Memorandum

City of Lawrence

Public Works

 

TO:

David Cronin, P.E., City Engineer

FROM:

Matt Bond, P.E., Stormwater Engineer

CC:

Charles Soules, P.E., Director of Public Works

DATE:

July 20, 2015

RE:

Maple Street Pump Station, 6th & Maple Street, Project No. PW1133,

Bid No. B1542 -  Project History, Description & Proposed Rebid Date

 

Project History & Description

In 2005 a comprehensive drainage study, known as the North Lawrence Drainage Study (NLDS), was completed for North Lawrence. This study examined existing flooding issues and provided options to improve or resolve them. "System 6" was one of the sub watersheds listed within the NLDS (see Figure A). The Maple Street Pump Station was identified as being too small to adequately drain "System 6" resulting in localized flooding of ditches, streets, and yards of area residents. 

 

In November 2008 the community voted in support of a 0.3% sales tax increase to fund infrastructure improvements.  The Maple Street Pump Station was identified as one of the projects to utilize these newly generated funds at an estimated cost of $4.5 million.

 

The engineering design team of Bartlett & West Engineers, Inc. and CDM Smith was chosen to perform the engineering design services.  During and after the development of the engineering drawings several public meetings were conducted.  These meetings consisted of a general public information meeting at the Train Depot, two presentations to the North Lawrence Neighborhood Association as well as meeting with individual property owners.  The engineering drawings for the project have been reviewed and approved by the U.S. Army Corps of Engineers.

 

The existing pump station is located near the northwest corner of 6th & Maple Streets.  The existing pump station is a converted sanitary sewer lift station with an 9” diameter outfall pipe and has a capacity of only 6 cfs (cubic feet/sec.).  The “System 6” water shed contains roughly 192 acres and experiences localized flooding during significant rainfall events.  The majority of the watershed is north of the Union Pacific Railroad Tracks and its vertical elevation is approximately ten feet below the tracks profile grade.  The property to construct both the pump station and the wet well were acquired in 2010 (see Figure B). 

 

Once stormwater has been collected at the pump station location it will then be pumped underneath the railroad tracks and into a junction box on the northwest corner of the intersection of 6th & Locust Streets.  From there it will drain by gravity to the Kansas River.   Coinciding with the construction of the new pump station a new outfall, gate well structure and the corresponding piping will be constructed through the levee. All of the private utilities have been relocated so that there are no conflicts with the proposed storm sewer alignment.

On March 3, 2015 bids were received for the Maple Street Pump Station Project No. PW1133, City Bid No. B1503 from the two (2) bidders listed in the table below.  The base bid included the pump station at 6th & Maple Street and the downstream system under the railroad and through the levee to the Kansas River.  In addition to the base bids, contractors also provided an alternate bid for the additional storm sewer work upstream from the pump station.  The alternate bid included extending the storm sewer north of the pump station along the west side of 6th Street and then east along the south side of Lincoln Street to Lyons Park. 

 

CONTRACTOR

BADE BID TOTAL

ALTERNATE BID TOTAL

GRAND TOTAL

Engineer’s Estimate

$4,128,379.00

$1,047,267.00

$5,175,646.00

BRB Contractors

$5,947,275.00

$1,589,338.00

$7,536,613.00

Nowak Construction, Inc.

$6,525,544.00

$1,503,376.00

$8,028,920.00

 

The lowest bid significantly exceeded the Engineer’s Estimate.  City staff recommended that the bids be rejected.  The City Commission formally rejected the bids at its March 10th City Commission Meeting. 

 

Subsequently City Staff and Bartlett & West Engineers, Inc., discussed potential ways with the bidding contractors to reduce costs.  The following design changes were implemented into the revised plans after getting direction from the City Commission to do so at its May 5, 2015 meeting:

 

Ř  Revaluated the hydrologic criteria including the soil permeability and impervious areas which reduced the overall design flow from 195 cfs to 100 cfs. The lower design flow also reduced the necessary pumping capacity of the pump station and the corresponding storm sewer pipe sizes. The design modifications still maintain a 10 year design frequency which is consistent with the City's Stormwater Management Criteria.

Ř  Utilized submersible pumps which are more readily available than the previously specified unique variable speed pumps.  This also results in higher upstream flow line elevations of the storm sewer system which in turn lowers installation costs.

Ř  Allowing the reuse of excavated soil as backfill for storm sewer installation.

Ř  Added polypropylene pipe as an alternate to concrete pipe for the storm sewer.

Ř  Specified the reconstruction the entire width of 6th Street as an asphalt road instead of replacing half of the road in concrete. 6th street is a residential street serving local traffic.  

 

The above changes to the original design project should result in lower bid prices according to the discussions with the original bidders.  It should also be noted that the waste water treatment plant originally bid on the same day as the Maple Street Pump Station which could have artificially limited the number of potential bidders.

 

Project Funding

This project is being funded with the previously mentioned Infrastructure Sales Tax Revenue. The NLDS estimated the construction cost for this project at $4.279 million. 

 

Action Request

Set a bid date of September 1, 2015 for the construction of the Maple Street stormwater pump station - Project No. PW1133 - New Bid No. B1542.