Cal. Gov't Code § 87100.1

(a) A registered professional engineer or licensed land surveyor who renders professional services as a consultant to a state or local government, either directly or through a firm in which the consultant is employed or is a principal, does not have a financial interest in a governmental decision pursuant to Section 87100 where the consultant renders professional engineering or land surveying services independently of the control and direction of the public agency and does not exercise public agency decisionmaking authority as a contract city or county engineer or surveyor.
(b) For purposes of this section, the consultant renders professional engineering or land surveying services independently of the control and direction of the public agency when the consultant is in responsible charge of the work pursuant to Section 6703 or 8703 of the Business and Professions Code.
(c) Subdivision (a) does not apply to that portion of the work that constitutes the recommendation of the actual formula to spread the costs of an assessment district’s improvements if both of the following apply:
1. (1) The engineer has received income of two hundred fifty dollars ($250) or more for professional services in connection with any parcel included in the benefit assessment district within 12 months prior to the creation of the district.
2. (2) The district includes other parcels in addition to those parcels for which the engineer received the income.
  The recommendation of the actual formula does not include preliminary site studies, preliminary engineering, plans, specifications, estimates, compliance with environmental laws and regulations, or the collection of data and information, utilized in applying the formula.