HomeMy WebLinkAboutFebruary 7, 2011 Agenda
AGENDA
CITY OF DENTON CITY COUNCIL
February 7, 2011
After determining that a quorum is present, the City Council of the City of Denton, Texas will
convene in a Special Called Work Session on Monday, February 7, 2011 at 11:30 a.m. in the
Council Work Session Room, 215 E. McKinney Street, Denton, Texas at which the following
item will be considered:
NOTE: A Work Session is used to explore matters of interest to one or more City Council
Members or the City Manager for the purpose of giving staff direction into whether or not such
matters should be placed on a future regular or special meeting of the Council for citizen input,
City Council deliberation and formal City action. At a Work Session, the City Council generally
receives informal and preliminary reports and information from City staff, officials, members of
City committees, and the individual or organization proposing council action, if invited by City
Council or City Manager to participate in the session. Participation by individuals and members
of organizations invited to speak ceases when the Mayor announces the session is being closed to
public input. Although Work Sessions are public meetings, and citizens have a legal right to
attend, they are not public hearings, so citizens are not allowed to participate in the session
unless invited to do so by the Mayor. Any citizen may supply to the City Council, prior to the
beginning of the session, a written report regarding the citizen's opinion on the matter being
explored. Should the Council direct the matter be placed on a regular meeting agenda, the staff
will generally prepare a final report defining the proposed action, which will be made available
to all citizens prior to the regular meeting at which citizen input is sought. The purpose of this
procedure is to allow citizens attending the regular meeting the opportunity to hear the views of
their fellow citizens without having to attend two meetings.
1. Receive a report, hold a discussion and provide staff direction on street pavement
conditions and recommended maintenance funding requirements.
CERTIFICATE
I certify that the above notice of meeting was posted on the bulletin board at the City Hall of the
City of Denton, Texas, on the day of 2011 at o'clock
(a.m.) (p.m.)
CITY SECRETARY
NOTE: THE CITY OF DENTON COUNCIL WORK SESSION ROOM IS ACCESSIBLE IN
ACCORDANCE WITH THE AMERICANS WITH DISABILITIES ACT. THE CITY WILL PROVIDE
SIGN LANGUAGE INTERPRETERS FOR THE HEARING IMPAIRED IF REQUESTED AT LEAST
48 HOURS IN ADVANCE OF THE SCHEDULED MEETING. PLEASE CALL THE CITY
SECRETARY'S OFFICE AT 349-8309 OR USE TELECOMMUNICATIONS DEVICES FOR THE
DEAF JDD) BY CALLING 1-800-RELAY-TX SO THAT A SIGN LANGUAGE INTERPRETER
CAN BE SCHEDULED THROUGH THE CITY SECRETARY'S OFFICE.
AGENDA INFORMATION SHEET
AGENDA DATE: February 7, 2011
DEPARTMENT: Water Utilities
ACM: Howard Martin, Utilities 349-8232*'---
SUBJECT
Receive a report, hold a discussion and provide staff direction on street pavement conditions and
recommended maintenance funding requirements.
BACKGROUND
Responsibility for Streets/Traffic operations and maintenance were transferred to the Water
Department in 2001. Funding for these two divisions continues to be provided from the general
fund. Staff would like to update the City Council on historical street maintenance issues, the
current maintenance activities, present the findings of a recently completed street condition
survey, and provide staff recommendations on the changes needed to adequately operate and
maintain the street system.
Funding levels for the Streets/Traffic Operations and Maintenance (O&M) budgets have increase
over the years but have not kept pace with the overall growth in income for the general fund as
the city has grown over the years. All routine maintenance for the city's street network is
contained in the Street Department O&M budget. This annual O&M budget expressed as a
percentage of the total General Fund has declined over the past two decades and they are
currently ranked sixth in overall priority from a funding perspective behind Police, Fire, Parks
and Recreation, Library and the Planning functions for the city. Twenty years ago, the Street
Department was ranked fourth in overall funding priority (Exhibit 1).
When the Water Utilities Department became responsible for the administrative management of
the Streets/Traffic O&M program the following items were identified as needing attention:
o Need for a defined program for technical evaluation of street conditions.
o Need for an inventory system to track street assets.
o Need for developing a maintenance plan with established goals and objectives.
o Re evaluation of the design criteria for streets with consideration for life cycle
costs.
o Determination of concrete verses asphalt pavements and equivalent pavement
sections.
o Quality control for materials testing and acceptance inspection for new pavement
installations needed improvement.
o Total annual funding levels for street maintenance and/or replacement needed
evaluation and improvement to keep pace with growth in the system and aging of
the street network.
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The City contracted with EKES Consultants in 2003 to perform an automated pavement
evaluation. This evaluation gave staff an assessment of the Overall Condition Index (OCI) of the
City of Denton street network. Based on the analysis of the road condition, the consultant
performed model nuns to determine the level of expenditure necessary to prevent the
deterioration of our roadway system. The 2003 pavement study also provided an initial baseline
which we will use to measure our progress with the street maintenance program. Since the
completion of the 2003 pavement study, staff has been tracking street maintenance activities
using a software program (CarteGraph Pavement View) and the model provided by EKES.
In the summer of 2009 we initiated the second automated pavement assessment project. With
this second project, we have contracted with Infrastructure Management Services (IMS) to
perform the automated pavement evaluation. The consultant has finished the survey and the
financial analyses and the final report (less the Appendix Sections) are attached (Exhibit 2). The
project manager (Stephen Smith, P.E.) has extensive experience in conducting similar automated
pavement surveys and analysis studies for municipal and county governments across the country.
Stephen will present an overview of the project as well as his recommendations for funding
levels for Denton's street maintenance program (Exhibit 3). The results of this analysis have
further refined the city's pavement condition model as well as providing a more detail financial
analysis and final report. Based upon the results of the 2003 and 2009 pavement condition
surveys, it is evident that the current level of resources allocated for street maintenance funding
continues to be inadequate to stop the relatively sharp decline in street conditions for the City of
Denton. Based upon these two studies, the OCI from the 2003 study was 69 compared with an
OCI of 63 for the 2009 study. These results indicate that the present funding level for street
maintenance over this time fame was unable to stop the decline in the condition of the street
network over the six year period. In addition, while the OCI at the time the pavement condition
survey was performed was 63, the modeled OCI for the final published report in 2010 was 61,
indicating that the present funding level will result in a OCI decline of approximately 2 points
per year.
Based on this comparison the data from these two studies have concluded that the OCI value for
the city's street network has continued to decline. The 2003 automated pavement study
indicated that to prevent the reduction of the OCI we should be spending 18 million dollars
annually. The 2010 automated pavement study estimates annual street maintenance expenses
would be approximately 10 million dollars per year to maintain the streets at the lower OCI value
of 61 and would be approximately 15 to 16 million dollars over the next five years to restore the
OCI to where it was in the 2003. The street maintenance spending levels recommended in these
two automated pavement surveys do not include the entire street department budgets that include
other activities that are not OCI maintenance related. These other areas include pot hole
patching, utility street cut patching, routine base failure patching, street sanding, sidewalk
replacements and repairs, bridge repairs and guard rail repairs. In addition, the analysis of street
maintenance funding level needs do not account for inflationary costs for these expenses.
Since the 2003 automated study the city has spent a total of 32.5 million on OCI improvements.
This total expenditure averaged approximately $4.64 million per year. It is important to note that
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these funding levels included unsustainable funding sources including one time funding from the
Denton County Transportation Authority's (DCTA) Enhanced Local Assistance Program
(ELAP), debt funding through 20 year General Obligation (GO) bonds and 20 year Certificates
of Obligation (CO) bonds. At the time of the 2003 study, staff estimated that the city was
spending approximately 2.1 million dollars each year for OCI related street maintenance. Based
upon the FY 20110 & M budget, staff estimates that the city is spending approximately 3.1
million dollars each year for OCI street maintenance (not including one time funding levels that
currently include CO and GO bonds). The total expenditures for OCI improvements since 1993
and their funding sources are attached (Exhibit 4).
Maintenance activities impacting the OCI values for asphalt streets include; crack-seal, micro-
seal, hot-mix asphalt (HMA) overlay, and street reconstruction. The crack seal program involves
the application of rubberized asphalt material into cracks that appear on the surface of the
roadway. This is a very important early maintenance procedure to prevent moisture from seeping
into the cracks. This prevents damage from the freeze thaw cycles in the winter and from
expansion/contraction cycles due to the expansive clay soils under the pavement.
Micro-seal is a more aggressive maintenance procedure providing a thin additional wear surface
and a sealant coating to the surface of the roadway. This material is comprised of rock, emulsion
asphalt, cement, and sand. This procedure seals the entire surface of the roadway protecting the
roadway and subgrade from moisture. Smaller cracks and more numerous cracks are more cost
effectively sealed using this maintenance procedure.
Hot-mix asphalt overlay (HMA) involves the milling of several inches of asphalt off of the
surface of the roadway and then replacing with three to four inches of hot-mix asphalt and then
roller compacting. Spot curb and gutter repairs are normally made during this procedure.
Total reconstruction involves the complete removal of the existing roadway and reconstructing
of the subgrade and placement of new asphalt layers or concrete. Normally, on a total
reconstruction project the curb and gutter sections were either partially or completely replaced.
Maintenance activities impacting the OCI values for concrete streets include: crack-seal, panel
replacements, and street reconstruction.
