The responsibility of developing standards for methods and materials used in conducting investigations to monitor groundwater and the vadose zone is the charge of ASTM (American Society for Testing and Materials) Subcommittee D-18.21 on Ground Water Monitoring. David M. Nielsen (IEP, Inc.) is chairman of the subcommittee, which is under ASTM Committee D-18 on Soil and Rock. A. Ivan Johnson (A. Ivan Johnson, Inc., Arvada, Colo.) is vice-chairman, and Joseph D. Ritchey (Keck Consulting Services, Inc., Williamston, Miss.) is secretary.