HomeMy WebLinkAboutAgenda - 03-02-2006-7bORANGE COUNTY
BOARD OF COMMISSIONERS
ACTION AGENDA ITEM ABSTRACT
Meeting Date: March 2, 2006
Action Agenda
Item No. ~ ~j
SUBJECT: Water and Sewer Capacity Implications of Increased Density in OWASA's
Carrboro-Chapel Hill Service Area
DEPARTMENT: County Manager PUBLIC HEARING: (Y/N) No
ATTACHMENT(S):
INFORMATION CONTACT:
OWASA Discussion Paper:
Water and Sewer Capacity
Implications of Increased Density in
OWASA's Carrboro-Chapel Hill
Service Area (Under Separate Cover)
Paul Thames, 919-245-2303
Ed Holland, OWASA, 919-968-4421
PURPOSE: To present information to the BOCC that is also being presented to the governing
boards of Chapel Hill and Carrboro relative to the relationship between increased development
density in Chapel Hill and Carrboro and OWASA water and sewer capacity,
BACKGROUND: At its October 24, 2005 meeting, the Chapel Hill Tawn Council requested that
OWASA provide a briefing about the effects of potential increases in allowable development
density on OWASA's ability tc meet future water supply and wastewater treatment demands,
That briefing will occur at the February 27, 2006 Chapel Hill Town Council meeting.
Presentations by OWASA Board members and staff have also been scheduled for the Board of
Commissioners and Carrboro Board of Aldermen on March 2 and March 14, 2006, respectively.
The attached discussion paper includes OWASA's response to the issues related to increased
development density and provides additional background information,
FINANCIAL IMPACT: There is no direct financial impact associated with this presentation,
RECOMMENDATION(S): The Manager recommends that the BOCC receive the information
and direct staff to provide any additional information as the Board desires..
®11VAS-A ORANGE WATER AND SEWER AUTHORITY
Quality .Service Since 1977
Discussion Parser
Water and Sewer Capacity Implications of Increased Density
in OWASA's Carrboro-Chapel Hill Service Area
February 22, 2006
Executive Summary
OWASA can meet the utility needs of increased development density within the currently
defined urban services area of Carrboro and Chapel Hill, but meeting those needs while
maintaining the level of service expected by OWASA's customers will require additional
collaboration among OWASA, local governments, and the development community..
Highly effcient water conservation technologies are readily available that can support
increased development density with little or no net increase in water service demands,
Many of these advanced efficiency measures can be implemented tluough existing legal
authority and local review and approval procedures that are already in place, but some
may require ordinance changes or new enabling legislation. OWASA is ready and
willing to provide technical assistance to Carrboro, Chapel Hill, and Orange County if
they choose to move in this direction, and we will consider adopting water use efficiency
standards for new development that will be served by OWASA.
The ultimate capacity of OWASA's water supply and wastewater treatment facilities are
based on projections of future water and wastewater treatment demands that correspond
to housing and employment levels that exceed Carrboro's and Chapel Hill's buildout
projections by more than 20 percent. We believe that this provides a conservative margin
of safety for meeting the capacity needs of future development.
OWASA's existing reservoir/quarry water supply system and its future expansion can
meet the buildout needs of the Carrboro/Chapel Hill/LJniversity community, including a
certain level of additional development density; however, our community will become
more vulnerable to severe drought conditions beginning around 2015 and lasting until the
Stone Quarry expansion is available for water storage in the mid-20.30s, The
OWASA/UNC water reuse system, which will initially serve the University's main
carnpus, is an essential tool for' reducing that future vulnerability, Other measures
include lowering projected water dematrds through conservation and improved efficiency,
and/or by developing additional supply sources. The primary goal of OWASA's long-
range conservation program is to reduce water shortage risks without having to rely on
additional sources.
OWASA water sales and reservoir withdrawals for the past four years have remained
below the historically high levels observed in 2001 and 2002. This is likely due to a
combination of weather factors, more conservative customer consumption, and the
recycling of water treahnent plant process water that was previously released to an
intermittent creek. Water withdrawals from University Lake and Cane Creels were 20
percent less in 2005 than projected in OWASA's 2001 Master Plan.
Substantial reductions in summer peak demurds at the .Tones Ferry Road Water
Treatment Plant indicate that customers are using less water for outdoor irrigation,
perhaps in response to OWASA's seasonal rate structure and to year-round conservation
standards enacted by Carrboro, Chapel Hill, and Orange County.
Decreasing peak flows at the Mason Farm Wastewater Plant during rainy periods suggest
that OWASA's long-term program to systematically identify, repair and replace older
sewer lines may be successfully reducing unwanted inflow and infiltration of stormwater
into the sewer system.
If these recent trends continue, lower peals demands will delay the need for costly future
expansions at both the water and wastewater treatment plants.
Despite significant reductions in overall consumption, the relative water demands of
major customer classes have remained virtually unchanged and are nearly identical to
those reported in the 2001 Master Plan: Single Family Residential (.31%), Multi-Family
Residential (24%), University (28%), and Connnercial/Other (16%).
The effects of increased development densities on wastewater treatment capacity are
more complex than effects on the water system. Treatment capacity is affected by both
the volume and quality of wastewater flow. The total maximwn daily load (TMDL)
restrictions for nitrogen and phosphorus that will be established by .Jordan Lake rules that
the North Carolina Envirorunental Management Commission is expected to consider later
this year may ultimately limit the amount of development that can be accommodated in
the Carrboro-Chapel Hill urban services area.
