Benzene concentrations (ppb) at one background and one downgradient well (eight monthly measures at each well).
A data frame with 16 observations on the following 3 variables.
a factor indicating the month of collection
a factor indicating the well type (background vs. downgradient)
a numeric vector of benzene concentrations (ppb)
USEPA. (2009). Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities, Unified Guidance. EPA 530/R-09-007, March 2009. Office of Resource Conservation and Recovery Program Implementation and Information Division. U.S. Environmental Protection Agency, Washington, D.C. p.16-9.
USEPA. (2010). Errata Sheet - March 2009 Unified Guidance. EPA 530/R-09-007a, August 9, 2010. Office of Resource Conservation and Recovery, Program Information and Implementation Division. U.S. Environmental Protection Agency, Washington, D.C.