When a regional board determines that a surface impoundment is polluting, or threatens to pollute, the waters of the state or that hazardous waste constituents are migrating from that surface impoundment into the vadose zone or the waters of the state, in concentrations which pollute the vadose zone, or pollute, or threaten to pollute, the waters of the state, the regional board shall either order the surface impoundment to close, if the regional board determines that requiring the installation of double liners and a leachate collection system and the conducting of groundwater monitoring, as specified in subdivision (a) of Section 25208.5, does not provide reasonable assurance of protection against future migration into the vadose zone or the waters of the state, or take both of the following actions:
Ca. Health and Saf. Code § 25208.6