The Successful Use of Excavation Models in the Layout, Management, Scheduling & Safety Planning of Pipe-Open Trenching

The Successful Use of Excavation Models in the Layout, Management, Scheduling & Safety Planning of Pipe-Open Trenching

By Tony Fiore, Fiore & Sons, Inc.

The $2.5 million Open Pipe Trenching project for Hewlett Packard Company in Colorado Springs, CO. was nothing short of exceptional for its innovation, quality and functionality of design.  The tenacity of Fiore & Son’s project team and leadership of Hewlett Packard’s team was profoundly important to the success of this complex open trench project.

The original design of the project remained essentially unchanged with the exception of minor adjustments in pipe elevations and routing due to underground issues.  The design team work very closely with the City of Colorado Springs to keep the project moving forward during various project discoveries.

The most revolutionary project achievement occurred during construction as the result of using excavation models in the layout, management, scheduling, and safety planning by the integrated project and owner teams that ensured a well-executed, successful project.

This new sanitary sewer project was comprised of 3,700 LF of new 12” sewer over rough mountainous terrain at elevations ranging from 15’ to 40’ excavated depth.  Preliminarily, excavated material was expected to be hard to very hard sandstone which as the project progressed was found to be arduous.  Half of the route was crossed with numerous utilities including a high power electrical duct, fibre optics, high pressure gas, water mains, and the existing sanitary sewer which was to remain uninterrupted.  It was discovered in 3D modeling and field investigation that several of these utilities had been improperly mapped.

Resolution of these initial challenges gave rise to the necessity of the team to create success through innovation, increased safety measures, heightened pre-planning efforts, and the purposeful use of technology.

The project began with Fiore & Sons, Inc. potholing all the existing utility locations to determine the depth and accuracy of the existing mapping.  As it was, numerous mapping errors were discovered which drove the need for a new “plan of attack”.  As resolution, Fiore & Sons, Inc. created a 3D CAD model that identified the actual location of existing utilities and how they impacted the planned excavations.

An existing electrical duct bank was identified at a miss-mapped location on site which required the design of a sophisticated, permanent shoring system. Working in cooperation with Hewlett and Classic Consulting Engineers, Fiore & Sons, Inc. assisted in the planning and pricing of the new shoring system and provided a 3D CAD design of the entire excavation plan, showing removal of overburden soils to a depth of 16’ above the proposed pipe elevation. This pre-planned attack triggered a two-week delay which later saved the project several weeks.

Completion of this critical task allowed Fiore & Sons, Inc. to create a remarkably safe working environment by using 16’ trench boxes in lieu of managing much deeper and heavier trench shoring systems.  As much as 24 feet of existing earth was removed in some locations.

Pre-planning of the entire dig also allowed Fiore to run a heavy over lot scraper crew directly in front of, and behind, the utility trench crew.  This allowed overburden soils to be removed which created a safer work bench for the utility crew.  These same soils were then carried around and behind the utility crew to be used in the restoration of the grade.

As the project progressed, several elevation errors and unknown utility crossings were encountered. Classic Consulting, Civil Engineers, worked closely with the City of Colorado Springs to approve minor changes and modifications, sometimes within 48 hours, to keep the project moving forward and uninterrupted.  This teamwork was a major contributor to the projects on-time completion despite the up-front 2-week delay.

Safety is #1 and under normal conditions Fiore & Sons, Inc. would keep heavy earthmoving crews a considerable distance from any utility operations for protection from collision or operator errors.  In order to make this job successful however, Fiore & Sons, Inc. coordinated the two crew types working in close proximity to each other using pre-planned excavations and haul routes.

A two-week schedule was maintained on a regular basis that identified stations and milestones for each crew during each week of construction.  As evidenced by this committed coordination, there were no collisions or near misses.  In addition, excavation slopes were pre-designed in the 3D CAD model, allowing engineers to review the deep excavation slopes and approve the design in advance of the work, contributing to overall safety and efficiency.

Using 3D CAD technology for excavation plans allowed the Owner and Consultants full awareness of excavation complexities and coordination that contributed to making critically important, informed decisions. The client wasn’t caught unaware of the scale of excavation, management of excess materials or storage piles, and construction traffic flow.  The Fiore & Sons, Inc. team was commended by both the Owner and Consultant numerous times for how they were alerted to project complexities, thus eliminating unpleasant surprises.

3D CADD also indicated equipment flow and stockpiling plans that were clear and fully anticipated.  Two additional examples of Fiore & Son’s innovative processes:  1) The excavation plan allowed Hewlett Packard to plan their business traffic, neighbor relations, and City relations in a highly collaborative and communicative way so that everyone was kept up to date and well-informed. 2)  At several stations, the hard sandstone conditions essentially disabled trench excavation with typical excavating equipment.  Fiore & Sons, Inc. engineered and assembled a single toothed ripper mounted on a 400 series excavator to overcome this issue.  The single tooth was used to break sandstone and keep the project moving without delay.

Construction quality, craftsmanship and management were inherently responsible for the successful completion of this project and the clear understanding of crew flow allowed all work to be paced in such a way that was not rushed, despite the undue burden to “make up time”.  All project work was managed and supervised, allowing each trade to provide the best product allowable.  The project was completed ahead of schedule.

 

 

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