Interlock Design Insights

July–August 2020

ISSUE FEATURES University of Toronto Tests PICP Cleaning Equipment Effectiveness Research Demonstrates Lower Deicer Use on PICP A National ASCE Standard for Permeable Interlocking Concrete Pavement HNA Awards: Call for Entries

TRENDING Hardscape Business Grows Amid COVID-19 Disruption — Despite dramatic impacts on public health and the economy, homeowners are investing in improvement projects inspired by their work from home routines.

Design Professionals Are Discovering New Distance Learning Opportunities — Unusual circumstances present unique opportunities. ICPI’s catalog of hardscape design courses hosted

by AEC Daily have seen a marked increase in traffic by landscape architects and civil engineers. he Hospitality Industry’s Job T Loss Is Becoming the Hardscape Industry’s Gain — Employees jolted from a frozen hospitality industry are seeking more stable career alternatives and many are finding opportunity in construction, hardscapes and landscapes.

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Dealing with the dirt: While infiltrating runoff, PICP captures sediment.

Soiled jointing stone blown to the surface of an 11-year old, never vacuumed pavement illustrates the need for regular cleaning.

University of Toronto Tests PICP Cleaning Equipment Effectiveness With millions of square feet (meters) in place since the turn of the century, permeable interlocking concrete pavement (PICP) continues as one of the most effective practices for managing stormwater runoff and pollution across the U.S. and Canada. PICP sidewalks, plazas, parking lots, alleys and roads typically render high infiltration rates for years without cleaning.

However, sediment filled runon from adjacent impervious surfaces requires routine cleaning to prevent PICP from clogging.

Answering Three Key Questions

Unfortunately, many PICP owners are not willing or able to conduct routine cleaning to prevent continued accumulation of sediment. Reduced surface infiltration rates that occurs requires more powerful equipment to increase and restore them to near post-construction levels.

Questions often raised by owners with clogged PICP are: ‘What’s the best equipment?’ ‘How do I know when to use it?’ and ‘How much does it cost to own or outsource such equipment?’

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Last year, Professor Jennifer Drake with the University of Toronto Department of Civil and Mineral Engineering helped answer the first question. She conducted an evaluation of five cleaning equipment technologies on simulated, highly clogged PICP.

Research objectives included:

• Testing the performance of various cleaning equipment technologies and develop best management practices for surface infiltration restoration.

• Investigating pre-cleaning practices (e.g. power washing) that might increase efficiency and effectiveness of various cleaning equipment technologies for restoring surface infiltration rates.

• Investigating cohesive (high clay content) vs non-cohesive sediments on their response to various cleaning equipment technologies and cleaning frequencies.

To meet these objectives, a PICP test pad was constructed in 2017 at the Toronto and Region Conservation Authority’s Kortright Centre for

Conservation in Vaughan, Ontario.

This pad consisted of seven 10 ft (3 m) square PICP cells with an underdrain. Five test cells were clogged with street sweepings that matched sediments sampled from mature PICP parking lots within the Greater Toronto Area. The PICP joints were clogged using a controlled procedure developed by the University. This resulted in a consistent mix of materials used to clog the joints. In addition, a mix of cohesive, clay-based sediment was developed, typical to that found in existing PICP sites in the region.

ASTM C1781 Standard Test Method for Surface Infiltration Rate of Permeable Unit Pavement Systems was used to measure surface infiltration rates on new and progressively clogged PICP joints. Restorative maintenance was required when mean surface infiltration measurements approached 10 in./hr (250 mm/hr). A video in Figure 2 illustrates this test method. Water is poured into a 12 in. diameter ring sealed to the PICP surface with plumber’s putty. A small, constant head of water is

maintained while pouring. The total time to infiltrate about 5 gallons (18 l) or 40 pounds (18 kg) of water is timed using a stopwatch on a cell phone. The total time is entered into a formula to obtain the infiltration rate in inches (or mm) per hour. If the total time to infiltrate is over 30 minutes (<20 in. per hour), the infiltration rate is considered very low and the surface needs immediate cleaning.

Cleaning equipment was allowed one pass at normal speeds.

Effectiveness of the equipment could be increased by performing multiple passes in actual field applications.

Five equipment technologies were evaluated as shown the video links on page 4.

