). Range 0.36 ppb 20 ppb TCE detected in 2 wells (Both City Wells). Range 0.65 ppb 0.75 ppb Cis-1,2 Dichloroethene detected in 1 monitor well at 0.52 ppb MTBE detected in 12 wells (11 MW and 1 City Well). Range 0.6 ppb to 48 ppb. 1,2-Dichloroethane detected in 9 wells (8 MW and 1 City Well). Range 0.35 ppb to 3.5 ppb.

16 Phase II PCE Concentrations and GW Elevations

17 Phase II MTBE Concentrations and GW Elevations

18 Pierre VOC Investigation Phase III PCE At this point the project was split into two investigations. One, PCE and other chlorinated solvents. Two, MTBE. Two Two additional, monthly sampling rounds planned for the wells associated with the PCE plume. Begin Begin developing a MTBE site characterization plan.

19 Phase III PCE Monitoring Well Information Only Only 13 wells samples. Focused only on the PCE plume Wells Wells were sampled for the VOC short list method Third Third sample round collected on September 29, 2005.

20 Phase III PCE Sampling Results Thirteen Wells Sample 10 MW and 3 City wells PCE detected in 5 wells (3 MW and 2 City Wells). Range 0.2 ppb 5.5 ppb TCE detected in 2 wells (Both City Wells). Range 0.24 ppb 0.37 ppb Cis-1,2 Dichloroethene not detected this round. MTBE detected in 10 wells (9 MW and 1 City Well). Range 1.3 ppb to 34 ppb. 1,2-Dichloroethane detected in 7 wells (All MW). Range 0.42 ppb to 4.2 ppb.

21 Phase III PCE Concentrations and GW Elevations

22 Phase III MTBE Concentrations and GW Elevations

23 Pierre VOC Investigation Phase IV PCE Second Second of two additional, monthly sampling rounds planned for the wells associated with the PCE plume. Only Only 13 wells samples. Focused only on the PCE plume Wells Wells were sampled for the VOC short list method Third Third sample round collected on October 28, 2005.

24 Phase IV PCE Sampling Results Thirteen Wells Sample 10 MW and 3 City wells PCE detected in 6 wells (5 MW and 1 City Well). Range 0.27 ppb 7.4 ppb TCE detected in 1 City Well at 0.69 ppb. Cis-1,2 Dichloroethene not detected this round. MTBE detected in 11 wells (9 MW and 2 City Well). Range 0.37 ppb to 53 ppb. 1,2-Dichloroethane detected in 2 monitor wells. Range 1 ppb to 2.3 ppb.

25 Phase IV PCE Concentrations and GW Elevations

26 Phase IV MTBE Concentrations and GW Elevations

27 PCE Source Investigation Worked Worked with the property owner and gained access to conducted a direct push study and delineate the soil and shallow groundwater contamination. Between Between January 16 and January 19, 2006 AET advanced 18 direct push borings in and around the suspected source area. A A total of 31 soil samples and 13 water samples were collected and sent for laboratory analysis.

28 PCE Source Investigation: Site Map

29 PCE Source Investigation: Results Area of significant soil contamination PCE range mg/kg 2200 Groundwater PCE concentration (ppb)

30 PCE Investigation: The Next Step Corrective action is necessary. In April 2006 the department named the owner of the dry cleaner as the responsible party and required him to initiate corrective action. To date, the responsible party has installed additional shallow monitoring wells and a source area SVE system. Plans are underway for a full-scale remediation system to address the remaining soil and ground water contamination.

31 Pierre VOC Investigation: MTBE Site Characterization Plan Step Step 1: Review all available historic MTBE data to determine possible extent of MTBE contaminated groundwater. Prepare Prepare a map showing locations of known historic MTBE detects. Prepare Prepare a map showing locations of known historic MTBE detects greater than 20 ppb.

32 Historic MTBE Detects

33 Historic MTBE Detects Greater than 20 PPB

34 MTBE Site Characterization Plan Goal: Define the nature and extent of MTBE contamination. Identify possible source areas AET installed 5 additional shallow monitoring wells and used 29 existing wells for a total of 34 wells in the monitoring network. Includes 8 City of Pierre water supply wells. Conduct four quarterly sampling events. Well installation complete and the first sampling round collected in January 2006.

