Title
143rd Street at John Humphrey Drive, Phase II Engineering, Supplement #1, Additional Geotechnical Investigations
History
Patrick Engineering (Patrick) is currently under contract with the Village of Orland Park (Village) to assist in preparing the contract and construction plans for the 143rd Street and John Humphrey Drive intersection which includes addressing differential settlement issues at the dry land bridge along 143rd Street just east of John Humphrey Drive. Based upon geotechnical studies conducted for the project, peat has been found in and adjacent to the project site. Peat is a partially decomposed organic layer of soil that accumulates in wetland conditions, such as peatlands, bogs, mires, moors, or muskegs. Peat is not a suitable material for foundations and requires additional geotechnical studies to establish its limits.
Therefore, additional geotechnical information within the project area is necessary to properly design the structural and subsurface remediation measures to provide a sound and stable roadway facility for the travel demand. Patrick proposes to obtain additional geotechnical borings, to supplement borings taken during earlier phases of the project, to develop a more accurate picture of the subsurface conditions in the area of the dry land bridge and the intersection. The previous geotechnical boring program performed by Patrick during Phase I was targeted at the areas at the immediate ends of the existing dry land bridge to determine the cause of the differential settlement that was resulting in safety issues along this heavily traveled roadway corridor. This effort identified the presence of seams of peat in these areas.
Based on these findings, a supplemental boring program was undertaken during Phase II, which was targeted at locating an area beyond the bridge limits where no peat was present, which would yield a suitable location where to end the bridge expansion and locate the approach slabs. This effort found some locations with no peat, however, they were at extensive distances away from the bridge, while areas closer to the bridge still had the presence of some peat.
The reason for the current proposed supplemental geotechnical boring program would be to seek areas closer to the bridge where there is no peat, so the engineers can limit the proposed bridge expansion to these areas and save a substantial amount of construction cost by keeping the size of the proposed bridge to a reasonable amount.
The need for this additional geotechnical investigation is underscored by recent observations of other dry land bridge projects beneath other roadways in the Orland Park area such as 159th Street project completed by Illinois Department of Transportation (IDOT). It is critical that this intersection be built with a solid foundation with low risk of future differential settlement as it serves as a major access from properties to the north and east to get to the Orland Square Mall without having to travel on the already overburdened US Route 45 (LaGrange Road).
Additionally, since the west end of the dry land bridge is extremely close to the 143rd Street intersection with John Humphrey Drive, in order to address concerns with limiting the settlement of the intersection, the proposed boring plan includes several borings within the intersection proper and extending slightly into the south, west, and north legs of the intersection. This will allow the engineers to better understand the actual limits of peat within the intersection area and design remedial soil treatment methods to address this condition for the long term stability of this importation intersection.
Based on this, Patrick proposed to conduct an additional 12-14 soil borings, comprising four days of drilling, including traffic control for proposed borings within the pavement, lab testing, and geotechnical analyses and recommendations. Patrick has proposed to perform this work for the not-to-exceed fee of $43,800. This additional testing will meet Patrick's engineering data requirements to allow engineers to be able to deliver acceptable contract and construction documents for the Village’s project. Patrick has agreed that any additional redesign for the project based on this collected information and analyses will be performed by Patrick under the current limits of their existing design contract. Patrick and its subcontractors are prepared to commence this work immediately upon the Village’s authorization to proceed.
Financial Impact
The additional cost of $43,800 for Supplement #1 will be paid by a budget amendment which will be presented to the Board in the near future.
Recommended Action/Motion
I move to approve Supplement #1, Additional Geotechnical Investigations for 143rd Street at John Humphrey Drive Project, Phase II Engineering Studies for a not to exceed amount of $43,800;
AND
Authorize the Village Manager to execute all related contracts, subject to the Village Attorney review.