Results Varied with the Equipment

A regenerative air machine restored 20% of the surface permeability. This suggests use of this equipment for routine cleaning to remove loose dirt, leaves, litter, etc. and not on clogged PICP surfaces. The true vac produced the most variable results.

Power washing and applying a Shop Vac improved surface infiltration by 25%. The waterless mechanical street sweeper restored the PICP’s surface infiltration capacity to 35% of its original condition, or about 139 in./hr (3,540 mm/hr). The high pressure-air and vacuum system fully restored the PICP to its baseline, post-construction surface infiltration.

Average surface infiltration rates were 2 to 6 times higher than from other equipment, ~508 in./hr or 12,900 mm/hr for cohesionless street sweepings mixed with jointing stone.

Other conclusions:

Figure 1. PICP test pad received consistently mixed and compacted sediment in joints for removal by various equipment

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• Not surprisingly, the depth of evacuation into joints was a strong indicator of overall maintenance effectiveness when clogged with similar materials, but not when clogged with different materials.

July-August 2020 PICP for more than 15 minutes after a rainstorm likely indicates a location that’s starting to clog.

• Orientation of street sweeper suction/collection heads greatly influenced the amount of joint materials removed. Passes in all joint directions can likely provide the highest results.

• Cohesive soils significantly decreased the effectiveness of restorative maintenance.

The high pressure-air/vacuum system was only able to restore the PICP’s surface infiltration to approximately 50% of the pavement’s original surface infiltration while removing cohesive sediment from the joints. In contrast, this equipment was able to fully restore infiltration when non-cohesive materials, i.e. street sweepings, occupied the joints.

Professor Drake’s “road test” of restorative cleaning equipment supports industry equipment demonstrations and published research on clogged PICP over the past 15 years. Other researchers include (but aren’t limited to) Tim van Seters with the Toronto and Region Conservation Authority, Ryan Winston with Ohio State University, Manoj Chopra with Central Florida University, John Kevern with the University of Missouri, David Leopold with the Chicago Department of Transportation, Jong-Yeop Kim from Florida Gulf Coast University, and Bill Hunt at North Carolina State University, as well as ICPI Technical staff Robert Bowers, P.Eng. and David R. Smith.

This body of research and experience was synthesized into guidelines on how to maintain infiltration rates via ICPI’s technical bulletin entitled Tech Spec 23 Maintenance Guide for Permeable Interlocking Concrete Pavements. This is a free publication—click image to download.

Ponding on the surface, usually starts at the impervious-permeable pavement interface. If the extent of ponding exceeds 20% of the PICP area, surface cleaning should be considered. Surface infiltration can be assessed using ASTM C1781. If the ponds are generating runoff that leaves the PICP, cleaning should be conducted immediately.

The 12-page bulletin emphasizes preventive, routine surface cleaning to remove accumulated sediment and detritus from the joints well before consolidation and compaction into them occurs. With some recent updates, the bulletin includes information from the University of Toronto study on restoring infiltration on highly clogged PICP. More importantly, Tech Spec 23 answers the question, ‘How do I know when to use it?’ Assessing surface infiltration is conducted by visual inspections for sediment-filled joints during dry periods and ponds on the surface during or just after rainstorms.

While a rainstorm’s exact conclusion is difficult to predict, standing water on

In addressing the third question, ‘How much does it cost to own or outsource the use of such equipment?’ equipment costs can be obtained from suppliers. For outsourcing routine, preventive maintenance equipment that removes loose sediment, leaves and litter from PICP is typically done with a regenerative air machine.

These are available through commercial companies that clean large (impervious) parking lots.

Companies usually charge by the hour with a minimum hourly purchase requirement. An acre of pavement can be cleaned for about $1,000. Caveat: Be sure to check the speed of the vac

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Ponding on PICP typically begins by adjacent impervious surfaces that deposit sediment on it. Inspection during a rainstorm identifies ponds as well as indicating if the water is infiltrating near it or running off.

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engine and adjust it so it withdraws as few jointing stones as possible.

The University of Toronto research noted that results from a (nonvacuum) sweeper machine showed some benefit in cleaning highly clogged PICP. For highly clogged PICP, vacuum and especially highpressure air machines appear to provide the highest restoration of surface infiltration. High pressure air that blasts out sediment and soiled

jointing stone followed by vacuum appears to be the most effective in increasing infiltration rates. This equipment is particularly wellsuited for municipalities because the equipment requires a large air compressor and a vac truck, items typically in a cityâ&#x20AC;&#x2122;s vehicle inventory used for other tasks.

