Environmental Protection

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1 FLORIDA DEPARTMENT O F Environmental Protection Northwest District 160 W. Government Street, Suite 308 Pensacola, FL Ron DeSantis Governor Jeanette Nuñez Lt. Governor Noah Valenstein Secretary April 10, 2019 mckbilly@co.walton.fl.us Mr. Billy McKee Walton County Solid Waste Manager 97 Montgomery Circle DeFuniak Springs, Florida Dear Mr. McKee: The Department has reviewed the December 2018 Semi-Annual Remediation Report, prepared and submitted by Dewberry Engineers, Inc., for the Walton County Central Landfill (FDEP ID Nos ; COM_326) located north of DeFuniak Springs, Walton County, Florida. The semiannual report is dated and was received on March 1, The report was due by December 1, However, time extensions were granted on October 17 and December 20, 2018 and January 31, 2019 due to significant damage from Hurricane Michael to the contracted laboratory. The adjusted due date was February 19, An original PE certification page was received on February 26, Missing field sampling logs and a table were requested on April 5, 2019 and received on April 9, Upon review, the report is generally complete and acceptable. Please review the bulleted items at the end of the review memorandum for additional concerns noted during our review. We concur with your consultant s recommendation to continue system operation. While it has been demonstrated that the treatment system is effective at removing iron from captured groundwater, it has not been demonstrated that the system has reduced iron concentrations in the downgradient seep channel. The Remedial Action Plan Approval Order needs to be modified to include the seep project sampling locations. For a more detailed discussion of our findings, please refer to the enclosed April 9, 2019 memorandum. Unless notified otherwise, we look forward to receiving the First 2019 Semi-Annual Remediation Report by June 1, If you have any questions or need additional information, please contact Suzanne Patrick by telephone at or by at suzanne.patrick@dep.state.fl.us.

2 Mr. Billy McKee Page 2 Sincerely, Bradley T. Hartshorn Environmental Administrator Waste Cleanup Section BTH/sp Enclosure: April 9, 2019 Memorandum c: Cliff Knauer, P.E., Dewberry Engineering, Inc., cknauer@dewberry.com Nicolas Howard, Dewberry Engineering, Inc., nhoward@dewberry.com Elizabeth Kennelly, Jones Edmonds & Assoc., ekennelley@jonesedmunds.com Troy Hayes, P.G., Jones Edmonds & Assoc., thayes@jonesedmunds.com

3 FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION MEMORANDUM TO: Bradley T. Hartshorn FROM: SUBJECT: Suzanne Patrick December 2018 Semi-Annual Remediation Report Walton County Central Landfill, Defuniak Springs, Walton County, Florida WACS ID#: 14755; COMET Site ID#: COM_326 DATE: April 9, 2019 I have reviewed the subject reports, prepared and submitted by Dewberry Engineers, Inc. (Dewberry), on behalf of Walton County. The semi-annual report is dated and was received on March 1, The report was due by December 1, However, time extensions were granted on October 17 and December 20, 2018 and January 31, 2019 due to significant damage from Hurricane Michael to the contracted laboratory. The adjusted due date was February 19, An original PE certification page was received on February 26, The report covers the period from June 1, 2018 through December 31, I concur with Dewberry s conclusion that continued operation of the remediation system is prudent. While it has been demonstrated that the treatment system is effective at removing iron from captured groundwater, it has not been demonstrated that the system has reduced iron concentrations in the downgradient seep channel. The Remedial Action Plan Approval Order (RAPAO) needs to be modified to include the seep project sampling locations. Other issues noted during my review are bulleted at the end of this memorandum. Semi-Annual Remediation Report The RAPAO was issued on January 15, 2002, and last modified on July 24, It includes operation of five recovery wells, a lined aeration basin for recovered groundwater, and six infiltration basins for the aeration basin effluent. Two of the aeration basins on the east side are being used to capture storm water to prevent washouts of the Seep-1 Pilot Project area and as infiltration basins for the seep project when the percolation pond is down for maintenance. The RAPAO needs to be modified to include the seep project. According to Table 3-1 embedded in the text, over the 214-day reporting period, a total of approximately 29.2 million gallons of groundwater was recovered. The combined average pump rate for all five recovery wells over the reporting period was approximately 94.8 gallons per minute (gpm). The average pump rates during the reporting period for individual recovery wells ranged from 9.5 gpm at RW-3 to 31.8 gpm at RW-1. The report text indicates that monthly flow rates are being collected and system checks are being conducted. However, Table 3-1 Remediation Log was missing from the report. The table was requested on April 5, 2019 and received on April 9, It appears that monthly inspections and readings were conducted during the reporting period. Monthly system inspections and flow rate readings should continue

