They are protesting a contentious proposal to truck in and dump treated bio-waste on to local farmer's fields as compost.
"Trucking thousands of tons of sewage treatment waste to be spread onto our farms, ranches and forests is not healthy for our lands," the chiefs said in a statement.
"We stand together to safeguard the environment for future generations. The traditional practices of harvesting from our lands and waterways, has been jeopardized by this risky practice."
The chiefs, who are demanding an immediate moratorium on the importation of biosolids into the Nicola Valley, say they plan to camp out indefinitely until their demands are addressed.
Last month, protesters opposed to the plan blocked a section of Highway 8 leading to the biowaste composting facility near Merritt.