Chip Seal over Gravel Road Project Improved Gravel Road Silver Creek Township July 2013 Project Number Project Leader Silver Creek Townboard Supervisors, Brian Opatz – Maintenance Supervisor and Thomas Wood – MnDot Research Project Supervisor (materials & road research) Agency Silver Creek Township – Northwestern Wright Co Mn 3827 134th St NW Monticello Mn 55362 Person Completing Report Chris Klein – Silver Creek Township Board Supervisor Phone Town Hall Clerk – 763-­‐878-­‐ 0141 or, Brian Opatz -­‐ 763-­‐286-­‐2988 Problem Silver Creek Township, Located in Northwestern Wright Co, has 44 miles of gravel roads to maintain and control, gravel, mud and dust, along with 22 miles of asphalt paved roads. The township wanted to find an affordable alternative to asphalt, for gravel roads that have low volume traffic, serve primarily residential homes and farms. The goal is to eliminate the expense of grading, roughness of the road, mud and dust and the expense of adding gravel lost to grading, snow removal and traffic. The other savings would be the elimination of the use of chloride solutions for gravel stabilization and dust control, to eliminate mud associated with gravel roads after rains and snows, and eliminate mud and dust that dirties vehicles, lawns and homes – in addition to eliminating air contaminates from that dust floating off gravel roads when vehicles traverse them. The expense to surface gravel roads with asphalt or concrete is too prohibitive for the townships budget, given the volume of traffic on these roads and the additional expense to maintain asphalt or concrete, which adds an additional layer of expense after the fact. Solution One solution, was to apply a designed flexible chip seal matt, on 4 miles of rebuilt gravel roads (Barton Ave NW, 155th St NW and Curtis Ave NW – forming a U loop starting and stopping on Co Rd 75 east of Hasty). The roads were recently rebuilt for grade and soundness, the previous years. A decision was made to apply a 3/8th granite chip (FA-­‐3A chip), on top of an emulsion primer coat (PEP), on top of graded prepared packed gravel surface. The cost savings of a chip seal matt over a common bituminous asphalt mix, is aproximently 75%. Other considerations were asphalt for these same roads surfaces. The preliminary estimates for asphalt, at the time, were coming in at $760,000, based on early season bituminous pricing and gravel shouldering. The additional cost with a bituminous asphalt surface, down the road, would be crack filling and chip sealing the asphalt surface and additional, continued shouldering gravel expense. After research and discussions, the town board decided to proceed, with the help of MnDOT research project coordinator Mr. Tom Wood, with the chip seal over gravel. The estimated budget cost of the improved gravel road chip seal project is $170,000. Procedure Testing of the road bed for soundness and bring up to specs or re-­‐grade road to paving asphalt specs. There should be no soft spots or frost boils. Ensure the road is graded and packed with a 4% to 5% crown or cross slope, for good drainage. Have a good gravel packed base to work with. (see fig 1) These roads were recently rebuilt in the last 2 yrs. Silver Creek Twp crushes its own gravel, as a class 1 modified gravel, ¾ minus, 10%-­‐14% passing 200 sieve. This material makes a solid hard packed base. Very little float rock/fines were present before PEP application. The design plan called for a penetrating emulsion primer (PEP) primer coat, applied at Fig 1 Gravel Road Prep -­‐ Crowning road to 5% the rate of 0.40 g/y² to the gravel surface. Then follow with 0.35g/y² of CRS-­‐2p, a FA-­‐3A chip, at a rate of 16 to 18 lbs. y² and followed with 0.10 g/y² of CSS-­‐1h diluted fog seal oil. The total quoted project costs for the 3 road segments were $171,223 On July 1st, 2013, construction of the prime and chip seal matt began. The first step was to apply water to the dry gravel base, to help with, and allow, the PEP to penetrate better