By Bennett Trenchless 0 Comments

Gray Lodge Wildlife Area Water Supply Project

Project Details

Microtunneling

  • 72″ ID steel raw water
  • Twin drives, 90′ long
  • UPRR and Kinder Morgan crossing

Geotechnical Conditions

  • Medium dense silty sand
  • Stiff sandy silt
  • High groundwater

Challenges

  • Watertight shafts required
  • Strict environmental constraints
  • Difficult site access
  • UPRR encroachment permit with waivers
  • Tight construction window

Project Overview

As a trenchless subconsultant to Provost and Pritchard, Bennett Trenchless Engineers provided feasibility analysis, full design assistance, and permitting assistance for twin 72-inch trenchless crossings of UPRR to increase water deliveries to the Gray Lodge Wildlife Area.  The US Bureau of Reclamation and California Natural Resources Agency both funded portions of the project.  Trenchless methods were necessary to install large diameter pipelines beneath a high-priority section of UPRR track.  To mitigate the risk of settlement to the railroad, microtunneling and watertight construction methods were specified.

Challenges on the project included high groundwater with a nearby source of recharge, environmental restrictions on allowable work area and construction season, difficult site access, and coordinating with UPRR to secure an encroachment permit.  The UPRR encroachment application requested a casing requirement waiver for the inverted siphon crossing due to the large diameter of the carrier pipe and the increased risk of settlement.  Through meetings with the client and UPRR engineering staff, Bennett Trenchless was able to demonstrate that UPRR’s concerns had been adequately addressed by the design documents.  Mitigation measures included a robust settlement monitoring program, use of Permalok casing to increase speed of installation, and use of contact grouting to stabilize the soils.

By Bennett Trenchless 0 Comments

Harvest Water Program

Project Details

HDD / MT / AB / OSPJ

  • 16- to 72-in pipelines
  • 18, 150-800 ft crossings of Elk Grove and Ehrhardt Channels, UPRR, Franklin and Stone Lake Creeks, etc.
  • Casing for 16 of 18 crossings

Geotechnical Conditions

  • Loose to dense silty sands and sandy silts
  • Groundwater table 60′ bgs

Challenges

  • Address UPRR requirements
  • Mitigate impact to traffic

Project Overview

BTE is providing trenchless consulting services, as a subconsultant to Brown & Caldwell/Carollo, for the trenchless feasibility, basis of design report, and program management (C-PMO) for the Harvest Water Program recycled water system.  The trenchless scope of work includes preliminary assessment of 18 trenchless crossings varying in diameter from 16 to 72 inches, and in length from 150 feet to 800 feet.  Trenchless methods under consideration along the various transmission main and distribution pipelines include: microtunneling, open-shield pipejacking, open-shield tunneling, pipe ramming, auger boring, and HDD.  Several trenchless crossings required pre-planning to meet UPRR permit requirements, and early permit coordination with CA DFW regarding impact mitigation to waterways.

By Bennett Trenchless 0 Comments

Outfall Sewer Replacement Project

Project Details

EPBM Pipe Jacking

  • BTE produced full design and provided on-site construction inspection services
  • 72-in FRPM, gravity sewer pipelines
  • 200-ft crossing of North Cliff Avenue
  • 350-ft crossing of I-229
  • No claims or CORs

Geotechnical Conditions

  • Moist fill with little gravel transitioning to clay and wet sand (North Cliff Ave.)
  • Sandy clay, clayey sand, and silt (I-229)
  • High groundwater

Challenges

  • Control groundwater inflow to shafts
  • Difficult geotechnical conditions
  • Cobbles, boulders, and fill debris encountered

Project Overview

BTE served as trenchless subconsultant to HDR on City of Sioux Falls, Outfall Replacement Project. BTE designed two trenchless crossings; I-229 and North Cliff Avenue. The projects were designed as microtunnel, direct jacked 72” nominal Hobas pipe. However, the Contractor, EJM proposed using an EPBM to install 96” steel casing, with the 72” Hobas carrier placed inside. The VE proposal was accepted. BTE planned the geotechnical investigation, including small diameter borings and large test pits and evaluated the results and construction implications. BTE was concerned about cobbles and boulders but was able to complete the crossings. No CORs or DSC claims were filed. BTE also proceeded on-site inspection services.

