Slug tests in the presence of background head trends.

We extend Bouwer and Rice (1976) slug test theory to incorporate background head trends that may be important in incompressible material of low permeability k. The extension, which features a convolution integral of the background head, is closed form for linear trends. A sensitivity study suggests that a rising background head can diminish the head changes associated with a slug-out test and underestimate k if it is ignored, as does falling background trend with a slug-in test. A falling background head can reinforce slug-in test head change and, if ignored, can overestimate k, as does a rising background head with a slug-out test. The simple extension is verified by field tests in glacial till and stratified drift deposits in eastern Massachusetts.