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APR 2 9 2016

April20, 2016

Alcoa Gum Springs Plant

500 East Reynolds Road Arkadelphia, AR 71923 Tel: 1 870 245 2700

Certified Mail, Return Receipt Requested

Ms. Tammie Hynum Chief Hazardous Waste Division Arkansas Department of Environmental Quality 5301 Northshore Drive North Little Rock, AR 72118-5317

Dear Ms. Hynum,

Enclosed is the ground water monitoring report of the latest semi-annual ground water monitoring event from the Reynolds Metals Company (RMC) Gum Springs landfill. This sampling event was conducted on February 9-11, 2016. Semi-annual ground water monitoring is required by Reynolds' RCRA Part B Permit Number 30H-RN1.

As you know, previous ground water monitoring has been performed as per Reynolds' Class III solid waste Permit Number 262-S. As per the February 18, 2000, letter from Dave Ann Pennington, Geologist, Solid Waste Division (SWD); SWD has defaulted solid waste ground water monitoring requirements to the hazardous waste ground water monitoring requirements as defined in Reynolds' RCRA Part B Permit Number 30H. A copy of this letter and enclosed report will be submitted to the SWD.

This sampling event' s analytical results and statistical evaluation (performed per current permit requirements) did indicate a statistically significant increase (SSI) over the background values for arsenic value at MW-16. As discussed in my March 15,2016, notification letter, RMC provided a demonstration that the regulated unit was not responsible for the increase.

No instances of potential noncompliance or noncompliance with Permit 30H- RN1-M004, which have not otherwise been reported, are known for the time period from the last report submittal to the present.

I certify under penalty of the law that this document and all attachments were prepared under my direction or supervision according to a :;ystem designed to assure that qualified personnel properly gathered and evaluated the information submitted. Based on my inquiry of the person or persons who manage the system or those persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief, true, accurate,

and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations.

Please contact Lyn Shepherd, our facility Environmental Manager, at (870) 245-2720 should you have questions or comments regarding this submittal.

Britt C. Scheer Plant Manager

Enclosure: First Half2015 Semi-Annual Groundwater Monitoring Report.

cc: ADEQ, Solid Waste Division (w/ electronic copy enclosure) Lyn Shepherd, RMC (w/ enclosure) · David Jaros, Terracon (letter only) File

C:\Users\shephdi\Documents\Part B Permit 30H\GW Monitoring Landfill\ lst Half2016\ lst Half2016 Semi-Annual GW Monitoring Report CV.doc

First Half 2016 Groundwater Monitoring ReportReynolds Metals Gum Springs Plant ■ Arkadelphia, ArkansasApril 11, 2016 ■ Terracon Project No. 35987017B

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with the flow direction determined by water levels measured during previous samplingevents.

Analytical Results

· EPA Primary Drinking Water Standard-Maximum Contaminant Levels (MCLs) were notexceeded in any of the monitoring well samples collected during the First Half 2016 samplingevent.

· The pH value for well MW-2 was below the Secondary Drinking Water Standard range forpH. The SDWS are set primarily for aesthetic reasons and are generally not consideredhealth-based criteria. Constituents covered by these regulations are those which mayadversely affect the aesthetic qualities of drinking water such as taste, odor, color, andappearance and are not federally enforced.

Statistical Evaluation

· During the First Half 2016 sampling event, arsenic and pH at MW-16 exceeded thebackground levels found in Module X Condition C.1. Subsequent statistical evaluationutilizing prediction intervals determined that arsenic at MW-16 was a statistically significantincrease (SSI).

· RMC notified ADEQ in correspondence dated March 15, 2016 that this SSI had occurred,and that in accordance with Module X Condition H.5(b) it can be demonstrated that theregulated unit was not responsible for the increase based on the following:

· Based on the analysis of leachate from the landfill, the major characteristicconstituents are fluoride, cyanide, arsenic, and high pH. Therefore, if a release fromthe regulated unit occurred, it would be assumed that other monitored parameterswould indicate statistically significant increases. However, the February 2016 resultsdid not indicate a statistically significant increase for these monitored parameters atany other of the monitoring wells up-gradient or down-gradient.

· This well is up-gradient of the regulated unit. Variations in up-gradient monitoringwell constituents are typically not indicative of potential releases from regulated units

· RMC believes that items noted above clearly indicate there is a likelihood that theindicated SSI is due to normal variations in the natural groundwater and/or due tovariability of the analytical procedure and is not an indication of a release from theregulated unit.

· Based on this demonstration, RMC proposes that no further action is necessary regarding