Memorandum

City of Lawrence

Public Works

TO:	David Corliss, City Manager Cynthia Wagner, Assistant City Manager Diane Stoddard, Assistant City Manager
FROM:	Matt Bond, Stormwater Engineer
CC:	Charles Soules, Public Works Director Dave Wagner, Director of Utilities Philip Ciesielski, Assistant Director of Utilities Mike Lawless, Assistant Director of Utilities
Date:	May 11, 2010
RE:	May 18, 2010 Agenda Item

Please include the following item on the City Commission Consent Agenda for consideration at the May 18, 2010 meeting.

Approval of final Change Order for the Bowersock Dam Maintenance Project.  This is the final construction contract change order covering all outstanding items.  The total change order amount is $40,297.61.

Project History.  The Bowersock Dam located on the Kansas River was inspected on January 23, 2009 to assess the condition of the dam.  The findings and assessments of that inspection resulted in the Bowersock Dam Maintenance Project. The elimination of water flowing through the dam was the primary goal of the project. 

To achieve this goal, sheet piling was driven parallel to and upstream of the existing dam face.  Rock fill was then placed between the existing dam face and the newly driven sheet piling.  A two foot thick reinforced concrete cap was then poured between the sheet piling and tied to the existing dam face.

On August 25, 2009 the Lawrence City Commission approved awarding the Bowersock Dam Maintenance Project (Project No. 6CP907, Public Works Project No. PW0931) contract to L.G. Barcus & Sons in the amount of $2,279,130.26

After the City of Lawrence received the required permits and authorizations from the US Army Corps of Engineers and the Federal Regulatory Commission (FERC) a NOTICE to PROCEED was issued to the contractor on September 21, 2009.

Selection of a geotechnical firm by the contractor, mobilization of geotechnical investigation equipment, mobilization of the contractor, design of the temporary bridge across the spillway and the acquisition of building materials preceded physical work completed on site.

Geotechnical field work was conducted in mid October and early November to aid the foundation design for the temporary bridge across the spillway and to help determine sheet pile lengths.  The month of January involved the mobilization of the contractor’s equipment, the placement of fill between the upstream face of the dam and the line of sheet pile and the construction of a rock causeway upstream of the sheet pile line.  The fill area and the causeway enabled the contractor to work from two locations. 

Tuesday, February 2, 2010 marked the first delivery of sheet pile to the site with the first one hundred linear feet of the concrete cap placed on Thursday, February 18^th.  Three additional concrete placement dates (February 26^th, March 2^nd and March 8^th, 2010) completed the concrete cap.  Work within the Kansas River itself was effectively delayed for a week immediately following the last concrete pour due to high river levels.

After the river level dropped, excess sheet pile length was cut to finish elevation and the remainder of the upstream work causeway was removed.  The removal of the superstructure of the temporary bridge and the restoration of the ramp to the lower concrete apron concluded the construction activities associated with the project.  The clearing of the outfall channel north of the spillway on April, 2010 marked the completion of the project 144 days ahead of the project schedule.

Project Status.  Although the construction project has been completed there are still a few issues that will need to be addressed when water levels recede.  The diversion of water through the spillway during construction subjected the downstream spillway apron to high water velocities and subsequent scour washing out a hole.  Once river water levels allow City crews will stabilize and fill in the hole.  The area in the spillway apron does not affect the integrity of the dam.

Future Maintenance.  Eventually the remaining southern third of the dam will need to be addressed.  The scour hole immediately downstream of the hydraulic Obermeyer Gates will eventually need to be addressed.

In addition annual inspections would be prudent to evaluate the downstream face of the dam to address problems as they arise to reduce the need for a higher costing future maintenance project.

Change Order Details.  The following major construction items are included within the final Change Order.

• Cold weather concrete, this was necessitated by specification to properly cure the concrete as well as speed the construction process. A "Thawzall" heating system was utilized to eliminate frost from the sub grade and to ensure proper concrete cure.
• Additional rock for a dual causeway, this allowed the contractor to work from two separate work platforms and speed construction.
• De-watering operations.  Extensive dewatering operations using several generators and pumps were needed to ensure the contractor could complete work items. De-watering was specifically identified at the time of the bid as an item that would be billed on a costs basis.
• Additional 40’ in project length. The project ended up with additional sheet pile as a result of cut-off lengths. Instead of scraping the excess material, it was used to extend the sheet pile wall an additional 40 feet. Additional costs included additional concrete, reinforcing steel, anchor system and labor.

Project Funding.  The project was funded by the Department of Utilities.  The Kansas Department of Transportation (KDOT) as well as the Bowersock Mills & Power Company also participated in the cost of geotechnical work across the width of the Kansas River in the amounts of $100,000.00 and $8,000.00 respectively.

COSTS
Original Contract	$2,279,130.36
Final Change Order	$40,297.61
Total Project Cost	$2,319,427.97

FUNDING
ACCOUNT #	AMOUNT	Resolution
501-7-7910	$1,170,000.00	6776
400-3-3000	$1,407,442.00	6854
TOTAL	$2,577,442.00

Action Requested.  Public Works staff requests approval of final Change Order in the amount of $40,297.61.

Respectfully Submitted,

Matt Bond, P.E.

Stormwater Engineer

Attachment- Final Construction Report to the Federal Energy Regulatory Commission (FERC)