What 'Detected,' 'Median,' and 'Range' Mean in the Sampling Record on This Page
When a laboratory tests water for arsenic, the report often lists concentrations in micrograms per liter (µg/L). In Harris County’s aquifer 121EVGL, arsenic was detected in every analyzed sample, meaning instruments measured it in all tested wells. The median value represents the middle point of the sample concentrations, which was 3.9 µg/L in the 58 results collected from 29 wells between 2010 and 2015. The range—from the lowest to the highest concentration recorded—spanned from 1.6 to 33.5 µg/L. It’s important to understand that 'detected' means measurement presence, not a breach of safety or legal limits.
How Sample Depth, Well Depth, or Source Type Changes What a Reader Should Expect
The wells sampled varied in depth from 1305 to 1965 feet, tapping deep groundwater sources. Arsenic concentrations often vary with depth and geological formations. Since these samples represent a broad range of well depths within Harris County’s aquifer, individual household wells especially those at different depths or tapping different sources, may experience different arsenic levels. Therefore, laboratory testing of your own water remains essential for precise knowledge.
What Changes for a Large Household, a Second Home, or a Seasonal Property
Household demand influences treatment needs but does not change the underlying arsenic presence in the water source itself. For larger households with greater daily water use, equipment that can process higher volumes efficiently is advisable. Seasonal or second homes might require treatment systems that maintain effectiveness even with intermittent use. These considerations affect equipment selection rather than the detected arsenic concentrations shown by area sampling.
What Questions a Commercial or Industrial Operator Adds That a Household Does Not
Commercial or industrial operators often need to consider regulatory compliance, process water purity for manufacturing, and large-volume treatment capacity. Households, by contrast, primarily focus on safe drinking water and typical residential use volumes. While area data provides useful context, commercial users should conduct specialized tests and meet applicable regulations for their operations in Harris County.
The Role of Plumbing Material and Age, Separate From the Source Water
Plumbing materials and the age of household pipes can affect arsenic measurements at the tap, potentially adding or altering water chemistry independently of source water. Corrosion or leaching of pipe materials could change arsenic levels seen at faucets versus the raw well source. Proper water treatment can address source contaminants, but understanding household plumbing influence is also a factor in water quality management.
A Worked Example: Reading the Record's Median and Range as a Homeowner Would
Imagine reviewing a water test report for a household well in Harris County. The regional data shows a median arsenic level of 3.9 µg/L, with a highest measured concentration of 33.5 µg/L in the sampled area. This sets a realistic expectation that your well water may have arsenic anywhere within this spread. However, only a dedicated water test of your own supply can confirm the actual concentration. Knowing this range helps select treatment equipment designed for the possible upper levels detected here, such as the C-Series Arsenic Filter, which is documented to reduce arsenic effectively.
This record comes from 58 samples collected from 29 separate wells between 2010 and 2015, representing Harris County groundwater’s aquifer 121EVGL. For full details and updates, consult the U.S. Geological Survey groundwater monitoring site.
Where this information comes from
Source: USGS groundwater sampling. Sampled 2015-07-20. These figures describe groundwater sampled in this area. They are not a test of any individual private well - only a test of that well can establish its own water.
On record: U.S. Geological Survey sampling of Arsenic in the 121EVGL aquifer (Harris County): 58 results from 29 wells, median 3.9 ug/L, range 1.6-33.5 ug/L; none above any federal threshold