One section of the tunnel was controversial because it called for of cut-and-cover tunneling, which would require digging an open trench through Central Park in Manhattan. In June 1970, Mayor John Lindsay told city engineers to write a report that studied ways to reduce the project's impact. The results of the report, released in January 1971, called for using tunnel boring machines underneath Central Park to reduce disruption. The following month, the NYCTA published advertisements in newspapers, seeking construction bids for the tunnels under Central Park, but withdrew them after objections from community and conservation groups. The NYCTA agreed to halve the width of the proposed -wide cut, which resulted in a proportionate decrease in the area of affected parkland. The NYCTA also agreed to reduce disruption to the Heckscher Playground, located above the proposed subway tunnel's path, by cutting construction time from three years to two years and by constructing a temporary playground nearby. The sections that connected to the existing Broadway and Sixth Avenue Lines were holed through on October 11, 1973. Construction on the section between 5th Avenue and Park Avenue began in August 1974. The project involved digging a -high cavern underneath the street.