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Water wells in the Lower Trinity, Blanco County, Texas

Home water wells that draw from the Lower Trinity in Blanco County, Texas are typically 410 to 660 feet deep (median 472 ft, 45 wells drilled in the last 10 years). It is a minor layer here: just 6% of the 771 wells the state's model covers; the main one is the Middle Trinity (70%). They run about 62 feet deeper than the county's median well (410 ft). Estimated cost of a complete well at the median depth: $14,500 to $35,000.

Updated every day from Texas Water Development Board driller reports. Last update: November 11, 2026, using the state file of November 10, 2026.

All wells in Blanco CountyLower Trinity across Texas

Which layer Blanco County wells draw from

  • Middle Trinity 70% · 542 wells
  • Near or below the base of the Trinity 20% · 156 wells
  • Lower Trinity 6% · 45 wells
  • Upper Trinity 4% · 28 wells
County home wells covered by the Hill Country Trinity model (in the last 10 years).

Home wells in Blanco County

Each dot is a home well from a state driller report, colored by depth. Tap one for its details and official report. Tap an empty spot to see what is under that point.

See underground

Well depth (ft)

  • <100
  • 100
  • 200
  • 300
  • 400
  • 600
  • 800+

Dark line: Blanco County

Key figures

Typical depth (middle half)
410 to 660 feet
Median depth
472 feet
Deepest 10% are past
735 feet
Water level (median)
245 feet
26 wells
Yield (median)
30 gpm
34 wells, gallons per minute
Wells used
45
In the last 10 years
Share of the county's wells
6%
All years on file
227
median 443 ft, since 2001
Confidence
Standard (30 or more wells)

When the wells were finished, the water stood a median 245 feet below the surface (26 wells).

What this layer is

The Lower Trinity groups the Sycamore Sand, the Sligo Formation and the Hosston Formation, under the Hammett Shale. It is the deepest of the four layers in the state's Hill Country model, so wells that draw from it are the deepest and cost the most to drill.

Checked against the state's own aquifer codes: where our method names this layer, the state agrees in 53% of 426 wells. Read it as the likely layer, not a certain one.

More about the Lower Trinity

Depth over time

There are not enough wells in both 2003 to 2007 and 2021 to 2025 (at least 30 in each) to say with confidence whether wells in this layer in Blanco County are getting deeper. For reference, the median was 430 feet in 2001 to 2005 (48 wells) and 472 feet in 2021 to 2025 (29 wells).

PeriodMedian depth (ft)Wells
2001–200543048
2006–201044593
2011–201544039
2016–202044214
2021–202547229
2026under 10 wells4

Common questions

How deep is a well in the Lower Trinity in Blanco County?

Home water wells that draw from the Lower Trinity in Blanco County, Texas are typically 410 to 660 feet deep (median 472 ft, 45 wells drilled in the last 10 years).

How many Blanco County wells draw from this layer?

It is a minor layer here: just 6% of the 771 wells the state's model covers; the main one is the Middle Trinity (70%). For 78% of these wells the report says where the water enters and we use the middle of that interval; for the rest we use the bottom of the hole, which tends to read one layer too deep.

How deep does the water stand?

When the wells were finished, the water stood a median 245 feet below the surface (26 wells).

What a well costs here

At the median depth for this layer in Blanco County (472 feet), a complete home well would cost roughly $14,500 to $35,000: $25 to $60 per foot for drilling, casing and seal, plus $2,500 to $6,500 for the pump, pressure tank, controls and hookup at the well. Across the whole middle half of depths (410 to 660 feet) the range runs from $13,000 to $46,000. This is TerraFunded's estimate from published Texas prices, not a quote, and it leaves out trenching and the line to the house. Get prices from at least two licensed drillers.

How these numbers are made

We count new and replacement domestic (home) wells with a valid depth on their report. We use the last 10 years when there are at least 30 wells; otherwise all since 2001. The median is the middle well and the middle half runs from the 25th to the 75th percentile.

To tell which layer a well draws from, we take the ground elevation at its location, subtract the depth of the interval where water enters (or the bottom of the hole when the report does not give one) and see which layer of the state's model that point falls in.

For 78% of these wells the report says where the water enters and we use the middle of that interval; for the rest we use the bottom of the hole, which tends to read one layer too deep.

How well it works: In 2,665 wells in the Texas Hill Country where the State of Texas recorded the aquifer, our estimate of the formation the well draws from names the same layer of the state's model in about 76% of them, and that layer or the one next to it in at least 98%.

  • The layers come from the Texas Water Development Board's Hill Country Trinity model, with 1 mile cells. It is a regional model, not a survey of any lot: between one model point and the next, the real depth of each layer can differ.
  • "Near or below the base of the Trinity" means the well reaches the bottom of the model or passes it, often by tens of feet. Older rock that the model does not include may lie there.
  • We never use the model's water levels. The water level on this page is the one each driller measured when the well was finished.

These are depths of real wells drilled nearby, not a promise about any property. Groundwater can change over short distances and with drought. A licensed water well driller can tell you what to expect on a specific tract.

Read the full methodology · Download the data (CSV, CC BY 4.0)

How to cite

TerraFunded (2026). Texas Well Atlas: Underground. From Texas Water Development Board driller reports and groundwater availability models (data as of November 10, 2026). https://terrafunded.com/wells/blanco-county/lower-trinity. License CC BY 4.0. https://doi.org/10.5281/zenodo.24126380.

Sources