OWASA - Wnter arrd Sewer Capacity 6nplicatiars oJhrcreaserl Deoelopnrent Densiry~
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Introduction and Back:sround
On October 24, 2005, the Chapel Hill Town Council requested that OWASA provide a
briefing about the effects of potential increases in allowable development density on
OWASA's ability to meet future water supply and wastewater treatment demands,
Copies of Council Member Jim Ward's petition and the Town Manager's letter to
OWASA are included as Attaclmnents A and B.
This Discussion Paper provides background for that briefing, which is scheduled for
February 27, 2006.. The paper will also support presentations to the Orange County
Board of Commissioners and Carrboro Board of Aldermen on Mazch Z and Mazch 14,
2006, respectively,
Purpose and Scope
Purpose: To provide information and generate discussion among local elected officials
and staff, OWASA Board members, interested citizens, azld the development community
about OWASA's water and wastewater capacity and our' ability to meet future demands if
higher development densities are allowed. Topics include:
• Long-term adequacy of the water supply.
^ Demand forecasts -how we generate them.
^ Options for additional supply.
• Conservation, demand management, and improved water efficiency.
^ Wastewater treatment capacity..
^ Pipes in the ground.
• Recent and aziticipated development trends in Cazrboro-Chapel Hill.
^ Recent trends in water and sewer service demands.
Scope: This report focuses primarily on issues related to residential, commercial, and
downtown development in Carrboro and Chapel Hill. It does not address increased
development density per se associated with UNC's main campus or Carolina North
development, although projections for these facilities have been factored into all demand
forecasts presented here. OWASA continues to work closely with the University in
supporting on-campus infrastructure needs -including water conservation and reuse
strategies for both the main campus and Carolina North -and has incorporated the most
up to date University information available in our estimates of long-teen water supply
and wastewater treatment demands for the OWASA system.
The Question: Can OWASA continue to meet ozer• community's water and wastewater
service needs if development densities are allowed to increase beyond the levels cza~rently
permitted by local comprehensive plans and >oning ordinances?
The Short Answer is Yes - To a Degree: We can and will meet the utility needs of
increased development density within the defned urban swvices w°ea of Car~•bor•o and
OWASA -Water and Sewer Capacity Implications of hrcreased Development Deasiry~
Page 3 of 21
Chapel Hill, but achieving tlzis while still maintaining the level of service desired by
OWASA's customers will require additional and cwztimted collaboration among OWASA,
local govet°mrtents, and the denelopmettt cotmnwtit~/. Amore complete answer is
provided below.
Long-Term Adequacy of OWASA's Water Supply
An overview of historic and projected water demands, current azzd future supply
capacities, and potential deficits is provided in Figure 1 and explained below.
'~ Existing System ~ Quarry Pump Improvements ~ Expanded Quarry
]O.Yr Salo Yiaitl
Without Rouse ,.,_._.,..._,~.~.-._._.._r.___._..-_._ _.- __._.- . _- -
LouROwa .{'
Wilh Reuse ~~~~' ____
Mare Reuw ... ~.~ _. _._._ _.._.__.___. __._. __.._. -
20Dt Master Pian _ _ _ _ _ ,
"Expectetl Growth" ~ " w ~ •YJN
300] arou0hl
~ i ~~ ~ ~ i-' Jordan lake (or orhersupply
---- ~~~s! ,~ ----* -~-- ----- ------ alternative) needed when average day
~~~ demand =target yield
` Eventual quarry storage volume: 2 4 - 3.0 bllllon gallons.
Reuse Demantls per McKim 8 Creed Technical Memorandum #3 (gl8/OS).
^ Solid Diamonds: actual raw (untreated) water pumped from University Lalce and
the Cane Creek Reservoir from 1980 tluough 2005. The substantial decrease during
the past tlnee years reflects reduced customer demands since 2002 and the recycling
of water treatment process water, first implemented in 2002. (Water that was
formerly discarded as part of the normal treatment process is now recycled back
through the water treatment plant.)
^ Dashed Black Line: raw water demands as originally projected in OWASA's 2001
Comprehensive Water and Sewer Master Plan.
^ Solid Red Line: our current estimate of future demands if the OWASA/tJNC
wastewater reuse project for the main campus is not implemented. (The reuse
project will enable UNC to use highly treated OWASA wastewater instead of
pWASA-Water and Sewer CapacityGnptications o~hlcreased Development Density
Page 4 of 2!
drinking water for certain non-potable purposes, such as heating and cooling, on the
main campus.)
^ Green Lines: firture demands with the OWASA/UNC reuse project on the main
campus in place and operating in 2008, The "Less Reuse" and "More Reuse"
boundaries indicate the likely rarrge of future demands, OWASA's projections
reflect all information currently available about ongoing and planned development
on the University's main campus and Carolina North, but do not include any
allowance for demands that could be met by water reuse at Carolina North, The
basis for these projections is discussed later in this report..
^ Black Stepped Horizontal Lines: the capacity of OWASA's University Lake/
Cane Creek/Stone Quarry reservoir system as currently configured, with planned
pump improvements, and with the Quarry's eventual expansion in the early 2030s,
The upper stepped line is the reliable "safe yield" of the system under drought
conditions that would be expected to occur approximately once in 30 years, The
lower stepped line is the safe yield under the drought-of-record conditions that
occurred in 2001-2002.
