Groundwater Policies & Non-Coal Surface Pit Mining for the Arbuckle-Simpson Aquifer

As a federally and state-designated sensitive sole-source groundwater basin, the Arbuckle-Simpson Aquifer (ASA) is the subject of major concern regarding overdraft and the impacts of potential contamination and has been given several legislative protections to address these concerns. In 2003, Oklahoma passed Senate Bill (SB) 288, which placed a ban on new permits and the sale of water outside of counties overlying the aquifer and required the completion of a hydrologic study of the aquifer to determine the Maximum Annual Yield (MAY) and Equal Proportionate Share (EPS) necessary to prevent reduction of the natural flow of springs and streams emanating from the aquifer.

While non-domestic groundwater use in the ASA requires a groundwater permit, non-coal surface pit mining, specifically sand and aggregate pit mining was allowed as an exception. These operations dig large pits, potentially hundreds of feet into the ground, to mine their product, and with the water table relatively close to the surface, these pits inevitably experience groundwater seepage. To continue mining, the pit water, composed of a mixture of groundwater seepage and surface runoff, must be removed and disposed of. Sand and aggregate operations are distributed throughout the aquifer basin, with active mines concentrated in several portions of the ASA (Figure 1). Understanding the location and extent of these operations is important because groundwater seepage into mining pits can result in substantial groundwater withdrawals that may influence local hydrologic conditions.  Despite the potentially large volumes of groundwater withdrawn from the aquifer, no groundwater permit or tracking of this water was required until the passage of SB 597 in 2011. This legislation sets additional rules specifically for sand and aggregate pit mining operations overlying the ASA, requiring these mines to track and report the volumes and disposition of groundwater seeping into their mining pits. The table below explains the differing requirements for the two categories as provided in the legislation. Currently, all permitted sand and aggregate pit mines operating over the ASA fall under the exempt category.

Exempt Mines	Non-Exempt Mines
Exemption applies to mines that existed or submitted mining applications prior to August 1, 2011.	Legislation applies to mines that submitted mining applications after August 1, 2011.
Not required to obtain a groundwater permit to remove mining pit water.	Required to obtain a groundwater permit to remove mining pit water.
No water management and conservation plan required unless consumptive use exceeds their EPS and they plan to claim surface flow or groundwater augmentation credits to offset the excess or to obtain additional acreage to increase EPS.	Required to develop a site-specific water management and conservation plan for augmentation of surface flow or groundwater in the event of consumptive use greater than their EPS.
Must submit quarterly and annual reports to the Oklahoma Water Resources Board that include information on surface water runoff and groundwater withdrawn from the pit, groundwater recharge or surface water augmentation, and consumptive use of the water.

Figure 1

Figure 1 showcases the ASA boundary and the footprint of the current existing mines within the ASA boundary.

Local citizen groups and tribal nations are concerned regarding the effectiveness of these regulations in protecting the ASA. Many of the SB 597 water reports from the mines indicate that most water withdrawn from the pit is used to augment surface flows and groundwater, with very little being reported as consumptive use. This reporting framework can produce results that are difficult to interpret. As shown in Figure 2, several mines report net water use values that are substantially reduced—or even negative—after accounting for augmentation credits. These reported values contrast with the actual volumes of groundwater being removed from mining pits and raise questions regarding whether the current reporting structure adequately reflects impacts to the aquifer.

Figure 2

Figure 2 showcases the total water used in 2024 by mining companies and by communities that the Oka' Institute works with that reside within the boundaries of the ASA.

The accuracy of these reports, specifically the groundwater augmentation claims, is a concern due to the complexity of the hydrology of the ASA and the difficulty in proving how much of that augmented water realistically enters and replaces the groundwater seeping into the pit mine. Figure 3 provides additional context by displaying the total groundwater pumped from mining pits during 2024. Unlike reported net water use values, these data illustrate the actual volume of groundwater removed from the aquifer system. Because groundwater must continually seep into pits to replace water that has been pumped out, these withdrawals may alter local groundwater conditions even when reported consumptive use is low or offset through augmentation credits.

Figure 3

Figure 3 showcases the total water pumped by the ASA mining companies in 2024.

Another concern is the lack of standards for the quarterly and annual water reports. While SB 597 provides an optional report form and formulas for mines to use, the quarterly and annual reports submitted by the mines are often done so in an alternative format and can be difficult to understand. Some mines provide volumes in acre-feet, while others use gallons; some claim no groundwater enters their pits despite steady production throughout the years; certain volumes are provided as negative amounts without clear indication of the intended meaning, as seen in Figure 2; and individual quarterly volumes in a given category do not always add up to the reported annual volume. Without clear and consistent standards, it is difficult to assume accuracy, compare reports across years, and apply the data to the overall picture of groundwater withdrawals and recharge of the ASA.

Research being conducted in cooperation with the Oka' Institute is examining how Oklahoma's groundwater regulations for non-coal surface pit mines have developed over time and where gaps may exist in the current framework. This work compares the regulatory requirements applied to mining operations with those imposed on other major groundwater users within the ASA. By identifying potential regulatory asymmetries and evaluating the effectiveness of current reporting requirements, the research seeks to inform future discussions on groundwater management and the long-term protection of one of Oklahoma's most important and vulnerable aquifer systems.