2011 NACE Conference by. Ken Skorseth SDLTAP Program Manager

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1 2011 NACE Conference by Ken Skorseth SDLTAP Program Manager

2 Paving or constructing asphalt surface treatments when asphalt prices were low. May not have been justified based on traffic, but it bought political favor and good will. Traffic volume and type was different in the 50s and 60s when many local roads were upgraded to asphalt surfaces.

3 Economics! Union County in SD experienced a 247% increase in seal oil cost from 2001 to Union has experienced a 99% increase for hotmixed asphalt paving at the same time. Truck/Equipment size. Agricultural yields and movement of product. Rural agribusiness and commercial development.

4 Simply go back to gravel? Stabilized gravel? Deep base with Asphalt Surface Treatments? ASTs (Blotters) Otta Seals

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6 What a change in 50 years!

7 Today! Largest Deere tractor in 1953!

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11 This decision needs very careful analysis. The SDDOT funded a study of surface selection for local government completed in Study can be found online at: ect_search.asp?projectnbr=sd Please consider a very brief summary on the following slides ---

12 Data provided by 26 counties (120 total roadway sections) 20 yr life-cycle cost used in the Study. Three surface types analyzed: 1. Gravel (Stabilized Gravel study also intended, but there was insufficient data for analysis). 2. Blotter (Asphalt Surface Treatments This in not pavement, but prime/chip seal on aggregate base) 3. Hot-mixed Asphalt Pavement

13 Agency Cost ($) Summary of gravel, AST and HMA surface life cycle costs related to ADT SDDOT Surface Selection Criteria Study $160, $140, $120, Gravel $100, cost effective to 150 ADT $80, AST (Blotter) cost effective to 650 ADT HMA Blotter Gravel Linear (HMA) Linear (Blotter) Linear (Gravel) HMA Pavement cost effective above 650 ADT $60, $40, $20, $- Gravel Blotter HMA ADT

14 2,000 to 2,500 vehicles per day!

15 Under 100 vehicles per day

16 Actual cost data from Marshall County for road rehab: 11 mile project Recycle, add 3 gravel $ 598, Construct blotter surface $ 490, Construct 3 asphalt pavement $2,200, Entire County Road Budget $1,600, (Opt-out from real estate tax freeze will add 585,000 dollars by 2012)

17 Dust problems (loss of fines) and aggregate loss combined with frequent blade maintenance makes life cycle cost very high.

18 Attempt at maintaining marginal quality, untreated gravel surfacing with approx 300 ADT.

19 This Brookings County road was once a blotter surface turned back to gravel successfully.

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27 Average cost of blading/gravel in past six years (2005 through 2010): Blade maintenance: $ per mi Regraveling: $ per mi. TOTAL $ per mi

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29 From SDDOT Rural Road Design, Maint, & Rehab Guide 14.5 inches of gravel needed to carry 25 to 50 trucks per day over weak subgrade!

30 Long term performance has been observed by SDLTAP on two roads in SD Lawrence County Brookings Township

31 A Chloride Stabilized Road Since 1998!

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35 Ordinary Twp road reshaped in Approximately two to three inches of gravel in place. Eight inches good quality surface gravel added. Liquid MgCl treatment applied after reshape each year.

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37 ADT exceeds 1000 in summer.

38 Eight inches of gravel originally placed after aggressive reshape in Liquid MgCl2 treatment applied annually thereafter. Four inches of gravel replaced after 12 years.

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41 Their Problems Serving Heavy Oil/Gas Development and Agribusiness

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48 Generally best application is between 150 and 500 ADT. (can be higher) Percentage of truck traffic must be considered before making blotter surfacing decision. Must have adequate base aggregate source do cost analysis between thick base/thin surface & vice versa.

49 Traditional pavement layer on base

50 Alternate design of thick base layer(s) with thin surface A Blotter surface is very thin no structural strength only weather proof surface.

51 From SDDOT Rural Road Design, Maint, & Rehab Guide >50 heavy trucks daily require 14 inches of base with 6 inches of HMA if subgrade has at least medium strength

52 City of Pierre, SD Constructed in Performance has been good thus far.

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54 Only works on deep base and stable subgrade. How deep? Depends on truck traffic and subgrade soil condition. Could require up to 20 inches of base depth!

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62 The decision to convert a paved road to gravel needs very careful planning: Life cycle cost analysis may show it wasn t the cheapest alternative if ADT is over 170, but also if truck traffic is high. Blotter on deep base may be a good alternative. Stabilized gravel is a viable alternative, but there is much yet to learn about this lack of good life cycle data on these surfaces. Go in with your eyes wide open!!!