The Reston Groundwater Dating Laboratory

Information Useful in Age Determination

Well Construction Data

Depth, elevation, construction (open hole, perforations, etc), depth below water table, length of screened interval, pump depth, casing material, etc.

Field Parameters

Oxygen, specific conductance, temperature, hydrogen sulfide (smell)

Collection

Pump type, discharge tubing (copper, Nylon, etc.)
Bubbles in discharge, particulates in water, cloudy water, raw or finished sample, etc.

Hydrology

Recharge or discharge area, confined or unconfined formation, fractured rock, karst, sand and gravel, etc.

Dissolved Gases

o₂, h₂s, ch₄, excess n₂, low ar and n₂-degassing

Water Chemistry

Fe²⁺, sulfide, etc.

Supporting Data

tritium, ³h-³he, sf₆, other

Chromatograms

Background constant (oxygen present) or very variable (reducing conditions)
Compare duplicate chromatograms (trends in concentration , random variation in concentration, etc. indicating draw-down or not purged sufficiently)
N₂O present? Nitrate reducing (fertilizers, etc)
H₂S present? Sulfate reducing
Other contaminants (halocarbons) present? Are the CFC's also contaminated?
Degradation of contaminants?