Section 4635 - Period of usefulness(a) The following maximum periods of usefulness are hereby prescribed for the respective projects authorized by this chapter, and the period of usefulness of any project, determined in any bond resolution shall, in no event, exceed the maximum period hereby prescribed for that project. (b) The acquisition, construction or reconstruction of a sewage system or an addition thereto, whether or not including treatment or disposal plants or buildings, original furnishings, equipment, machinery or apparatus, or the replacement of such equipment, machinery or apparatus, is 40 years; the replacement or the later addition of furnishings is 10 years. 9 Del. C. 1953, § 4634; 56 Del. Laws, c. 103, § 13.;