National parks are struggling with an $877 million backlog of plumbing problems at restrooms and wastewater facilities with a shortfall of workers needed to make repairs, according to an audit released last week by the Interior Department’s inspector general. Moreover, the park system — which hosted 332 million visits last year at more than 400 sites — also lacks a system to track critical wastewater hazards identified by NPS’ Office of Public Health, the report said. The Office of Inspector General surveyed 30 public health assessments for parks and found 87 critical-level deficiencies such as permit violations for sewage discharges, wastewater spills and other problems.