1. photograph the event if possible;
2. Write a brief statement about the event and describe as precisely as possible how to arrive to the location (if there is a correct address, some visible object, distinctive sign and the like.)
3. City or Municipality (Department of municipal services) for all open dumps, whether or not it is a private or public area. If it is a dangerous type of waste, the report should be sent to the Inspection of Environmental Protection at the Ministry of Environment and Nature Protection. If you found the perpetrators on the spot or recorded their registration plates, you can notify the police.

WHOM TO CALL: and/or Green Phone service for your county (072 123 456) - the report may be sent anonymously, too.
NOTE: You can always call the service 112, especially if it is a matter of great urgency, and during the weekends, holidays or at night