Watershed Technical Workgroup Publications

The charge of the cross-sector Watershed Technical Workgroup is to provide a forum for communication and discussion between and among the jurisdictions and other CBP participants on technical issues related to Best Management Practices (BMPs), Chesapeake Bay Watershed Model processes, and management strategy development and implementation reporting.

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Advanced OWTS BMP Panel report

The Chesapeake Bay On-site Wastewater Nitrogen Removal BMP Expert Review Panel was reconvened to specifically evaluate two proposed BMPs:

  1. Drip irrigation (at a higher TN reduction credit than currently given under the “Shallow-Placed, Pressure-Dosed Dispersal” BMP) and
  2. Peat biofiltration systems discharging to a pad or trench

Upon review of available data, the Panel recommends creating a new, creditable BMP for Drip Irrigation, which has been shown to result in a 50 percent net TN reduction through Zone 1 in the drainfield. Qualifying characteristics for the new BMP, which are described in detail in the report, require the use of pressure compensating emitters, maximum not to exceed loading rates for three different soil types and exclusion of the credit for drip systems installed in Type I (sand textured) soils.

The Panel recommends that peat systems discharging to a pad or trench not be included by the CBP as a new BMP. In particular, existing data were from studies not designed to explicitly address nitrogen removal and the TN results were highly variable and thus inconclusive. The data do appear to support crediting peat filters a 20 percent net TN reduction as an ex situ BMP, consistent with similar technologies which fall under creditable BMPs: Intermittent Media Filters and NSF Standard 40 Systems.

The Panel further recommends that the CBP track efforts underway in EPA Regions 1 and 2 to develop nitrogen sensors specific to monitoring on-site wastewater systems and to consider using such sensors (or other appropriate methods) to verify the performance of BMPs that have been approved and are being implemented in the watershed. Recommendations for outstanding research questions are also provided (the reader is further referred to the 2014 predecessor report on OWTS Nitrogen Removal BMPs and the 2016 OWTS Nitrogen Attenuation report for additional recommendations for the CBP).

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A Ten Year Summary of Concurrent Ambient Water Column and Sediment Toxicity Tests in the Chesapeake

Published on January 7, 2001

The goal of this study was to identify the relative toxicity of ambient areas in the Chesapeake Bay Watershed by using a suite of concurrent water column and sediment toxicity tests at seventy-five ambient stations in 20 Chesapeake Bay rivers from 1990 through 1999. Spatial and temporal variability was examined at selected locations throughout the 10 yr. study. Inorganic and organic contaminants were evaluated in ambient water and sediment concurrently with water column and sediment tests to assess possible causes of toxicity although absolute causality can not be established. Multivariate statistical analysis was used to develop a multiple endpoint toxicity index (TOX-INDEX) at each station for both water column and sediment toxicity data.

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