Workers need to enter a below-ground, concrete-lined vault to repair a leaking valve that controls the flow of wastewater from several buildings at your plant. The opening for the pit is outdoors and secured with a 36-inch diameter manhole cover. The pit is 12 feet deep, and the walls are 6 feet x 6 feet wide. The valve is at the bottom of the vault. You opened the cover, tested the atmosphere, and found oxygen levels to be at 16%. No toxic substances were detected. After ventilating the space for 15 minutes, the oxygen reading reached 18% and remained at that level.
Address the following items:
Using the flow chart in Appendix A of 29 CFR 1910.146, determine the classification of the space.
Explain how you reached the decision.
Based on your determination, develop an OSHA-compliant standard operating procedure (SOP) for workers to follow when entering the space to repair the valve. Include the citation(s) from 29 CFR 1910.146 for each step of the procedure.
Your submission must be a minimum of two pages in length (double-spaced). Be sure to include a title page.

To Appendix A of 29 CFR 1910.146
https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9798