The Tahoe Regional Planning Agency's Regional Plan Update is headed to court.On Monday, the Sierra Club and Friends of the West Shore filed a lawsuit in federal court challenging the TRPA's long-discussed plan for Lake Tahoe's future.The environmental groups contend the Regional Plan Update violates the TRPA's Bi-state Compact because it will not achieve and maintain the agency's environmental standards, improperly delegates TRPA's project review to local governments and does not reduce the environmental impacts from development to less-than-significant levels."Because the Plan Update improperly delegates project review and approval to local governments, fails to require minimum regional standards, and is …