<p><p><h2>Commentary</h2>Typical contract pay items and units of measurement used for mechanical stabilization of subgrades and base courses include:<br><ul> <li>Geosynthetic (fabric or grid) measured by the square yard in-place</li> <li>Granular material measured by the ton</li></ul>The equipment used to construct mechanically stabilized subgrades and base courses is common to highway construction projects; therefore, additional mobilization costs are negligible.</p><p>Fiber reinforcement of subgrades and base courses is an emerging technology for which there is limited field experience. Construction costs for fiber reinforcement should be similar to those for chemical stabilization of subgrades. Users should consult fiber suppliers for approximate material costs.<br><h2>Cost Information Summary</h2>The total labor and equipment cost associated with mechanical stabilization of subgrades and base courses is minimal. Geosynthetics may be used to reduce the quantity of granular materials by approximately 30% for subgrade with a CBR < 3, or to improve the performance of the base layers without reducing the thickness of granular material. Material costs comprise the vast majority of total cost. Production rates for the installation of geosynthetics are controlled by related construction activities (e.g., placement of base course(s) and paving). Equipment and labor resources are easily adjusted to match the production rate of controlling activities with little effect on total cost. The following table lists construction cost items associated with mechanical stabilization of subgrades and base courses, along with approximate cost ranges. Cost ranges are based on data from 2009 through 2010. Readers should carefully examine the project characteristics and constraints and determine to what degree if any these factors may influence the actual cost associated with implementing Mechanical Stabilization of Subgrades and Base Courses processes.</p><p><table class='tablepress' id='tablepress-107'><thead><th>Pay Item Description</th><th>Quantity</th><th>Unit</th><th>Low Unit Price</th><th>High Unit Price</th><th>Factors Which May Potentially Impact Costs</th></thead><tbody><tr><td >Geosynthetic</td><td >Greater Than 5,000
</td><td >SY</td><td >$1.00</td><td >$5.00</td><td >Geogrids are more expensive than fabrics
Woven fabrics are more expensive than nonwoven fabrics
Heavier fabrics cost more
Smaller dimension grids and heavier grids cost more
Specified lap widths impact the total quantity of material required
Production rates do not significantly affect unit costs</td></tr><tr><td >Granular Material</td><td >Greater Than
1,000
</td><td >TON</td><td >$-</td><td >$-</td><td >Use historical costs that are representative of the project quantity, project conditions and project location</td></tr></tbody></table><h2>Historical Cost Information</h2>A sample of actual project costs is shown in the table below.</p><p><table class='tablepress' id='tablepress-108'><thead><th>Pay Item Description</th><th>Quantity</th><th>Unit</th><th>Low Unit Price</th><th>High Unit Price</th><th>Average Unit Price</th><th>No. of Bids</th><th>Bid Date</th><th>Source/Agency</th></thead><tbody><tr><td >Reinforcement Grid (Biaxial, Type 2)</td><td >90,023</td><td >SY</td><td >$2.53</td><td >n/a</td><td >n/a</td><td >1</td><td >7/29/2009</td><td >Florida DOT</td></tr><tr><td rowspan=3 >Geogrid Base Reinforcement</td><td >72,000</td><td >SY</td><td >$1.00</td><td >$2.40</td><td >$1.79</td><td >10</td><td >6/5/2009</td><td rowspan=3 >Arizona DOT</td></tr><tr><td >28,100</td><td >SY</td><td >$1.75</td><td >$3.25</td><td >$2.21</td><td >9</td><td >6/12/2009</td></tr><tr><td >5,735</td><td >SY</td><td >$1.60</td><td >$3.50</td><td >$2.22</td><td >6</td><td >9/25/2009</td></tr><tr><td rowspan=2 >Stabilization Geotextile, Special</td><td >12,320</td><td >SY</td><td >$1.46</td><td >$4.80</td><td >$2.55</td><td >12</td><td >3/5/2010</td><td rowspan=2 >Michigan DOT</td></tr><tr><td >3,210</td><td >SY</td><td >$2.45</td><td >$3.25</td><td >$2.65</td><td >4</td><td >10/1/2010</td></tr><tr><td rowspan=3 >Geotextile Stabilization</td><td >32,367</td><td >SY</td><td >$0.84</td><td >$1.46</td><td >$1.15</td><td >6</td><td >3/25/2010</td><td rowspan=3 >New York DOT</td></tr><tr><td >5,200</td><td >SY</td><td >$1.09</td><td >$2.51</td><td >$1.58</td><td >8</td><td >5/20/2010</td></tr><tr><td >13,459</td><td >SY</td><td >$1.05</td><td >$2.51</td><td >$1.46</td><td >7</td><td >6/10/2010</td></tr><tr><td >Special – Geogrid, Type P2 (WT:06)</td><td >6,300</td><td >SY</td><td >$3.36</td><td >$3.52</td><td >$3.44</td><td >2</td><td >7/15/2010</td><td >Ohio DOT</td></tr></tbody></table><h2>Conceptual Cost Estimating Tool</h2>The conceptual cost estimating tool is intended to be used to develop a preliminary project scoping cost estimate. This preliminary estimate can be based on the typical construction cost item values as contained in the Cost Information product or from user specified cost values when such are known. Users should read and understand the information in Cost Information product prior to using the cost estimating tool. You can download the Cost Estimating Tool to open a cost estimating spreadsheet for producing a preliminary project scoping estimate.</p><p><a class="arrow-link" href="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/… the Cost Estimating Tool</a></p></p>