EcoScience Corporation - a division of PBS&J - Raleigh, North Carolina: Environmental Surveying, Planning and Engineering Services

Piedmont Triad International Airport Authority
Indirect & Cumulative Impact Pollutant Analyses
Greensboro, North Carolina

EcoScience Corporation (ESC) performed nutrient and sediment yield comparative analyses for the proposed expansion of the Piedmont Triad International Airport (PTIA). The purpose of the study was to address potential indirect and cumulative impacts that could occur as a result of the proposed airport expansion. The study was required by the North Carolina Division of Water Quality (NCDWQ) for issuance of 401 Water Quality Certification.

PTIA’s proposed expansion includes development of a regional hub for Federal Express (FedEx) in Guilford County, NC, a new 9,000 foot runway, construction of a 371,500 square foot air cargo sorting facility, a 49,700 square foot maintenance building, a 31,400 square foot administration facility, associated infrastructure for FedEx on 178 acres, development of a cross field taxiway, and relocation of existing parking lots and other miscellaneous cargo facilities in order to accommodate airport growth.

The analyses included predictive modeling to determine future nutrient and sediment load trends. Land use growth trends were derived through cooperation and coordination with local municipalities. All study protocols were reviewed by NCDWQ prior to initiation of the models.

Work performed by ESC for these analyses included:

Existing land use in PTIA Study Area

Existing annual nitrogen loading

Land Use Development
EcoScience personnel generated several land use scenarios of the study area, ranging from “reasonably foreseeable” development to year 2019 predicted growth. ArcView Geographic Information System (GIS) software was used to generate these scenarios. Current conditions served as a baseline against which future land use scenarios could be generated and compared.

Land Use Controls
Land use (density) restrictions and utilization of structural and nonstructural Best Management Practices (primarily buffers and stormwater detention basins) were evaluated as part of this modeling effort. Measures implemented as part of these analyses include riparian buffers, mandated conservation easements of floodplains, steep slopes (over 15 percent slope), and wetlands protection. Stormwater ponds were created and used to update land use in future scenarios.

Nutrient and Sediment Analyses
We were able to accomplish nutrient and sediment analyses by utilizing Annualized Agricultural Non-Point Source (AnnAGNPS), a continuous simulation, surface run-off, pollutant loading computer model. The mathematical processes utilized within AnnAGNPS included weather generation, run-off volumes from precipitation, peak run-off from major storm events, erosion, and sediment delivery. We also used the Center for Computational Hydroscience and Engineering One Dimensional model (CCHE1D), which simulates bed aggradation and degradation, bed material composition (hydraulic sorting and armoring), bank erosion, and the resulting channel morphologic changes under unsteady flow conditions.

Summary

EcoScience Corporation personnel performed comparative analyses of nutrient and sediment yields produced by multiple, hypothetical future land use coverages. ESC compared reasonably foreseeable development to projected growth by 2019, and included several land use controls aimed at reducing comparable pollutant yields.

These studies are expected to provide detailed data on water quality issues from overland and instream nonpoint pollutant sources. These techniques are applicable to a wide range of watershed planning opportunities.

Tel: 919-828-3433

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