Memorandum

City of Lawrence

Public Works

 

TO:

Dave Corliss, City Manager

FROM:

Shoeb Uddin, City Engineer

CC:

Chuck Soules, Diane Stoddard, Matt Bond

Date:

June 25, 2009

RE:

Bowersock  Dam

Proposed Rehabilitation and Repair Plan (PRRP)

 

Introduction

Bowersock Dam was constructed in the 1870’s. Information about the original construction is unknown; as a result, there is an unavoidable element of uncertainty (that may require field adjustments) in the Proposed Rehabilitation and Repair Plan (PRRP) outlined in this memo. It is, however, important to note that the PRRP has been developed based on the results and recommendations of previous engineering studies, proposals, field data, and consultations and conceptual concurrence with experienced engineers, contractors, and various state and federal agencies with jurisdictional authority over Bowersock Dam.

 

Repair / Rehabilitation Strategies

City Staff, in consultation with representatives from Bowersock Dam, Hamm Construction and United Construction (United is the contractor for the KTA bridge over the Kansas River, currently under construction) developed a preliminary rehabilitation and repair strategy for the Bowersock Dam. This preliminary plan has since been modified based on discussions with various state and federal agencies [e.g. Federal Energy Regulatory Commission (FERC), US Army Corps of Engineers, Division of Water Resources of the Kansas Department of Agriculture, Kansas Wildlife and Parks and Kansas Department of Transportation]. Following are the major components of the proposed plan (see attached drawing).

1.            Build a Rock Work Platform (Rock Cofferdam / Causeway) upstream of the dam, face up stream side, with clay.   Pump out water between the work platform and the dam which will enable closer and thorough examination of the extent of leaks and damage on the upstream face of the dam.

2.            There is a lot of concrete debris and riprap from the old highway bridges.  Some of this material will need to be removed in order to drive the sheet piling. 

3.            Backfill the area between the sheet piles and dam and place a concrete cap.

4.            Repair cracks, holes, erosions, and gaps in the existing dam to protect the timber structure.  These repairs were previously recommended and received concurrence from city staff, Bowersock Mill and various state and federal agencies.

5.            This work will provide a long term solution for the north half of the dam.

6.            The south half of the dam is a masonry structure that appears to be stable (not leaking through the structure); however, there is a scoured area on the downstream side.  Repair of this area is not included in this project scope.

 

Project Schedule

The PRRP has to be carried out during low flow season in the river; low flow period in the river typically ranges from August through February. In order to ensure completion of this project before February of 2010, it is important that this project proceeds as quickly as possible with a start date preferably in August 2009. Maintaining low outflow from the upstream dams (Perry, Tuttle Creek and Milford) will be necessary to ensure low flow at the Bowersock Dam during construction. Staff is currently working with the Upstream Dam Authorities to assemble a coordinated plan.

 

 

 

Project Cost /Funding

Estimate cost for the work outlined is approximately $2-2.5 million.  Staff is currently exploring the potential for funding from various other state and federal sources.  Additional stakeholders may include Bowersock Mill, KDOT, Westar, and KU. 

 

There have been significant discussions with Hamm Construction and United Construction about this project.  This estimate is staff’s best effort at this time without being able to physically examine the site.  It needs to be realized that costs may increase/decrease based upon what the condition of the face of the dam actually is, and/or the depth of rock will affect pile driving efforts. 

 

Contractor Selection

Hamm Construction has been involved with this project for several months.  They have considerable knowledge about the challenges and opportunities associated with this project.

 

With the KTA river crossing, we also have an opportunity to work with a large contractor, United Construction, who are very experienced working in this environment.  United Construction has significant equipment, material, and personnel resources in Lawrence.  This project could work into their schedule and the City would see savings in mobilization, material delivery, and equipment on site.  United Construction also potentially has much of the sheet piling available.

 

Typical City process would include receiving formal bids.  A formal bid process is problematic. To develop plans would include hiring an engineering firm.  A work platform would need to be built and dewatered.  After thorough investigation, a plan could be created for bid.  This approach would take months and could potentially amount to significant cost.  Staff is recommending, with City Commission approval, that we proceed to negotiate pricing with Hamm and United Construction. 

 

Permitting Requirements

Permits from state and federal agencies will have to be obtained prior to beginning work on the dam. Staff has been in contact with all agencies (Federal Regulatory Commission, Corps of Engineers, Kansas Division of Water Resources, Kansas Wildlife and Parks) and has obtained commitment for an expedited permitting process. Typically, some of these agencies take up to 6 months to review Permit application. It is anticipated that all necessary permits will be in place by August 15, 2009.

 

In order to proceed further the City needs to confirm the scope of the project.  This will allow staff to formally submit applications and request funding.

 

Summary

  1. The Bowersock Dam Proposed Rehabilitation and Repair Plan included the construction of a work platform, driving sheet piling, backfilling, and placing a concrete cap between the sheet pile and dam.
  1. Regulatory agencies are conceptually “on board” with the PRRP.  Details will need to be finalized.
  1. Timing is important.  This project is safer, will be more reliable, and will cost less during low flow periods (August-February).
  1. Hamm Construction and United Construction are available and qualified to complete this work.
  1. Estimated cost is $2-2.5 million.
  1. Need confirmation of project for permitting and potential funding requests.

 
  1. A specific and detailed scope of work and cost will be worked out for various portions of the project.
  1. Alternative project, as previously proposed, included placement of grout bags upstream to fill/plug the flow of water through the dam, fill eroded concrete areas, and repair failed shotcrete.   Estimated cost $650,000-$750,000 depending on river conditions. 

 

Action Requested

  1. City Commission direction on scope of project.
  2. Authorization to negotiate a scope of work and cost with Hamm Construction and United Construction as outlined.
  3. Waive City bid requirements.