California Code, Government Code - GOV § 66456.2

(a) An improvement plan being processed in conjunction with either an approved tentative, parcel, or final map shall be prepared by a registered civil engineer and acted on within 60 working days of its submittal, except that at least 15 working days shall be provided for processing any resubmitted improvement plan.  The 60 working day period shall not include any days during which the improvement plan has been returned to the applicant for correction, has been subject to review by other than the local agency or, following that review, has been returned to the applicant for correction.

(b) The time limits specified in this section for acting on improvement plans may be extended by mutual consent of the subdivider and the advisory agency or legislative body required to act.  However, no advisory agency or legislative body may require a routine waiver of time limits as a condition of accepting the improvement plan.  A routine waiver may be obtained for the purpose of permitting concurrent processing of other requirements related to the improvement plan or map.

(c) If, at the time of submittal or resubmittal, the local agency or designee determines it is unable to meet the time limits of this section, the local agency or designee shall, upon request of the subdivider and for purposes of meeting the time limits, contract or employ a private entity or persons on a temporary basis to perform services necessary to permit the agency or designee to meet the time limits.  However, a local agency or designee need not enter into a contract or employ those persons if it determines either of the following:

(d) “Improvement plan” means the plan for public improvement as described in Sections 66418 and 66419.