The intersection of the diagonal demand lines in Figure 1 with the horizontal capacity
lines represent periods when anticipated demand will equal or exceed the estimated safe
yield of the reservoir/quarry system, This does not mean that we will run out of water at
that time; but, the system will only be able to provide the indicated amount of wcztet• if the
30~~eat° or 1001 drought-of-record should recur. On the basis of nearly 80 years of
hydrologic records, the probability that .30-year drought conditions will not occur in any
given year is 29 out of 30, or nearly 97 percent. In other words, there is a 97 percent
chance that the reservoir/quarry system will produce more than the specified safe yield in
any given year. The probability of exceeding the record drought yield (which is less than
the 30-year yield) is even greater.
The probability of depleting OWASA's reservoir/quarry system under various conditions
of supply and demand is illustrated in Figures 2, .3, and 4. These figures also provide
graphic guidelines for determining when to invoke different levels of OWASA's water
conservation standards,
^ Each cell of the table contains an integer and a percentage, which represent the
probability that reservoir levels will decline to 20 percent or less of full capacity
during the following 18 months, These results were derived from spreadsheet
model runs of almost 80 years of daily streamflow data, updated through January
200.3, and driven by monthly water demand and reservoir storage at the begimiing of
each month, Calculations were based on average amoral raw water withdrawals of
9.15 million gallons per day (mgd) for Figure 2; 10 mgd for Figure .3; and 11 mgd
for Figure 4, and adjusted with shorter term demand ratios, which are reflected in
monthly demands shown at the top of each column. (Actual reservoir withdrawals
during 2005 averaged 8.4 mgd,)
OWASA - Water and Sewer Capnci(y /mplicntioas of G~creased Development Densi(y
Pnge S of 2!
^ Each row of the table corresponds to a month, and each column corresponds to
reservoir storage at the begimiing of that month. Storage is subdivided into five-
percent increments and also expressed as millions of gallons of total storage.
^ Colors indicate the corresponding conservation stage or risk level implied for each
condition. Colored borders around selected cells represent actual reservoir storage
conditions at the begimring of that month during the severe drought year of 2002
(black), last year 2005 (blue), and the current year 2006 (orange).
Figure 2. Reservoir Drawdown Frequency and Guidelines for
Conservation Triggers, Average Demand = 9.15 mgd
Number of times (or percent of years) during the 77-year streamflow record in which
reservoir storage would have declined to 20% or less during the following 18 months,
Jan Feb Mar Apr May Jun Jui Aug Sep Oct Nov Dec
6.0 6.2 60 6.3 B.2 9.8 10.5 106 t03 98 9.0 61
tl mtl m tl m tl mtl m tl m e an d an d m tl mtl m tl
m 0 0 0 e. 0 0 0 0 '. 0 :0 0 :' 0 0
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v-' i 27% ¢B%'!= 22R ~='6 90% ` 4%
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rc n e to 27 ;: 2s '~ ~ 3
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3 4 6 ~~t7 93 ~ ~i6 ";- 5
Conservation Stages and NORM ADV #t #2 #3 EMRG
Risk Levels - o-t%£ a.fi^r. 6-21% 9td7°{y
2002 Reservoir Levels ~ 2005 Reservoir Levels f 2006 Reservoir Levels
OW~1SA -Water and Sewer Capaciq~ Gnplicatious oJLrcreased Development Deu-si{y
Page G of ? l
Figures 3 acrd 4 illustrate the relative risks and conservation guidelines of the current
reservoir/quarry system under demand conditions of 10 mgd and 11 mgd.
Figure 3. Reservoir Drawdown Frequency and Guidelines for
Conservation Triggers, Average Demand = 10 mgd
Conservation Stages and NoeM nov ai ax as emac
Rlsk Levels - °t% sex amx fx.azX
2002 Reservoir Level I 2005 Reservoir Levels 2006 Reservoir Levels
OWASf1 -Water and Seiner Cnpnci(y /nxplicntiorrs of Lxcreased Development Deirsity
Pnge 7 of l /
Figure 4. Reservoir Drawdown Frequency and Guidelines for
Conservation Triggers, Average Demand = 11 mgd
2002 Reservoir Levels , 2005 Reservoir Levels 2006 Reservoir Levels
Figures 1 tlu-ough 4 indicate that our community will become more vulnerable to severe
drought conditions, especially beginning around ?015 until the expanded Stone Quarry is
available for water storage sometime in the mid-2030s. We can lessen that vulnerability
by reducing projected water demands and/or by developing additional water supply
sources. The primary goal of OWASA's conservation and demand management
program, as adopted by the Board of Directors in April ?005, is to reduce water shortage
risks without having to rely on water from additional sources. Suggestions about how
this might be achieved through increased water use efficiency, especially in new
development, are discussed later in this report.
OWASA - Wnter and Sewer Capacity /niplicafions oJGrereased Derelopnient Density
Page 8 of ? l
Conservation Stages and NORM AOV #i #2 !!J EMRG
Risk Levels onx' aax pax z+~azx'
Mow Does OWASA Estimate Future Demands for Water and
Wastewater Service?
Future demand projections axe generated from currently available information about
plans for major new development activities (such as UNC's main campus and Carolina
North), changes in local building trends, recent water consumption data and trends, reuse
projections from the University, and assumptions about future water conservation anxong
all customer classes. A list of key assumptions and information sources on which
OWASA's most current projections axe based is presented in Attachment C. Wastewater
demand projections are generated by applying an empirically derived factor of 0.92.3 to
corresponding drirllcing water demand projections, reflecting the fact that only a portion
of the drinking water used in the community is returned as wastewater, A spreadsheet
with detailed calculations and results is available on request..
