Under the wastewater effluent system regulations, municipal governments do have to do environmental effects monitoring, and they provide that data to the department. To my knowledge we don't make it public, but we do collect information to make sure that they're meeting the requirements under the regulations.
You're right to point out waste water as a source of contaminants. That's why those regulations were put in place. They spell out the timelines for municipal governments to make sure that their waste water treatment systems are dealing with the waste water to bring it to at least a secondary treatment level, which removes between 90% to 95% of contaminants.