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Home My WebLink About0163.094Febr~ary 24~ 1994 THE HONORABLE CITY COUNCIL palo Alto~ California ~ement Maintenance Manag~ment Prog~ Members cf the Co~~cil~ Report in Br:i.ef ;, -" ... -, This is an infortUOi.tional report on t.he status of the anntial pavement maintenance program. No Cour,cil action is required at this cime. This report diacusees proposed :;:lew iuitiacives in the manner and type of pavement maintenance to be performed. Staff is proposing to add slurry seal surface coating work to this year's contract street maintenance work, in addition to the recent practice of resurfacing wi.tb asphalti.c concrete. This ';Iiill enable a 150 percent increase {2 l/2 times as much) in the area of streets to receive maintenance treatment by contract this year, as compared to or..ly overlaying within the same budget. Additionally~ the street maintenance and sidewalk repair prograJtlS will be integrated to perform curb, gutter, driveway and sidewalk repairs on the streets which are reaurfaced~ This will provide the residents on these streets with a one time comprehensive repair project and min~m~ze disruption. This item ~ill return to Council when the construction contract is recommended for award in April. Background Up to 1986~ the City incorporated overlays and slurry seals~ plus an oc.caBional chip seal, in the paveme.nt maintenance program. From 1986 to last year;s program, only overlays were performed to take advantage of matching State funding. Due to ~hrinking matching funds and a need to address preventive maintenance for surface wear conditions, starf is re-incorporating surface r:reatment in thi.6 year's paveme:1t maintenance program. Please refer to Attachment "A far a brief tecr~ical description of the City's Pavement Maintenance Management program. Discussion CURRENT PROGRA."'f: This year' B pavement maint.enance program not only involves overlaying streets, but includes two additional items, i. CMR:163:94 -1- --~---~-- -, / e., slurry seal and a total ir.tegrated street repair concept: ("initiated t.his year) fOr streets that are receiving an asphalt overlay~ Approximately 13 lane miles of streets will receive an application of slurry seal to seal the surface of the street froro water intrusion and provide a ne .... wearing surface at a cost of approximately $200 1 COO. Approximately 6"5 lane miles of streets will be oyerlayed this year at. a cost of approximately $900,000. Staff is initiating an integrated street repair concept th~s year. Under the int.egrated street repair conceptr when streets are overlayed, all curb. ~~tter, driveway and sidewalk adjoining the street that meet the City's replacement policy will be repaired and curb ramps installed. Therefore~ the street will receive a one time compreheneive repair project, minimizing disru.ption to the residents along the street. CUrrently, separate CIPs proyide street . .overlays for streets needing structural strengthening, sidewalk repairs foY sidewalks that exceed the City's replacement criteria and curb ~~d gutter repairs for curb and gutter tha~ impair storm water flows. This concept will not eliminate the gep~rate curb, gutter and sidewalk repaire CIPs, but will be done in coordination with, ~~d as supplement to them. A portion of the funding for the sidewalk replacement CIP and Storm Drainage Utility (curb a!ld ~~tter replacement) will be used in ~ombination with the resurfacing fund. In order to create a jOintly funded integxated street repair project containing elements of both CIPs. In addition to the aboVe progratr,. staff is initiating another program to remove asphalt overlays from concrete streets that have been overlayed. The City started overlaying concrete streets in the early 1950's. Though expedient in the short run. in the long run successive overlays of concrete streecs eventually fill in curbs a..'F}d cause drainage problems. While aome concrete st.reets are economically unrecoverable due to numerous structural failures. t:here are many concrete streets that were overlayed to correct minor flaws or to smooth the s\.iZ-face of the street. These streets can be returned to concrete. surface streets by virtue of new technology and equipment for grinding the surface of the streets to a B~th finish. Embarcadero Road (off ramp) between High Street and Alma Street" is the firBit street to be cho!;len for this remediation work and is included in this year' 5 prO']ram. The experience gained from this year will determine the future course of action for other concrete streets. PILOT PROJeCT: In the past, chip seals have had limited application due to the problems of loose rock chips and dU9t:. However. new materials are available whi.:-h effectively eliminate these problems. To determine if these chips seals are acceptable. staff will conduct a pilot project this fall involving placement of two different types of chip seals, i. e .• Polymer Based Asphalt chip seal and Crumb Rubber chip seal, on various streets. The prcj ect will monitor cost, appearance, applicabilitYI resistance to wo;ar, neighborhood disrupt.ion and public acceptance for the t'Wo types of chip seal. If results are favorable, these chip ae~ls will be added to the pavement maintenance program and used where app~icahle. Please refer to Attachmem: A for fUrther discussion on chip seals. CMR.:163:94 -2- ~--. - .~ " .. ~;r ""' .. Economics/Recycling The a.ddition of a.sphalt surface treac.rnents to the Clr.nual pavemer~t program greatly increae.es the number of streets that recei-..re remedial treatment. While an asphalt surface treatment, such as slurry seal~ does not reatore the str,Jctural capacity of the s~~et. a surface treatment, applied at the right time, can extend the life of the existing street and therefore delay or eliminate the need for an ov~rlay. Decreasing the amount of asphalt overlays reduces the consumption of natural materials and energy and reduces waste by source reduction. Also, the Crumb Rubber chip seal utilizes rubbe= from recycled tires. RWespect~ted' A. CARLSON nior Engineer ~baJ...t", "EORGE BAGDON Assistant Director of Public Works GLENN S. ROBERTS Director of Public Works ~",~ BERNARD M. S11W,JN'{ Assistant City Manager Attac~~ent A -Pavemen~ Maintenance Management Program CMR:163:94 -3- "> I I ATTACHMENT A PAV§:.MENI MAHITENANe'E MANAG&foP...NT PROGRAM A proficient pavement maintenance program provides a sound basis for prolonging the economic life of City streets and is a pre qualifier for some State and Federal funding. In 1981. the Public Works Department instituted a computerized Pavement Maintenance Management program to provide a systemized method to identify the condition of City streets, recommend remedial action and pl.