By Bennett Trenchless 0 Comments

Upper Bee Branch Creek Restoration Railroad Culvert Crossing

Project Details

Microtunneling

  • BTE provided design and permitting assistance and periodic site inspection services as subconsultant to Strand
  • 6 each 101-in 1.5″ thick steel, storm drain pipelines
  • 120-200 foot crossings or multiple Canadian Pacific Railyard tracks
  • No claims or CORs, no damage to CPRR

Geotechnical Conditions

  • Loose sand and fill
  • Soft to firm clay
  • High groundwater

Challenges

  • Mitigate impact to Canadian Pacific operations
  • Difficult geotechnical conditions
  • Low Earth cover

Project Overview

BTE provided design and permitting expertise to Strand Associates of the City of Dubuque for 6 101” steel storm drains beneath multiple sets of CPRR tracks. Earth cover was adjacent to the Mississippi River and only 12-14’, with about 9-10’ of loose wet fill with debris underlain by soft wet clay in the tunnel horizon. Another layer of loose wet sand was encountered below the clay. The parallel microtunnels had only 8’ horizontal separation.

An extensive settlement risk evaluation monitoring program were implemented, with stringent constraints for allowable settlements. The contractor was required by CPRR to maintain rail tamping crew on-call. The parallel crossings were completed while protecting the rail yard. No excessive settlement occurred. No CORs or DSC claims were made. Huxted Microtunneling was the microtunneling subcontractor; Tricon was the General Contractor.

By adminbt 0 Comments

Upper Northwest Interceptor, Section 9

Project Details

HDD

  • 24- and 36-inch VCP and PCP
  • 27,200 feet of gravity sewer
  • 42 shafts and 41 drives

Geotechnical Conditions

  • Medium to very dense sand
  • Stiff to hard silt and clay
  • Perched groundwater

Challenges

  • Congested urban area
  • Tight work areas and traffic control
  • Sequencing constraints

Project Overview

As the trenchless subconsultant to HDR, Bennett Trenchless Engineers provided preliminary and final design services for the trenchless installation of 27,200 feet of 24- and 36-inch gravity interceptor and trunk sewer pipe through a congested urban area. In addition to the tight construction areas, other challenges encountered in the design of the pipeline included high traffic volumes, high groundwater levels, utility conflicts, sequencing constraints, non-disruptive shaft construction methods, and minimizing impacts to residents and businesses.

Bennett Trenchless Engineers led the evaluation of shaft locations, shaft types, staging areas, and trenchless construction methods. Bennett Trenchless Engineers also reviewed geotechnical information, prepared cost estimates, recommended pipe materials, evaluated potential settlements, prepared specifications for trenchless work, developed construction schedules and provided input for design drawings. The construction methods selected for the final design were microtunneling and open-shield pipejacking. Bennett Trenchless Engineers also provided engineering services during construction for this project.

By adminbt 0 Comments

U & S Street In-Line Storage Project

Project Details

Microtunneling

  • 72-inch RCP
  • 550 feet of gravity sewer
  • Interstate 5 crossing

Geotechnical Conditions

  • Soft to very soft soil
  • High groundwater

Challenges

  • Congested urban area
  • Tight work areas and traffic control
  • Nearby critical utilities

Project Overview

As a subconsultant to CH2M Hill, Bennett Trenchless designed a 72-inch diameter by 550-foot microtunneled gravity sewer pipeline crossing of Interstate 5 at U Street in Sacramento, CA. Challenges included soft to very soft soils, severe work area restrictions, multiple critical nearby utilities, and permitting issues.

Bennett Trenchless Engineers conducted preliminary design analysis and calculations, prepared preliminary design report, technical specifications, drawing details, assisted with Caltrans permit, and prepared the Geotechnical Baseline Report. Bennett Trenchless also provided submittal review and full-time on-site inspection services of the trenchless components of the work.

By adminbt 0 Comments

Secret Town Pipeline – Phase II Improvements

Project Details

Microtunneling

  • 54-inch casing for 36-inch ID RCP water
  • 257 feet of microtunneling
  • Crossing of Interstate 80

Geotechnical Conditions

  • Highly fractured rock
  • Moderately weathered
  • No groundwater

Challenges

  • Difficult access to working areas
  • 50-foot elevation difference
  • Difficult ground conditions

Project Overview

As the trenchless subconsultant to Hydroscience, Bennett Trenchless Engineers assisted with the design and inspection of 257 feet of 54-inch casing for a 36-inch ductile iron water carrier pipe. Trenchless construction methods were required to cross beneath Interstate 80. Bennett Trenchless was contracted to design the crossing and to assist with the Caltrans permit application. Microtunneling was selected to install the pipeline to effectively excavate the fractured rock and ensure a stable excavation to minimize settlement risk to the Interstate. The stable soil conditions and lack of groundwater allowed the use of trench boxes for the shafts.

