To: Honorable Mayor and Members of Town Council
From: Mark Marlowe, P.E., Utilities Director
Title
Resolution Approving Additional Funds to Complete the Plum Creek Alluvial Well Field Project for the Plum Creek Water Purification Facility
Body
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Executive Summary
The purpose of this memorandum is to request Town Council Approval of an increase to the encumbered amount associated with a contract awarded to Velocity Constructors Inc. through Resolution 2015-103 for a project which will provide renewable water supply to the Plum Creek Purification Facility (PCWPF) (see Attachment A). The contract amount awarded was $1,722,543 with a Town-managed contingency of $120,578 for a total encumbered amount of $1,843,121. This project is one of the first one of its kind that is being completed in a municipal environment. In fact, Aurora Water has visited the site and has requested to visit the South Well Field while it is under construction to learn more about the construction methodology. In addition, others have also inquired about the project as far away as Bozeman, Montana, as a potential solution of obtaining water in an economic manner.
During construction Utility staff recognized some opportunities to modify the design of the project that would bring potentially higher renewable water yields and efficiency to the well field. This along with some unforeseen challenges with this relatively new approach to installing horizontal wells has used much of the contingency. In addition, the vertical portion of one of the wells was hit by the horizontal drilling in an attempt to get the lateral arm as close to the side of the vertical well as possible. Since this type of well construction is relatively new and getting the lateral arm close enough to the vertical well carries some risk, the bid documents were set up to provide for shared risk (50/50) between the Town and the contractor with respect to any damage to a vertical well. This ensured the Town did not pay for the entire risk on the front end and allowed contractors to provide more competitive bids. The fact that one of the vertical wells was hit; however, means the well needs to be replaced. The cost according to the contract is to be shared by the Town and contractor. With the cost of the vertical well and some other unforeseen items, staff is requesting Town Council increase the total encumbered amount for the project by $76,500 from $1,843,121 to $1,919,621.
Discussion
The Plum Creek Alluvial Well Field project is an innovative approach to obtain the Town of Castle Rock’s existing local water rights at a fraction of the cost to obtain and import renewable water. While constructing the project, Town Staff identified opportunities to modify the project that would result in longer life and potentially higher yields and efficiency to the well field. One of the more notable changes is using slotted stainless steel and wire wrapped well screen in place of slotted high density polyethylene pipe (HDPE). This allows for a longer life of the well and more percentage of open space to allow the water to be collected. To our knowledge this is the first application of wire wrapped screen used in horizontal water wells. The lateral arms and the vertical wells are not physically connected. The theory is that by placing the lateral arm in near proximity to the vertical well it will help increase the production in the vertical well by giving the well a larger area of influence. During the drilling of one of the horizontal wells, one of the vertical wells was damaged and will need to be replaced.
All entities involved in the project identified the potential risks involved with the project and agreed to share the potential risks in the contracting. Unfortunately, the vertical component of Well AL-18 was damaged during the drilling of the horizontal lateral and was damaged beyond repair. Several different attempts and methods were used in trying to repair and assess the damage. Utility staff consulted with Leonard Rice Engineers, Inc, who is the contracted design and oversight engineer for this project, and we have concluded that the contractor followed reasonable standards within the industry. Therefore based on the terms of the contract documents, cost of the replacement vertical component for Well AL-18 should be split equally between the contractor and the Town. In addition, Utility staff has recognized the need for more development time for each well than what was identified in the original contract to properly clean and clear the wells of drilling fluids to allow optimal production from the wells.
The quoted price to re-drill the well is $71,786 which will be shared equally between the Town and the contractor. Utility staff is requesting authorization from Town council of additional funding in the amount of $76,500, which includes $35,893 to re-drill AL-18, additional monies for development of the wells and a small amount of contingency to cover any other additional unforeseen expenses. The new total project encumbrance is $1,919,621. The hope is to still try to complete the majority of the earth moving parts of the project by April 30 to avoid disturbing the Preble’s mouse; however, we do plan to ask United States Fish and Wildlife for an extension to the allowable time to work in the Prebles mouse habitat to complete the development and pump testing of the well after April 30.
Budget Impact
If Town Council approves the additional funding for the project, Utilities will prepare the appropriate budget transfer from 211-4375-443.77-30 (Alternative Source of Supply) in the amount of $76,500. The costs associated with this project will be charged to the project line shown below.
Project Original Original Additional Total Amount
Amount Contingency Request
211-4375-443.76-63 $1,722,543 $120,578 $76,500 $1,919,621
Plum Creek Central Wellfield
Staff Recommendation
Staff recommends approval of additional funding for the re-drill of the vertical component of Well AL-18, additional time for developing the wells and a small contingency to cover any additional unforeseen expenses in the amount of $76,500 for a total encumbered project amount of $1,919,621.
Proposed Motion
I move to approve Resolution: Approving Additional Funds to Complete the Plum Creek Alluvial Well Field Project for the Plum Creek Water Purification Facility
Attachments
Attachment A: Resolution