However, the cost of restorative cleaning includes replacing the removed soiled jointing material

with clean stone. This cost, plus equipment operation and crew means much higher costs than that associated with routine cleaning, perhaps as much as four or five times higher. This cost difference might help provide some incentive for PICP owners to conduct routine, preventive surface cleaning that prevents clogging and related high cleaning costs in the first place. u

Click the images below to view videos of the various types of cleaning equipment tested.

igure 2. ASTM C1781 test F to approximate the vertical surface infiltration rate of PICP

igure 3. Regenerative air F machine

Figure 4. True vac machine

igure 5. Waterless F Mechanical Sweeper

igure 6. Power washing F before applying a Shop Vac

Figure 7. Applying a shop vac

igure 8. High pressure F air system blows soiled aggregate

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igure 9. Soiled aggregate is F vacuumed away

July-August 2020

Melted plowed snow and infiltration into PICP means less deicer use

Research Demonstrates Lower Deicer Use on PICP When thereâ&#x20AC;&#x2122;s sunshine at below freezing air temperatures, permeable interlocking concrete pavement typically rids itself of snow and ice.

Instead of re-freezing, snowmelt infiltrates into the surface, even when the air temperature is below freezing.

Besides decreasing slips and falls, this also reduces deicer use.

Anecdotal information from PICP owners in cold climates have consistently noted snow melting faster and not re-freezing compared to that on conventional impervious pavements especially after plowing.

This begs the question on possible reduction in deicer use. A researchbased answer has come from a two-winter study by the University of Toronto Department of Civil and Mineral Engineering. Research

by Professor Jennifer Drake

demonstrated that PICP can reduce deicer use by as much as 50%.

Reduced deicer use can also extend pavement life.

Thereâ&#x20AC;&#x2122;s way too much deicers spread during the winter. Increasing fear of liability from winter slips and falls plus loss of vehicular control on snow and ice comes with an increasing use of deicers. Their increase in snowmelt and stormwater runoff results in environmental damage to lakes, streams and rivers. This results in economic damage to communities, i.e. lost revenue from recreational activities such as swimming, boating and fishing. Additionally, there is the increasing cost of deicers and their application. Municipalities can use of more permeable pavement systems concomitant with lower deicer use as a means to preserve water-based recreation plus surface drinking and groundwater resources.

Research Objectives

The study compared winter performance of impervious and permeable pavements, specifically slip and skid resistance, time to melt/bare pavement, and re-freezing characteristics under various deicer loads and timing. In addition, deicer concentrations were measured in surface runoff from impervious and PICP and in underdrains exiting the latter. From this data, recommended best practices for snow and ice management were provided for PICP. To conduct this investigation, an outdoor pavement test pad was constructed in August 2017 at the Toronto and Region Conservation Authorityâ&#x20AC;&#x2122;s (TRCA) Kortright Centre MORE

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PICP and Asphalt Deicer Test Pads at TRCA in Vaughan, Ontario for Conservation located in Vaughan, Ontario. The test pad consisted of four 6.6 ft (2 m) square PICP cells (level) with underdrains and an asphalt control cell (2% slope to a catch basin). Each pavement cell was enclosed with concrete to prevent lateral subsurface flows between them. Installed in an open field, the cells received no pedestrian or vehicular traffic throughout the two-year study. The allowed researchers to observe differences snow and ice melting with the deicers. Deicer types were sodium chloride (rock salt) and sodium chloride mixed with beet juice.

Conclusions from the study include the following:

• PICP treated with a low application rate of road salt (5 lb/1000 ft2 or 0.024 kg/m2) provided similar levels of safety as PICP treated with a medium application rate of road salt (10 lb/1000 ft2 or 0.049 kg/m2).

• Friction measurements pointed toward PICP providing equivalent

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or higher levels of friction with using 50% less deicers compared to asphalt. While using less deicers, PICP can have a lower risk of slips and falls for pedestrians and lower risk of skidding for vehicles throughout the winter.

