If you operate oil and gas assets in Texas, Statewide Rule 36 is probably familiar territory. But a regulatory update that took effect last year, combined with ongoing enforcement activity from the Texas Commission on Environmental Quality, makes this a good time to take a hard look at where your H2S management program actually stands.
Here is what has changed and what it means operationally.
This post is intended as a general regulatory overview and does not constitute legal advice. We encourage operators to work with qualified environmental counsel for guidance specific to their situation.
SWR 36 Was Just Amended
The Railroad Commission of Texas (RRC) Statewide Rule 36 (16 TAC §3.36) has governed oil, gas, and geothermal operations in hydrogen sulfide areas since 1976. A package of amendments published in the Texas Register on February 14, 2025, took effect February 18, 2025.
The changes to §3.36 itself update references to brine resources and geothermal resources within the rule. More significant from a practical standpoint is the concurrent adoption of new §3.82, which creates a regulatory framework for brine production projects. That new rule explicitly requires brine production operators to comply with §3.36 if their spent brine contains hydrogen sulfide.
Why does that matter beyond brine mining? It signals a broader direction: the RRC is actively expanding the operational categories where H2S compliance obligations formally attach. If your operations involve produced water handling, disposal wells, or fluid streams with variable H2S content, it is worth revisiting whether your compliance posture reflects current requirements, not what was in place several years ago.
The RRC and TCEQ Use Different Thresholds, and Both Apply
This is probably the most important gap for operators to understand, and it catches people off guard regularly.
The RRC’s SWR 36 kicks in when H2S concentration reaches 100 ppm or greater. Below that, most SWR 36 requirements do not apply, though personnel training obligations remain.
The Texas Commission on Environmental Quality (TCEQ) draws its sour gas line at approximately 24 ppm, equivalent to 1.5 grains per 100 cubic feet. Operations at or above that concentration require a TCEQ air authorization, typically under the Permit by Rule (30 TAC §106.352) or the Standard Permit (30 TAC §116.620), depending on site configuration and proximity to receptors.
A site running at 50 ppm H2S has no SWR 36 obligations beyond personnel training. That same site is classified as sour by TCEQ and subject to air permitting requirements, fugitive emissions controls, and potentially enhanced equipment inspection obligations.
Both agencies have independent enforcement authority. Compliance with one does not satisfy the other.
TCEQ Is Recommending Re-Testing at Aging Wells
TCEQ guidance specifically calls out a risk that tends to be underappreciated: as oil and gas wells age, H2S concentrations can increase. A well that tested clean several years ago may no longer reflect current conditions.
TCEQ recommends that operators periodically review H2S concentration data and re-test any site where the last gas analysis is more than two years old. The practical concern is straightforward: if a well has crossed the 24 ppm threshold since its last test, it is out of compliance with TCEQ air authorization requirements from the moment it crossed, regardless of when the operator discovers it.
Regular testing is not just good housekeeping. In the current enforcement environment, it is the most cost-effective way to avoid the kind of retroactive compliance problem that is expensive to unwind.
Permian Basin Operations Have Been Under Active Monitoring
In response to increases in oil and gas activity and reported emissions events, TCEQ conducted multiple mobile monitoring surveys across the Permian Basin specifically targeting H2S and sulfur dioxide concentrations. Those surveys focused on areas where emission sources were in proximity to populated or publicly accessible locations and on operators with histories of emissions events or complaints.
That kind of field surveillance changes the enforcement equation. Historically, H2S compliance issues surfaced through self-reporting or scheduled inspections. Mobile monitoring means elevated concentrations can be detected and traced back to a specific site without prior notice or complaint.
For Permian operators, the relevant question is not whether your emissions are detectable. It is whether you are in a defensible compliance position when they are.
A Quick Summary of SWR 36 Compliance Tiers
For operators who have not reviewed the rule recently, the compliance structure works on a sliding scale based on your radius of exposure (ROE) calculations at both the 100 ppm and 500 ppm thresholds.
Operations with H2S below 100 ppm are largely exempt from SWR 36, with the exception of personnel training requirements. Once the 100 ppm threshold is met, the compliance level required depends on whether and how far the radius of exposure extends into public areas. At the higher end, when the 100 ppm ROE exceeds 50 feet and includes a public area, or when the ROE exceeds 3,000 feet regardless of public area, full compliance requirements apply: contingency plan, H2S detection equipment or formal safety procedures, Form H-9 certification, and enhanced signage and fencing.
Certificates of compliance are non-transferable. When an operation changes hands, the incoming operator must file a new Form H-9. The RRC maintains a publicly accessible H2S fields and concentration listings database drawn from H-9 filings on record, which can be a useful reference for understanding H2S activity in a given area.
Where Scavenger Chemistry Fits In
Scavenger programs are often the most operationally flexible tool for managing H2S concentrations at the production and gathering level, where volumes are variable and treatment can be adjusted in the field.
A few things worth keeping in mind as you think about your scavenger program in this regulatory context.
First, TCEQ’s 24 ppm threshold means that keeping concentrations below 100 ppm does not automatically put you outside TCEQ’s jurisdiction. Know where your concentrations actually are, not where they were at last measurement.
Second, documentation matters to both agencies. Application logs, H2S concentration test results, and ROE calculations should be current and accessible for inspection.
Third, if a process change including a change in scavenger chemistry, injection rate, or treatment point results in increased H2S concentrations, it may trigger notification requirements to the RRC district office, a contingency plan revision, or in some cases a formal public hearing before it can proceed.
The Bottom Line
The February 2025 amendments to SWR 36, TCEQ’s surveillance activity in the Permian Basin, and the re-testing guidance for aging wells all point in the same direction: the regulatory environment for H2S management in Texas is not static.
Operators who stay ahead of it are running current concentration data, keeping Form H-9 filings up to date, understanding where TCEQ obligations begin independently of the RRC, and treating their H2S removal programs as part of a broader compliance strategy.
This post is for informational purposes only and does not constitute legal advice. Regulatory requirements are subject to change, and nothing here should be relied upon as a substitute for guidance from qualified environmental counsel familiar with your specific operations. Always verify current requirements directly with the RRC and TCEQ.