Pima County Department of Environmental Quality monitors ambient (outdoor) air pollutants throughout eastern Pima County, including the Tucson metropolitan area and Green Valley. There are six principal pollutants, called “criteria” pollutants that are monitored in accordance with the National Ambient Air Quality Standards set by the Environmental Protection Agency to comply with the Federal Clean Air Act. These standards were established to protect public health and the environment from harmful levels of air pollution.

The Pima County Department of Environmental Quality has prepared this document to be submitted to the U.S. Environmental Protection Agency, Region IX. The purpose of the Ambient Air Monitoring Network Plan is to determine if the network is achieving the air monitoring objectives specified in 40 CFR Part 58 Appendix D, which mandate adherence to certain number, type and location requirements of monitoring sites and specific site criteria such as monitoring inlet height. The review should also determine if modifications should be made to the network (e.g. through the termination or relocation of unnecessary stations or addition of new stations). In addition, the review is necessary in order to ensure that the residents of Pima County are provided adequate, representative and useful air quality data, and to provide adequate protection to public health.

Builds upon the "Biological Stress Assessment" through the identification of threats and stressors to watercourses within Pima County. It provides background on technical and water policy matters, describes potential and existing impacts to watercourses within Pima County, suggests options for reducing stressors, and outlines a number of issues for discussion withing each watershed planning unit.