• Under icy conditions, the PICP and asphalt surfaces had similar levels of surface friction prior to salting. Asphalt and PICP receiving a medium application rate of road salt (10 lb/1000 ft2 or 0.049 kg/m2) provided similar levels of safety soon after snow began to melt. Melting and drying of the PICP surfaces occurred more rapidly with the medium application rate or when using road salt pre-wetted with beet juice.

• Re-freezing of melted snow and ice after sunset was observed on the asphalt surface but could not occur on the PICP surface.

The meltwater infiltrated into the PICP leaving the surface dry.

• Conductivity measurements demonstrated that the PICP attenuated and buffered the release of deicing materials in stormwater discharge. Peak conductivity levels were reduced by over 85% by the PICP. Chloride concentrations in sampled asphalt runoff exceeded US EPA chronic concentration limit of 230 mg/L and an acute concentration limit of 860 mg/L (needed to sustain aquatic life) by several magnitudes.

Sampled PICP effluent from underdrains never exceeded the acute concentration limit due to infiltration of some water into clayey subgrade soils. u

July-August 2020

A National ASCE Standard for Permeable Interlocking Concrete Pavement David R. Smith, Technical Director Interlocking Concrete Pavement Institute At the start of the current century, permeable pavements entered the stormwater management/LID toolbox.

The three primary permeable pavement types are pervious concrete (PC), porous asphalt (PA) and permeable interlocking concrete pavement (PICP). All are constructed over opengraded aggregates that store and typically infiltrate stormwater into the soil subgrade. Permeable pavements enable compliance with NPDES permit regulations for pollutant reductions, reduce combined sewer overflows, recharge groundwater, decrease runoff volumes and reduce flooding.

Since permeable pavements support vehicles while managing stormwater, a savings in land utilization for detention/ retention facilities is realized.

igure 1. Parking lot at Elmhurst F College, Illinois

In contrast, state and local road agencies have been slow in adopting permeable pavements for full-width roads in part due to lack of design, construction and maintenance experience, as well as guidelines and standards. A core concern is performance in subgrades saturated for extended time periods, a realm unfamiliar to many pavement designers as well as to stormwater managers. It is from this lack of experience and concerns a national standard on PICP emerged from the American Society of Civil Engineers (ASCE) Transportation and Development Institute.

Labeled ASCE 68-18, this national standard on PICP codifies proven design, construction and

igure 2. â&#x20AC;&#x2DC;Greenâ&#x20AC;&#x2122; Alley in F Richmond, Virginia

maintenance practices. Fullscale load testing translated into practitioner-ready subbase thickness tables and simple, reliable design procedures can instil confidence in civil engineers who spend a small fraction of their professional time designing pavements and even less for permeable ones. Much of the groundwork in the developing ASCE 68-18 on PICP was originally detailed in the 2017 manual, Permeable Interlocking Concrete Pavement by the author of this article.

PICP project examples are shown in Figures 1, 2 and 3.

Site Suitability Considerations

ASCE 68-18 first walks the designer through a checklist of site suitability

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igure 3. PICP street in F Meridian, Idaho

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Figure 4. PICP with full infiltration design.

igure 6. PICP with a no infiltration design using an F impermeable liner

igure 5. PICP with a partial infiltration design using an F underdrain. considerations that includes but are not limited to the following:

estimated depth to the seasonal high ground water table, depth to bedrock or other confining layers

properties such as strength (typically soaked California Bearing Ratio or R-value), particle size distribution, permeability, etc.

• Federal, state, provincial, or municipal rainfall design criteria such depths, percentile, return period, intensity, and storm duration

• Hydrologic soil groups (i.e., A, B, C, D) defined in Chapter 7 of the Engineering Handbook Part 630 published by USDA NRCS

• Site history of fill soil, contamination, previous disturbances, or compaction

• Underlying geology and soils maps, horizons, soil types, and

• Soil classification (Unified or AASHTO) and mechanical

• Natural drainage systems including intermittent/perennial

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streams, lakes, rivers, and wetlands • Surrounding land use and potential sources of contributing runoff and pollution • Existing underground utility lines • Applicable NPDES, TMDLs, brownfield or other special requirements • Identification and avoidance of stormwater hotspots

System Components and Design Options

ASCE 68-18 defines PICP components and options as illustrated in Figures 4 through 6.

