Small doses of a pesticide long banned from West Marin will now be allowed for use in septic systems under a new agreement between the Marin/Sonoma Mosquito and Vector Control District and the West Marin Mosquito Council . Capping off months of negotiations mediated by Supervisor Steve Kinsey, the parties signed a four-year agreement earlier this month that keeps many pesticides out of West Marin—and newly permits the district to apply between two and four parts per billion of methoprene to the region’s estimated 5,000 septic systems. Methoprene—which some studies have shown to be toxic to fish and which many members of the council have adamantly opposed—was prohibited from use in West Marin for a decade under the previous agreement, though the district has called it the most effective means of combating adult mosquito populations. “I’m not happy about the methoprene, but I can live with it,” said Grace Godino, a director with the Bolinas Community Public Utility District who has led the council in recent months. The agreement does open the possibility for the district to replace methoprene with alternative pesticides approved by the Organic Materials Research Institute should any become available. Signed in 2005 and set to expire at the end of June, the previous agreement received a series of renewals that blacklisted methoprene in West Marin—though a district committee last October sought to push through a resolution aimed at allowing methoprene that was shot down by strong opposition from West Marin activists. That occasion revealed tensions between the council and the district that, according to the district’s general manager, Phil Smith, have since cooled. “We found out we had a lot more in common than divided us, particularly a common interest in safeguarding the public’s well-being,” he said. The council plans to hold a town hall on the agreement this summer.