The Clean Construction requirements of Section 6.25 and Environment Code Chapter 25 are mandatory for Public Work or Improvements to be performed within the City and estimated to require 20 or more days of work to complete. For other Public Work or Improvements, Department Heads are encouraged to require the use of off-road equipment and off-road engines that meet or exceed the standards in Chapter 25, or to use Bid criteria that favor the use of such equipment and/or engines. Department Heads are particularly encouraged to do so wherever the project is located within 500 feet of a Sensitive Site, as defined in Health Code Section 3804.