into the gravel surface. (see fig 2) (Fig 2 – Wetting gravel for better PEP penetration) The second step was to apply the primer (PEP). The design called for PEP to be applied at the rate of 0.40g/y². The township personnel, the chip seal contractor and with the help of researcher Tom Wood, made field adjustments as needed for this project. The decision was made to start the application rate at 0.30g/y², as it was felt a higher rate of PEP would be too much. Aproximently 1000 ft. was applied and observed at the 0.30g/y². (see Fig 3) (Fig 3 – 0.30g/y² PEP applied – some run off occured) After noticing runoff, it was decided to lower the PEP rate to a final 0.25g/y², which solved the run off concerns. (fig 4) (Fig 4 – 0.30g/y² run off ) 0.25g/y² final PEP Rate After run off concerns were solved and waiting 20 min for curing, the PEP had not completely penetrated into the road surface. Personnel, onsite, decided to apply sand to the surface, to allow traffic during the PEP curing process. Aproximently 6-­‐8 lbs. y² of dresser trap rock sand (-­‐ #8 or smaller sized material) were applied after the PEP had cured for 20 – 30 minutes. It was then rolled in, with pneumatic rollers. (See fig 5) Fig. 5 Rollering Trap Sand into PEP After the application of the sand, the PEP was allowed to cure for a minimum of 3 hours – after which, excess sand was swept off and the chip seal emulsion applied. Application of CRS-­‐2p Oil The next step, after the PEP primer / sand was cured and swept off, the Chip Seal matt was placed with 0.35g/y² CRS-­‐2p emulsion oil followed by 16-­‐18 lbs./y² of a FA-­‐3A granite chips rolled in. All areas primed, were chip sealed the same day to protect the PEP from traffic damage. See 3 pics in Fig. 6 (fig 6 – 3 pics of FA-­‐3 granite chip applied on sanded PEP) The original design plan was modified as follows – it was planned to fog seal over the final chip. The fog seal was changed to another application of CRS-­‐2p at a rate of 0.23g/y² and followed with the same dresser trap rock sand used to blot the PEP primer, on top of the FA-­‐3A granite chip. The township felt since the PEP primer volume had been reduced, an extra layer of the CRS-­‐2p poly modified asphalt would help the integrity of the chip seal matt. The contractor agreed to the field adjustment for an extra $10,000 for the 4 miles. The first 700 ft. of Barton Ave, off Wright Co Rd 75, is a fogged sealed FA-­‐3A chip, with no dresser rock – this section is as originally designed. The next 700 ft. is the modified design, but, has a fog seal on top of the dresser rock/FA-­‐
3 chip. So, there is a section that is PEP (0.25g/y²), CRS-­‐2p (0.35g/y²), FA-­‐3A chips (16-­‐18 lbs) and fog seal (Css-­‐1h 0.10g/y²). The next section consists of PEP, CRS-­‐2p, FA-­‐3A chips, CRS-­‐2p (0.23g/y²), dresser trap sand (6-­‐8 lbs/y²) and fog seal (CSS-­‐1h 0.10g/y²) And the rest of the roads were PEP, CRS-­‐2p, FA-­‐3A chips, CRS-­‐2p and dresser trap sand, no fog seal. These test sections are for observation and the dress trap rock, for the possible use in urban areas, where a smoother surface maybe needed or used. (Trails, paths for biking, hiking, roller blading, cal de sac’s, parking lots, etc., etc.) Total cost of project -­‐ $182,499 Fog seal over Dresser Rock Sand st
Fog seal over FA-­‐3A Chip – 1 section off Co Rd 75 Results: Overall, the Township Board and the residents that live on the road; are very happy with the design and performance of this improved gravel surface. It has met all the goals of an improved gravel road. It is smooth and rides well. The road isn’t muddy or dusty. It has not required grading or chloride solution expenses. It is performing like a bituminous asphalt road, at far less costs. We anticipate the chip seal matt will be flexible and require little maintenance in its expected life (5-­‐7 yrs.). It appears to be wearing well and rides nicely. It is inexpensive and easy to repair. There should be no cracks to fill, as is common with asphalt or concrete. It