Objective

The purpose of this assignment is use your spreadsheet to develop a feasible detention pond design for one of the sites assigned to your group in lab.

The purpose of this part of the assignment is to estimate the cost of cut-and-fill and the detention pond volume. This application will support your designs for the detention pond project. Your spreadsheet should allow a user to enter the row and column spacing of the elevation grid, the original elevations at each grid line intersection, and the proposed elevation. In addition, your spreadsheet should graph the original and the proposed elevations. Click here for a typical layout for the input section of the cut-and-fill workbook. The data contained in this table is available in spreadsheet form by clicking here Cut-and-Fill Example data.

Your proposed elevations should be input on a separate worksheet in cells corresponding to the original elevations. A set of proposed elevations for this example problem are shown below. Note that the top of the proposed detention pond embankment is colored orange, the outside lope changes are in green, and the slope changes inside the pond are in gray.

Once you have entered the original and the proposed elevations at the grid points, simple subtract the proposed elevations from the original elevations to computer the change-in-elevation value for each grid point. In this case, negative (-) values will indicate fill points and positive (+) values will indicate cut values.

The user should also be able to enter a value for the lost of fill due to compaction. Once the change-in-elevations are computed, adjust the fill values (negative values) for compaction. To adjust each negative change-in-elevation value, divided the value by (1 - %compaction). In the example show below, each negative change-in-elevation value in divided by 80%. The adjustment for fill effectively increases the amount of cut volume to balance the required compacted fill volume.

After the the change-in-elevation values have been corrected for compaction, the volume of cut-and-fill should be estimated. To calculate the value of cut-and-fill for each grid cell, multiple the average of the four corner change-in-elevation values by the area of the grid cell [remember negative (-) area is fill and (+) area is cut]. Sum the cut-and-fill volumes for all the grid cells to estimate the total cut-and-fill for the entire site. Report if the cut-and-fill is balanced, or if there is more cut or fill required to reach the proposed elevations. Also, compute the total volume of cut and the total volume of fill required at the site. All volumes should be reported in cubic yards (yd³).

Next, estimate the cost of the cut-and-fill earthwork. Recall, on-site cut and fill costs $5 per yd³ and off-site fill costs $25 per yd³ and off-site cut costs $15 per yd³. Remember, if the cut and fill do not balanced, than the remaining material must be removed/brought off-site at the off-site rate. An estimate for the cut and fill volumes and the associated earthwork costs using the data presented in the example is shown below. Note the volume calculations results (in purple) have one less column and one less row in the worksheet due to the averaging of adjacent cells - in other words, four cells in the proposed elevation worksheet define one volume cell. The total cut and the total fill are shown in green and the earth costs are in blue.

An estimate of the pond volume can be computed in a manner similar to that used in the can-and-fill volume calculation. First, estimate a pond elevation by subtracting the proposed elevations from the pond elevation. Inside the proposed embankment structure, positive (+) values of the difference between the pond elevation and the proposed elevations (DP) indicate that water is detained in the pond. Negative (-) values of the DP indicate the proposed elevation are above the pond elevation. Positive (+) values of DP outside the embankment structure should be ignored in the pond volume calculation. Using the data presented in the example above, the values of DP are shown in the worksheet below. Note the proposed pond elevation is given in cell I3.

The pond volume for this example is computed in the worksheet shown below. Note the volume is computed in ft³ and converted to gallons (1 ft³ = 7.48 gallons). Note that the positive (+) DP cells outside the proposed embankment are deleted from the pond volume calculation.

This website was originally developed by Charles Camp for CIVL 1112.
This site is maintained by the Department of Civil Engineering at the University of Memphis.
Your comments and questions are welcomed.