HomeMy WebLinkAboutAgenda - 04-19-2011 - 8cORANGE COUNTY
BOARD OF COMMISSIONERS
ACTION AGENDA ITEM ABSTRACT
Meeting Date: April 19, 2011
Action Agenda
Item No. ~ r G
SUBJECT: Buckhorn-Mebane Economic Development Area Water and Sewer Design
DEPARTMENT: Planning
ATTACHMENT(S):
1. Buckhorn-Mebane EDD Concept
Sewer Layout -Phase 2
2. Buckhorn-Mebane Area Map with
Acreages
PUBLIC HEARING: (Y/N) 0
INFORMATION CONTACT:
Craig Benedict, Planning Director, 245-
2592
Kevin Lindley, Staff Engineer, 245-2583
PURPOSE: To consider an optional design alignment and sewer facility for Phase 2 of the
Buckhorn-Mebane Economic Development Area (EDD) water and sewer infrastructure.
BACKGROUND: The Board of County Commissioners (BOCC) approved a contract with
Hobbs Upchurch Associates (HUA) in November 2010 for the design of water and sewer
infrastructure to serve a portion of the Buckhorn-Mebane EDD known as Area "D1" (shown on
Attachment 1). This portion of the EDD is generally described as being bounded by Gravelly
Hill Middle School to the east, Buckhorn Road to the west, West Ten Road to the south and
Interstate 85/40 to the north. The portion of the infrastructure being designed has been
generally referred to as Phase 2 and is part of a multi-phase approach to design and build water
and sewer infrastructure to eventually serve the entire Buckhorn-Mebane EDD. Phase 1 water
and sewer infrastructure, which has already been installed and is currently in operation, serves
Gravelly Hill Middle School and several houses along Buckhorn Road and West Ten Road.
Design Options
After an initial review of the topography in the area and the draft phasing plan provided by the
County, HUA proposed two design scenarios to County staff. Option 1 is to pump the sewer
flow from Area D1 of the EDD via a force main along West Ten and Bowman Roads all the way
to Mebane's Southeast Regional Pump Station. This design option was the basis of HUA's
design contract price of $192,000 which the BOCC approved in November 2010. Option 1 also
added a backbone gravity sewer line westerly from Gravelly Hill Middle School towards
Buckhorn Road in a 400+/- acre area. Option 2 is to pump via force main along West Ten
Road to the intersection of West Ten Road and Bowman Road, at which point a gravity line
could be constructed to flow cross-country north of Bowman Road to the Southeast Regional
Pump Station. These two design alternatives are shown on Attachment 1 and labeled as
"Phase 2B-Option 1" and "Phase 2B-Option 2".
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Design and Construction Cost Considerations
Both of the design options will accomplish the original design goal of providing sewer service to
Area D1 of the Buckhorn-Mebane EDD. The design and construction of Option 1 would be the
less expensive option. The design costs for Option 1 are already a part of the contract amount
of $192,000, as noted above. For design Option 2, there would be additional design costs.
Though many parts of the design process are similar, designing a gravity sewer system is more
intricate work than designing a force main. However, HUA has stated its additional design costs
for a gravity sewer line north of Bowman Road would not cause the total contract amount to
exceed the original $200,000 cap placed in the design contract. This means that the maximum
design cost differential would be $8,000.
When considering the construction cost differential between the two design options, only the
portions of the two design options that are different will be outlined in this abstract. The majority
of the project will remain unchanged regardless of which of these design options is chosen.
The current construction estimate for the roughly 1.8 miles of sewer force main along the north
side of Bowman Road in Option 1 is .approximately $475,000. The construction of a gravity
sewer line is much more expensive than construction of a force main. The work goes slower
because precise slopes have to be maintained and often the excavation is deeper than for a
force main. In addition, because of the need to follow the natural topography, the length of the
line is longer. The current construction estimate for the roughly 2.2 miles of gravity sewer outfall
north of Bowman Road in Option 2 is approximately $1,150,000. To put this into perspective,
the total estimated cost for construction of Phase 2 water and sewer infrastructure is
approximately $3,000,000 for Option 1, so choosing to construct the gravity outfall in Option 2
would represent about a 23% increase in the construction costs.
Benefits of a Gravity Outfall in Option 2
As was noted above, choosing to construct a gravity outfall along Bowman Road will add to the
design and construction costs. However, it also adds functionality and flexibility to the sewer
design. The gravity outfall would be installed in Area "A" (shown on Attachment 1, 423 acres)
which was recently added to the County's utility primary service area in the Water and Sewer
Management, Planning, and Boundary Agreement (WASMPBA). The gravity outfall would
serve the dual purpose of transporting sewer flow from the Phase 2 area of the EDD and
allowing property owners in this 423 acre area access to public sewer. Also, because the
length of force main would be reduced substantially, the pump station upgrades necessary to
pump the wastewater to Mebane's Southeast Regional Pump Station could be less robust, e.g.
smaller horsepower pumps could be used to pump the same amount of wastewater.
If Option 1 is chosen and a force main is constructed along Bowman Road, there would be no
access to public sewer for Area A. If service is desired, a gravity sewer outfall would eventually
have to be designed and constructed to serve these properties at a later date. The design and
construction costs for the gravity sewer as a stand-alone project would be approximately $1.25
million. In addition, once the gravity sewer outfall was in place, the force main along Bowman
Road would most likely be taken out of service and abandoned and the initial $475,000 for the
force main construction would have been spent on infrastructure that is no longer in use.
Another point to consider is the current development activity in the area around the Southeast
Regional Pump Station, west of Area A. If the County had a viable design for a gravity sewer
outfall that connected to the SE Regional Pump Station, there is the potential for developers
interested in this area to help fund the construction of this portion of the sewer infrastructure. It
is much more feasible for a developer to pay for several hundred feet of sewer line extension to
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a development in Area A along Bowman Road than it would be to pay for the major extension
required to serve a development in the Phase 2 portion of the EDD. Regardless, because Area
A is near existing development, it has the potential to develop before the Buckhorn-Mebane
EDD Phase 2 area.
Land Use Plan
If the gravity outfall in Option 2 is chosen, there are some Land Use Plan changes that would
have to made in Area A, north of Bowman Road. There has been a preliminary meeting with
area residents in the Option 2 area. Staff explained the background of the area relating to land
use and utility engineering. Staff will be proposing a Land Use Plan amendment for this area
for the May 2011 quarterly public hearing to be consistent with the WASMPBA. The Efland-
Mebane Small Area Plan recommended the change for this area from AR (Agricultural
Residential) to Mixed Use (a new land use category) with a limited residential component.
FINANCIAL IMPACT: Choosing design Option 1 will not result in any changes in either current
design cost or the currently estimated construction cost in the County's draft Capital Investment
Plan for FY2011-2016. Choosing design Option 2 will result in a maximum design cost increase
of $8,000 which can be accomplished within the present budget. Construction estimates are in
the Capital Investment Plan but are presently unfunded. A $675,000 increase in the total
project construction cost could be lessened by the lower bid costs that are presently being
realized in current economic conditions.
RECOMMENDATION(S): The Manager recommends the Board:
1. Approve design Option 2 to add a 'backbone' gravity sewer to 423 acres;
2. Direcf staff (Attorney, Planning, Financial Services) to initiate any contract amendments
necessary;
3. Authorize the County Manager to sign the contract amendment; and
4. Authorize staff to begin necessary Land Use Plan amendments.
U Parcels ~ Area A ~ Central Efland Phase 2 Area D4
~ City Limits Area B Area D1 Area EFGH
ETJ 0 Area C ~ Area D2
Central Efland Phase 1 Area D3
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