is a thin flexable matt of oil and rock (1/2 or so thick). It should not be compared too thicker asphalt or concrete matts or surfaces. We have had several incidents of vehicles damaging the matt within the first month. We have had a self-­‐propelled Ag Spray tear through the matt on the shoulder, had a straight dual wheeled truck pivot its steering wheels and tear through the matt, as the driver decided to turn around in the middle of the road. We had a brush broom burn through the mat, while sweeping the excess rock off and had a tractor skid its right brake, tearing the matt at an intersection. The damaged areas really are easy to repair and much, much less costly to fix then concrete or asphalt. These same vehicle damaged areas, would have left deep marks on fresh asphalt, had the township gone with asphalt type surface. We have observed cars “squealing” their tires on the matt and not do any damage, but leave skid marks. We have observed wheel spin gouges from the gravel up to the chip seal matt, the vehicle dug into the gravel road, but came up on top of the matt, with no damage to the matt. We have had excavation equipment unloaded on it (ramps) – with no physical damage, only cosmetic marks/marring. The repair process is simple. We bought a couple pails of foundation coating from Menards. Clean and pack out the damaged area. Pour in some foundation coating oil. Add the FA-­‐3A chips and pack level. (See pics) Menards Foundation Coating Damage from Ag Spray coming out of Ditch Repaired damage From Ag Sprayer Oil dumped on gravel and chips applied, filling hole level Damage from Sweeper Brush that Burned through Matt Repair of Broom Brush Damage Damage from Steering Tires on Straight Truck Repairing Puck Hole, from Steer Tire Finished Chip Sealed Gravel Road – Late Summer Recommendations And Other Considerations The matt is thin, around ½ inch. Care should be taken to grade and pack the gravel surface smooth. Do not allow wheel/tire marks in packed surface from grader, packer, tractor or vehicle traffic – the thin matt will take on all imperfections and surface of the gravel road surface. The improved gravel road / chip sealed matt, should have a life expectancy of 5-­‐7 yrs (depending on traffic volume). Cost Comparision between Gravel, Improved Gravel and Asphalt Roads, Gravel road costs, for this 4 mile loop of roads ~ • Cloride solutions for gravel stability and dust control Per Yr -­‐ $11,500 yr (0.90¢ gal chloride) • Gravel savings @ 1300 yds per yr @ $8 bucks yrd applied ($10,400 per yr saveings on gravel) • Gradeing @ $150 per hour – 5 to 6 times yr $3000 per yr • Tractor and Packer @ $75 per hour 5-­‐6 times yr $1500 per yr • Asphalt and shouldering costs estimated at $760,000 or around $11.15 y² Improved Gravel (Chip Seal on Gravel Surface) ~ • Removed mud and dust complaints from Residents • Chip Seal cost about $2.60 -­‐$2.75 per square yard, on gravel • Chip seal is a flexible matt, that should move with freeze thaw cycles • No crack filling necessary or expense required • No shouldering expense • If asphalt would have been applied, a chip seal would be necessary to top off and seal the asphalt surface in 3ys or so – cost $1.75 y² or $114,000 This will be a ongoing evaluation to the roads involved. There is some sentiment, to add a new layer of chip, to what we did in July of 2013, before the 5-­‐7 yrs. The feeling is more structure . . . . In reality, I believe, there is plenty of structure – the hard gravel is the structure and the chip seal matt is the water proofing necessary to keep mud and dust from forming. There will be tears and damaged to the matt, but, it’s quickly, easily and affordably fixable. I see no reason the chip seal matt (improved gravel surface) will not hold up to wear for at least 5 yrs. Is the foundation coating oil the best solution for a township to use as repair oil ? I plan to evaluate and look for other repair oil resources. FA-­‐3A Chip with Fog Seal Dresser Trap Rock/Sand Over FA-­‐3A Chip w/Fog Seal