Regional Downgradient Investigation

Upper Left: February 2017 AECOM field team sampling Las Vegas Wash. Upper Middle: February 2017 AECOM field team canoeing to sample location in Las Vegas Wash. Upper Right: January 2017 AECOM field team with stream gauging station. Lower Left: February 2017 AECOM field team measuring water quality parameters in Las Vegas Wash. Lower Middle: February 2017 AECOM biologists during biological survey. Lower Right: May 2017 AECOM field team installing transducer inside flush mount groundwater well. — **Upper Left**: February 2017 AECOM field team sampling Las Vegas Wash. **Upper Middle**: February 2017 AECOM field team canoeing to sample location in Las Vegas Wash. **Upper Right**: January 2017 AECOM field team with stream gauging station. **Lower Left**: February 2017 AECOM field team measuring water quality parameters in Las Vegas Wash. **Lower Middle**: February 2017 AECOM biologists during biological survey. **Lower Right**: May 2017 AECOM field team installing transducer inside flush mount groundwater well.

Background

Following initiation of Phase I of NERT’s Remedial Investigation, NDEP took the lead role on a separate parallel investigation, implemented to determine if perchlorate and chlorate had migrated from the NERT site and impacted groundwater quality near the Las Vegas Wash. To that end, NDEP hired AECOM with the goal of identifying the extent of perchlorate and chlorate impacts along the Las Vegas Wash and areas of perchlorate flux from groundwater to the Las Vegas Wash. The Las Vegas Wash is the central physical feature that defines the downgradient area. The objectives of the downgradient investigation include:

Characterize magnitude and extent of groundwater impacts from the former Kerr-McGee/Tronox site to the Las Vegas Wash. (This is the big picture view point.)
Evaluate pathways allowing perchlorate to move from groundwater into the Las Vegas Wash. (Where is the perchlorate coming into the Wash.)
Quantify perchlorate flux into Las Vegas Wash. (How much perchlorate is coming into the Wash.)
Complete downgradient investigation such that the results can be incorporated into NERT’s Remedial Investigation. (Keep both investigation parallel and not sequential.)

Current Status

Downgradient Investigation Field Work

AECOM started its field work in the downgradient investigation in Spring 2016. Preliminary results confirm the presence of perchlorate in shallow groundwater along the Las Vegas Wash. To date, two Technical Memorandums have been finalized and will become part of NERT’s Remedial Investigation report. Field work to date includes:

One round of groundwater samples have been obtained, analyzed, and reported.
One round of surface water and seep grab samples have been obtained, analyzed, and reported.
Geophysical pilot testing of various geophysical methods has been completed to assess the ability to remotely sense the changes in geology with the subsurface. Field work was conducted during Winter 2016-2017 and a report is pending.
Installation of ten temporary surface water gages and data recorders.

The next steps for AECOM are filling data gaps that were found after examining existing and recently collected data. Field work for this part of the investigation should begin in 2017.

Dewatering Ion Exchange System

NERT began construction of an ion exchange treatment system near the Las Vegas Wash in the third quarter of 2017. In January 2018, the system began treating shallow groundwater associated with the construction of the Southern Nevada Water Authority's final two erosion control structures along the Las Vegas Wash. Dewatering and treatment of the dewatered water is expected to continue until September 2018. More than 4,000 pounds of perchlorate were removed between January and May 2018.

Aerial photograph of the weir dewatering ion exchange treatment plant. — Aerial view of the weir dewatering ion exchange treatment plant.

Downloadable Documents

2019 Community Mailing and Fact Sheet - English (PDF, 3.37 MB)

2019 Community Mailing and Fact Sheet - Spanish (PDF, 3.13 MB)

Groundwater Data Gap Investigation Technical Memorandum - October 2018 (16.7 MB)

Surface Water Investigation Technical Memorandum - October 2017 (PDF, 12.7 MB)*

Geophysical Pilot Test Technical Memorandum - September 2017 (PDF, 17.9 MB)

Groundwater Sampling Technical Memorandum - July 2017 (PDF, 4.14 MB)*

September 2017 Notice for Construction Activity / Weir Dewatering Door Hanger (PDF, 169 KB)

2017 NERT Community Interview Meeting Presentation (PDF, 2.08 MB)

NERT Fact Sheet

Downgradient Investigation - Frequently Asked Questions

Surface Water and Seep Grab Sampling Technical Memorandum - November 2016 (PDF, 23.9 MB)*

Visit the Nert Document Repository to download additional documents.

*Appendices have been omitted from this document. For a copy of the full report, please contact Carlton Parker.

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Disclaimer: The Nevada Division of Environmental Protection does not offer any guarantee, express or implied, regarding the accuracy, validity, or completeness of the information presented by a third-party. Furthermore, the views or opinions expressed by a third-party do not reflect the views or opinions of the Division.

Additional Information

For more information, please contact Carlton Parker at jcarltonparker [at] ndep.nv.gov or 702-668-3908.