Long-term demand forecasts extend through 2050, when we assume that build-out will
have occurred; i.e., forecasts for 2050 represent OWASA's best guess at "ultimate"
capacity needs. We recognize that Carrboro's and Chapel Hill's projections of future
population and emplo}anent, as reflected in Transportation Analysis Zone (TAZ) data, do
not extend beyond 2030 or 20.35, and that both towns expect to be substantially built out
by then. OWASA's pr~ojectioras of future water mrd wastewater treatment demands
therefore con°espwtd to housing and employment levels that exceed Cm°rboro's ar:d
Clsapel Hill's buildout projections by more than 20 percent. We believe that tlris
provides a conservative margin of safety for meeting the capacity needs of future
development.
We also recognize that the actual pace and timing of growth in the community and the
University may result in short-terns departures from our projected demand trends, but
such departures are not expected to affect long-terns estimates of water and sewer system
capacity needs. As more detailed o owth plans are developed by Carrboro, Chapel Hill,
and UNC, OWASA will continue to revise and refine our pxo,jected demands accordingly..
We expect, for example, that the more or less linear pattern assumed for future b owth (as
depicted in Figure 1), will likely bend upward in the middle years before leveling off at
or below projected buildout levels,
Are There Any Options for Additional Water Supply Sources That
Could Reduce Our Vulnerability to Severe Droughts Before the
Expanded Stone Quarry Is Available in the 2030s?
OWASA's 5 percent allocation of the Jordan Lake water supply storage capacity will
yield an average of about 5 mgd. If used by our community, this could substantially
reduce our vulnerability to severe droughts until the expanded Quarry Reservoir is
available in the 20.30s. However, constructing facilities to obtain and transport water
from Jordan Lake to OWASA's water treatment plant in Canboro would cost
approximately $45 million in today's (2006) dollars - an expensive investment for a
OWASA -Water and Sewer Capacity /mplicatiars of tncrensed Derelopnrent De»sity
Page 9 0~ ZI
relatively small amount of additional capacity that OWASA would no longer need after
the expanded quarry is developed.
A more viable scenario might be to obtain supplemental water through a paztnership with
neighboring utilities, such as Durham, Cary, or Chatham County, who already have
developed - or plan to develop - water supply facilities at Jordan Lake. One option
would be for OWASA to buy in to the construction or expansion of facilities could
,jointly serve two or more entities. We would then receive treated water directly through
our existing intercomnection with Durham. Contractual agreements could be
appropriately structured to guazantee a desired amount of water under specified terms.
(Any such agreements would be subject to local approval per the Water and Sewer
Management, Planning and Boundary Agreement to which OWASA is a pazty along with
the Towns of Carrboro, Chapel Hill, Hillsborough, and Orange County.) A special study
is currently underway tlu-ough the UNC Water Resources Research hrstitute's Urban
Water Consortium to analyze the overall treatment, transmission, and interconnection
capacities needed for OWASA, Durham, and Cary to meet their long-term demands with
supplemental water from .Jordan Lake. The study will also outline a range of potential
terms and agreements that might accomplish that goal.
Conservation, Demand Management and Improved Water Efficiency
In April 2005 OWASA's Board of Directors adopted a Goal and Objectives ,for
OWASA's Long-Teem Water Conservation and Demand Martagernet¢t Program. For dre
first time, this policy identif es conservation as a key element of our overall water supply
planning process and commits to the creation of a long term conservation and demand
management prograzn. Highlights of the policy include:
Overall Goal: "To develop, fund, and implement acost-effective water conservation
and demand management program that will meet our community's long-term water
supply needs (tlu-ough 2050) by making the highest and best use of our local water
resources and eliminating the need for costly new water supply sources azrd facilities."
For Water Supply Sources: "To assure that amiual average day raw water demand does
not exceed the reliable capacity of OWASA's existing and plazmed supply sources (Cane
Creels Reservoir, University Lalce, and the Stone Quarry Reservoir), where "reliable
capacity" is the estimated yield of the system under extended periods of low streamflow
conditions, such as those that recur approximately once every .30 years, or under more
extreme conditions, such as those of the 2001-2002 "drought ofrecord."
For Treatment, Storage, and Distribution Facilities: "To manage peals day treated
water demands in ways that will allow the deferral of major capital projects, such as
expansion of the .Tones Ferry Road Water Treatment Plant and associated finished water
pumping and storage facilities."
OWASA - [4'nter mid Server Cnpnctty lmplicatians aJ /ucreused Development Densit)+
Page l0 oJ2/
A key objective is to pursue conservation measures that are acceptable to and cost-
effective for current and future customers.
Improved Water Use Efficiency Is Part of the Answer
With effective planning, existing water conservation technologies can support increased
development densities with little or no net increase in water service demands. By
reducing expected water use by 25 percent, a given volume of water can accommodate .3.3
percent more units, where a "unit" may be a dwelling unit, plumbing fixture, square foot
of developed area - or any other wait to which a rate of water use can be assigned. Let's
assume, for example, that each unit of a 50-unit multi-family residential project uses 100
gallons of water per day (gpd), for a total of 5,000 gpd, If water use is reduced by 25
percent (to 75 gpd per unit), the same 5,000 gallons of water can support a total of 67
units rather than ,just 50, representing a "density increase" of 33 percent with no net
increase in the projected water needs. Greater or lesser improvements in water efficiency
could accommodate greater or lesser density increases.
Such efficiency improvements (conservation) are achievable through existing and readily
available technologies. If desired, marry of these can be implemented through
development review and approval procedures that already exist locally, Examples
include:
• Rainwater "harvesting" for non-potable uses, such as irrigation or toilet flushing,
• Specifications for drought tolerant and sustainable landscaping and/or irrigation
system design.
