53 Pa. Stat. § 5433
It shall be the duty of the political subdivisions joining in such purchase to award the contract of purchase on competitive bids to the lowest responsible bidder. Any published notice for bids shall contain full plans and specifications, or refer to the places where copies thereof can be obtained, and give the time and place of meeting of the representatives from the corporate authorities of the political subdivisions joining in such purchase for the purpose of opening bids. At least one representative from each of the political subdivisions joining in such purchase, shall be present at such meeting, and such meeting may be adjourned from time to time on six days' notice of the same kind until the proper representation can be present.
53 P.S. § 5433