| Return to index
(a) When the preliminary investigation of a tunnel project is conducted, the owner or agency proposing the construction of the tunnel shall submit the geological information to the Division for review and classification relative to flammable gas or vapors. The preliminary classification shall be obtained from the Division prior to bidding and in all cases prior to actual underground construction. In order to make the evaluation, the following will be required:
(1) Plans and specifications;
(2) Geological report;
(3) Test bore hole and soil analysis log along the tunnel alignment;
(4) Proximity and identity of existing utilities and abandoned underground tanks.
(5) Recommendation from owner, agency, lessee, or their agent relative to the possibility of encountering flammable gas or vapors;
(6) The Division may require additional drill hole or other geologic data prior to making gas classifications.
(b) The Division shall classify all tunnels or portions of tunnels into one of the following classifications:
(1) Nongassy, which classification shall be applied to tunnels where there is little likelihood of encountering gas during the construction of the tunnel.
(2) Potentially gassy, which classification shall be applied to tunnels where there is a possibility flammable gas or hydrocarbons will be encountered.
(3) Gassy, which classification shall be applied to tunnels where it is likely gas will be encountered or if a concentration greater than 5 percent of the LEL of:
(A) flammable gas has been detected not less than 12 inches (304.8 mm) from any surface in any open workings with normal ventilation.
(B) flammable petroleum vapors that have been detected not less than 3 inches from any surface in any open workings with normal ventilation.
(4) Extrahazardous, which classification shall be applied to tunnels when the Division finds that there is a serious danger to the safety of employees and:
Flammable gas or petroleum vapor emanating from the strata has been ignited in the tunnel; or
(A) A concentration of 20 percent of the LEL of flammable gas has been detected not less than 12 inches (304.8 mm) from any surface in any open working with normal ventilation; or
(B) A concentration of 20 percent of LEL petroleum vapors has been detected not less than three inches from any surface in any open workings with normal ventilation.
(c) A notice of the classification and any special orders, rules, special conditions, or regulations to be used shall be prominently posted at the tunnel job site, and all personnel shall be informed of the classification.
(d) The Division shall classify or reclassify any tunnel as gassy or extrahazardous if the preliminary investigation or past experience indicates that any gas or petroleum vapors in hazardous concentrations is likely to be encountered in such tunnel or if the tunnel is connected to a gassy or extrahazardous excavation and may expose employees to a reasonable likelihood of danger.
(e) For the purpose of reclassification and to ensure a proper application of classification, the Division shall be notified immediately if a gas or petroleum vapor exceeds any one of the individual classification limits described in subsection (b) above. No underground works shall advance until reclassification has been made.
(1) A request for declassification may be submitted in writing to the Division by the employer and/or owner's designated agent whenever either of the following conditions occur:
(A) The underground excavation has been completed and/or isolated from the ventilation system and/or other excavations underway, or
(B) The identification of any specific changes and/or conditions that have occurred subsequent to the initial classification criteria such as geological information, bore hole sampling results, underground tanks or utilities, ventilation system, air quality records, and/or evidence of no intrusions of explosive gas or vapor into the underground atmosphere.
NOTE: The Division shall respond within 10 working days for any such request. Also, the Division may request additional information and/or require specific conditions in order to work under a lower level of classification.
NOTE: Authority cited: Sections 142.3 and 7997, Labor Code. Reference: Sections 142.3 and 7997, Labor Code.
1. Amendment of section and new Note filed 3-5-96; operative 4-4-96 (Register 96, No. 10).