• Requirements for effective ultra-low flow (high efficiency) plumbing fixtures that
are more efficient than required under the National Energy Policy Act of 199?.
• Required retrofit of older plumbing fixtures to high efficiency fixtures upon resale
or redevelopment of existing properties (may need enabling legislation).
• Individual metering or sub-metering of new multi-family construction,
• Requirements to extend or connect to OWASA's reclaimed water system, where
such service becomes available,
• Other conservation management practices, as may be appropriate
Mazzy of these and other water efjzciencar measures can be implemented through e.;ristizzg
Town and County review and approval procedures -both at the administrative and
policy level - without the need for local ordinance changes or new enabling legislation.
OWASA is ready and willing to provide tecTvzical assistance to the Towns and County if
they choose to move in this direction. Additionally, we will consider the feasibilit)r of
adoptizzg "watez° use e~ciezzcy stazzdards of service"for new developments that will be
sewed by OWASA.
04t~ASA -Water mzd Seiner Cnpnciry /mplicatio»s of7ncreased Development Densiry~
Page l 1 of ? l
Does Conservation and Improved Efficiency Save Capacity at the
Wastewater Plant?
The effects of increased development densities on wastewater treatment capacity are
more complex than on the water system. Wastewater plant capacity is substantially
affected by both the volume of flow (which is mostly water) acid the strength or amount
of the waste contained in that flow. Using water more efficiently through practices such
as those outlined above can help reduce the volume of wastewater, but the amount of
pollutants in the untreated sewage that must be treated will remain the same. Waste loads
(the actual amount of pollutants) will generally increase with increased development
density.
OWASA addresses wastewater treatment and capacity issues though the selection of
specific processes or combinations of processes needed to produce a high quality effluent
(treated wastewater released to the enviromnent) that meets applicable environmental and
water reuse standards. Those decisions are made in the context of capital improvement
projects needed to periodically increase treatment capacity and/or to respond to new or
anticipated regulatory requirements. The estimated buildout capacity and future plans for
OWASA's Mason Farm Wastewater Treatment Plant are based on our best projections of
future flow, wastewater strength, and regulatory requirements. Long-teen plans for the
wastewater plant will continue to evolve as treatment technology evolves and as other
assumptions change or become better defined.
Although increased development density may increase the amount of waste that OWASA
must ultimately treat, it is w4ikely that this will affect total capacity or future treahnent
plant decisions as signif candy as new or more stringent regulatory requirements, such as
the total maximum daily load (TMDL) restrictions for nitrogen and phosphorus that will
be set forth in .Jordan Lake rules that the North Carolina Enviromnental Management
Commission is expected to consider later this year.
Pipes in the Ground
OWASA's overall water and sewer infrastructure -the pipes in the ground - is adequate
to accommodate reasonable increases in development density.
The water distribution system (pumps, pipes, and storage tanks) is generally designed to
meet fire flow requirements that are substantially higher than everyday needs. The
wastewater collection system, with a minimum pipe diameter of eight inches, is able to
accommodate flows from most foreseeable residential or commercial development. The
capacity of downstream sewer outfalls and interceptors is reviewed systematically
through capital improvements projects such as those underway or about to begin in the
Morgan Creels and Upper Bolin Creels sewer subbasins, These evaluations rely
extensively on existing or proposed land use, zoning, and density scenarios to estimate
the capacity needs of downstream sewers.
OWASA -Water and Sewer Capacit)~ hnplrcations oJGicrensed Development Densiry~
Page 1? of 2/
As with other components of the OWASA system, our water distribution and wastewater
collection needs are reviewed azid updated as new requirements or revised information,
such as anticipated development density, become available.
Recent and Anticipated Development Trends
The plazming staffs of Carrboro, Chapel Hill, and OWASA recently convened to discuss
local development trends, water and sewer utility implications, azrd information issues
related to growth and buildout forecasts for OWASA's Carrboro-Chapel Hill service
area. Staff participants were in general consensus on the following:
• Recent trends reflect the decreasing supply of raw land available for new residential
and commercial development in the Cazrboro-Chapel Hill Urban Services Area.
Traditional patterns are shifting toward infill and redevelopment at higher densities
than we have historically experienced.
• The number of detached single family homes constructed on relatively large
undeveloped lots appears to be declining from the very stable rate of about .350-400
new homes per year observed since the early 1980s, More single family residential
construction is occurring on smaller (undeveloped) lots; a greater number of older
homes are being renovated and/or expanded; and, more requests are being filed for
tear-down re-development and/or subdivision of existing in-town lots.
• Similar trends toward buildout are occurring in both Canboro and Chapel Hill.
Although there are still large tracts of currently open land in Canboro's Transition
Area, development plans already exist or have been approved for a large portion of
that area. The areas already spoken for include properties in perpetual conservation
easements, large-lot subdivisions, public school/park property, a Town of Carrboro
public works site, and several locations where development applications aze under
review. Approximately half or less of the wrdeveloped/underdeveloped properties in
Carrboro's Transition Area are not included in any of these categories and are
therefore considered to be available for new development.
• Consistent with these observations is an increasing proportion of new attached,
townhouse style residential construction as well as applications for mixed-use
(residential/commercial) projects.
• Based on existing water use data, OWASA staff expects the shift towazd smaller
residential lot sizes and more townhouse/multi-family construction to result in
decreased demands per unit for water and wastewater service..
• Detailed plans are underway for mixed use redevelopment projects in Carrboro (the
new Arts Center complex, Butler property, Calvin Mellott property, Concrete Plant
Site (the undeveloped portion)) and in Chapel Hill (Wallace Parking Deck, Lot 5
Redevelopment, University Village, Greenbridge, and more).
