Monday, June 23, 2008 : 3:10 p.m.

Development and Application of a Nitrogen Loading Model to Assess Impacts to Groundwater from Sanitary Wastewater in Suffolk County, New York

Daniel O'Rourke1, Mary Anne Taylor1, Robert Fitzgerald, PE2, Martin Trent3 and Andrew Rapiejko4, (1)CDM, (2)CDM Inc., (3)Suffolk County Health Services D, (4)Suffolk County Department of Health Services

As part of a comprehensive water resources management plan for Suffolk County, a nitrogen loading model was developed utilizing three-dimensional numerical models to evaluate groundwater impacts associated with increased development in unsewered areas. The model allows for simulation of more than 10,000 point sources representing nitrogen loads from on-site disposal of sanitary wastewater on a parcel-specific scale. Input files to the model are generated using a spreadsheet that calculates nitrogen loading from standard land use types specified by the Suffolk County Planning Department. Land use attribute information from Suffolk County GIS data are incorporated into the spreadsheet and nitrogen loading rates are calculated for each land use and can be adjusted to reflect fertilizer application, population density, septic tank removal and other parameters.

 

As a case study, the nitrogen loading model was applied to an area within the Town of Brookhaven that is proposed for re-development. The model was used to simulate nitrogen loading from more than 12,500 parcels. Model simulated groundwater nitrogen concentrations from existing land use conditions were compared to observed data. Simulated nitrogen concentrations were in general agreement with groundwater samples collected at several monitoring and non-community supply wells in the area. The model was then applied to re-development scenarios having various degrees of sanitary sewering to evaluate potential impacts to groundwater quality. Using the proposed re-development land uses, shallow groundwater nitrogen concentrations are projected to increase by 18% in the study area, indicating that greater levels of wastewater treatment may be required.

 

Utilizing existing Suffolk County models as a framework, this model can be applied by the County to other areas within Suffolk to assess potential impacts of proposed developments. This paper focuses on the development of the Suffolk County nitrogen loading model and describes the results from the case study within the Town of Brookhaven.

Daniel O'Rourke, CDM Dan O’Rourke is a Project Hydrogeologist located in CDM’s Edison, New Jersey office. He has been with CDM since 2002 and has worked on various water resources projects pertaining to ground water and surface water quality. He has a Masters Degree in Geosciences/Hydrogeology from the State University of New York at Stony Brook and a Masters Degree in Environmental Engineering at Manhattan College. Mailing Address: CDM, Raritan Plaza I, Raritan Center, NJ, 08818; Phone: 732-225-7000; Fax: 732-225-7851; E-Mail: orourkede@cdm.com.

Mary Anne Taylor, CDM Mary Anne Taylor, P.E. is an Associate located in CDM’s Woodbury, New York office. She obtained a Bachelor’s Degree in Civil Engineering and a Masters Degree in Environmental Engineering, both from Manhattan College. Ms. Taylor was CDM’s Project Manager for the Long Island SWAP Project, as well as for the Nassau and Suffolk County Groundwater Modeling projects. Mailing Address: CDM, 100 Crossways Park West, Suite 415, Woodbury, NY 11797, Phone: 516-496-8400; Fax: 516-496-8864; E-Mail: taylormb@cdm.com.

Robert Fitzgerald, PE, CDM Inc. Mr. Fitzgerald is a Senior Groundwater Modeler who has been responsible for numerous studies of groundwater flow and dissolved and separate phase contaminant transport in aquifers. Mr. Fitzgerald also has extensive experience in hydrology, hydraulics and water resources management, emphasizing the application of computer simulation models. He has been responsible for the use of models in analyzing and developing programs for groundwater management and remediation, flood alleviation, reservoir yield augmentation and water quality assessment.


[ Manuscript ] Manuscript

2008 NGWA Conference on Eastern Regional Ground Water Issues