Phase II field methods

The common tools, and what each one answers.

Soil borings

Drilled with direct-push rigs (Geoprobe is a common brand) or hollow-stem augers, borings collect soil at chosen depth intervals for laboratory analysis. They answer the source question: is contamination present in soil at the suspected release point, how deep, and at what concentration. Field screening (a photoionization detector, visual and olfactory logging) guides which samples go to the lab.

Groundwater

Temporary sampling points or permanent monitoring wells answer the migration question: has contamination reached groundwater, and which way is it moving. Permanent wells, surveyed and sampled after development, produce data regulators accept; three or more allow the gradient to be triangulated. Grab samples from temporary points are faster and cheaper but carry more uncertainty, and some programs discount them.

Soil vapor

Vapor probes and sub-slab samples answer the exposure question for volatile contaminants: are vapors migrating toward or into buildings at concentrations that matter. Vapor intrusion has grown into one of the most regulator-scrutinized pathways, and vapor data is often the difference between a manageable finding and a re-opened one.

Utilities and access

Before any of it: a utility locate, because borings meet buried lines badly, and access agreements when points sit on a neighbor's land. Off-site access is regularly the schedule's long pole.

Laboratory analysis

Samples go out under chain of custody to accredited laboratories, with methods and reporting limits matched to the screening criteria chosen at scoping. A result the lab cannot report below the screening level is money spent to learn very little.