OWASA -Water mrd Se~oer Capacity Gnplicatious of hrcreased Development Density
Page l.? of 31
Recent Trends in OWASA Water and Sewer Demands
Water sales have remained below historical highs recorded in 2001 and 2002 even
though single family home construction has increased at a stable rate (Figures 5 and
6). Withdrawals from the University Lake/Cane Creek Reservoir/Stone Quarry
system during 2005 were 20 percent lower than projected in OWASA's 2001
Contprebensive Water and Sewer Master Plan (Figure 7)-
1989-iB09 Av9rav9:
0.t90 m9tl Now
Oomantl pvr Yoar
Figure 6. Single;Family Residential Accounts
Calendar Years 1992-2004
t4,o99
m
c to 099 __ __.
~ 1002.2004 AVemge
-
v 000 ---
tT 366 New SPR -. ~
_
Q , Account, per Year
Y
tt,999
ai
r
E 19,999': - ~ .- ° -
~
~.
~ ~ ."
9,999
1992'. '1984 - 1996 1998 2000: 2002 ' 2004;
Figure 7.
11 Projected and Actual Raw Water Demands
a :9m arolaaoa .~
. .
"
n
w r~
~
~
y
o
0 '; '~
~ Y
7
r
t;
_ ..,
_
2000 2001 2002 2003 2004 2005
Projected Demantls: per OWASA's 2001 Master Plan
Recycletl Process Water: Water Ihat was formetly discardetl as paN of the normal
Irealmenl process is now recycletl IhmuOh the water treatmem plant
Raservoir Withdrawals: Total water pumpetl directly from reservoirs to the
Irealment plant
aaanwa
Pmcaaawamr '.
n .,..
OW~tSA -Water mfd Sewer Capacity Implications of Increased Development Density
Page 14 of Zl
• Substantial reductions in summer peak demands at the .Tones Ferxy Road Water
Treatment Plant indicate that customers are using less water for outdoor irrigation,
perhaps in response to OWASA's seasonal rate structure and to year-round
conservation requirements enacted by Catrboro, Chapel Hill, and Orange County
(Figures 8 and 9).
Figure S. ! Average;and Peak Day Demands, 1996-2005
`£
1a ____ ... ___ _ - - - -
q
12
~
~
"~ _
}'.
_ ~
`
._
__
r-
-
,E ,~ y, ~ ,
,
~ ~ ~
e
~
~
~ _
,~^
'' G
Q ~ :~ ~ .~
4
1996 1997 1996 ' 1999 200D ( 2D01 2002 4 2003 20D4 2005
Figure 9, ti Water Demand Peaking Factors, 1996-2005
':7
-----.
.7D
1.65: -~ ~ ~-~ ~- ~ ~ ~- ~-~- Mastar Plan AssumPtlon = 7.65 --.--
~ 16D --- --- =~ --_ __ _ ___
~ 1
55 -- _. a ___ .f _~ __ _--
.
8 1.50
_
- ~ ._. ~%~-_
C
1.45:
' ----- --- --- Adoplod Gaal: To not oxcoad 1.45 --
a _
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n 136
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.zo
1996 :1997 1999 !1999 2000 20D1 2002 .'.2003 2D04 'P2005
V5 s
%~C,Sk~f34tl/i
tr(t~Ui'ati~
Peaking Factor =Maximum One-Day Demand Divided by Average Annual Demand
• Decreasing peals flows at the Mason Farm Wastewater Plant during rainy months
suggest that OWASA's long-term program to systematically identify, repair and
replace older sewer lines is successfully reducing unwanted inflow and infiltration of
stormwater into the sewer system (Figure 10).
figure l0. : Wastewater Plant Peaking Ratios 1996.2005
Maximum Month Fiow : Annual Average
tso
10
' 3001 Mastor Pian Assumod
c 1.40
' .. ~.~~~_~.~..~..~ , Peakin0ftatlo=1.4
€ ~..~_~_~.~_~_~_~ ..
c
.
Q '. Ac Wa120D0.20D6 PaakinD
•• i.]D
L ---_ ... _._..____ ,G3 ...___. ___ ____.__.. _ _._ ftalio=1.10
C
g° R 120 = T ;ter- - ,'
w ~" , : _ `~ - -
q ~s' .
~~' .+~ ,
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~ 110 - " _ r^~' ~ - _- .~
100 ~"'_,> 3/,`Y! - ~' ~_ :' ~ _ ~ _
'
0
90 ""' "'
.
.
1996 1997 1996: 1999 2000 2001 2002 2003 2004 2005
OWAS~1-Water and Se+aer Capacity Inrplications of Increased Del~elopmerrt Densit7~
Pnge 1.5 of 21
• If these recent trends continue, lower peak demands at both the water and wastewater
treatment plants will delay the need for costly future expansions. The red and
b ~een stars in Figures 11 and l2 illustrate the substantial effects that demand
management or peak flow reductions can have on the timing of major expansions at
both plants.
Figure 11. Jones Ferry: Road Water Treatment Plant
' 'Peak Day Finished Water Demand vs. Plant Capaci
as
o a0' Projected Demand
~ No Reuse, PF - 1.65
c 25 _ __.~__._.__ ....____ _.. ..._. -_.__
m
m
WTP Capacity Projected Demand
~ zo ~----- - - - - With Reuse, PF =1 45
m
0
s
m i5'.