35 MTBE Monitor Well Locations

36 MTBE Investigation: January 2006 Results

37 MTBE Investigation: July 2006 Results

38 MTBE Investigation: October 2006 Results

39 MTBE Investigation Conclusions Widespread MTBE contamination in both deep and shallow monitoring wells One, One, primary MTBE source area Several Several secondary MTBE source areas Low Low levels of MTBE contamination in as many as four city of Pierre drinking water wells

40 What to Do about the MTBE Contamination? Because Because of the wide spread MTBE contamination and multiple source areas the department decided to use LUST Trust money to address the problem. Two Two major tasks Continue monitoring plume behavior and early warning system for city wells Conduct a MTBE remediation pilot study

41 MTBE Remediation Pilot Study Purpose: Purpose: To determine if Kerfoot Technologies C-C Sparger Ozone Oxidation System will effectively reduce MTBE source area concentrations below target levels. To determine if Kerfoot Technologies C-C Sparger Ozone Oxidation System will be effective as full-scale treatment system for the MTBE contamination.

42 MTBE Remediation Pilot Study Remediation Technology Due to the limitations of using AS/SVE on MTBE contamination our consultant recommended Kerfoot Technologies C-SpargerC Sparger Ozone Oxidation System Unlike AS which induces a MTBE phase change for contaminant removal via SVE the C-Sparger injects an oxygen/ozone mixture through Spargepoints into the groundwater destroying the MTBE in-situ.

43 MTBE Remediation Pilot Study Remediation Technology Benefits In-situ remediation Ozone breaks down into oxygen oxygen levels in the aquifer increase enhancing bioremediation Flexibility The The system is installed into a small trailer that can easily be moved from site to site The The system can operate as many as 16 Spargepoints

44 MTBE Remediation Pilot Study Site Photos

45 MTBE Remediation Pilot Study Site Photos

46 MTBE Remediation Pilot Study Test Areas Chose Chose to test the remediation system at two different areas within the MTBE plume Area 1 Abandoned gas station Not Not a source area (low starting concentrations) No No infrastructure Scheduled for redevelopment Area 2 Active gas station Source Source area (high starting concentrations both MTBE and BETX) Active Active station

47 MTBE Remediation Pilot Study Test Area Map Area 1 Area 2

48 MTBE Remediation Pilot Study Area 1 Site Layout

49 MTBE Remediation Pilot Study Area 1 MTBE Results Area 1 MTBE Results 120 MTBE (ppb) H-1 HMP-1 HMP /23/07 03/23/07 04/23/07 05/23/07 06/23/07 07/23/07 08/23/07

50 MTBE Remediation Pilot Study Area 1 Dissolved Oxygen Results Area 1 Dissolved Oxygen Results 14 Dissolved Oxygen (ppm) H-1 HMP-1 HMP-2 03/14/ /14/ /14/ /14/ /14/ /14/2007

51 MTBE Remediation Pilot Study Area 2 Site Layout

52 MTBE Remediation Pilot Study Area 2 MTBE Results Area 2 MTBE Results MW-17 MP-1 MP-2 MP-3 MTBE (ppb) /12/ /19/ /26/ /02/ /09/ /16/ /23/ /30/ /06/ /13/ /20/ /27/2007

53 MTBE Remediation Pilot Study Area 2 Benzene Results Area 2 Benzene Results MW-17 MP-1 MP-2 MP-3 Benzene (ppb) /12/ /19/ /26/ /02/ /09/ /16/ /23/ /30/ /06/ /13/ /20/ /27/2007

54 MTBE Remediation Pilot Study Area 2 Dissolved Oxygen Results Area 2 Dissolved Oxygen Results MTBE (ppb) MW-17 MP-1 MP-2 MP /12/ /26/ /09/ /23/ /06/ /20/ /04/2007

55 Conclusion PCE: PCE: RP lead. Source area SVE system currently operating. Plans are underway for a full-scale remediation system to address the remaining soil and ground water contamination MTBE: MTBE: Complete pilot study at Area 2. Compile and evaluate results and begin development of a full-scale remediation system.