The use of wetland treatment systems (WTS), or constructed wetlands, for treating municipal wastewater is increasing in the United States, but little is known about the ability of these systems to duplicate or sustain wetland functions. The purpose of the field operations report is to document field methods and activities as they were conducted during the 1991 field season. The report includes details of sampling procedures, criteria used for making sampling decisions, data that were collected at each site, and analysis of quality control data, and a discussion of difficulties encountered. The field operations report will cover only the field work pertaining to compiling data on selected indicators of wetland condition by taking measurements at sites and utilizing the Wetland Evaluation Technique (WET), to evaluate habitat quality and other values of WTS and to assess the technique's utility for WTS evaluation.