Challenges on the project included coordination with Caltrans, difficult ground conditions, a 50-foot elevation difference between the jacking and reception shafts, tight working areas, and access issues. The project site was very remote and access to both shaft locations was constrained and difficult. In addition, the reception shaft was located within a steep ravine and presented challenges for shaft construction and microtunnel machine retrieval.

By adminbt 0 Comments

Folsom South Canal Connection Project

Project Details

Microtunneling

  • 84-inch ID RCCP raw water
  • 430-foot river crossing
  • First Cutter Soil Mixing shafts constructed in United States

Geotechnical Conditions

  • Soft rock
  • High groundwater

Challenges

  • Very deep watertight shafts required
  • Strict environmental constraints
  • Tunneling through rock

Project Overview

As the trenchless subconsultant to Fugro West, Bennett Trenchless Engineers provided full design assistance and full-time construction inspection services for four trenchless crossings on the 19-mile raw water pipeline project connecting EBMUD’s Folsom South Canal to the Mokelumne Aqueducts. Microtunneling was used for three of the four crossings and open-shield pipejacking was used for the fourth. The crossings ranged from 110 feet to 430 feet in length and 84– to 102-inches in diameter. Trenchless methods were used to cross beneath the Mokelumne River, California Highway 12, a major surface road, and a wetland area.

The most challenging trenchless crossing was the 430-foot microtunneled crossing of the Mokelumne River. Shafts were constructed using a new technology called Cutter-Soil Mixing that allowed the construction of deep, watertight shafts through very difficult soil and rock conditions. A specialized drill rig created interlocking panels of soil-crete to form the shaft walls. This project was the first project completed in the United States using this technology to create shafts for microtunneling. Additional challenges on the crossing included construction of deep shafts, high groundwater, the presence of soft rock at the tunnel elevation, a prohibition on rescue shafts in the river should the machine have gotten stuck, and tight environmental restrictions.

By adminbt 0 Comments

Raw Water Intake Expansion Project

Project Details

Microtunnels

  • Nine 60-inch intake tunnels, 90-160 feet long
  • Twin 30-foot diameter shafts

Geotechnical Conditions

  • Karstic limestone and fissile shale
  • High groundwater, nearby source of recharge

Challenges

  • Underwater MTBM retrieval
  • Shafts constructed by blasting
  • Challenging ground conditions

Project Overview

As a sub-consultant to MWH, Bennett Trenchless Engineers conducted the feasibility/preliminary design evaluation, planned and conducted the geotechnical investigation, prepared Geotechnical Data and Baseline Reports, evaluated alternative construction methods, conducted a design workshop, and provided design services for twin intake shafts and eight 60-inch diameter intake tunnels to triple water supply capacity from 80 MGD to 220 MGD.

The twin shafts were 30 feet in diameter and 100 feet deep, excavated through very challenging karstic limestone and fissile shale. The eight 60-inch tunnels varied from 90 to 160-feet and required underwater retrieval of the MTBM after each bore. The limestone contained numerous solution features and caves, and had unconfined compressive strengths up to 28,000 psi. Bennett Trenchless Engineers provided full-time construction management/inspection. The project was completed within budget and schedule, with no claims.

By adminbt 0 Comments

A-Line Relief Interceptor Phase 2A

Project Details

Earth Pressure Balance Pipejacking

  • 96-inch ID RCP gravity sewer
  • 3,000 feet in two drives (Record Length)

Microtunneling

  • 72-inch ID RCP gravity sewer
  • 1,000 feet in two drives

Geotechnical Conditions

  • Soft to stiff fat clay, high groundwater

Challenges

  • Traffic control in urban area
  • Very shallow grade
  • Flight path restrictions
  • Golf Course protection

Project Overview

As the trenchless subconsultant to Carollo Engineers Inc., Bennett Trenchless Engineers provided preliminary and final design services for the trenchless installation of 4,000 feet of 72- and 96-inch gravity sewer through a golf course and a congested urban area. In addition to reducing impacts to residents and businesses, challenges included coordination with the local airport, limited work areas at shaft locations, high groundwater levels, low earth cover, utility conflicts and limiting impacts to a high traffic bike trail.

Bennett Trenchless Engineers led the evaluation of shaft locations, staging areas, and trenchless construction methods. Bennett Trenchless Engineers also reviewed geotechnical information, and prepared cost estimates, pipe material recommendations, settlement evaluations and monitoring plan, specifications, and construction schedules. The construction methods selected for the final design were earth pressure balance pipejacking for the 96-inch pipeline, and microtunneling for the 72-inch pipeline. Bennett Trenchless also provided construction inspection for the trenchless components of this project. The project was completed within budget with no claims.