HomeMy WebLinkAboutA018 - August 11, 2026, Regular Meeting of the Ames City CouncilITEM #:18
DATE:08-11-26
DEPT:PW
SUBJECT:13TH STREET EMERGENCY STORM SEWER PIPE REPAIR - APPROVAL
OF CHANGE ORDER NO. 2
COUNCIL ACTION FORM
BACKGROUND:
In late March 2026, City staff responded to reports of sinkholes on the north side of 13th Street
near Veenker Memorial Golf Course. An investigation determined that the existing 12-foot
diameter corrugated metal pipe (CMP) conveying Clear Creek beneath 13th Street has
deteriorated significantly. The culvert, which was installed prior to the area's annexation
into the City of Ames, has experienced extensive corrosion of the pipe invert beneath
the westbound lanes of 13th Street.
As a result, stream flow has migrated beneath the pipe, eroding the supporting soil and
creating large underground voids. The erosion has resulted in multiple soil voids adjacent to
the culvert outlet, extending beneath and around the pipe. While the voids are currently
located north of the roadway, continued erosion poses a risk of undermining 13th Street and
could ultimately lead to structural failure of both the roadway and the culvert if left
unaddressed.
Because of the implications to public infrastructure, staff evaluated repair alternatives with
specialty contractors. Pressure grouting (mudjacking) was selected as the most appropriate
short-term stabilization method because it restores structural support to the existing culvert
without requiring emergency replacement of the crossing. This repair will stabilize the
culvert and roadway while allowing the City to evaluate and program a permanent
replacement or rehabilitation of the crossing within the next five to seven years.
Proposals for the grouting work were solicited and a contract awarded to Denco Highway
Construction of Mingo, Iowa, in the amount of $40,360. Change Order No. 1 in the amount
of $10,130 was approved by City Council on July 14, 2026 to address voids that were
larger than initially anticipated in the original bid documents.
In order to access certain areas, selected tree removal was necessary. The construction plans
included leaving the removed trees adjacent to the work areas and allowing them to naturally
decay. Many of these trees were on Iowa State property adjacent to 13th Street. However,
during construction, Iowa State staff notified the City that the cleared tree cannot be
kept onsite and must be removed.
The original construction plan also allowed for the fence adjacent to 13th Street right of way to
stay in place during construction without the need for removal. Due to the extent of the voids
found during the repair work, the fence had to be removed and replaced in order to
properly perform repair work.
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This City Council Action is to approve Change Order No. 2 in the amount of $14,500.
The scope of work will include fence removal and replacement and brush clearing and
chipping.
Revenue for these expenses is available from unobligated Storm Sewer System
Improvement funds, where there is an available balance of $170,965. The table below
shows project revenues and expenses:
Description Revenue Expense
Bid Price $40,360
Change Order No. 1 10,130
Change Order No. 2 (this
Council Action) 14,500
Storm Sewer System
Improvements (unobligated)$170,965
Totals $170,965 $64,990
ALTERNATIVES:
1. Approve Change Order No. 2 to Denco Highway Construction, of Mingo, IA, in the
amount of $14,500.
2. Direct staff to pursue changes to the project.
CITY MANAGER'S RECOMMENDED ACTION:
The proposed change order will allow for proper access to repair the voids as well as
meeting the restoration requirements for the project as required by Iowa State.
Therefore, it is the recommendation of the City Manager that the City Council approve
Alternative No. 1 as described above.
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