Which department oversees health-related matters regarding septic systems in Washington State?

The Washington State Department of Health is the correct answer because it is primarily responsible for overseeing health-related matters connected to septic systems in the state. This department manages regulations and guidelines to ensure that septic systems are installed, maintained, and operated in a manner that protects public health and the environment. They work to prevent health hazards associated with improperly managed septic systems, such as contamination of drinking water and transmission of waterborne diseases.

The other departments mentioned have distinct roles that do not focus specifically on septic systems. The Environmental Protection Agency works at a federal level on broader environmental regulations, while the Washington State Department of Transportation is concerned with transportation infrastructure and safety. The Department of Natural Resources primarily manages the state's natural resources, including forests and wildlife, and is not involved in health matters related to septic systems.