Based upon the results of the two automated roadway evaluations, additional resources need to
be programmed for street maintenance to reverse the overall deterioration of the street network.
This situation has developed over several decades and has resulted in an overall deterioration of
the street network. Unless major changes in the street maintenance program are made soon, the
street system will deteriorate to an unacceptable level and reasonable options for addressing the
issue may not be available. A financial plan must be developed to reverse the current trend and
restore the street program to a viable level. Based on the large size of this funding gap, easy
financial solutions will not be available. The financial plan must consist of a number of sources
of additional funding and a prioritization of existing funding sources to be successful. Staff will
discuss funding options with Council in the future and seek guidance on how to provide for the
funding shortfall.
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EXHIBITS
1. Street Funding as a Percentage of the Total General Fund by Decade
2. IMS Pavement Management Analysis Report, December 2, 2010
3. IMS Pavement Presentation to Denton City Council
4. Historical Street Maintenance Expenditures
Respectfully submitted:
Jim Coulter, Director of Water Utilities
4
Exhibit 1
Streets Funding as a % of Total General Fund by Decade
1989-1990 1999-2000 2009-10
Police & Animal Control $ 5,733,199 21% $ 11,055,890 24% $ 23,476,871 26%
Fire $ 4,786,639 18% $ 9,744,530 21% $ 20,752,595 23%
Parks & Recreation $ 2,276,262 9% $ 4,417,550 10% $ 10,559,577 12%
Planning $ 903,505 3% $ 2,399,987 5% $ 5,588,326 6%
Library $ 941,206 4% $ 1,873,066 4% $ 5,184,358 6%
Streets $ 1,491,843 6% $ 2,129,248 5% $ 4,475,492 5%
30%
Police
25%
Fire
20%
15%
Parks & Rec
10%
Planning
Library
5%
0%
1989-1990 1999-2000 2009-10
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IMS Infrastructure Management Services
1820 West Drake Drive, Suite 108, Tempe, AZ 85283
Phone: (480) 839-4347, Fax: (480) 839-4348
www.ims-rst.com
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Transmittal Imm
IMS Infrastructure Management Services
1820 W. Drake Drive Suite 108, Tempe, AZ 85283
Phone: (480) 839-4347 Fax: (480) 839-4348
www.ims-rst.com
To: Tim Fisher, P.E. Date: December 6th, 2010
City of Denton cc:
From: Stephen Smith Project: Denton
Subject: Pavement Report Rev 2 Final Project No.: 14208
Enclosed is the final Denton Pavement Management Report for your usage and records. The report
follows up on the comments made in the draft report and uses higher unit rates as discussed for the
analysis. The report identifies a $10M annual budget required to maintain the network OCI at 63, and a
$15M budget required to raise it to a value of 69.
The report builds off the 2004 study in that it updates the pavement performance curves to match the
current data OCI profile and expands the rehabilitation strategy selection process to include a continuous
spectrum of options as well as OCI constraints.
The report contains the City's street Inventory and condition summary, as well as key operating
parameters used in the analysis. I have also included the $10M rehab plan as a separate attachment
after Appendix B (I wanted to keep it separate incase you wanted to circulate the report without the rehab
plan).
It has been our pleasure to work with the City of Denton and we look forward to completing the last few
tasks on the current assignment and keeping up with the City over the next few years.
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TABLE OF CONTENTS
TABLE OF CONTENTS I
1.0 PROJECT DESCRIPTION 1
1.1 Principles of Pavement Management 1
1.2 The Pavement Management Process 4
1.3 Understanding the Pavement Condition Score 5
2.0 CITY OF DENTON NETWORK CONDITION AND FINDINGS 7
2.1 Roadway Network Size 7
2.2 Network Present Condition 9
2.3 OCI Distribution by Pavement Type 11
2.4 Functional Class OCI Distribution 12
2.5 Arterial Structural Analysis 13
2.6 Load Associated Distress Analysis 15
2.7 Reconstruction Backlog 16
3.0 REHABILITATION PLAN AND BUDGET DEVELOPMENT 18
3.1 Key Analysis Set Points 18
3.2 Fix ALL Today Estimate and Steady State 23
3.3 Rule of Thumb Estimates for Maintaining OCI = 63 24
3.4 Network Budget Analysis Models 25
3.5 Current funding and Maintain Existing OCI Model Runs 29
3.6 Network Recommendations and Comments 31
APPENDED REPORTS Following Page 22
Appendix A Inventory and Condition Summary
Appendix B City of Denton Operating Parameters
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1.0 PROJECT DESCRIPTION
1.1 PRINCIPLES OF PAVEMENT MANAGEMENT
Nationwide, billions of dollars have been invested in roadway networks by municipal, state and federal
governments. Locally, the City of Denton has over 70 miles of major roadways (major, Principal and
secondary arterials) plus an additional 360 miles of minor roadways (residential and collectors)
encompassing over 61.OM square feet of asphalt and concrete surfacing. At a replacement cost
approaching $750,000 dollars per mile - not including the value of the land, the City has over $320 million
invested in their paved roadway network.
C&G/Drainage, 34.2, 11'
Sice„all:_• 5.5,1, _Striping/Signage, 7.1, 2%
Corcrete Pavements. 77.1•
Z +"s, Landscaping, 4.0, 1%
:Miscellaneous, 15.4, 5%
RD'a l Prep./SL: hgracie Base.
39.4. 12"~
~;,phal' P~,,ert ent.. '?1.4
Figure 1 - Replacement Value of the Denton Paved Roadway Network ($M,
Total = $324M
Preservation of existing road and street systems has become a major activity for all levels of government.
There is a shortage of funds to maintain street systems at the state and local government levels. Funds
that have been designated for pavements must therefore be used as effectively as possible. One proven
method to obtain maximum value of available funds is through the use of a pavement management
system.
I.11SInfrastrueture.llnnngementServices Denton Report Rec2.doc page 1
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Pavement management is the process of planning, budgeting, funding, designing, constructing,
monitoring, evaluating, maintaining, and rehabilitating the pavement network to provide maximum
benefits for available funds. A pavement management system is a set of tools or methods that assists
decision makers in finding optimum strategies for providing and maintaining pavements in a serviceable
condition over a given time period. Streets that are repaired when they are in a good condition will cost
less over their lifetime than streets that are allowed to deteriorate to a poor condition. Without an
adequate routine pavement maintenance program, streets require more frequent reconstruction, thereby
costing millions of extra dollars.
On a typical roadway, over time pavement quality drops until the pavement condition becomes
unacceptable. The actual pavement condition score at which the street is deemed unacceptable is
dependent on local definitions for acceptable level of service and the condition rating system employed.
Also, the shape of the curve, and hence rate of deterioration for each street is dependent on many factors
- foremost of which are the strength of the roadway structure and traffic loading. The key to a successful
pavement management program is to develop representative pavement condition scores with reasonably
accurate performance models that match the distress profiles of the network, and then identify the optimal
timing and rehabilitation strategies. The resultant benefit of this exercise is realized by the long term cost
savings and increase in pavement quality over time.
Figure 2 highlights the principles of pavement management and the concepts of early rehabilitation
intervention. As illustrated, pavements typically deteriorate rapidly once they hit a specific threshold -
generally on the order of 40% of their effective life. Thus, a $1 investment in a light-weight rehabilitation,
such as a surface treatment or thin overlay, after 40% lifespan is much more effective than deferring
maintenance until heavier overlays or reconstruction is required just a few years later.
40% of pavement life
Excellent -
has a 15% drop in quality
Very Good 16% pavement life
_a
Good $1 spent now
CY has % r i quality
E Fair
d
Ca
a-
Poor Costs $8 if delayed
AaV N~ent PQ
Very Poor Cgrve "na",
Time
Figure 2 - Pavement Deterioration and Life Cycle Costs
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Once implemented, an effective pavement information management system can assist agencies in
developing long-term rehabilitation programs and budgets. The key is to develop policies and practices
that delay the inevitable total reconstruction for as long as practical yet still remain within the target zone
for cost effective rehabilitation.
That is, as each roadway approaches the steep part of its deterioration curve, apply a remedy that
extends the pavement life - at a lower cost, thereby avoiding costly heavy overlays and reconstruction.
Thus, the goal of a pavement information management system is to identify the optimal level of funding,
timing, and renewal strategy agencies should adopt to keep their roadway network at a satisfactory level
of service. Figure 3 illustrates the concept of extending pavement life through the application of timely
rehabilitation activities.
Pavement Life Cycle Curve
Target Zone for Pavement Rehabilitation
CJ
W Increased Pavement Life
E
a
• Un-rehabilitated -
Pavement•pe1.~or.•
ance
Time
Figure 3 - Pavement Life Cycle Curve
Ideally, the lower limit of the target zone shown in Figure 3 would have a minimum value that is close to
the condition score requiring a thin overlay or less (for Denton, thin overlays are scheduled in the 65 to 75
range). The upper limit would tend to fall close to upper range of the very good category - that is a
pavement condition score of 85. The actual limits of the target zone for implementation of perpetual
pavements are dependent on numerous factors such as user-defined levels of service for acceptability,
functional class, pavement condition and subgrade strength, and rehabilitation budgets plus available
contractors (there is not much use in programming a rehabilitation if the local contractors cannot complete
the work or the agency has no budget available).
