AGENDA REPORT
DATE: May 22, 2023
TO: City Commission
FROM: Bill McDaniel, City Manager
SUBJECT: Carriage Court Sinkhole Stabilization
EXECUTIVE SUMMARY:
On Sunday, April 23, 2023, a depression developed in the eastbound lane of Carriage Court. Under the City Manager's emergency authority, Madrid Engineering Group (Madrid) mobilized professional engineering and geologist staff to investigate and advise City staff. Subsequently the City Manager authorized Madrid to conduct a thorough investigation and prepare a report with a plan of action for stabilization. Engineering Work Order 21-020-05C-03 dated May 5, 2023 was issued for $17,648. Madrid submitted their report dated May 8, 2023, summarizing their findings and recommended plans and specifications for stabilization repair of the sinkhole.
The proposed method of repair is pressure grouting with low mobility grout. This method had been utilized in 2010 by the City on Timberlane Drive and at the elevated water tank on National Guard Drive. Due to the urgency of returning this dead-end street to service, staff requested that Madrid subcontract the work to a qualified and readily available pressure grouting firm. Under this modification, Madrid will utilize CPWG Constructors to subcontract with Earth Tech, LLC to complete the stabilization work in two sequential phases. The initial phase will pressure grout the area most central to the geophysical anomaly (loose soils). If sufficient subsoil compaction is achieved, then grouting will be terminated at this stage. Otherwise, the work will proceed to a larger area surrounding the loose soils until sufficient compaction is achieved, or until plan quantities have been met. Madrid and Earth Tech are prepared to begin work onsite within a week of Notice To Proceed, and anticipate completion within twelve days. The Modification includes accelerated payment provisions to expedite the work.
Modification #1 to EWO 21-020-05C-03 includes all subcontracted services necessary to perform the stabilization repair. Modification #1 increases the contract amount by $313,180.00, for a total Not to Exceed contract amount of $330,828.00. Modification #1 increases the contract time by 45 days for a total contract time of 60 days.
RECOMMENDATION:
That the City Commission authorize the City Manager to execute Modification #1 to EWO 21-020-05C-03 with Madrid Engineering Group, in the amount of $313,180.00, for the Carriage Court sinkhole.
FISCAL IMPACT:
This stabilization will be charged to the Street R & R Fund, CIP # SH001 - Sinkhole - Carriage Ct. A budget adjustment is included in the agenda for this purpose.
Prepared by: Frank Coughenour, P.E., Senior Engineer