25 Pa. Code § 299.111 – General requirements.

A person or municipality that stores residual waste may not do the following:

(1) Mix the waste with hazardous waste that is regulated under Article VII (relating to hazardous waste management), except for purposes of treatment at permitted hazardous waste management facilities.
(2) Mix the waste with, or store the waste in proximity to other solid waste to create a risk of fire or explosion, or a risk of the accumulation of poisonous or otherwise harmful vapors or gases.
(3) Mix the waste with special handling waste.
(4) Allow waste or constituents of waste to be blown or otherwise deposited outside of the storage area.

This section cited in 25 Pa. Code § 299.101 (relating to scope).