Other functions of a pavement management system include assessing effectiveness of maintenance
activities and new technologies; storing historical data and images; and providing a central point of
access for as-built records, easements and agreements, and right of way assets.
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1.2 THE PAVEMENT MANAGEMENT PROCESS
The actual pavement management process involves three unique, but important steps, and is presented
graphically in Figure 4. Each activity builds on the previous, until the end result is a prioritized paving and
rehabilitation program.
1. System Configuration Local constraints &
requirern_snts
ISu or y, #'mJ'dnanr~ei+,,. ,qa
,'loam tv.tianh1g& Map
r {3r3~'uT~ '
J Utilfties, Othr s.~
e
~
^r; Departments &
Council
73txird r,:,m DhWrtsSions
2, Fi ld SL,rveys Air rl; -.i~ .ind Report ng
rg Draft Prioritized
Roadway Qa1as Pavement Paving Plan
. rl . Ma neyeroent _
System
Rou:
y t
s•~ ? Q~aP
a K' Structwx[ integrated
Tebling blistery, costs Pa°ink Plan
& local practices
Figure 4 - The Pavement Management Process
The final Overall Condition Index (OCI) is made up from two inputs, namely Surface Distress Index (SDI),
and Roughness Index (RI), with a third index - Structural Index (SI) used in rehabilitation selection for
arterials. Definitions and operating parameters used in the analysis are as follows:
A. Surface Distress Index (SDI) = 100 - sum of distress deducts according to ASTM D6433-09,
corrected for the number of active distress observations. SDI is used to quantify the pavement
surface condition by measuring the extent and severity of selected pavement defects. D6433-09
is a common industry standard developed by the U.S. Army Corps of Engineers and defines how
defects are to be categorized and measured. D6433-09 has separate distresses for asphalt and
pavement types.
Asphalt distresses are further broken down into load associated and non-load associated
distresses. Load associated distress (LAD) are those that are caused by traffic and include
rutting, alligator (fatigue) cracking, longitudinal cracking, edge cracking, distortions and patching
and potholes. The remaining non-load associated distresses (NLAD) are material or
environmental in nature and include transverse cracking, block (map cracking), bleeding and
raveling. Examination of the amount of load associated distresses compared to the overall
condition index provides an insight into subgrade quality.
B. Roughness Index (RI) _ (10- 3*LN(IRI) x 10, where IRI is the International Roughness Index
measured in mm/m and is the industry and World Bank standard for measuring roughness.
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C. The Overall Condition Index (OCI) followed the City's existing formula of OCI = 20% RI + 80%
SDI. Common percentages for roughness contribution to the OCI range from 0% (meaning the
OCI is based on SDI only) to 50% on larger - highway based networks. Splits of 33/67 to 20/80
are common on systems using surface distress and roughness as key pavement quality
indicators, thus the 20/80 split selected for the previous study is an acceptable ratio and has been
maintained.
The structure capacity of arterial roadways was also measured using a Falling Weight Deflectometer
(FWD). FWD's are used to develop a Structural Index (SI) by imparting a known load on the pavement
and measuring the response through a series of geophones. The data quantifies the load carrying
capacity of the base and pavement layers and consists of the Dynamic Maximum Deflection (DMD),
Surface Curvature Index (SCI), Base Curvature Index (BCI) and Percent Spreadability (%SP). Both
Asphalt and Concrete roadways were assessed - but used different parameters to develop the structural
index score. The Cartegraph software does not have the ability to integrate Structural Index information
into the OCI score, thus the SI was used as a qualifier in the rehabilitation selection process.
1.3 UNDERSTANDING THE PAVEMENT CONDITION SCORE
The following illustration compares the life cycle of a typical street section against its Overall Condition
Index using common used descriptive terms.
100
Excel lent = Routine and preventative maintenance, crack and joint sea Iin p
90 - so Very Good= surface treatments, localized repairs
70 Good surface treatmentsto thin overlays, local panel replacement
p GO ( Fair =1`hin to moderate overlays with localized R&R,
moderate panel replacement
0
0
50 Vlarpi nal = prod ressively thicker overlays and patching,
extensive panel replacement
v
m
40 Poor thicker overlays with patching,
possibly with surface removal and replacement
20
Very Poor - Full reconstruction
10 0
0 10 20 30 40 50
Pavement Age in Years
Figure 5 - Understanding the Overall Condition Index Score
IJISInfrastructure .11anagementServices Denton ReportRec2.doc page
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The divisions between the terms are not fixed and the age at which they occur may vary, but are meant to
reflect common perceptions of condition. The OCI ranges and descriptions apply to both asphalt and
concrete roadways, however it is important to note they are rated using different distress assessment
protocols as defined in ASTM D6433.
The general idea of what these condition levels mean with respect to remaining life and typical
rehabilitation actions is included in the following table:
Relative
OCI Range Description Remaining Life Definition
85 - 100 Excellent 15 to 25 Years Like new condition - little to no maintenance required when
new, routine maintenance such as crack and joint sealing with
age.
75 - 85 Very Good 12 to 20 Years Routine maintenance such as patching, crack sealing with
surface treatments such as slurries and micro surfacing.
65 - 75 Good 10 to 15 Years Thin overlay or possible thin overlay with localized repairs.
Localized panel replacements.
45 - 65 Fair to Marginal 7 to 12 Years Progressively thicker overlays with localized repairs and
possible subgrade stabilization. Moderate to extensive panel
replacements.
30 - 45 Poor 5 to 10 Years Sections will require very thick overlays, surface replacement,
base reconstruction and possible subgrade stabilization.
0-30 Very Poor 0 to 5 Years High percentage of full reconstruction.
It should be noted that the relative remaining pavement life presented in the table above is not the same
as pavement age presented in Figure 5. Relative remaining pavement life is the timeframe expressed in
years, in which a street section will provide acceptable levels of service before a rehabilitation needs to
be applied under optimal funding and operating conditions. The relative remaining life can certainly be
exceeded with no rehabilitation or maintenance and the pavement allowed to continue to deteriorate until
it eventually returns to gravel or is unserviceable. The remaining life may also be extended by effective
maintenance activities.
Pavement age is the reported time since it was constructed or last had an OCI score of 100. For
example, a recently constructed street might have an OCI of 91. Assuming Figure 5 is the appropriate
performance curve for the functional classification and subgrade strength, the age of the street may be
estimated to be on the order of 5 years old, and its remaining life before it requires a thin overlay is
approximately 15 years.
The above table using generic terms such as thin, thick or extensive to quantify the pavement
rehabilitations. This terminology was used specifically for illustration purposes only as the selected
rehabilitations vary between pavement types and functional classification. The actual thickness and type
of rehabilitation are defined in Section 3 of this report.
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2.0 CITY OF DENTON NETWORK CONDITION AND FINDINGS
2.1 ROADWAY NETWORK SIZE
The paved roadway network consists of five functional classes, covering approximately 434.5 centerline
miles of pavement. The average overall pavement condition of the roadway network at the time of survey
in 2009 was 63. The current OCI due to deterioration during data processing and analysis is 61 (for all
intense and purpose these two values are interchangeable). The network has two pavement types -
asphalt and concrete, with asphalt being the most predominant. The following table summarizes the
functional class - pavement type splits within the system.
Classification Pavement Type Length (ft) Length (Mi) Area (ft2) Width (ft) OCI
Major Arterial AC Asphalt Concrete 4,242 0.8 203,616 48.0 87
Major Arterial PCC Jointed Concrete 6,484 1.2 311,232 48.0 97
Primary Arterial AC Asphalt Concrete 38,034 7.2 1,441,616 37.9 63
Primary Arterial PCC Jointed Concrete 38,705 7.3 1,378,382 35.6 87
Secondary Arterial AC Asphalt Concrete 253,664 48.0 8,281,458 32.6 51
Secondary Arterial PCC Jointed Concrete 40,027 7.6 1,099,591 27.5 87
Collector AC Asphalt Concrete 390,208 73.9 11,788,863 30.2 50
Collector PCC Jointed Concrete 47,117 8.9 1,691,868 35.9 89
Residential AC Asphalt Concrete 1,058,504 200.5 25,486,406 24.1 52
Residential PCC Jointed Concrete 423,432 80.2 10,193,804 24.1 90
Totals: AC Asphalt Concrete 1,744,652 330.4 47,201,959 52
PCC Jointed Concrete 555,765 105.3 14,674,877 90
All Streets 2,300,417 435.7 61,876,836 61
In addition, from previous surveys, the city also has in its pavement management system the following:
Functional Average
Classification Length (ft) Length (Mi) Area (ft2) Width (ft)
Airport Roads 5,509 1.0 152,772 27.7
Alley 16838 3.2 136,302 8.1
Residential - non surfaced 8060 1.5 203532 25.3
All streets were surveyed on a block by block basis matching the City's current GIS topology. The
amount of sections contained in the database differs slightly from the City's last survey in that:
1. New Streets have been added to the network.
2. Numerous segments were subdivided into several shorter sections.
3. Small segments that formed crossovers or offset intersections were rolled into the adjacent
section to prevent these short sections from becoming stand alone projects, as shown below.
Section 329-2W1 forms the median
• crossover - it was surveyed as part of
Highview Circle
LUSInfrastrueture.llnnngementServices Denton Report Rec2.doc page 7
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Major Arterial, 2.0, 1%
I' Primary Arterial, 14.5,3%
Residential, 280,7. 6474.
