This document presents the treatability test plan for pilot-scale pump and treat testing at the 200-BP-5 Operable Unit. This treatability test plan has been prepared in response to an agreement between the U.S. Department of Energy (DOE), the U.S. Environmental Protection Agency (EPA), and the State of Washington Department of Ecology (Ecology), as documented in Hanford Federal Facility Agreement and Consent Order (Tri-Party Agreement, Ecology et al. 1989a) Change Control Form M-13-93-03 (Ecology et al. 1994) and a recent 200 NPL Agreement Change Control Form (Appendix A). The agreement also requires that, following completion of the activities described in this test plan, a 200-BP-5 Operable Unit Interim Remedial Measure (IRM) Proposed Plan be developed for use in preparing an Interim Action Record of Decision (ROD). The IRM Proposed Plan will be supported by the results of this treatability test plan, as well as by other 200-BP-5 Operable Unit activities (e.g., development of a qualitative risk assessment). Once issued, the Interim Action ROD will specify the interim action(s) for groundwater contamination at the 200-BP-5 Operable Unit. The treatability test approach is to conduct a pilot-scale pump and treat test for each of the two contaminant plumes associated with the 200-BP-5 Operable Unit. Primary contaminants of concern are 99Tc and 6°Co for underwater affected by past discharges to the 216-BY Cribs, and 9°Sr, 23924°Pu, and Cs for groundwater affected by past discharges to the 216-B-5 Reverse Well. The purpose of the pilot-scale treatability testing presented in this testplan is to provide the data basis for preparing an IRM Proposed Plan. To achieve this objective, treatability testing must: Assess the performance of groundwater pumping with respect to the ability to extract a significant amount of the primary contaminant mass present in the two contaminant plumes.