Final Environmental
Assessment –
Sweeney WTP Expansion
Proposed Project
Description
1. Proposed Project Description
1.1 Introduction
The City of Wilmington’s water treatment and distribution system is entirely owned and operated by the
City. The City operates the 27.5 million gallon per day (mgd) Sweeney Water Treatment Plant (WTP),
serving a population of approximately 121,000 (as indicated by the North Carolina Division of
Environmental Health [DEH], Public Water Supply) within the limits of the City’s distribution system as
well as a variety of commercial, governmental, and industrial customers. Bulk customers include the
Wilmington International Airport Authority, University of North Carolina at Wilmington, and New
Hanover Regional Medical Center. The Sweeney WTP consists of two parallel plants that are referred to
as the South Plant (1943 plant) and the North Plant (1998 expansion). The Sweeney WTP treats surface
water from the Cape Fear River either pumped from its own intake or purchased from the Lower Cape Fear
Water and Sewer Authority (LCFWASA).
The City commissioned the 2005 Water System Master Plan from ARCADIS in order to develop 20 and
50-year water demand projections for the existing and potential service areas and evaluate needed water
system improvements. The Master Plan includes recommendations for infrastructure planning for the
City’s water supply, water treatment, and water distribution facilities through 2025 and long-term planning
through a 50-year planning horizon. This study found that additional water treatment capacity will be
needed by 2010 and recommended that the City evaluate alternatives for expanding the Sweeney WTP as
soon as possible. It also recommended the City continue to place priority on implementing aquifer storage
recovery (ASR) projects and carefully allocate remaining water treatment capacity until the Sweeney WTP
can be expanded.
Water is a regional resource, and local governments must begin working together in order to ensure that
adequate water quality and supply are available for years to come. The City of Wilmington has had
discussions with New Hanover County, the Town of Carolina Beach, and the Town of Wrightsville Beach
concerning their future water supply needs. The City has presently secured verbal agreements with
Carolina Beach and Wrightsville Beach to provide both of these communities a maximum of 1 mgd each.
The City also plans to serve some areas of New Hanover County south of the City limits. Expansion of the
City’s facilities will benefit the area by providing a reliable source of high quality drinking water to citizens
and businesses.
1.2 Proposed Project Scope
This project consists of a State Environmental Policy Act (SEPA) Environmental Assessment (EA) to
allow the City of Wilmington to apply for approval to expand the Sweeney WTP from a treatment capacity
of 27.5 mgd to a final capacity of 44 mgd. The Sweeney WTP will be designed for a treatment capacity of
44 mgd, but will have a permitted capacity of 35 mgd initially, pending demonstration testing to re-rate the
filters. Pursuant to SEPA, any proposed WTP capacity increase greater than 1 mgd requires an EA to be
ARCADIS Project No. NC706001.0002 1-1
Final Environmental
Assessment –
Sweeney WTP Expansion
Proposed Project
Description
completed and a Finding of No Significant Impact (FONSI) to be granted before the DEH will issue
permits and approvals for this project.
The City of Wilmington requests approval for this expansion in order to meet the projected demands of the
existing service area and provide water to neighboring communities where water resources are limited.
The 2005 Master Plan showed that additional water treatment capacity will be needed by 2010 in order to
meet the needs of existing City of Wilmington customers. These demands have been updated for this EA,
and current projections show that additional water treatment capacity will be needed by 2011.
Additionally, neighboring communities have requested water from the City, including Carolina Beach,
Wrightsville Beach, and Monterrey Heights. These neighboring systems obtain their water supply from
wells, which are experiencing increasing chloride concentrations due to saltwater intrusion. The City’s raw
water intake on the Cape Fear River is protected from saltwater intrusion by Lock and Dam No. 1. The
City will be unable to meet these additional needs without the proposed project.
This EA includes evaluations of the general environmental issues related to the project as well as the
impacts of specific infrastructure components of the proposed WTP. This EA will document the need for
the project, provide an analysis of the project alternatives, and describe the existing environment, predicted
environmental impacts, and mitigative measures.
1.3 Project Area Description
The proposed service area for this project encompasses 71 square miles, including the City of
Wilmington’s existing water system service area, the existing water service areas for Carolina and
Wrightsville Beaches, un-served areas south of the City including the Cameron Property, and one area
south of the City currently served by New Hanover County (Figure 1-1).
The project area includes the service area and a 25-mile long, 50-foot wide corridor along the existing raw
water transmission main easements between the Sweeney WTP and the raw water intake at the City’s
Kings Bluff Pump Station on the Cape Fear River. The project area is illustrated in Figure 1-2.
ARCADIS Project No. NC706001.0002 1-2
NEW HANOVER
COUNTY
Raw Water Transmission Easement
Sweeney Water Treatment Plant
Wilmington
Wrightsville Beach
ATLANTIC
OCEAN
Cape F
1 inch equals 2 miles
ear Riv
0 0.5 1 2 3 4
Miles
e
Legend
r
BRUNSWICK
City of Wilmington Existing Water System Service Area
COUNTY
Carolina Beach Existing Water System Service Area
Wrightsville Beach Existing Water System Service Area
Proposed Future Service Area
Carolina Wilmington Corporate Limits
Beach County Boundary
Streams and Lakes
Figure 1-1: Service Area -
City of Wilmington Sweeney
Water Treatment Plant
Expansion Project
BLADEN COUNTY
Pump Station and Intake Sites
PENDER COUNTY
Raw Water Transmission Easement
NEW HANOVER COUNTY
COLUMBUS COUNTY
Sweeney Water Treatment Plant
Wilmington
Wrightsville Beach
BRUNSWICK COUNTY
ATLANTIC OCEAN
Legend
Raw Water Transmission Easement
RIVER
City of Wilmington Existing Water System Service Area
Carolina Beach Existing Water System Service Area
CAPE FEAR
Carolina
Wrightsville Beach Existing Water System Service Area Beach
Proposed Future Service Area
Figure 1-2: Project Location Map -
County Boundary
1 inch equals 3 miles City of Wilmington
Wilmington Corporate Boundary 2.5 1.25 0 2.5 5 7.5 Miles Sweeney Water Treatment Plant
Streams and Lakes
Expansion Project