Secondary Arterial, 55.6,
13%
Figure 6 - Network Split by Functional Classification (miles,
PCC_+eioted Corr rete, 105.3.
Figure 7 - Network Split by Pavement Type (miles,%)
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2.2 NETWORK PRESENT CONDITION
Figure 8, presented below shows distribution of pavement condition for the paved roadway network in the
City of Denton on a 0 to 100 scale, 0 being worst and 100 being best condition. The average OCI for the
network in 2010 is 61 (63 in 2009). However, the roadway network displays atypical pavement condition
characteristics when compared to other agencies of similar size. The three variances of the distribution
profile are:
1. The distribution profile is quite flat - typically a more uniform bell shape curve - with a peak
centered in the 60 to 65 range is encountered.
2. The City has more streets than typically encountered in similar sized agencies in the 80 plus
range. Denton has approximately 32% of its network above an OCI of 80, similar agencies
typically have less than 20 to 25% in this range.
3. Conversely there is a higher than expected number of streets in the 50 and below range.
20
15 ,
v
a
Y
a
z" 10
0
m
m
c
a
a
0
0 to 10 10 to 20 20 1,'. i 30 to 40 40 to 50 50 to 60 60 to 70 70 to 80 80 to 90 90 to 100
Overall Condition Index JOCI]
Figure 8 -Roadway Network Present Status
The atypical distribution of OCI in Denton is indicative of three potential contributing factors:
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1. City's that have experienced rapid growth in a short time frame typically have a moderate to high
OCI rating, with higher than normal streets above an 80. The periphery around the City has
newer subdivisions, and hence higher rated streets, while the core has an older street network.
2. The distribution is reflective of a network, or large portions of a network, that are relatively
moderate in age and have had deferred maintenance efforts over time - hence the high number
of streets below 50.
3. Other contributing factors include combinations of weak subgrades with insufficient overlay
thickness resulting in premature road failures, and incorporation of roadways that were originally
built to lower or insufficient standards for their current use.
The following graph (Figure 9) plots the same pavement condition information, but instead of using the
actual Overall Condition Index value, descriptive terms are used to classify the roadways. From the chart,
27% of the network can be considered in excellent condition with an OCI score greater than 85. These
roads are in like new condition and require routine maintenance such as crack sealing. Nationwide, the
amount of roadways falling into the very good category is about 15%, so this value is considerably higher
mainly as a result of the concrete roads within the City. Again, the high number of streets in the excellent
category is primarily reflective of newer subdivision streets, and the high percentage of newer concrete
roadways and not necessarily an effective pavement rehabilitation program.
30 ,
is
20
v
a
Y
a
~ 15
0
m
nq
m
c
a
a
10
s
Very Poor (0 to 30) Poor ~0 to 45j kla -final i 45 to 55) Fair (55 to G' Good 5 to 75 Very Good (75 to 85) Excellent (85 to 100)
Overall Condition Index JOCI]
Figure 9 - Present Status Using Descriptive Terms
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8% of the network falls into the very good classification. These are roads that benefit the most from
preventative maintenance techniques such as microsurfacing, slurry seals and localized repairs. If left
untreated these roadways will drop in quality to become overlay candidates. Streets that fall within 2 to 3
points above the very good rating of 75 (the transition from very good to good) are considered "critical"
surface treatment candidates - that is, these streets should be rehabilitated in a timely fashion with a
slurry or microsurfacing in order to prevent more costly rehabilitation being required.
23% of the network can be considered in fair or marginal condition, representing candidates for
progressively thicker overlay based rehabilitation or panel replacements. If left untreated, they will
decline rapidly into reconstruction candidates. The remaining 29% percent of the network is rated as
"poor" or "very poor", meaning these roadways have failed or are past their optimal point for overlay
based rehabilitation and may require progressively heavier or thicker forms of rehabilitation (such as
surface reconstruction or deep patch and paving) or total reconstruction. Roadways falling progressively
into the very poor (OCI less than 30), should be considered the City's "backlog" of immediate work to do.
These are the roadways that require rehabilitation efforts, in thicker depths, or reconstruction. Average
cities typically have between 12 and 15% of their roads as backlog, so the Denton network is displaying
slightly higher values in this regard.
2.3 OCI DISTRIBUTION BY PAVEMENT TYPE
Separating and then plotting the OCI by pavement type - that is concrete for all rigid roadways and
asphalt for all flexible pavements, reveals considerable difference in distribution of pavement condition
between asphalt and concrete roadways. The following plots highlight the OCI distribution of the asphalt
paved and concrete networks.
25.
20 .
m
m 10
5
o-
V,r, Poor (0 to ~ Poor ,0to4F•) Marginal (45 to 55) Fair(55to6,~ Good (65 to 7511 Very Good(75to F.~ FreIl-t(85ton
Overall Condition Index (OCI)
Figure 10 - OCI Distribution by Pavement Type = Asphalt
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loo
90 -
Concrete
so
70
> 60
6
m 40
30
20
10
Very Poor (0 to 30] Poor (30 to 45J Marginal (45 to 55) Fair M to 65J Good t65 to 75J 6 Good (75 to 8' I - (lent (85 to loo)
Overall Condition Index (OCI)
Figure 11 - OCI Distribution by Pavement Type = Concrete
Examining the OCI distribution in Figures 10 and 11 indicate the concrete paved roadways display
considerably better performance than the asphalt network - both in terms of structural capacity and
overall condition. The concrete network (24% of the total network by area, shown in blue in Figure 11 has
a higher average OCI (89) with virtually no backlog as compared to the asphalt roadways (OCI = 53) as
shown in red in Figure 10. The asphalt backlog exceeds 20%.
The difference between the two pavement types is not to be unexpected. The older and rural portions of
the network tend to be asphalt. These two environments also have some of the poorest performing
pavements in the City and thus a present and OCI distribution heavily skewed to the left. Conversely, the
concrete roadways are generally located in the newer subdivisions and present a higher OCI distribution.
Also, concrete roadways tend to deteriorate at a slower rate than asphalt. Thus when compared, two
roadways of equal age with similar subgrade conditions and traffic, the concrete road would generally
have a higher OCI value over an equivalent asphalt roadway.
2.4 FUNCTIONAL CLASS OCI DISTRIBUTION
Figure 12, presented below highlights the OCI distribution (based on OCI weighted by area, not length) by
functional classification for all pavement types. As can be seen from the plot, the collector network
(representing 22% of the network by area, 19% by length) is in the poorest condition with an average OCI
of 55 and a backlog of 18%. The residential roadway network has an average OCI of 63 with a 14%
backlog rate (representing 58% of the network by area, 64% by length), while the arterials have an
average OCI of 61 and a backlog of 15%.
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Arterials - OCI = 61
30 Ia Collectors -0(:1- 55
M P,esidentials -OCI = 63
25
m
a
y
20
`a
3
a
Z
0
a
m 15
a
10
5
0
Very Poor Poor IvIar=inal Fair Good Very Good F ell lit
(0 to 30) (30 to 45) 15 to 55) (55 to 65) (6S to 75) (75 to 95) (95 to 100)
Overall Condition Index (OCI]
Figure 12 - OCI Distribution by Functional Class
2.5 ARTERIAL STRUCTURAL ANALYSIS
Structural testing and analysis was completed on the arterial roadway network using a Falling Weight
Deflectometer (FWD). FWD's apply a known load to the pavement and measures the pavement
response to the load through a series of geophones. From these results, the structural integrity of the
roadway segment may be assessed. The purpose of the structural analysis is threefold, namely:
1. The results are used to identify and report sections with inadequate structural capacity by
completing a layer analysis of the subgrade, base and pavement layers.
2. The structural index provides input into which performance curve each segment is to use -
performance curves are used to predict pavement deterioration overtime.
3. Assists in rehabilitation selection by constraining inadequate pavement sections from receiving
too light weight of a rehabilitation.
As a pavement ages, its OCI score deteriorates from a potential high of 100 to a lower value until it is
rehabilitated - the deterioration is fairly predictable using pavement performance curves based on current
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conditions and testing. Along with the drop in OCI, a corresponding decrease in structural capacity (as
represented by its Structural Index - SI) also occurs.
The following plot (Figure 13) presents the structural adequacy of the arterial roadway network against its
average pavement condition, each marker represents one segment of roadway.
100
90 so
70
t,
a mm~
60 a ~
m
L Sa
~ aetc, en e 3 area creed revi. uu
40 as to why they have a high 00 vague
o and Structuae Index les. than 7"
Streets below diagonal line are not
?0 b achieving; full structural life
a
20
~ ~ 1~slrhakRoads
® Concrete Roads
10
gy
a
10 20 30 40 So 60 70 80 90 100
Overall Condition Index (OCI)
Figure 13 - Structural Adequacy of the Major Roadway Network
The diagonal blue line in the plot provides an indication of roadway segments that are performing above
structural expectations and those that do not provide full structural benefits over the life of the pavement.
The large number of roadways falling below the diagonal line indicates the City has a high percentage of
roadways that are structurally inadequate. This is typically the result of insufficient base and structural
materials during the original construction, or the application of overlays that were too thin during the
lifetime of the roadway - these roads have been flagged in the database as having weak subgrade (which
may also be indicative of a thin pavement structure). Street segments falling 20 points above the blue
line were marked as having strong subgrade, while the remaining were noted as moderate.
