The bureau performs surveillance to assess environmental quality trends, address compliance issues, and follow up on complaints, pollution events and existing issues identified through environmental monitoring. Surveillance includes visits to locations to make observations, conduct ambient monitoring and sampling. Surveillance also includes evaluation of ambient air and surface water monitoring data. Ambient air monitoring data surveillance is used to evaluate air pollutants in various air monitoring sites in the city. Surface water monitoring data surveillance is used to asses watersheds and identify water quality trends.