Hydrologic design options provide

for full, partial or no infiltration. Full infiltration allows all rainfall and runoff to infiltrate the soil subgrade; partial infiltration enables some infiltration with the remainder exiting via perforated underdrains usually connected to raised outlets. Partial infiltration is the most common design with use over low infiltration (typically clay) soils. No infiltration designs store water inside the base/ subbase using an impermeable liner for eventual release.

Concrete pavers assembled in a pattern creates joints or openings filled with permeable jointing material. The paving units comply with ASTM C936 in the U.S. or CSA A231.2 in Canada which require 8,000

psi (55 MPa) compressive strengths.

For vehicular traffic, pavers are used with a length to thickness ratio equal to or less than three and a minimum thickness of 31/8 in. (80 mm). The designer may consider using paving patterns suitable for machine installation which accelerates construction. A 45- or 90-degree herringbone pattern is recommended for vehicular pavements. Alternative laying patterns for machine installation are provided in the standard and may be considered as long as they are functionally and structurally equivalent to herringbone patterns. The pavers rest on a 50 mm (2 in.) thick layer of ASTM No. 8 stone or similar gradation.

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Figure 7. Permeable pavement design flow chart (Smith 2017)

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Structural and Hydrologic Design Methods

Structural and hydrologic design processes for determining the subbase thickness are illustrated in Figure 7. First, the designer conducts a structural analysis. Pavement design requires determining the subgrade soil strength and traffic loads expressed as lifetime ESALs or Caltrans Traffic Index. From there, the pavement structure (surface and base/subbase) are determined. For PICP design, the surface, aggregate bedding, and base layers remain at consistent thicknesses, i.e., the paver thickness plus 2 and 4 inches or 50 mm and 100 mm for the bedding and base for vehicular applications.

(Pedestrian and residential driveways only require a thickened base without a subbase.) The design engineer

develops a pavement thickness solution for the subbase layer with additional consideration given to the number of days per year water stands in the subbase for at least 24 hours (saturated conditions).

(ESALs or TI), and the number of days per year water stands in the subbase (a function of the soil infiltration rate). The tables appear in ICPI PICP manual and in the ASCE 68-18 standard.

The structural design procedure is developed from full-scale accelerated load testing of PICP by the University of California Pavement Research Center (UCPRC) in 2014.

The load testing, mechanistic design procedure, and subbase thickness design tables are in the UCPRC report, Development and HVS Validation of Design Tables for Permeable Interlocking Concrete Pavement: Final Report, (Li 2014).

These subbase thickness are shown in Tables 1 and 2 which are derived from the soil strength, traffic loads

Next, the designer conducts hydrologic analysis to develop a subbase thickness to store water.

Inputs include the:

Table 1. PICP Subbase Thickness Design Table

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• Design storm or storms (typically provided by the local municipality) • Any runoff that becomes inflow from adjacent pavements or roofs • The soil subgrade infiltration rate and water volume into the subgrade • and outflow from underdrains if required

July-August 2020

The Engineer calculates the base and subbase thicknesses required to store and infiltrate water and drain any excess water via underdrains as needed. This analysis involves manual or computer modeled movement of water into the subgrade and underdrain outflow over the analysis time, usually 48 to 72 hours, or as specified by the stormwater regulatory agency. This analysis characterizes the volume and rate water enters and leaves the pavement structure. The resulting subbase thickness is derived from finding the maximum water storage volume required for the rain event(s) plus any surface inflow while accounting for subgrade infiltration and subbase outflow over the analysis time.

From the structural and hydrologic analyses, the engineer selects the

thicker pavement subbase section for the project.

Construction Guidelines

PICP construction for vehicular applications follows the steps listed below. ASCE 68-18 includes guide construction specifications for modification to project conditions. The following lists construction steps: • Attend a pre-construction meeting • Plan site access and keep PICP materials free from sediment • Excavate soil or remove an existing pavement • Avoid soil compaction unless required in the plans and specifications

• Install geosynthetics, impermeable liners and underdrains per the plans and specifications • Place and compact the aggregate subbase and check compaction with a lightweight deflectometer • Install curbs or other edge restraints • Place and compact the aggregate base and check compaction with a lightweight deflectometer • Place and screed the bedding layer • Install pavers manually or with mechanical installation equipment • Fill the paver joints and sweep the surface clean

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Table 2. PICP Subbase Thickness Design Table (continuation of Table 1)

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July-August 2020 • Compact the pavers • Top up joints with jointing stone if needed and sweep the surface clean • Return within 6 months to inspect pavement and refill joints with aggregate

In addition, ASCE 68-18 includes a thorough construction inspection list for agency, owner and contractor use.