It should be noted that two segments can have similar OCI values yet have differing subgrade ratings
based on their testing results. Once they enter the rehabilitation planning, the Structural Index value
would also ensure a thicker overlay or additional localized repairs are applied to the street segment with
the lower SI score.
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Street segments that have an OCI greater than 75, yet a structural index score less than 75 represent a
small number of like new streets that have a low structural index (highlighted in the shaded blue area of
figure 13) yet are relatively new in age. The exact cause of low SI score is underdetermined and beyond
the scope of this assignment, however, resources permitting, the City may wish to investigate these
segments to identify the cause of the low SI through core holes and project level testing.
The horizontal green lines highlight the Structural Index ranges used as selection criteria during the
budget analysis. The structural adequacy of a road is expressed as a 0 to 100 score with several key
ranges: roadways with a Structural Index greater than 75 are deemed to be structurally adequate for the
loading and may be treated with lightweight surface treatments or thin overlays; those between 50 and 75
typically reflect roads that require additional pavement thickness; and scores below 50 typically require
reconstruction and increased base and pavement thickness.
2.6 LOAD ASSOCIATED DISTRESS ANALYSIS
Not all streets had structural testing and analysis completed on them. In order to gauge the
subgrade/pavement strength of these segments, an assessment of the quantity of load associated
distresses (LAD) was completed. The assessment was also used as a qualifier for rehabilitation
selection. Load associated distresses are surface defects that arise for traffic loading and principally
include fatigue cracking, rutting and longitudinal cracking.
100
90 Overall Condition Indexes Distress Deducts
Asphalt Roads Only
a
so « o
Load Associated Distress Deducts
70 " • y, 4«
Non-Load Associated Distress Deducts
.a
a v ,'au
fl
60
n a
m
50
O x 6'
\ m
'ArongS"bgrade f,li I-rai. WeakS"bgrade
g m
30
20
10
0
0 10 20 30 40 50 60 70 80 90 100
Overall Condition Index (OC1(
Figure 14 - Load and Non-load Associated Distresses
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Figure 14 plots the relationship of the load and non-load associated distresses against pavement
condition (OCI). The Y axis of the plot is the sum of the distress deducts for either load (red) or non-load
(blue) associated distresses. As can be seen from the plot, it is the load associated distresses (red
symbols) that affect the overall pavement condition at a higher rate than non-load associated distresses
(blue symbols) - the greater the sum of load and non-load associated distresses, the lower the OCI.
Closer examination of the surface defects as they relate to the overall pavement condition support the
findings of the structural testing. Generally, load associated distresses affect the overall condition score
more than non-load associated distresses - and this is the case in Denton.
Street segments displaying a low sum of load associated deducts to OCI ratio were deemed to have a
strong subgrade (streets falling below the lower black diagonal line), while the remaining were classified
as moderate (between the two black diagonal lines) or weak (above the upper black diagonal line) as
shown above.
It should be noted that two segments can have similar OCI values yet have differing load and non-load
associates totals based on the distresses encountered. Similar to the Structural Index value, the sum of
the load associated distresses are used to select the performance curve to be used in the pavement
modeling and act as a qualifier for rehab selection. Once a segment enters the rehabilitation planning
process, the sum of the load associated distresses would ensure a thicker overlay or additional localized
repairs are applied to the street segment with the higher LAD amount.
2.7 RECONSTRUCTION BACKLOG
Backlog roadways are those that have dropped sufficiently in quality that surface based rehabilitation
efforts would no longer prove to be cost efficient and require either partial or total reconstruction. Backlog
is expressed as the percentage of roads requiring reconstruction as compared to the network totals.
The concept of Overall Condition Index (OCI) score and backlog must be fully understood in order to develop an
effective pavement management program. The OCI score indicates the overall pavement condition and
represents the amount of equity in the system and is the value most commonly considered when gauging the
overall quality of a roadway network. It may also be used to define a desired level of service - that is an agency
may wish to develop a pavement management program such that in 5 years the overall network score meets a set
minimum value. It is the backlog however, that defines the amount of work an agency is facing and is willing to
accept in the future. Further, it is the combination of the two that presents the true picture of the condition of a
roadway network, and conversely defines improvement goals.
Generally a backlog of 10% to 20% of the overall network is considered manageable from a funding point
of view - a target value of less than 15% would be considered ideal as it strikes a balance between
economic manageability of the backlog and maximizing services life of each roadway. A backlog below
10%, while certainly desirable from a service perspective, may represent a non-optimal expenditure of
funds if rehabilitation dollars are limited. Backlogs approaching 20% and above tend to become
unmanageable unless aggressively checked through larger rehabilitation programs.
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Along with the current network average OCI of 61, maintaining the City's current reconstruction backlog at
or below 16% may be used as measure of success for ongoing pavement rehabilitation activities. As
such, the City must develop strategies on how best to achieve that goal. Options include:
• Scheduled - Reactive - Complaint Driven - these three forms of selecting rehabilitation
candidates are driven more from external forces than pavement condition and are not
recommended for consideration.
• Worst First - under this option, the streets are lined up according to their OCI rating and the worst
streets are rehabbed first. The primary concern with this option is that unless the City has
unlimited funding, deterioration of the network exceeds the City's capability to fund the required
rehabilitations.
• Prioritization - under this option, streets are assigned user defined priorities and weightings such
that when combined with their OCI score, they are rehabbed in order of aggregated priority.
Weighting may include items such as functional class, pavetype, environment etc. For example,
an agency may select to place more emphasis on asphalt urban arterials over concrete
residentials, such that when two streets of similar OCI are considered for selection, the arterial is
selected first. This is the process used for Denton.
• Prioritization - Optimization - using the priorities defined above, this option takes into account
expenditure of monies to obtain the maximum benefits for the agency. The City's Cartegraph
software has limited optimization capabilities.
The City of Denton needs to develop a plan that accomplished three primary objectives:
1. Check the deterioration of the roads in the "poor" and "marginal" ratings from becoming full
rehabilitation candidates. If allowed to slide, these streets may potentially overwhelm the City's
ability to reconstruct them within a relatively short time frame.
2. Maintain the streets in the "good" and "very good" ratings through early intervention with
lightweight overlays and surface treatments. While it may seem counter-intuitive to address
streets with such high ratings over reconstructs, from a long-term cost benefit perspective, it
provides greater return for the City (this is referred to as partial optimization).
3. As funding permits, address the backlog of reconstruction candidates. These streets receive a
lower priority for two reasons, firstly these street sections have already reached their useful life,
thus deferring rehabilitation will not cause further deterioration and hence costs. Secondly, the
cost to rehab these street sections is on an order of magnitude greater than a light weight overlay
or surface treatment - given limited funds, the network overall receives a greater benefit by
rehabbing more streets with a lighter rehab than a select few at a much higher unit rate.
Section 3.0 of this report details the priorities developed for rehabilitation analysis recommended for
Denton.
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3.0 REHABILITATION PLAN AND BUDGET DEVELOPMENT
3.1 KEY ANALYSIS SET POINTS
Pavement management system requires user inputs (referred to as operating parameters) in order to
complete its condition forecasting and develop a prioritized rehabilitation plan. Key operating parameters
used in the 2010 analysis are as follows:
• Pavement Performance Curves - the pavement performance curves were modified to reflect
the current OCI distribution and results of the deflection and load analysis. Curves were
developed for each functional class - pavement type combination and separated in weak,
moderate and strong subgrade classifications. At the request of the city, based on local
experience resulting from early failures of pavements, the weak curves were adjusted slightly to
reflect overlay based rehabilitation Iifecycles as short as 10 years in place of curves that had
extended out to 14 years. Sample curves for asphalt pavements with moderate strength
subgrades are presented in Figure 15.
100 I Routine MaI
intenae
90
84
U 70 ll,ir, _-tla-
Q
'G 50 C
C ~
.Q
50 ll,i r1.
C
O
U
ro 40
F+rtial F- n .h 11, ti-r,
3
0 30
20 Principal Arterial - Moderate Subg raid
Secondary Arterial - Moderate Subgrade
Collector- Moderate Subgrade Fall Rewnstruction
10 --Pesidentlal - Moderate Subgrade
0
0 5 10 15 20 25 30 35 40 45 50
Time (Years)
Figure 15 - ACP Performance Curves for Moderate Subgrades
Performance curves for weak subgrades shift the curves to the left (steeper), while strong
subgrades flatten out the curves and shift them to the right. The curves used for this analysis
were developed using the 2009- 2010 data collection protocols and distribution.
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The current performance curves do not relate to the 2004 analysis in that the OCI distribution has
changed considerably and the concept of subgrade strength has been introduced. Four critical
aspects of the 2004 curves require updating:
1. The 2004 asphalt curves for arterial, collector and residential roadways had OCI drops of
20 to 25 points in the first 5 years of their life cycle, as well as 50 point drops in the last 7
years of the life - neither of these configurations are appropriate for the current OCI
distribution. Similarly, all concrete curves drop 50 points in 5 years once they are below
an OCI of 50.
2. The asphalt curve for urban residentials had no deterioration between years 10 and 15,
while the rural residentials had no deterioration between years 4 and 7. Concrete curves
for urban residentials (both continuous and jointed) and continuous collector also have
flat curves for between 5 and 9 years duration. One of the basic premises of pavement
management is that all streets are subject to deterioration throughout their life cycle.
