Northeastern Plant

September 2019

Public Service Company of Oklahoma (PSO) continued its groundwater monitoring activities around Northeastern 3 & 4 Plant’s coal ash storage sites. Data was analyzed relative to EPA groundwater protection standards.

Analysis of this data by an independent third party indicates that the bottom ash pond potentially is causing the level of lithium in groundwater within the plant site to rise above EPA standards. We did not find impacts from the landfill.

PSO will cease operating Northeastern 3 & 4 in 2026. At that time, we will stop placing material in the pond and close the site. Meanwhile, we will begin taking steps to mitigate groundwater impacts. We are proactively meeting with plant neighbors and community leaders to answer questions and discuss next steps.

March 2018

Public Service Company of Oklahoma (PSO) has completed the first steps in the new groundwater monitoring program under this rule.

PSO took a series of groundwater samples at the boundaries of both ash storage sites. We took some samples before the groundwater passed beneath the ash storage sites. (The reports refer to this as up-gradient.) We took other samples after it passed beneath the sites (down-gradient). We used the data to establish baseline levels for 21 different substances in the groundwater. Moving forward, we will use these baselines to help determine if our ash storage sites are impacting the groundwater.

It is important to remember that variations in the level of these substances in groundwater are natural and occur for many reasons.

The initial data at Northeastern Plant show potential groundwater impacts very close to our bottom ash storage site. This led us to expand our groundwater monitoring program at Northeastern 3 & 4 to look at 21 different substances in the groundwater at the plant.

We are working to understand what the numbers mean. We will do additional monitoring and analysis to determine if there are groundwater impacts from our storage sites farther from the immediate area.

We proactively reached out and met with plant neighbors and community leaders to answer questions about the data collected so far and to discuss next steps.

Independent third parties completed Alternate Source Reviews for the landfill and bottom ash pond sites at Northeastern Plant. The reviews consider other factors that could impact sampling results as the groundwater passes the CCR storage sites.

We completed a successful Alternate Source Review for groundwater impacts at Northeastern Plant’s landfill site. The plant will continue sampling groundwater at the landfill to determine any future need for additional monitoring.

An alternate source for groundwater impacts was not found for the bottom ash pond.

November 2018

The CCR rule established location restrictions for coal ash storage sites. It requires that storage site locations be evaluated regarding proximity to groundwater aquifers, wetlands, fault areas, seismic zones and unstable areas (example: presence of quicksand).

AEP and PSO recently completed the required review of location restrictions for Northeastern Plant’s CCR storage sites. This review found:

• The Northeastern bottom ash pond is separated from the uppermost aquifer by less than the five feet specified by the rule. It does meet the other four restrictions.

• The Northeastern landfill meets all location restrictions.

• PSO will continue to test water from all of these wells in the groundwater monitoring program twice each year.

• Unit 4 was closed in 2016. Northeastern 3 & 4 Plant has a complete closure date of no later than 2026. At that time, we will stop putting material into the bottom ash pond and will begin closure activities.

• PSO will develop a mitigation plan to address the groundwater impacts. We will consider public input before making a final decision as to what measures we will take to mitigate groundwater impacts.