Maintenance guidelines

The first maintenance requirement is a PICP owner willing and able to conduct periodic surface cleaning.

Like all permeable pavements, regular surface cleaning is key to maintaining surface infiltration rates throughout the pavement life. The standard provides a complete maintenance checklist for project owners and facility managers.

Conclusion

Like all ASCE national standards, the 90 pages of ASCE 68-18 present best practices for design, construction and maintenance. The intent of this standard is reference and use by national, provincial, state and local stormwater and road agencies, as well as by consulting engineers. The standards-making effort will result in higher consistency among users that result in successful projects while

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allowing for adjustments according to local stormwater management objectives/regulations, materials, construction and maintenance practices.

ASCE 68-18 can be purchased from https://ascelibrary.org/doi/ book/10.1061/9780784415009.

Additional resources include free continuing education presentations on PICP design fundamentals, inspection, and maintenance. These are available at https://aecdai.ly/icpi.

ICPI offers technical bulletins, detail drawings and guide specifications on www.icpi.org. Structural and hydrologic design software called Permeable Design Pro is available on www.permeabledesignpro.com.

The program can be accessed for no charge through an ICPI manufacturing member searched on www.icpi.org. Finally, ICPI offers a PICP one-day PICP Specialist course for contractors and inspectors as well as installer certification.

Classes are offered across the U.S. and Canada mostly in the fall and winter. See www.icpi.org for class schedules. u

References

AASHTO 1993. “Guide for Design of Pavement Structures”, American Association of State Highway and Transportation Officials, Washington, DC. AASHTO 2010. “Geotextile Specification for Highway Applications,” AASHTO Designation M-288, in Standard Specifications for Transportation Material and Methods of Sampling and Testing, Part IB: Specifications, 31st Edition, American Association for State Highway and Transportation Officials, Washington, DC. Smith 2017. Smith, D.R., “Permeable Interlocking Concrete Pavements”, Interlocking Concrete Pavement Institute, Chantilly, VA. www.icpi.org.

Li 2014. Li, H., Jones, D., Wu, R., Harvey, J., “Development and HVS Validation of Design Tables for Permeable Interlocking Concrete Pavement: Final Report”, University of California Pavement Research Center, Davis, CA, http://www. ucprc.ucdavis.edu/PDF/UCPRCRR-2014-04.pdf

Hardscape North America Awards Move Forward for 2020 From humble beginnings at the Orpyland Hotel in Nashville, TN in 2007, Hardscape North America has grown by 280% to its current distinction as the largest annual trade show and learning event for hardscape professionals across North America. Frequently referred to by its popular moniker “HNA,” this 3-day event attracts hardscape design and construction professionals with a wide variety of roles, and interests.

Interrupted by COVID-19 this year, the continued growth trajectory for this event, none the less, shows a great deal of promise. Co-located with GIE+EXPO, Hardscape North America has become an ideal opportunity showcasing two great events in one location for landscape and hardscape professionals to learn best practices, discover new tools and technologies, experience hands-on demonstrations, network with peers, and gain a valuable competitive edge.

This year, Hardscape North America will host the annual presentation of the HNA Awards virtually. This popular awards program recognizes excellence accomplished by project teams, including designers, product producers, and installers working together on objectives ranging from small residential improvements through major commercial projects. This year’s HNA Awards program Call-For-Entries recently launched with information available at https://hna.secure-platform.com/a/ organizations/main/home.

ICPI Executive Director, Charles McGrath offered this assurance for the HNA road ahead: “While the engaging in-person HNA experience will be missing this year as we focus on protecting the health of all attendees and staff, rest assured, HNA teams are already hard at work ensuring that the HNA event we all look forward to will be back, bigger and better than ever in 2021.” u

Reach Over 11,000 Design & Construction Professionals With Your Message Here.

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Interlock Design Insights is published bi-monthly by members of the Interlocking Concrete Pavement Institute (ICPI) for producers, suppliers, contractors, specifiers, and users of interlocking concrete pavements.

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e answers you seek are just a quick click away.

icpi.org David R. Smith Technical Director, Interlocking Concrete Pavement Institute