3. All asphalt curves had no life past 28 years (20 years for rural residentials up to 28 for
urban residentials), while all concrete curves terminated at either 40 or 45 years.
4. Once the curves are merged with the rehabilitation OCI limits, asphalt roadways below an
OCI of 60 have no rehabilitation option except for reconstruction.
The basic shape of the curves follows traditional sigmoidal performance models such as those
contained in MicroPaver with several key changes:
• Between OCI values of 95 and 100 there is a slight deflection in the curves. This was
introduced to balance field measurements against theoretical values for new streets. On
new pavements, roughness measurements rarely reflect a perfect 100 - meaning there is
always some inherent roughness using Class I profilometers. Within 5 years, roughness
measurements and theoretical models tend to align closer and thus without the small
deflection, the curves would have an OCI intercept on the order 97.
• Depending on the subgrade strength, the curves were designed to have post rehab
overlay cycles ranging from 10 years (weak arterials) to 20 years (strong residentials).
• The Full Reconstruction limit was designed to match the City's life cycle experience and
OCI distribution. In the above example, the curves were designed to have ultimate life
cycles of 30, 35 and 41 years for arterials, collectors and residential roadways
respectively ultimate life cycle is where a road that is not subject to rehab or maintenance
cross the full reconstruction OCI limit of 30. This is not meant to imply all roads stop
functioning at an OCI of 30, but rather they have reached their useful life and are now
candidates for reconstruction.
• The curves were set to be asymptotic to age to reflect the residual value of the roadway
itself - meaning they continue to exist and never have a modeled OCI value of 0.
Similar curves were created for concrete pavements. All curves are contained within the software
and appended to this report.
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• Priority Weighting Factors - establishment of user defined weighting factors are required in
order for the software to develop a listing of rehabilitation candidates that annual budget may be
applied against in order to develop a prioritized rehabilitation plan. Key weighting factors used in
the Denton analysis include:
Functional Classification:
Principal Arterial 100
Secondary Arterial 90
Major Arterial 85
Collector 80
Residential 65
Pavement Type:
Asphalt 100
Concrete 90
Environment:
Urban 100
Rural 90
Once combined, the priorities have the affect of selecting higher functional classes that are
asphalt and urban over other roadways. Once combined with the OCI scores, the priorities were
designed to direct monies to the higher functional classes and overlay/slab replacement based
rehabilitations.
The priorities were modified from the 2004 to reflect the current OCI distribution by functional
class and pavetype. The environment priority factor was introduced as a new concept to balance
the population density of urban versus rural environments - meaning urban road benefit more
users.
• Post Rehab OCI - after a rehabilitation is completed an OCI score is assigned to reflect the
improved conditions. The post rehab OCI is a fixed value based on the rehab activity. This
method was selected over the alternate of adding a set number of points to the current OCI value
as it more accurately reflects actual field activities - that is assuming all rehabs are completed
according to project level testing and analysis design. Post rehab OCI values range from 92 for
surface treatments through to 100 for full reconstruction.
For example, let's assume a street requires a thin overlay. The basic premise of pavement
management is that the rehab completed on a street is designed and executed such that a goal
of near perfect restoration is attained - meaning the street returns to a near perfect OCI of 96 to
98. The rehabilitations and analysis programmed into the software take into account subgrade
strength and variable distress conditions within each rehabilitation zone, and assigns additional
funding for streets with lower strengths and/or higher amounts of distress. Thus, regardless of
whether the thin overlay starts at a 65 or 75, sufficient field work is completed (and funds
provided) to return it to a 96 to 98 OCI. In the case where sub-standard rehabs are applied -
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such as a slurry seal on a street with an OCI of 30, when the data base is manually updated, it is
expected the OCI would be overridden to reflect the substandard work.
In the above example, using the fixed gain approach to post rehab OCI values, the street with an
OCI of 75 would bump up 20 points to say a 95, while the street with an OCI of 65 would only
achieve an 85 - in which the basic question of why do the work to only restore it to an 85 would
need to be asked.
• Structural Analysis - Structural index (arterials) and sum of load associated deducts (collectors
and residential) values are now used in the rehab selection process - basically these criteria act
as additional qualifies to the OCI based selection and result in the addition of local remove and
replace (RR) costs in the unit rate. A print out of the full rehab selection criteria for each rehab
option is appended to this report (they are quite detailed and not overly easy to read).
• Rehabilitation Strategies and Unit Rates - The rehab strategies, unit rates and OCI ranges
were modified to reflect current city practices and OCI distribution, as well as availability or
structural analysis. The following table summarizes the asphalt rehab strategies, unit rates and
selection criteria (OCI range and/or structural/load analysis).
The number designations following the primary rehab name and the term RR" (short for
remove and replace) is used to reflect that an increased amount of preparation may be required
as a result of the structural analysis and thus increase the rehabilitation cost. Cartegraph
requires separate names for each OCI and Structural Index/LAD combination - hence the
addition of the 1,2,3 designators.
Arterials COL & RES
OCI Range SI Range LAD Range Unit Rates ($Nd2)
w
y U 0 O N N J J
V R X X X N J F
> CL ACP Rehab a E 2 2 2 W U
Surf Trtmt 1 (Slurry) ACP 92 75 85 75 100 0 10 4.25 4.50 4.75
Surf Trtmt 2 + RR (Micro) ACP 92 75 85 60 75 10 20 4.75 5.00 5.25
Surf Trtmt 3 + RR (Micro) ACP 92 65 75 75 100 0 10 5.25 5.50 5.75
Thin Olay 1 ACP 2" 95 75 85 0 60 20 100 22.00 23.00 24.00
Thin Olay 2 ACP 2" 95 65 75 60 75 10 30 22.00 23.00 24.00
Thin Olay 3 + RR ACP 2" 95 65 75 45 60 30 100 23.00 24.00 25.00
Thin Olay 4 + RR ACP 2" 95 55 65 75 100 0 20 24.00 25.00 26.00
Moderate Olay 1 ACP 3" 96 55 65 60 75 20 40 26.00 27.00 28.00
Moderate Olay 2 + RR ACP 3" 96 55 65 45 60 40 100 27.00 28.00 29.00
Moderate Olay 3 + RR ACP 3" 96 45 55 75 100 0 30 28.00 29.00 30.00
Moderate Olay 4 + RR ACP 3" 96 65 75 0 45 30.50
Moderate Olay 5 + RR ACP 3" 96 30 45 75 100 31.00
Thick Olay 1 ACP 4" 97 45 55 60 75 30 50 30.00 31.00 32.00
Thick Olay 2 + RR ACP 5 97 45 55 45 60 50 100 31.00 32.00 33.00
Thick Olay 3 + RR2 ACP 5" 97 30 45 60 75 0 40 32.00 33.00 34.00
Thick Olay 4 + RR2 ACP 5" 97 55 65 0 45 34.00
Partial Recon 1 ACP 98 30 45 45 60 40 75 35.00 40.00 45.00
Partial Recon 2 ACP 98 45 55 0 45 45.00
Full Recon 1 ACP 100 30 45 0 45 75 100 45.00 55.00 65.00
Full Recon 2 ACP 100 0 30 0 100 0 100 45.00 55.00 65.00
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The following table presents the rehabilitation strategies for concrete roadways. In place of load
associated distress analysis being used as a qualifier for residential and collector roadways,
surface distress conditions were included in the selection process.
Arterials COL & RES
OCI Range SI Range SDI Unit Rates $Nd2
_ _
CL w
U _ p
U O N N
> x N X N X N F
PCC Rehab a 2 2 2 W U 4W
Local R&R/Cracksealing PCC 92 75 85 70 100 65 100 2.50 2.75 3.00
Localized PNL Rplcmnt 1 PCC < 2% 95 75 85 0 70 0 65 6.75 7.00 7.25
Localized PNL Rplcmnt 2 PCC < 2% 95 65 75 70 100 50 100 7.25 7.50 7.75
Moderate PNL Rplcmnt 1 PCC < 5% 96 65 75 0 70 0 50 10.25 14.00 17.75
Moderate PNL Rplcmnt 2 PCC < 5% 96 45 65 70 100 40 100 11.25 15.00 18.75
Extensive PNL Rplcmnt 1 PCC < 10% 97 45 65 50 70 0 40 16.75 23.00 29.25
Extensive PNL Rplcmnt 2 PCC < 10% 97 30 45 70 100 30 100 18.75 25.00 31.25
Partial Recon 1 PCC 98 45 65 0 50 73.00
Partial Recon 2 PCC 98 30 45 0 70 0 30 46.75 62.50 78.00
Partial Recon 3 PCC 98 0 30 50 100 83.00
Full Recon 1 PCC 100 0 30 0 50 0 100 75.00 100.00 125.00
The rehabilitation strategies have been enhanced from the 2004 analysis in that:
1. They incorporate strength (for arterials - asphalt and concrete) and load associated
distress (asphalt collectors and residentials) constraints for asphalt roadways and do not
just rely on OCI values. By introducing the concept of selection based on PCI and either
a structural constraint or load associated distress constraint, the rehab strategy selection
may be fine tuned to the actual needs of the pavement based on its performance and
distress profile.
