Contract 2 specified that traffic upon the streets of lower Manhattan not be disrupted. At its shallowest, the tunnel would be only below the bottoms of the street car conduits along Broadway. Accordingly, the contractor proposed replacing the pavement with a planked roadway and excavating beneath this temporary surface. To address concerns that leakage from the gas mains beneath the roadway and within the excavation would produce a devastating explosion, the contractor moved the pipes to above the street. Furthermore, precautionary measures had to be undertaken during the construction of the tunnel in front of Trinity Church, adjacent to the Wall Street station. The spire of the church rested upon a shallow masonry foundation built upon a deep layer of fine sand. The spire's foundation was behind the subway tunnel's exterior wall, and the bottom of the spire foundation was below street level, much shallower than the subway's foundation. Accordingly, the tunnel nearest the spire's foundation was constructed in three sections, and steel channels were used as sheet piling around the subway excavation. After the excavation was completed, these steel channels were left in place to prevent the soil from settling. No "measurable or movement of the spire" occurred during or after construction.