All staking and marking utilized for the location of underground facilities shall contain letter designations which will clearly identify the type of underground facility so staked or marked. Such letters shall comply with the following code:
(a) C - Communication facilities (other than telephone service).
(b) CH - Chemicals.
(c) CTV - Cable television.
(d) E - Electrical power.
(e) FS - Fire signals.
(f) G - Gas.
(g) HPW - High-pressure water (100 psig or more).
(h) P - Petroleum.
(i) PP - Petroleum products (naphtha, gasoline, kerosine and similar products).
(j) S - Sewer.
(k) ST - Steam.
(l) T - Telephone company services.
(m) TC - Traffic control signals.
(n) W - Water.
(o) O - All other facilities.