Groundwater Professional Bulletin Board

P WELLS

P wells are discussed in the October 15, 1997, Tank Memo (page 9) and on pages 60–62 of the Iowa RBCA Software for Windows/Version 2.30 User’s Manual. A “P well” has a concentration above the groundwater source SSTL and is not between the source and the receptor. In other words, it is on the other side of the source line from the receptor. P wells are wells in the "primary area" that do not fall between the source and receptor, but have concentrations above the groundwater source site-specific target level (SSTL) for the receptor. Since it is not between the source and receptor, a P well would generally not be suitable as a T and G well. P wells are required for actual receptors only, and should be sampled annually. P wells must meet steady and declining criteria, and the last sample must be less than the SSTL in order to get reclassification to NAR.

The problem is that software versions prior to 2.2 did not automatically select P wells. The P wells will be automatically selected if a user reads a file into v2.2 or 2.4 created in v2.17 and clicks autoselect. In many instances, these P wells have not been included in previous SMR monitoring plans.

To correct this situation, we will not be evaluating SMRs for P well monitoring compliance when software versions 2.17 or earlier were used to conduct the RBCA evaluations. We will be conducting monitoring compliance for P well sampling in SMRs based on RBCA evaluations using v2.2 and later software.

Contact Elaine Douskey at (515)281-8011 or elaine.douskey@dnr.state.ia.us if you have questions concerning this posting.