California Code, Water Code - WAT § 13399.35

(a) The regional board may allow a person to reduce the penalties described in subdivisions (a), (b), and (c) of Section 13399.33 by up to 50 percent by undertaking a supplemental environmental project in accordance with the enforcement policy of the state board and any applicable guidance document.

(b) For the purposes of this section, a “supplemental environmental project” means an environmentally beneficial project that a person agrees to undertake, with the approval of the regional board, which would not be undertaken in the absence of an enforcement action under Section 13399.33.