-ioritize the list of candidate streets. All City Etreete are reviewed every two years and are rated baaed on the following indicators of wear and stro2!Ss. 1. Alligator cracking. an indicator of st~ctural pavement failure .. ~. Block cracking, an indicator of oxidation and brittle asphalt leading to structural pavernsnt failure. and 3. Surfacing raveling, and indicato:r of incipient oxidation and loes of surface asphalt. Priority listings al.'e established by a formula incol.-porating the above indicators pIllS traffic volume. An asphalt overlay is specified for street.s needing atructul:al strengthening and an asphalt surface treatment is specified for streets showing surface distress. Separat.e lists of candidates are established for asphal t overlay and asphalt surface treatment. Each year candidate streets are taken from the priority lists to matcb available funds from the gas tax and users utility tax funds. Before the lists are finali2ed~ other City Departments are conaulted for conflicts with their construction projects, such a,s utility repair ~~d replacements. Candidates are delayed to avoid conflicts with construction projects scheduled up to three years in the future. Candidates effected by projects scheduled more that three years in the future are reviewed on a case by cas~ basis. ASPH?.LTOVERLAY Asph~lt o'.rerlays are placed when a pavement requires etruct· .... ral upgrading. The structural integrity of an asphalt pavement can be compromised by several factors such as an wlanticipated increase in truck or bus traffic, moisture from the ground or through cracks in the pavement~ lack of periodic maintenance for failures and surface wear, utility trenches or time. A well timed overlay can recapture the structural integrity of the pavement. If the street is not properly maintained, street reconstruction will be necessary. Currently. streets needir.g structural upgrading are pa-"ed la7ith an 1·1/2 inch minimum thick.~ess asphalt overlay with a pavement fabric interlayer membrane to reduce reflective cracking. Thicker overlays are ?laced if needed. All base failures are repaired and cracks exceeding lis inch are sealed with asphalt. For cracks -4- exceed1ng 1/4 inch. a fabric membrane is placed cver the crack. Trees are trimmed by professional t.ree trimmers prior to the overlay operations. The cost of an 1-1/2 inch overlay is approximately $1.00 per sq. ft. ASPHAI.T SURFACE 'I'REA'I'MENT~ The first evidence of stress ir~ a street is surface raveling and Bupe~ficial cracks. This stress is cauge~ by traffic, moisture and oxidation of the asphal t . The surface of t.he asphal t becomes brittle, wears off ar.d cracks. If left unattended. the raveling decreases the thickness of t.he asphalt pavement allowin.g water to enter; and the cra.cks extend do·ofIli'!l. through the depth of the asphalt pavement and the structural capability of the street becomes compromised. A Bi.!rface treatment seals t.he surfa-:-e from oxidation and moisture and fills in t.he minor cracks. Surface treatlT',entl9 have a life of up to 10 years depending upon the t~e of seal and type and amount of t.raffic. The cost of a surface treatment varies from 15 to 40 cents per sq. it. depending on the type of treatment. '!'ypically~ these streets receiving a seal do not contain b~se failures and have only minor cracking. There are two types of seal being considered for use by staff, i. e.~ slurry seal and chip seal. Slurry seal can be applied at three different rates· Each rate results in a different aggregate size and thickness of slurry seal. The thickest application is approximately 1/4 inch thick. The pros for slurry seal are ease of application, minor disruption to property owners and visual appearance of the final product. The con is that slurry seal is not very fleXible and will reflect cracks over time. Slurry seals are proposed for the current year and have been exclusively used in the past by the City. The chip seal most used is applied by spraying a layer of asphalt emulsion on the road, immediatel}~ spreading a layer of rock chips over the asphalt emulsion and rolling the rock chips with a steel dr.J.m compactor. This standard chip seal provides the shortest street closure. time of the seals but h36 the inherent problems of loose rock chips and dust from the rock and therefore has not been used by staff. However, tnere are two different types of chip seals which elirr.inates these problems. The two types of chip seal being considered for use by staff are Polymer Based Asphalt (PBA) chip seal and Crumb Rubber chip seal. The PBA and Crumb Rubber chip seals are similar looking and are similarly applied. These chip seals are applied hot -with the rock mixed ..,ith the asphalt and because of the application, there are no loose rock chips and d'..lst ~ith this chip seal. However, due to the additives~ PBA or Crumb Rubber, the applications are very sens_ltive to temperature and other environmental conditions. Due to the PBA and Cr~mb Rubber additives these chip seals remain flexible longer that the standard chip seal and slurry seal. However, these additive roughly double the coat of the standard chip seal. CMR,163 ,94 -5- • Staff pr~BeB to seal several 5~reets with PBA and Crumb Rubber chip seals later this year through the Santa Clara County pavem~nt progr~s~ The City will contract with the Co~~ty to perform the work~ The County chip seals throughout the County every year and will inc~rporate our streets in with their program. Staff will monitor the applications. complaintB, c~sts and quality of product in place. The results will dictate the ~xtent to which these chip Beals will be ~8ed in the future. -6-