Carbon tetrachloride (CCL4) concentrations (ppb) at five wells (four monthly samples at each well).
A data frame with 20 observations on the following 3 variables.
a numeric vector of carbon tetrachloride concentrations (ppb)
a factor indicating the month of collection
a factor indicating the well number
USEPA. (1992c). Statistical Analysis of Ground-Water Monitoring Data at RCRA Facilities: Addendum to Interim Final Guidance. Office of Solid Waste, U.S. Environmental Protection Agency, Washington, D.C. p.80.