4 Walton County Central Landfill April 9, 2019 Memorandum Page 2 of 4 to ensure proper maintenance for optimal performance, and to prevent damage to pumps and other equipment. Water levels were measured on November 26, Groundwater is depicted as flowing toward the north, east, and south from a high at MW-24, and is consistent with historical observations. Groundwater flow in the immediate area of the South End Remediation System is toward the south and southeast. Of the wells located on the southern half of the site, groundwater elevations from April 2018 to November 2018 generally increased an average of 5.69 feet. Most of the WCA wells increased an average of 1.51 feet. The groundwater elevations at WCA-5 and WCA-7 decreased slightly. Groundwater sampling was conducted from November 27 through 28, 2018 by The Water Spigot. Sample analyses were sub-contracted by The Water Spigot due to hurricane damage at their laboratory. It appears that sampling was done in accordance with the 2009 RAP Modification Approval Order. The field sampling logs for Seep-2 through Seep-5 and MW-13 were not included in the report. The field logs were requested on April 5, 2019 and received on April 9, The following table summarizes the analytical results for the reporting period. Analytical results from the WCA wells, MW-10, MW-11, MW-13, the seeps, and the three south end surface water sampling locations are included in the table in order to evaluate the effectiveness of the remedial system. Analytical results exceeding a regulatory standard for either groundwater or surface water are in bold. Benzene Vinyl Chloride Ammonia TDS (total) (dissolved) Arsenic mg/l mg/l GW Standard MW U 0.36U I 20U 3 IV MW-11 Abandoned due to transfer station construction; to be replaced MW U ,900 64,000 7 IV WCA U 0.36U ,700 30,000 2U WCA QU 0.36QU I 20U 3 IV WCA QI 0.36QU ,100 20,000 3 IV WCA QU 0.36QU I 20U 3 IV RW QU 0.36QU NA NA NA RW-2 1.5Q 0.36QU NA NA 31,700 34,000 NA RW IQ 0.36QU NA NA 57,800 62,000 NA RW-4A 1.3Q 0.95 IQ NA NA 51,400 53,000 NA RW-5A 1.2Q 0.6 IQ NA NA 89,100 88,000 NA Pond Eff. 0.21QU 0.36QU NA NA 24,100 1,000 NA

5 Walton County Central Landfill April 9, 2019 Memorandum Page 3 of 4 Benzene Vinyl Chloride Ammonia mg/l TDS mg/l (total) (dissolved) Arsenic SW Standard None 1,000 1, Seep-2 NA NA NA NA 26,600 NA NA Seep-3 NA NA NA NA 2,910 NA NA Seep-4 NA NA NA NA 1,160 NA NA Seep-5 NA NA NA NA 1,460 NA NA SW U 0.36U U NA 3 IV SW U 0.36U U NA 3 IV SW U 0.36U U 30 1,770 NS 2 IV 1 Unionized Ammonia NA = Not Analyzed; NS = Not Sampled Many of the iron trend plots are at a scale that trends are not discernable. It is recommended that the data be plotted using a logarithmic scale. The dissolved iron concentration in the aeration pond effluent sample during this sampling event indicates that the system was effectively treating recovered groundwater. The dissolved iron concentration was above the Chapter , F.A.C. Secondary Drinking Water Standard (SDWS) but equal to the Chapter , F.A.C. Class III Fresh Surface Water Standard (FSWS) during this sampling event. It should be noted that the turbidity in the pond effluent sample on Table 3-5 should be 24.5 NTU and not 245 NTU. The iron concentration at Seep-2 continues to exceed the FSWS. at Seep-3 increased above the FSWS during this event. at Seep-4 was also above the FSWS during this event. It should be noted that the turbidity levels in the seep samples were again high. The report indicates that a sample was collected from Seep-1, however, Seep-1 no longer exists. According to Figure 3-6, the sample labeled Seep-1 was collected at the pilot study interception trench (the pilot study MS-1 sampling location). Samples were not collected from the Seep Pilot Project sampling locations during this event. These sampling locations need to be incorporated into the semi-annual sampling events. at surface water compliance location SW-8, where the seeps merge into one flow channel, has continued to exceed the FSWS even after the interception trench was installed. The iron concentration farther downstream at compliance sampling location SW-2 decreased below the FSWS after exceeding the FSWS during the previous event. As noted above, there are issues with the seep and surface water trend plots. Trends are not discernable on many of the plots due to the scale. Arsenic was in several samples was flagged with a V qualifier indicating arsenic was also reported in the associated method blank. There was no quality control information provided for

6 Walton County Central Landfill April 9, 2019 Memorandum Page 4 of 4 arsenic in any of the laboratory analytical reports. Quality control information should be included for all analytes with the laboratory analytical reports. Benzene was reported above the Chapter , F.A.C. Primary Drinking Water Standard (PDWS) in one of the south end monitor wells and three recovery wells during the reporting period. However, only the benzene concentration at RW-2 is considered an exceedance due to current rounding guidelines. Vinyl chloride was not reported above the PDWS during this sampling event. It should be noted that many of the samples analyzed for volatile organic compounds were flagged with the Q qualifier indicating that the samples were analyzed outside of hold times. Analyses should be conducted within specified sample holding times. Conclusions and Recommendations I concur with Dewberry s conclusion that continued operation of the remediation system is prudent. While it has been demonstrated that the treatment system is effective at removing iron from captured groundwater, it has not been demonstrated that the system has reduced iron concentrations in the downgradient seep channel. The RAPAO needs to be modified to include the seep project sampling locations. While it has been demonstrated that the treatment system is effective at removing iron from captured groundwater, it has not been demonstrated that the system has reduced iron concentrations in the downgradient seep channel. As noted above, iron at SW-8 has continued to exceed the FSWS. The following issues were noted: Arsenic was flagged with a V qualifier indicating that is was detected in the method blank. There was no quality control information provided for arsenic in any of the laboratory analytical reports. Quality control information should be included for all analytes with the laboratory analytical reports. Many of the volatile organics were flagged with a Q qualifier indicating that they were analyzed outside of hold times. Analyses should be conducted within specified sample holding times. The field sampling logs for Seep-2 through Seep-5 and MW-13 and Table 3-1 Remediation Log were not included in the report. The missing items were requested on April 5, 2019 and April 9, Future reports should include the field sampling logs. The trend plots should be revised. It is recommended that a logarithmic scale be used due to the wide variation in concentrations historically. The Seep Pilot Project sampling locations should be incorporated into the semi-annual sampling events. SEP