Texas Subdivision Groundwater Study Requirements

Groundwater Availability Studies (GAS): What Developers Need to Know in 2024 and Beyond

As of January 2024, any subdivision in Texas that is not connected to a municipal water supply must complete a Groundwater Availability Study (GAS) and submit a Groundwater Availability Report (GAR) to the local municipality, TCEQ, and—if applicable—the regional groundwater conservation district. This requirement is now a standard part of the development process for rural and suburban properties.

At Legacy Engineering, we approach this requirement as more than just a box to check. A properly executed GAS helps protect your investment, validate feasibility, and streamline the subdivision approval process.

Why a Groundwater Availability Study Matters

Although a GAS is required by state law, its purpose goes beyond regulatory compliance. The GAS is designed to stress the aquifer for a short period of time and collect accurate data from two wells. This data helps determine whether the groundwater beneath the property can reliably support the proposed development.

The test evaluates aquifer characteristics such as:

• Transmissivity

• Storage coefficients

• Drawdown response

• Long-term production potential

These measurements are then used to estimate whether the property can sustain expected water use. And that’s where the challenge comes in: water demand varies. Variables like pools, irrigation, fire suppression, and household usage can significantly affect long-term demand. A good GAS considers realistic assumptions and provides a conservative, defensible analysis so developers can proceed with confidence.

How a Groundwater Availability Study Works

A complete groundwater study consists of two phases:

1. Field testing, and
2. Technical reporting.

1. Field Testing (48-hour pump test)

The field portion involves either drilling new wells or using existing wells—provided they meet spacing and data-collection criteria. Depending on the size of the subdivision, one or multiple study points may be needed. Each study point requires two wells:

• Pumping well: Equipped with a pump and sensor, operated at the maximum sustainable rate to stress the aquifer.

• Observation well: Equipped with a sensor only.

Pumping at the maximum rate isn’t intended to simulate household use—it’s done to stress the aquifer, which reveals how water moves, replenishes, and behaves under load.

2. Groundwater Availability Report (GAR)

After testing, the data is analyzed and compiled into a report that includes:

• Aquifer characteristics

• Pump test results

• Long-term production estimates

• Maps of groundwater availability across the property

• Conclusions on whether the proposed subdivision has adequate water supply

This report is then submitted to TCEQ, the municipality, and the groundwater conservation district.

Well Placement: Why It’s More Complicated Than It Seems

Choosing well locations is one of the most common pain points in a GAS. Several regulations restrict where wells can be placed:

• Well pairs must be 150' to 300' apart

• Wells must be at least 50' from property lines (unless certain conditions are met)

• Wells must be 100' or more from septic systems, leach fields, etc.

These rules seem straightforward—until the lot layout changes.

Because groundwater studies are typically required before preliminary plat approval, developers must balance two risks:

• Start too early: lot lines may shift, forcing wells into non-compliant locations

• Start too late: the groundwater study delays plat submission, adding interest and carrying costs

This timing balance is why proactive planning and experienced engineering guidance matter.

How Developers Can Avoid Sunk Costs

A common concern is whether the GAS cost is “lost” if the project doesn’t move forward or if wells can’t be used later. At Legacy Engineering, we work with developers to minimize that risk.

Here’s how:

• Existing wells can be turned into a selling feature
• If handled correctly, test wells can be incorporated into the subdivision and sold with the lot—often adding value for rural buyers who prefer lots with completed water infrastructure.

• We strategically select well locations
• We help determine well locations that remain compliant even if the lot lines shift during design.

• We manage the entire GAS/GAR process

From planning and drilling to pump testing and final report submission, we coordinate everything with:

• TCEQ

• Local municipalities

• Groundwater conservation districts

Our goal is to ensure the study supports—not slows down—your subdivision timeline.

Final Thoughts

For rural subdivisions in Texas, a Groundwater Availability Study isn’t just a regulatory requirement—it’s a crucial part of confirming project feasibility. With the right approach, it doesn’t need to introduce risk or unnecessary cost.

At Legacy Engineering, we act as your partner throughout the process:

• Planning well locations

• Coordinating drilling and testing

• Performing the analysis

• Submitting the official GAR

• Helping you maximize value from completed wells

If you're planning a subdivision outside a municipal water service area, connect with us. We’ll guide you through every step of your groundwater evaluation and ensure your project moves forward smoothly and confidently.