Manganese concentrations (ppm) at four background wells (eight quarterly measures at each well).
A data frame with 32 observations on the following 3 variables.
a numeric vector indicating the quarter the sample was taken
a factor indicating the well number
a numeric vector of manganese concentrations (ppm)
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.14-5.
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.