Memorandum
City of Lawrence
Public Works
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TO: |
David P. Cronin, P.E., City Engineer |
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FROM: |
Matt Bond, P.E., Stormwater Engineer/Farmland Project Manager |
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CC: |
Charles Soules, P.E., Director of Public Works |
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Date: |
March 22, 2016 |
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RE: |
Agenda Item - Project PW1330 - Change Order Regional Detention - Lawrence VenturePark |
Approval of Change Order No. 2 - PW1330 Regional Detention
This is the second construction contract change order covering all outstanding items. The total change order amount is $50,955.53.
Project History
On September 29, 2010 the City of Lawrence officially acquired the former Farmland Nitrogen Plant site. The site is being redeveloped as Lawrence VenturePark. Bids for Project PW1330, the construction of the Regional Detention Basin for Lawrence VenturePark, were originally opened on August 26, 2014. The project was awarded to RD Johnson Excavating Company in the amount of $649,919.50 by the City Commission at its September 9, 2014 meeting.
Project Details
The two existing effluent ponds are to be combined into one large basin that will provide stormwater detention storage for the majority of future development within Lawrence VenturePark. The remaining required detention is provided by a detention basin just west of the new Westar substation. With the acquisition of the property the City is bound to the conditions of Consent Order (CO) No. 10-E-94 BER. One of the conditions of the CO requires the City to adhere to the environmental remediation measures listed within the Corrective Action Decision (CAD). One of those measures requires that prior to the existing effluent ponds becoming regional detention they are to have all of the existing sediments lying within them removed. The principal construction item included with this change order involves the furnishing of fill dirt for the basin. Unfortunately the depth of the sediments to be removed from the ponds is greater than originally anticipated and in order to achieve the desired profile grade of the basin extra fill dirt is needed.
During the re-grading of the main drainage channel traversing the site and leading into the new regional detention basin the Kansas Department of Health & Environment (KDHE) required additional testing for soil within that area for potential nitrate impaction. After reviewing those additional soil samples KDHE made the determination that the impacted soil needed to be removed and replaced and therefore necessitated the additional cost.
The third and final item of this change order involved the relocation of a pressurized ground water collection line traversing the outfall of the regional detention basin. This lines elevation was originally thought to be low enough to clear the bottom of the new outfall channel. During the channel excavation the line was in fact exposed and needed to be relocated at a deeper depth. The relocation of the line did however enable the installation of a check valve which will help with its future operation.
By providing one large regional detention basin each individual property will not have to set aside space for stormwater detention nor incur the cost of a drainage study since the regional detention basin will account for stormwater runoff for the entire park. It should also be noted that the Remedial Action Plan (RAP), the document that the CAD was based upon, estimated the construction of regional detention at $1,546,612.
Project Status
Work on the project has currently been halted until Change Order No. 2 has been approved.
Project Funding
The project is being funded with the environmental remediation fund obtained with the acquisition of the site and has been approved by the Kansas Department of Health & Environment.
Action Request
Public Works staff requests approval of Change Order No. 2 in the amount of $50,955.53 to R.D. Johnson Excavating Inc. in order to complete the contract (Project No. PW1330) for construction of the regional detention basin at Lawrence VenturePark.