<p><p><h2>Commentary</h2>The costs of Prefabricated Vertical Drains (PVDs) on a highway project are typically captured in a contract bid item, which is measured by the Lineal Foot (LF). Included in this bid item are associated incidental costs such as:<br><ul> <li>Additional excavation and embankment<br><ul> <li>To provide a reasonably level working surface</li> <li>That which may be necessary for constructing and removing temporary access routes for construction equipment</li></ul></li> <li>Instrumentation for monitoring settlement</li> <li>Augering through stiff upper layers of soil which lie above the soft compressible layer(s) (except when an additional pay item is included in the contract – see below)</li></ul>Other costs associated with the installation of PVDs which may be measured and paid for separately include:<br><ul> <li>Mobilization</li> <li>Drainage layer – this may be granular material or a series of horizontal strip drains</li> <li>Surcharge embankment and removal</li> <li>Augering through stiff upper layers of soil which lie above the soft compressible layer(s)</li></ul><h2>Definitions</h2><ul> <li>Preload – embankment material placed within the area of PVD installation that is part of the final roadway cross-section.</li> <li>Surcharge – additional embankment place above the design profile grade line that is used to accelerate settlement and/or minimize secondary consolidation</li></ul><h2>Cost Information Summary</h2>An average production rate for the installation of PVDs ranges from 10,000 to 15,000 LF per day. The following table lists items which are associated with the cost of PVDs and approximate cost ranges. Cost ranges are based on data from 2005 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 the installation of PVDs.</p><p><table class='tablepress' id='tablepress-116'><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 >Mobilization</td><td >1</td><td >LUMP SUM</td><td >$10,000</td><td >$20,000</td><td >Depths greater than 70 feet may require a crane in lieu of a modified hydraulic excavator, this may increase mobilization costs
Mobilization cost increases for distances greater than 500 miles
Phased projects may require multiple mobilizations</td></tr><tr><td >Prefabricated Vertical Drains</td><td >Greater Than 10,000</td><td >LF</td><td >$0.50</td><td >$1.50</td><td >Projects which require a crane may reduce the average production rate, thus increasing the average unit cost
A minimum overhead clearance of 10 feet greater than the installation depth is required; areas with less than 10 feet overhead clearance will cause costs to multiply
Installation of PVDs is generally not feasible for quantities less than 10,000 LF; quantities greater than 100,000 LF generally have lower unit costs
Stiffer soils will reduce the production rate, resulting in an increased unit price
Obstructions will decrease the average production rate, resulting in higher unit costs</td></tr><tr><td >Granular Drainage Layer</td><td >5,000 to 25,000</td><td >TON</td><td >$7.50</td><td >$25.00</td><td >Primarily sensitive to the cost of granular materials (including freight)</td></tr><tr><td >Horizontal Strip Drain</td><td >5,000 to 25,000</td><td >LF</td><td >$0.50</td><td >$1.50</td><td >Material type specified is the primary cost variable</td></tr><tr><td >Augered Holes</td><td >1,000 to 10,000</td><td >LF</td><td >$5.00</td><td >$15.00</td><td >Soil stiffness and obstructions may impact the cost</td></tr><tr><td >Surcharge Embankment</td><td >10,000 to 50,000</td><td >CU
YD</td><td >$3.00</td><td >$10.00</td><td >Haul distance and haul unit type for the embankment are the primary cost variables</td></tr><tr><td >Surcharge Removal (waste)</td><td >5,000 to 50,000</td><td >CU
YD</td><td >$3.00</td><td >$10.00</td><td >Haul distance and haul unit type to waste surcharge material should be considered
There is no additional project cost attributable to PVDs when the surcharge can be utilized within a project embankment – project sequencing may impact whether this is feasible
</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-117'><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 >Special – Wick Drain (WT:NR)()WT:NR)</td><td >31,600</td><td >FT</td><td >$0.50</td><td >n/a</td><td >n/a</td><td >1</td><td >4/1/2010</td><td rowspan=3 >Ohio DOT</td></tr><tr><td >Special – Wick Drain (WT:NR)()WT:NR)</td><td >83,100</td><td >FT</td><td >$0.49</td><td >$1.05</td><td >$0.64</td><td >8</td><td >11/22/2006</td></tr><tr><td >Special – Wick Drain (WT:NR)()WT:NR)</td><td >452,735</td><td >FT</td><td >$1.05</td><td >$2.30</td><td >$1.51</td><td >13</td><td >2/8/2006</td></tr><tr><td >Misc. Wick Drain</td><td >191,700</td><td >LF</td><td >$0.42</td><td >$1.25</td><td >$0.56</td><td >3</td><td >2/5/2010</td><td >Missouri DOT</td></tr><tr><td >Surcharge Excavation</td><td >145,000</td><td >FT</td><td >$0.52</td><td >$1.00</td><td >$0.67</td><td rowspan=2 >6</td><td rowspan=2 >9/22/2005</td><td rowspan=4 >Oregon DOT</td></tr><tr><td >Wick Drains</td><td >5,000</td><td >CU
YD</td><td >$2.00</td><td >$25.00</td><td >$13.42</td></tr><tr><td >Granular Drainage Blanket (Surcharge)</td><td >80,893</td><td >FT</td><td >$0.62</td><td >$0.93</td><td >$0.70</td><td rowspan=2 >8</td><td rowspan=2 >3/24/2005</td></tr><tr><td >Granular Drainage Blanket (Surcharge)</td><td >7,042</td><td >TON</td><td >$9.25</td><td >$16.90</td><td >$10.97</td></tr><tr><td >Vertical Drainage Wicks</td><td >146,971</td><td >LF</td><td >$0.50</td><td >$0.80</td><td >$0.66</td><td rowspan=2 >5</td><td rowspan=2 >6/28/2006</td><td rowspan=2 >Florida DOT</td></tr><tr><td >Embankment Surcharge</td><td >8,471</td><td >CY</td><td >$12.00</td><td >$35.00</td><td >$23.60</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>