Missouri Department of Natural Resources

Chemists use complex instruments to analyze samples. Sometimes the substance of concern is not present in high enough concentrations for the instrument to “see” or detect. If a substance was not detected by the laboratory’s instrument, it may be reported in one of two ways. You may see a “less than” or left pointing arrow (<) followed by a number in the results column. Alternatively, there may be a value with no arrow followed by an “ND” in the Qualifier column to the right of the number.

In each of these cases, the number in the Result column for that parameter/analyte is the Method Detection Limit (MDL) for that substance. So, for example, if the substance Trichloroethene (TCE) on the sample analysis report has “1.0” in the Results column, “ND” in the Qualifier column, and “ug/L” in the Units column, it means the lab instruments did not detect any TCE in this sample at or above 1.0 ug/L. The MDLs sometimes differ because the instruments vary in sensitivity to each substance.

If a substance was detected in the sample, you will see a number in the Results column without a “less than” arrow beside it, and without an “ND” in the Qualifier column. These numbers require careful interpretation. In order to determine whether the chemical is present at a concentration that may be of concern, the number should be compared to a specific screening benchmark. The department staff evaluating your results will conduct these comparisons and provide more information for any chemicals detected above these benchmarks.

Sample Event Type

This indicates the reason the sample was collected.

Monitoring – Is established to collect information from a site on a routine basis to make sure the site in compliance with Missouri and Federal Laws.
Inspection – This is a review of the facility to insure they are meeting and support all compliance and enforcement regulations.
Complaint – This is from the result of a public call, email, letter or inquiry about a violation of the environmental law.
Emergency Response – This is from a result of an emergency from a spill or accident.
Bypass/SSO – A bypass is when partially treated wastewater is discharged from a permitted outfall, Sanitary Sewer Overflow occurs as an unpermitted discharge from the collection system.
Special Project – This would be something that is not typically done but for some reason a need is seen to sample.
Investigation - This is the result of a Hazardous Waste inquiry.

Sample Type

This provides further information on the nature of the material collected and analyzed.

Discharge - Wasterwater Treatment Plant, Industrial, Power Plants
Drinking Water – Private Wells, Household taps
Soil – Lake/Stream Sediment, Encores
Sludge – Drum Sampling
Stormwater – Construction Run- off, Drainage areas, CAFO’s
Sediment – Lake, Stream
Air – SUMMA Canisters
Spill – Chemical, Oil, Fuel, Pure Products
Organic – Drum Sampling, Pesticides, Herbicides, Pure Products
Container – Drums, Tanks
Surface Water – Lakes, Streams, Ponds, Springs, Leachate
Groundwater – Caves, Springs, Monitoring wells
Wipes – Chemical Substances

Analyses/Test Type

This is the type of test that was used

Parameter/Analyte

The sample was tested to see if it contained the substances in this column

Result/Unit

The results are shown here. The results are compared to either a sample from an uncontaminated area (background sample) or a specific health-based standard before drawing conclusions. See Common Notations below.

Common Notations and unit definitions
- < A symbol for “less than”. It means a substance could not be detected by laboratory instruments. The number following the symbol indicates the instrument’s lowest possible setting for the sample.
- ug/kg This means micrograms per kilogram. This measurement is generally used with soil samples. It is also often referred to as parts per billion (ppb).
- mg/kg This means milligrams per kilogram, which is also referred to as parts per million (ppm). This measurement is generally used with soil samples.
- ug/L The means micrograms per liter. This measurement is generally used with water samples. It is also referred to as parts per billion (ppb).
- mg/L This means milligrams per liter, which is also referred to as parts per million (ppm). This measurement is generally used with soil samples.
- cfu/100ml This means colony-forming unit per 100 microliters. This measurement is used with water samples.
- NTU This means nephelometric turbidity unit. This measurement is used with water samples.
- Please use the contact email for unit definitions not listed.