Doing business with DNREC during the coronavirus period. More Info

Delaware.gov logo

A Watershed Approach



The Watershed Approach to Toxics Assessment and Restoration (WATAR) is a watershed-scale approach to evaluating where contamination comes from, how it gets into Delaware’s waterways and water bodies, and what effects it has on watershed health.

WATAR is a cooperative project drawing on the expertise of staff within the Division of Waste and Hazardous Substances and the Division of Watershed Stewardship to create a framework for implementing remediation and restoration in Delaware watersheds impacted by toxic pollutants.

The long term goals are to return watersheds to fishable status as quickly as possible, control releases from remaining land-based sources, and create innovative strategies to mitigate legacy contamination in sediment.

WATAR Projects

Toxic substances in Delaware surface waters are largely a legacy issue. The primary contaminants of concern are persistent, bioaccumulative, and toxic substances such as PCBs, dioxins and furans, mercury, and organochlorine pesticides. The primary media affected are fish, sediments and soils. The heaviest contamination is in areas of greatest industrial and urban land use.

Although the situation is improving and programs have been effective overall, problems remain, partly due to a compartmentalized approach in the past.

NVF Remediation

DNREC has implemented a multi-faceted remediation, restoration and resilience project at the former NVF Facility in Yorklyn, DE along the Red Clay Creek. Several DNREC programs have been involved, each with an important role. The Division of Waste and Hazardous Substances operated a treatment system in conjunction with active removal of zinc from the site. With the goals of reducing risk for redevelopment along with eliminating loading of contaminants to the Red Clay Creek, DWHS made the NVF site ready for reuse for Delaware State Parks and other residential and commercial ventures. By linking the goals at the site with the improvement of surface water quality, the WATAR team compelled improvements at the NVF property that will be seen further downstream in the Christina River Basin. A wetland has been created on site for the purposes of habitat restoration and flood water storage capacity.

A Street Ditch Remediation

Several projects are underway in the City of Wilmington that address legacy environmental contamination, historic flooding, and provide access to the Christina River and surrounding wetlands. In conjunction with the South Wilmington Wetlands restoration project, DNREC’s WATAR Team and project partners are implementing an innovative polychlorinated biphenyl (PCB) remediation pilot study in a water conveyance known as the A-Street Ditch. This project builds on the success of the Dover-based Mirror Lake project, where SediMite™ was applied to lake sediments to sequester contaminants, thereby reducing the bioavailability of PCBs and other organic compounds. The A-Street Ditch project adds a population of micro-organisms (inoculant) to the remediation technique that aims to break down/destroy the PCB molecules into inert substances.

Based upon sampling data collected 5 months after application of the inoculated SediMite™, total PCB concentrations in surficial sediments across the study area have dropped between 25% and 28%, with an average reduction of approximately 25%. Total PCB concentrations in surface water across the study area have dropped 23% to 47%, with an average reduction of approximately 35%. Finally, and most impressive, concentrations of total PCBs in sediment porewater, have dropped between 49% and 77%, with an average reduction of approximately 67%.

Additional monitoring is scheduled for 1 year and 3 years post-remediation, or June 2020 and June 2022. The comparison of these data will show the long-term effectiveness of the inoculant and will also help to foster other PCB cleanup projects in Delaware, including the Christina/Brandywine River Remediation, Restoration and Resilience (CBR4) project that was kicked off in September 2019.

Sampling the Christina River Basin

As part of the first WATAR 5-year implementation plan, the Team sampled toxics-impaired waterways throughout the state. The Christina River Basin, Delaware’s former industrial home, was sampled in 2015. WATAR sampling provides a comprehensive look at toxic contaminants in sediment, surface water and fish tissue  to assess current ecosystem health and also aids in the identification of potential contaminant source areas that will need further attention. Several DNREC programs participated in this 3 week sampling event.

The study results provided the WATAR team with a clear picture of where to focus future source trackback and remediation efforts, but also showed that past efforts made by multiple DNREC programs over time are having a positive impact. The informed decisions that DNREC can make from sampling events such as this one will create a more efficient pathway to achieve the goal of fishable, swimmable and potable surface water in Delaware.

Christina-Brandywine River Remediation Restoration Resilience (CBR4)

The Christina-Brandywine River Remediation Restoration Resilience (CBR4) project area is approximately 2,183 acres / 7 linear miles of the tidal main stems of the Christina and Brandywine Rivers and surrounding riparian areas in the City of Wilmington and New Castle County.

The current stage of the CBR4 is a feasibility assessment and plan to guide and complete the transformation of the lower Christina and Brandywine Rivers in Wilmington into a fishable, swimmable and potable river in the shortest timeframe possible. This will include using a logical stepwise ecosystem-based approach to assess, prioritize and plan for a suite of coordinated projects.

Mirror Lake Project

In November 2013, DNREC staff volunteers joined community volunteers, including AmeriCorps, Delaware’s Boot Camp Program and residents from a local shelter, to help with an innovative remediation and restoration project at Mirror Lake in Dover. Mirror Lake’s health has been in decline for several decades due to contaminants in bottom sediments that accumulate in fish, stormwater runoff and sedimentation, and invasive plants.

The project, co-managed by DNREC’s Remediation Section’s John Cargill and Watershed Assessment and Management Section’s Rick Greene, uses activated carbon – the same technology used in many water filters – to bind contaminants in lake sediments, rendering them unavailable for uptake by biological inhabitants.

More information on the technology and the joint DNREC-University of Maryland, Baltimore County (UMBC) partnership: Piloting New Technology at Mirror Lake.

With the addition of a new intertidal wetland that was planted in Spring 2014, the combined remediation and restoration project has helped to improve the natural beauty of the lake, increase the lake’s ecological function, and helped make the fish there safer for human consumption.

More information: Restoring Mirror Lake. Presentation: Mirror Lake Restoration.

Little Mill Creek/Meco Drive Project

In Delaware, property owners along the Little Mill Creek in New Castle County can breathe a little easier now that the Phase II Flood Risk Mitigation project has been completed. This was a joint state and federal project in which several DNREC Divisions played a pivotal role. Little Mill Creek has a long history of damaging floods. For over 60 years, extensive flood damage has been attributed to development along the flood plain on Meco, Germay and Brookside Drives, all historically built on filled wetlands. During heavy rains, the run-off from paved areas flows into the Little Mill Creek, overtoppings its banks and flooding the surrounding area. In addition, a hazardous substance cleanup site, the Meco Drive Site, was contributing petroleum contamination and PCBs to the watershed. The coordinated project provided a longstanding solution to the flooding, as well as the contamination issue. More information: The Big Clean at Little Mill Creek

PCB Mass Loading in Delaware

PCB Mass Loading in Delaware is a DNREC collaborative study between DNREC’s Division of Waste and Hazardous Substances’ Remediation Section and the Division of Water Resources’ Watershed Assessment Branch (WAB). It is a key and integral component of a much larger project that aims to link upland sources of PCBs with their primary impact in surrounding waterways. In Delaware, as with many states, PCBs are a major cause for issuing fish consumption advisories. The project considers all sites known to be contaminated with PCBs in Delaware and the information gathered will allow DNREC to look at the cumulative impact of PCBs in the area. This brings a new and more holistic perspective to the problem, which in turn could lead to innovative management solutions. Looking at all sites at once will also allow DNREC to prioritize sites for remediation based on their relative impact. For more information on PCBs, please visit EPA’s website: PCBs

DNREC’s goal is to systematically clean up these sites so these properties are useful and no longer release PCBs to area surface waters. In so doing, PCB levels in the fish will slowly improve over time and people will once again enjoy the health benefits of consuming fish.




+