What critics called a “poison pill” clause in the recently approved interim stream conservation ordinance for unincorporated Marin has proven to be just that: environmental groups last week sued the county over the rules, rendering them null.

The lawsuit, filed by the Salmon Protection and Watershed Network and the Center for Biological Diversity, a national organization that often partners with smaller groups like SPAWN, trips up the ordinance thanks to a clause that stipulates the temporary rules would not take effect if a group filed litigation to challenge them. 

It is the third lawsuit SPAWN has filed over stream protections in Marin.

The ordinance, approved by three county supervisors last month, established a permit zone for development up to 100 feet from stream banks. The type of development and the potential environmental impacts of the work would dictate whether the county would hold public hearings on permits. 

The county says its passage of the ordinance ended a court-ordered building moratorium in the San Geronimo Valley, though lawyers for SPAWN say they believe the moratorium is still in place.

SPAWN has argued that the interim ordinance would encourage too much development in the watershed and harm endangered coho salmon there, while other local environmental groups like the Marin Audubon Society and the Marin Conservation League supported it.

Many homeowners, concerned about their ability to develop their own properties, also supported the ordinance. They hope a work program that was included in the ordinance will lead to less stringent buffer zones around ephemeral streams; that program will kick off in 2014.