2. The current rehabilitation options recognize that if a roadway has a strong subgrade (or
pavement structure), or low amount of load associated distresses, it can receive a lighter
rehabilitation. Conversely, the rehab selection methodology prevents strategies that may
possibly be too light from being applied.
3. The rehabilitation strategies provide a continuous spectrum of every increasing
rehabilitation options as the OCI value drops over time. In the 2004 analysis, once a
roadway passed an OCI of 60, its only rehabilitation option was full reconstruction, and
then selected again for a surface treatment within 5 years. By incorporating a full
spectrum of rehab strategies, streets may be intercepted earlier and their life cycle
extended before a full reconstruction is required.
IJIS Infrastructure .Management Services Denton Report Rev2.doe page 22
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3.2 FIX ALL TODAY ESTIMATE AND STEADY STATE
The Fix All Today total is the theoretical value to rehabilitate all streets in the network to an OCI value
approaching 100. The Fix All Today estimate is developed by manually applying the appropriate rehab
and unit rate to each street segment and then totaling up the results. The estimate ignores time,
deterioration and inflation as it is a theoretical exercise used to estimate the total dollar value deficiency in
the network. The Fix All Today estimate for Denton is approximately $157M broken down as follows:
Fix All
Pavement Rehabilitation
Asphalt Full Reconstruction 55,887,000
Asphalt Partial Reconstruction 36,771,000
Asphalt Thick Overlay 21,782,000
Asphalt Moderate Overlay 21,948,000
Asphalt Thin Overlay 17,193,000
Asphalt Surface Treatment 2,307,000
Asphalt Routine Maintenance 268,000
Concrete Full Reconstruction 0
Concrete Partial Reconstruction 50,000
Concrete Extensive Panel Replacement 6,000
Concrete Moderate Panel Replacement 23,000
Concrete Localized Panel Replacement 88,000
Concrete Localized R&R 501,000
Concrete Routine Maintenance 870,000
Totals 157,694,000
The main functions of examining the Fix All Today estimate is to identify the upper ceiling of rehabilitation
costs the network may require as well be used as a quality control check against the analysis using the
Cartegraph application. For example, the fix all total for Denton is estimated at $157M and annual
amount to maintain the OCI at 63 is estimated at $10.1 M per year (as discussed in Section 3.3). Dividing
the $157M by $10.1/year yields an approximate 15.5 year rehabilitation cycle which is deemed
reasonable and within acceptable limits. If the steady state analysis using the pavement management
system resulted in annual budget of $20M, this would result in a 6 year rehab cycle ($125M / $20M = 6.25
years), which would then raise concerns as it is far too short and outside acceptable norms.
The Denton Fix All Today rehabilitation activities breakdown as follows:
Activity Fix All % Typical Range
ACP Reconstructs 55,887,000 35.4 25 - 50
Progressively Thicker Clays 80,501,000 51.0 50 - 75
Surface Treatemts to Thin Clays 19,500,000 12.4 10 - 15
Routine Maintenance 1,138,000 0.7 1 -5
PCC Rehab 668,000 0.4
Totals 157,694,000 100
LUS Infrastructure .Management Services Denton Report Rev2.doe page 23
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3.3 RULE OF THUMB ESTIMATES FOR MAINTAINING OCI = 63
Two methodologies exist for estimating the annual cost to maintain the 2009 network OCI at 63. Both
methods are completed external to the software and are simply used to develop a better understanding of
the needs of the system and as a quick check of the Cartegraph based analysis results.
• Method #1 - Network Averaging: Under this method the selected rehabilitation is based on the
network average OCI and a mid range life cycle and unit rate applied. For Denton, the average
annual cost to maintain the current OCI is estimated as follows:
2009 Network OCI: 63
Average Rehab Based on OCI: Moderate Overlay
Mid Range Overlay Unit Rate ($/ft2): 3.00
Average Life Cycle for an Overlay (years) 17.5
Percentage of network completed each year 1/17.5 * 100): 5.7
Total Network Area (ft2): 62,000,000
Area Completed Each Year (ft2): 3,543,000
Estimated Annual Cost 10,600,000
The results of the network averaging provide only a ballpark estimate / - $1M at best) as it
assumes all streets perform in a similar fashion and treats asphalt and concrete streets the same.
• Method #2 - Fix All Life Cycle Analysis: Under this option, the Fix All Today estimate developed
in Section 3.2 for each street segment is divided by the expected life cycle for the applied
rehabilitation and the entire network summed up. For example, a street segment may require a
thin overlay for a cost of $114,000 and have an anticipated life cycle of 11 years. Its annual
contribution to maintaining the current OCI is then estimated by dividing the total rehab cost by
the life cycle, or in this case $114,000 / 11 years = $10,360/year.
The cost to maintain an OCI = to 63 is estimated as follows:
Fix All Fix All Life Cycle
Pavement Rehabilitation Contribution ($/yr)
Asphalt Full Reconstruction 55,887,000 1,863,000
Asphalt Partial Reconstruction 36,771,000 1,471,000
Asphalt Thick Overlay 21,782,000 1,452,000
Asphalt Moderate Overlay 21,948,000 1,829,000
Asphalt Thin Overlay 17,193,000 1,433,000
Asphalt Surface Treatment 2,307,000 769,000
Asphalt Routine Maintenance 268,000 268,000
Concrete Full Reconstruction 0 0
Concrete Partial Reconstruction 50,000 2,000
Concrete Extensive Panel Replacement 6,000 1,000
Concrete Moderate Panel Replacement 23,000 2,000
Concrete Localized Panel Replacement 88,000 7,000
Concrete Localized R&R 501,000 167,000
Concrete Routine Maintenance 870,000 870,000
Totals 157,694,000 10,134,000
I.IIS Infrastructure .Management Services Denton Report Rev2.doe page 24
32
Methodology #2 is slightly more accurate as it separates asphalt from concrete and recognizes
need on a street by street basis. From these two estimates, the cost to maintain the OCI at 63
may be estimated to be on the order of $10.0 to $11.OM annually.
3.4 NETWORK BUDGET ANALYSIS MODELS
A total of 7 budget runs or models were ran in order to fine-tune the recommendations for City of Denton
roadway network. The budgets were based on the following scenarios:
Unlimited budget -similar to the Fix All Today assessment, the unlimited budget assumes the City
has unlimited funding over 5 years and takes into account network deterioration and allows
repeat rehabilitations to occur. The Unlimited budget will never raise the OCI to a perfect 100 as
it is mathematical impossibility due to the fact that streets are only rehabbed as they become a
need which starts at an OCI of 85 (meaning streets are allowed to deteriorate from a 100 to an 85
before rehabilitation occurs and thus the average can never be 100). Also not all rehabs results
in a perfect 100. As mentioned in Section 3.1 post rehab OCI's range from 92 to 100. What the
unlimited budget does is rehab each street as it becomes a need and identifies the theoretical
maximum value the City would ever spend. It is always on the same order of magnitude as the
Fix All estimate but never equal.
The unlimited funding budget is approximately $30M/year or a total of $150M and raises the OCI
to a peak of 92 and then deteriorates to an 87 over the next 4 years as street segments wait for
their next rehabilitation.
Do Nothing option - this analysis run highlights the detrimental effect of spending no capital
funding on the roadway network. The network OCI would drop from a 2009 value of 63 to 52 at
the end of 5 years. The Do nothing option is run in order to identify equity being removed from
the system due to deferring of rehabilitation activities.
5 year Budget runs of $2M, $4M, $8M, $10M and $16M. Under these scenarios, streets are
selected according to their priority and then scheduled as funding becomes available.
5 analysis runs we completed examining the current $3.2M annual funding level as requested by
the City, plus an additional 5 runs to maintain the current OCI . The results of these runs are
discussed in Section 3.5
1 Run to target an OCI of 69 over 5 years. This is also discussed in Section 3.5.
The results of the analysis are summarized in Figure 16. The X axis highlights the annual budget, while
the Y axis plots the 5 year-post rehab network average OCI value. The diagonal green line is the
resultant network OCI value for any given annual budget (the same amount spent each year for 5 years).
The plot may be used to interpolate between analysis runs amounts to fine tune budgets and desired
level of service targets. For example, to maintain the 2009 OCI of 63, an annual budget of approximately
$10.3M would be required. To target OCI's of 65 or 70, budgets of $11.7M and $16.OM annually would
be required. Also, Figure 16 provides a quick reference to the "what if' question of what would happen to
the network if the budgets were raised or lowered by a fixed amount without having to re-run the models.
I.IIS Infrastrueture.llnnngement Services Denton Report Rev2.doc page 25
33
Please note, Figure 16 is plotting the network average OCI after 5 years of rehab have been completed
against annual budget amounts. Figure 16 does not provide a year by year trace of the network OCI (that
is contained in Figure 17). All plots use an OCI starting point of 63 as measured in 2009. The current
OCI in 2010 is estimated at 61.
75
74 ,
s 65
0
2009 OCI 6-S
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
w
v
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60 Budget= $151VI j yr
E
u, ~,,,A•T
Maintain OCI :03
y € udget=, $10M/yr
55
y,it
50
0 2 4 6 S 10 12 14 16 18
Annual Budget ($M/Year)
Figure 16 -5 Year Post Rehab Network OCI Analysis Results
Figure 17 presents the same analysis results on an annual basis. In this plot, the X Axis is now the
analysis year, and the Y axis the network average OCI for each year of the analysis. The plot lines are
the year by year network average OCI.
