Junkyards are required to make provisions
to prevent any contamination of the domestic water supply or excessive surface run-off from the property into adjoining lands or streams." For automobile salvage yards, a drainage plan must be approved by the DEC "specifying the method of disposing of surface run-off from the site (FNSBC 18.96.130.C).
The DEC administers a permit that covers runoff from an "automobile salvage yard." So, if the junkyard is predominately automobiles, then the facility would need to apply for coverage under a Multi-Sector General Permit and develop a Stormwater Pollution Prevention Plan (SWPPP). Although there is no size threshold for the junkyard, it must be a business enterprise, not an individual with 20 cars on their home lot.
The SWPPP can be prepared by the operator and does not necessarily require hiring a professional. The DEC has a template for the operator to fill in and an EPA Manual that helps describe the process of assembling the SWPPP. If you are considering submitting a SWPPP, please look at the DEC website and then call the Stormwater Section of the Division of Water at 907-269-6283 for assistance through the process.