Groundwater and Nitrogen Modeling to Prioritize Management Strategies for Suffolk County’s Estuaries

Monday, December 4, 2017: 4:30 p.m.
101 C (Music City Center)
Daniel O'Rourke, P.G. , CDM Smith, Edison, NJ
Mary Anne Taylor, P.E. , CDM Smith, Woodbury, NY
Kenneth Zegel, P.E. , Office of Ecology, Suffolk County Department of Health Services, Yaphank, NY
Joshua Registe , CDM Smith, Woodbury, NY
Qitao Gao , CDM Smith, Edison, NJ

Nitrogen loading to groundwater from surface activities has caused degradation of aquifer and surface water quality. In Suffolk County, New York, more than 70% of the county relies on on-site wastewater disposal systems such as septic systems and cesspools. Nitrogen loading from these systems impact both ground and surface waters. Due to the appearance of harmful algal blooms, the loss of sea grass as well as increasing nitrate concentrations in water supply wells of the sole source aquifer, evaluating nitrogen loading within the County is a priority.

Utilizing groundwater models allows for a better understanding of the impacts of historic, existing and potential future land uses on aquifer nitrogen concentrations and ultimate discharge to water supply wells and estuaries. Groundwater models were utilized to better understand nitrogen loading from various land uses within watersheds as well as the impact of potential nitrogen reduction strategies such as the use of innovative alternative onsite wastewater treatment (I/A OWTS), clustered/decentralized treatment, or traditional sewering. Nitrogen loading models have been coupled with groundwater models to simulate the fate and transport of parcel-specific nitrogen loading throughout the County.

Suffolk County has launched a Subwatersheds Wastewater Plan in which baseflow contributing areas (subwatersheds) were simulated for more than 180 surface water bodies. For each subwatershed, time of travel (from the water table to surface discharge) zones are quantified and nitrogen loading from surface activities including wastewater, fertilizer application and atmospheric deposition are calculated. The nitrogen loads were simulated as parcel based point sources using fate and transport groundwater models which ultimately provided discharge loads to the subwatersheds and more than 700 community water supply wells. Simulated nitrogen loads to surface waters were compiled with quantitative and qualitative data and utilized in a decision support tool to rank and prioritize the subwatersheds for future management strategies.

Slides in PDF
Daniel O'Rourke, P.G., CDM Smith, Edison, NJ
Dan O’Rourke, P.G. is a project hydrogeologist located in CDM Smith’s Edison, New Jersey office. He has been with CDM Smith since 2002 and has worked on various water resources projects pertaining to ground water and surface water quality and supply. He has a B.S. degree in Earth and Environmental Sciences from Lehigh University, a M.S. degree in Geosciences/Hydrogeology from the State University of New York at Stony Brook and a M.S. degree in Environmental Engineering at Manhattan College.

Mary Anne Taylor, P.E., CDM Smith, Woodbury, NY
Mary Anne Taylor, P.E. is a Vice President of CDM Smith, located in CDM Smith's Woodbury office. She holds a Bachelors degree in Civil Engineering and a Masters degree in Environmental Engineering, both from Manhattan College. She is CDM Smith’s Project Manager for the Subwatersheds Wastewater Plan, as well as for the previous groundwater model development and application projects. E-Mail:

Kenneth Zegel, P.E., Office of Ecology, Suffolk County Department of Health Services, Yaphank, NY
Kenneth Zegel, P.E., is an Associate Public Health Engineer for the Office of Ecology in the Suffolk County Department of Health Services. He is currently project manager for the Suffolk County Subwatersheds Wastewater Plan.

Joshua Registe, CDM Smith, Woodbury, NY
Joshua Registe is a junior environmental engineer in CDM Smith's Woodbury, New York office.

Qitao Gao, CDM Smith, Edison, NJ
Qitao Gao is a junior water resources engineer in CDM Smith's Edison, New Jersey office.

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