Restoration and monitoring of an urban estuary in northern New Jersey. The Hackensack River estuary in northern New Jersey sits just six miles west of Manhattan Island. It is surrounded by some of the most densely populated and industrialized areas of the nation. In the early 1900s, municipal landfills were established in the estuary and in 1922 a dam reduced the flow of fresh water thus greatly limiting the natural flushing ability of the system. For years, toxic substances seeping from the landfills entered directly into the estuary. Frequent spills from oil storage facilities and oil slicks from illegal dumping were common, and overtaxed sewage treatment plants discharged 115 million gallons per day of minimally treated sewage directly into the nearby creeks and waterways. In the 1930s, residue from nearby chromite ore processing plants was used as foundation material for industrial sites as well as wetland backfill and even scattered into the neighboring urban environment. Records show that between 1929 and 1972 more than 268 tons of mercury-contaminated toxic waste was dumped into creeks that today show some of the highest concentration of mercury in sediments in the world. Coal power plants continue until today to emit greenhouse gases and associated heavy metals into the surrounding air. By the 1970s the estuary was considered destroyed; a highly disturbed and truncated ecosystem where many of the shellfish, crustaceans and finfish had been eliminated. Thirty years later, the estuary is showing signs of improving, and it is seen as a patient that has been under intensive care for the past 30 years. Landfills have been closed, and most of the point sources of pollution have been eliminated as sewage treatment plants have been closed or re-engineered and upgraded. Restoration efforts include replacing contaminated surface sediments with re-engineered clean sediments, removing invasive species, re-grading, and re-establishing native plant communities and tidal flows. Marsh elevation and plant community development over time are monitored using modern remote sensing techniques (e.g. hyperspectral and LiDAR). Plant, benthic invertebrate, fish and bird diversity and density are central to the biodiversity monitoring efforts. Sediment chemistry conditions are monitored to verify that restored areas are not being re-contaminated by tidal waters. The presentation will show how restoration efforts — coupled with biodiversity measurements and continuous air, sediment and water quality monitoring efforts — are helping to return many of the lost ecosystem services. The presentation will also provide reliable baselines to measure progress and lay out the scientific foundation on which to base policy decisions.