-._- ____._-. _... ...___ _ _
a ••
••
• •~•
~
10
1995 2000 2005 2010 2015 2020 '2025 2030: 2035 2040 2045 2050
Present Treatment Capacity = 20 MGD
PF =Peaking Factor =Ratio of Peak Day to Average Day
The red line in Figure 11 represents peals day demand projections for OWASA's
.Jones Ferry Road Water Treatment Plant assuming a higher one-day peaking factor of
1.65, as proposed in OWASA's 2001 Master Plan, and no OWASA/UNC reuse
project. The sreear line represents demand projections with a lower peaking factor of
1.45, which was adopted as a long-teen goal by the OWASA Board of Directors in
April 2005, and assuming the reuse project is in place. As noted by the red and
green stars, implementing the wastewater reuse program with IJNC and reducing the
peak day demand factor from 1,65 to 1.45 is expected to defer the next major
expansion of OWASA's water treatment plant by more than 10 years.
Figure 12. 'Mason Farm Wastewater Plant Capacity vs.
ao Actual and Projected Max Month'Flows
Projactotl Maz Month
~ 25 - -.. ......_..._.._ with PF=1.4 _
O
m
a 20'.
__ _..._____.- --._._ __ _....~__._.
N -
o WWrP Capadry
t j 75 _ -_._'..".'_ _ _. ___. __-- -- Praloctotl Maz Month `
c wi(h PF = 7.2
S
5
~ ~.
1995 2000 2005 2010 2015 2020 '.2025 2030 '2035 2040 2045 2050
Present Treatment Capacity of 12 MGD Will Be Increased to 14.5 MGD
When Current Upgrade is Completed in 2008
OWASA -Water and Sewer Cnpncity Guplicatiorzs of hrcreased Del~elopmwtt Detrsity
Page lG oj2l
PF =Peaking Factor =Ratio of Max Month to Annual Average
Similarly, the red line in Figure 12 represents maximum-month flows at the
wastewater treatment plant projected with a maximum month peaking factor of 1,4, as
proposed in the 2001 Master Plmt. The green line represents projections at a lower
peaking factor of 1.2, which appears to be more typical of actual maximum flows in
recent years, perhaps reflecting the results of OWASA's long-term program to reduce
stonnwater infiltration and inflow, As with the water treatment plant, these peak flow
reductions could allow substantial deferrals of the next major wastewater plant
expansion.
• Despite significant reductions in overall consumption when compared to pre-drought
levels, the relative water demands by major customer classes (Single Family
Residential, Multi-Family Residential, UNC, and Commercial/Other) have remained
virtually unchanged from those reported in the 2001 Master Plan (Fig. 13).
Fig. 13. Percent of Total Use By Major Customer Group
Calendar Years 1999-2004
m
N
~ 100% t
~
~
DD%
18/p
°
~
- 18/0
° ~
'!B°1°
..1~,.
8%
AB%'
~ ~~
^18% . Comi7VOtha/
~ 70% .- _- _ _ _.
~ ,60% - - _ __ _
Q 50% ^._" _ ~r
I"' 40% 25°fo 24°k 2d% 23% 24% 24%
`o ._>, "'f = MutiiFalnily~=
_ _ ~~
~ 31% 38% i 31/ 31% 31% 31°/
a 10% -- ~ --~ ~~_f -- -- -~ ~ _-~ Single Family
0%
1999 2000 2001 2002 2003 2004
Summary
A combination of factors and trends support the conclusion that OWASA cats meet the
utility needs of increased development density within the currently defined urban services
area of Carrboro and Chapel Hilh
The ultimate capacity of OWASA's water supply and wastewater treatment facilities are
based on projections of future water and wastewater treatment demands that correspond
to housing and employment levels that exceed Carrboro's and Chapel Hill's buildout
projections by more than 20 percent. This provides a conservative margin of safety for
meeting the capacity needs of future development. Recently declining bends in water
consumption, as well as the shift toward smaller residential lot sizes and more
OWASA -Water and Sewer Capnci[7~ Litplications of /ncreased Development Density
Page 17oJ?I
townhouse/multi-family construction with lower demands per unit for water and
wastewater service, may offer additional margins of safety,.
The existing reservoir/quarry water supply system and its future expansion can meet the
buildout needs of the Carrboro/Chapel Hill/iJniversity cormmunity, including a certain
level of additional development density; however, our community will become more
vulnerable to severe drought conditions begiiming around 2015 until the Stone Quarry
expansion is available for water storage in the mid-20.30s,. This vulnerability can be
lessened by reducing projected water demands -especially through such essential
programs as the OWASA/IJNC reuse project -and/or by developing additional supply
sources. However, the primazy goal of OWASA's long-range conservation program is to
reduce water shortage risks without having to rely on additional sources.
The effects of increased development densities on wastewater treatment capacity are
mare complex than effects on the water system, Wastewater treatment capacity is
affected by both the volume and quality of wastewater flow, The total maximum daily
load (TMDL) restrictions for nitrogen and phosphorus that will be set forth in Jordan
Lake rules that the North Cazolina Environmental Management Commission is expected
to consider later this year may ultimately limit the amount of development that can be
accommodated in the Carrboro-Chapel Hill urban services area,
Meeting the needs of additional density while still maintaining the level of service
desired by OWASA's customers will require additional and ongoing collaboration among
OWASA, local governments, and the development community,
~i~
Edward A. Holland, AICP
Plamiing Director
OWASA -Water and Server Capacit)+ Lnplications of Lvcrerrserf Development Density
Page /8 of 3l
Attachment A.