The Unlimited budget contains a large jump in OCI followed by a gradual decline. This is how an
unlimited budget is supposed to look. In year one, it rehabilitates every street that is a need - essentially
it fixes all streets below an OCI of 85. In the subsequent years, it rehabs only those streets that drop
below an 85. It does not return each street to a perfect 100 in each year of the analysis.
IJIS Infrastructure .Management Services Denton Report Rev2.doc page 26
34
loo
90 $2M annual
$4M annual
U $101VI hall LIal
O
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4
$16M anllu8l
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ttnlllnlted
70 -Do Nothing
60
50
0 1 2 3 4 5
Year End Analysis Results [0 = 2010)
Figure 17 -5 Year Annual OCI
By examining the differences between the various budgets and OCI results, the benefits of maintaining
the system at its current level of service may be compared against letting the system deteriorate and then
attempting to rebuild it (essentially the cost of the Do Nothing option in terms of returning the system back
to its original OCI). The amount of cost savings for Denton may be estimated at:
1. The Unlimited budget raises the OCI from 63 to a peak of 92 and costs approximately $160M or
$5.5M per point increase (63 = starting OCI, 92 = Final OCI, $160M / (92-63) _ $5.5M per OCI
point raised).
2. The $10.OM annual budget maintains the OCI at 63 and invests approximately $50M over 5
years.
3. The do nothing drops the OCI from 63 to 52 for an 11 point OCI drop. At $5.5M per point (as
developed in item 1. above) this equates to $60M being required to return the system to an OCI
of 63. (63-52) x $5.5/pt = $60M
4. The cost to maintain the system on an annual basis therefore $10M dollars less than letting it
deteriorate and then attempting to rebuild the network ($60M - $50M = $10M).
IJIS Infrastrueture.11anagement Services Denton Report Rev2.doc page 27
35
Selecting the steady state budget a budget of $10.OM, the following OCI distributions may be plotted after
5 years of rehab effort against the current network profile OCI:
* 2010 0C:1
30
* 5Yrpo Nothin
* }10.01V! Annual
25
r
20
`a
3
a
Z
m 15
a
10 -
I
j
5 1 j
1 I
o
Very Pool, Poor Alai inal Fair Good Very Good E_ellent
(0 to 30j (A to 15) (45 to 55) (55 to 65) (65 to 75) (75 to 85) (85 to 100) ~
Overall Condition Index (OCI]
Figure 18 - OCI Distribution after 5 Years at $8.OM and $12.OM/year
The plot also presents the effects of the Do Nothing option. As can be seen from the plot, at $10.OM
annually, the growth in backlog has been virtually checked, in addition to a considerable drop in streets
rated as poor through fair. A significant increase in the excellent and very good streets is the most
notable affect of this budget option. The City may consider altering the priority strategies to put slightly
more emphasis on reconstruction in order to lower the Very Poor percentage below the final result of 17%
(the $10.OM hit dual targets of maintaining the OCI and backlog, however locally, the people of Denton
may want to decrease the backlog at the expense of OCI - this the purpose of the City taking over the
pavement management system so they complete unlimited analysis runs to investigate a wide array of
"what if' options).
LUIS Infrastructure Management Services Denton Report Rev2.doc page 28
36
3.5 CURRENT FUNDING AND MAINTAIN EXISTING OCI MODEL RUNS
The City requested analysis options based on the current funding level of $3.2M annually and certain
restrictions on spending. Figure 15 discussed earlier indicates that at $3.2M unconstrained a 5 year post
rehab OCI value of 54 would be maintained. The following analysis runs were examined:
1. $3.2M Apportioned - Restricting funds proportionally to the splits identified in Fix All estimate
discussed in Section 3.2.
2. $3.2M No Reconstructs - Restricting funds with a best first approach using no reconstructs, the
only rehabs used surface treatments and overlays.
3. $3.2M Worst First - Restricting funds with a worst first approach using no surface treatments or
overlays, the only rehabs used are reconstructs based upon worst OCI first.
4. $3.2M Arterials and Collectors - Restricting funds proportionally to the Fix All estimate but also
restricting them to Arterials and Collectors only.
5. $3.2M - Residentials Only - Restricting funds proportionally to the Fix All estimate but also
restricting them to Residential streets only.
The results of the analysis are summarized in the following table:
O co
o
co y
O y
Y O
U
3 p co
m a m a)
co co co L- L- O
Y
V
Q Description W) W) m
3.2 1 Rehabs Apportioned to Fix All 55 26 98
3.2 2 No Reconstructs 52 30 114
3.2 3 Worst First - Reconstructs Only 54 26 98
3.2 4 Arterials and Collectors Only 54 26 98
3.2 5 Residentials Only 55 25 95
At a funding limit of $3.2M annually, the best estimate for the OCI value is a drop from 63 (as measured
in 2009) to on the order of 54 to 55 in 5 years. However, it is the amount of backlog of reconstruction that
is the primary concern as it has the potential to increase from a manageable 16% to a minimum of 26%.
The column titled Backlog Cost Estimate ($M) attempts to put a dollar value on rehabilitating all streets
that fall below an OCI of 30. The cost ranges from $95M to $114 depending on the strategy used.
The City also request a series of analysis runs investigating the costs to maintain the OCI at its current
level - for these runs a starting OCI of 61 was used. The same 5 analysis runs described above were
considered. The results are as follows:
I.IIS Infrastructure .Management Services Denton Report Rev2.doe page 29
37
9
O
~ o N
a, w
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°
m V
c
_ a m a~
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O
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8.2 1 Rehabs Apportioned to Fix All 61 19 72
28.0 2 No Reconstructs 60 26 98
28.0 3 Worst First - Reconstructs Only 60 19 72
8.2 4 Arterials and Collectors Only 60 19 72
7.0 5 Residentials Only 61 19 72
15.0 No restrictions 69 11 42
From the above, it is apparent a budget of slightly more than $8.2M will be required to target an OCI of
61, however the backlog does increase (the Cartegraph software can only target one of the two
requirements and not both). As discussed in Section 3.4, $10.0 annually is required to check the growth
in backlog and target an OCI of 63.
Analysis Runs #2 and #3 have misleading results. By eliminating reconstructs as a rehab option, the
software recycles pavements before they need to in order to maintain the target OCI value, thus wasting
money on needless overlays - by eliminating recycling of projects, the actual budget would be on the
order of $8.5M.
A final run targeting an OCI of 69 was also completed. At an annual budget amount of $15.OM, a 5 year
post rehab OCI of 69 with a backlog of 11 % can be achieved.
The results of the analysis runs discussed in Section 3.5 are provided in electronic format and are not
appended to this report.
IJIS Infrastructure .Management Services Denton Report Rev2.doe page 30
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3.6 NETWORK RECOMMENDATIONS AND COMMENTS
The following recommendations are presented to City of Denton as an output from the pavement analysis,
and must be read in conjunction with the attached reports.
1. The City should adopt a policy statement selecting a fixed target for network level of service and
acceptable amount of backlog. We suggest an OCI target of 65 to 70, with less than 20% backlog.
The 65 to 70 range was selected as the target for two primary reasons: On average an OCI of 65 to
70 is generally accompanied by a backlog of 15% - thus providing a high level of service with a
manageable backlog. And secondly, an OCI of 65 to 70 provides the travel public with a relatively
good roadway network and an economic balance between pavement expenditures and service life
(at an OCI of 65, pavements are just entering the steepest part of their deterioration curve).
An annual budget dedicated to roadway rehabilitation of $12.0 to $16.OM is required to
achieve this goal. A budget of $15M will achieve an OCI of 69.
2. A budget of $10.OM would maintain the OCI at 63 with 17% backlog - that is it would maintain a
steady state level of service.
3. An annual budget of $3.2M will result in a network OCI of 55 with 26% backlog. Applying current
priorities and pavement management principles to an agency that is this severely underfunded does
not produce a satisfactory pavement management plan - all it does is delay the inevitable.
4. One potential to attempt to defer the decline in condition is to adopt a policy of applying
substandard rehabs to all roadways. The plan would be to crack seal, patch and slurry all roadways
with the intent of gaining 4 to 5 years in which to secure adequate funding. This approach can only
be done once and afterwards, full rehabilitations need to be implemented otherwise the roadways
will continue to deteriorate at an accelerated rate.
5. The full suite of proposed rehabilitation strategies should be reviewed prior to finalization of these
budgets, and then again annually as they can have a large effect on the analysis. Current asphalt
pavements focus on full depth paving. Based on the results of the structural testing, subgrade
removal and replacement and stabilization, along with granular base may possibly facilitate long
rehabilitation cycles for the city.
6. Compliance with the Americans with Disabilities Act is required on all roadway rehabilitation
projects including: the provision of para-ramps at all crosswalks, minimum of 30 inch obstruction
free clearance along all sidewalks, and a maximum of 1 inch lip of asphalt above the curb line.
7. The City should consider integrating their pavement management capabilities with other business
functions relating to roadway performance including:
• Enhanced roadway construction inspection, testing, acceptance and long term
performance monitoring.
• Mix designs, structural design, materials and construction specifications.
• Data management for GIS updating and passing data from GIS to pavement
management including acceptance dates.
LUS Infrastructure .Management Services Denton Report Rev2.doe page 31
39
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