SAN FRANCISCO — A veteran deputy city attorney who was fired after 20 years is striking out against San Francisco City Attorney Dennis Herrera, claiming he sidelined and then removed her to derail an investigation into questionable city payouts.

Joanne Hoeper, formerly Herrera’s chief trial deputy, alleges she uncovered signs of corruption while looking into $19 million spent by the city to replace sewer lines based on claims they had been damaged by the roots of city-owned trees.