MEMORANDUM
TO: Mayor and Town Council
FROM: Jim Ward, Council Member
SUBJECT: Comprehensive Plus
DATE: October 24, ?005
Recently the Council briefly discussed the possibility of revisiting all or portions of the
Comprehensive Plan, to consider in greater detail, areas within the Town's zoning
,jurisdiction, where additional density may be appropriate. The Council requested that the
Mulager prepare a report with options for the Council's consideration about how the
Council might approach updating segments or all of the Comprehensive Plan.
As one of our considerations, Ibelieve we need to understand the effects of denser
development on demand for water supply and wastewater treatment. I believe the density
chuiges considered by the Council to date (i.e., downtown economic development
initiative and University Village) will not have a significant effect on either water supply
or waste water treatment capacity.: However, as we advance the broader issue of
increased density within our urban services boundary, it is important that we schedule
early and ongoing input from the Orange Water and Sewer Authority (OWASA) in order
to ensure the adequacy ofwater and sewer services for the long term.
Therefore, I request that the Council seek a briefing from the Orange Water and Sewer
Authority about projected capacities of water supply and waste water treatment systems
and the assumptions upon which their projections are based, along with discussion of the
potential effects of allowing greater density within the Town's zoning jurisdiction.
OW~ISA -Water mul Sewer Cnpacig~ hnplicatiorts of hicreaserl Development Density
Page ! 9 0~ 2!
Attachment B.
~,~~
. .
f'h;,
,, I0
Town of Chapel Hill
November S, 2005
Mr, Ed Kerwin
Executive Director
Orange Water and Sewer Authority
400 Jones Petry Road
Carrboro, NC 27510
Dear Mr. Kerwin:
At its October 24, 2005 meeting, the Town Council requested that we communicate with you to
request a briefing about the effects of increases in development density on the ability of the
Orange Water and Sewer Authority to meet water supply and wastewater treatment demand,
More specifical]y, the Council has considered certain development proposals that would increase
development densities at specific sites, and has expressed interest in considering increases in
development densities at other sites throughout Town, principally at the present locations of
commercial development The Council wishes to hear from OWASA about the potential impact
of such actions before it makes further decisions.
I will be pleased to discuss the Council's interests as you desire, We ltope t11at you would be
able to prepare materials for the Council's consideration at a meeting in January or February,
2006. A brief presentation also would be useful,
Please let lmow your preferences so that we may agree on a specific schedule.
Sincere
~~
W. Calvin Horton
Town Manager
405 Martin Luther King Jr Blvd, Chapel HIII, NC 27514-5705 (919) 968-2743 (919) 969-2063 fax
www.townofchapelhill org
Attachment C.
OWASA Water Demand Projections
Basic Assumptions and Information Sources
(The following assumptions and information were used to generate demand projections in
March 2005. Modifications will be made, as appropriate, when revised projections are
produced in the near future.)
I. Water sales to all non-UNC customers were assumed to increase at a constant rate of 0.145
mgd year, which is intermediate between the historic rate (1980-2002) of 0.1907 mgd/year
for all OWASA customers and the long-term projected rate of 0.106 mgd/year with passive
conservation, assumed in Technical Memorandum 3.3 of the 2001 Comprehensive Water° and
Server Master Plan. Staff believes that the 0.145 mgd/year rate reflects a degree of
permanent conservation that has occurred during recent years.
2. UNC Main Camuus demand assumptions were based on Brown & Caldwell's 2002 UNC
Water and Seiner Master Plan, which contains specific Main Campus demand forecasts for
2008 and final buildout, for which no fixed date was specified,. OWASA's demand forecasts
assumed that Main Campus buildout will occur in 2026, which is the same assumption used
in our previous demand forecasts. It should be noted that UNC Main Campus demand
projections were subject to a higher degree of uncertainty than other customer classes, due to
the intense level of facility construction and rehabilitation either planned or underway, as
well as the dynamic nature of the University's development process.
3. UNC Carolina North demands were based on building category estimates of the Ayers/Saint
Gross Cm•olina North Master Plan and water usage factors of the 2002 Brown & Caldwell
UNC Water and Sewer Master Plan. Carolina North water use was assumed to begin in 2008
and to increase by 0.0.37 mgd/year until buildout, which was assumed to be in 2050.
However, specific plans for Carolina North remain highly uncertain. Although we anticipate
that highly treated wastewater will be reused for non-potable purposes at Carolina North, that
assumption has not been applied to current projections; i.e., current projections assume that
no reuse will occur Carolina North.
4, Projections for non-potable Water Reuse on UNC's Main Campus were based on University
staffs best estimates for reclaimed water demands for four individual chiller plants.. The
reuse system was assumed to begin operating in FY 2008. The Lesser Reuse projections
include currently programmed uses that were expected to reach 0.9 mgd by 2026 and, include
only the four existing chiller plants located on the south side of the campus. The More
Reuse projections include approximately I.0 mgd of additional demand for other facilities
and uses (Cogeneration Plant cooling towers and boiler makeup, new Northeast Chilled
Water Plant, new Manning Drive Steam Plant, existing UNC Hospitals chilled water plant,
and irrigation of certain athletic fields), but plans and commitments for these have been less
definite. (Note: revised reuse forecasts that were provided by the University in September
2005 are not reflected in the numbers discussed above.)
5. All Raw Water Puuivalent demand forecasts assume an "unbilled" treated water fraction of
10 percent; i.e., OWASA pumps and treats 10 percent more raw water from our reservoirs
than is accounted for in metered billing records. The raw water projections assume that
treatment plant process water at the Jones Ferry Road Water Treatment Plant continues to be
fully recycled and not discarded.
DWASA -Water and Server Capacity Gnplications oJGrcreased Development Density
Page 2/ oJ21