2023 – The TWDB publishes a guidance document to amend BGPZs.

Staff Report & Agenda Item Details

7. 2023 – The TWDB publishes a guidance document to amend BGPZs. 5 Figure 1. Brackish groundwater production zones (BGPZs) designated in the Rustler Aquifer on October 20, 2016 (from Mancha (2016)). 6 2.02 REQUESTING A ZONE AMENDMENT FROM THE TWDB To date, there is no publicly available information regarding an entity submitting a formal amendment request for a BGPZ. Consequently, the amendment request discussed in this report will likely represent the first submittal of its kind to the TWDB. The TWDB’s 2023 Guidance Document for Amending Brackish Groundwater Production Zones establishes the framework, procedural requirements, and expectations for submitting and evaluating amendment requests. This section provides a high-level summary of key elements outlined in that guidance. The guidance document specifies several technical and procedural requirements for requesting a zone amendment, while also providing for some flexibility (TWDB, 2023). A BGPZ may be amended if new data is available that, if known at the time or the original designation, would have affected the zone’s delineation (Table 1). Although the amendment criteria are prescriptive, the types of supporting data that may justify an amendment are intentionally broad to accommodate a range of hydrogeologic and technical conditions. The guidance document states that the data must support the reason for the amendment, but that it may include well data that was unavailable to the TWDB at the time of designation, new modeling data that show hydrogeologic barriers are insufficient, or that improved modeling that shows BGPZ pumping volumes are not supported over 30 or 50 years, etc. The TWDB’s guidance further stipulates that the request for an amendment must come from a GCD. For BGPZs that expand across multiple GCDs, the TWDB (through their guidance document) requires that all affected GCDs reach a consensus on amendment request. The guidance document states that “written resolution adopted by each of the affected groundwater conservation districts supporting the requested amendment” and “evidence of the proposed zone amendment discussion with each affected district in a public forum (copies of meeting agenda, minutes, and/or notices).” 7 3.00 METHODOLOGY FNI conducted a comprehensive review of well records within the MPGCD to determine whether any qualifying wells were omitted in the 2016 zone designation. Primary data sources included the submitted driller’s report (SDR) database (TWDB, 2025b), the groundwater database (GWDB; TWDB, 2025b), and the MPGCD registered well database (MPGCD, 2025). We supplemented these records with Bulletin 6106 (B6106; Armstrong and McMillon, 1961), the Texas Commission on Environmental Quality (TCEQ) plotted well database (TCEQ, 2025), and the Texas Railroad Commission well database (TxRRC, 2025). For wells drilled to depths sufficient enough to be completed in the Rustler, we reviewed the MPGCD registered well database to determine if (1) well use was associated with a qualified use type (domestic, municipal, or agricultural) and (2) whether the well predated the 2016 zone designation. Additionally, Mr. Ty Edwards indicated that wells initially drilled to support oil and gas drilling operations are commonly converted to a livestock water supply well after drilling operations cease (Edwards, 2025). For well records in the MPGCD database listed with a well depth of “0” feet (the MPGCD code for “unknown”), we cross-referenced the SDR, GWDB, and B6106 to determine whether any of these wells were completed in the Rustler Aquifer. Additionally, we reviewed the TCEQ scanned well reports to identify older wells at predate the modern SDR database. In addition, the TxRRC database was also evaluated to determine whether each potential Rustler well was initially drilled for water supply or oil and gas exploration purposes. In parallel with the well record evaluation, we also performed a targeted literat