Cal. Gov. Code § 66474.63

In cities having a population of more than 2,800,000, the advisory agency, appeal board or legislative body shall determine whether the discharge of waste from the proposed subdivision into an existing community sewer system would result in violation of existing requirements prescribed by a California regional water quality control board pursuant to Division 7 (commencing with Section 13000) of the Water Code. In the event that the advisory agency, appeal board or legislative body finds that the proposed waste discharge would result in or add to violation of requirements of such board, the body making such finding may disapprove the tentative map or maps of the subdivision.