The total length of sewer pipes in Japan that have been judged to require countermeasures due to risks such as cave-ins has reached 748 kilometers, the infrastructure ministry said Tuesday.The figure accounts for about 16% of the sewer pipes totaling 4,692 km that were inspected by the end of February, according to the results of intensive inspections.The ministry will ask 383 municipalities and organizations managing the sewer pipes to take immediate measures, such as repairs.