Peterborough Street Apartments


Revitalization of a site three blocks from historic Fenway Park involved construction of a new 5-story apartment building located immediately surrounded by existing 3-story residences.

Geotechnical Conditions:

Soil conditions consisted of up to 9 feet of loose to medium dense “urban” sand fill underlain by soft peat and organic clay/silt to 28 feet.  The fill and organics were underlain by very soft to medium stiff clay extending to a depth of 175 feet where bedrock was encountered.

Project Challenge:

  • Economically supporting heavy building loads through deep, soft soils with minimal vibration in a congested residential neighborhood


  • Significant cost savings over traditional H-piles and drilled micropiles
  • Limited vibrations in sensitive residential area
  • Rapid DIP installation – more than twice as fast as alternatives
  • Easy access to the urban site
  • Eliminated time and costs associated with pile splicing
  • Limited laydown area on congested site due to modulus pile system

Design and Construction Solution:

With loads approaching 600 kips, deep foundation support was required at the fill/soft soil site.  The project team initially considered driven steel H-piles with 100 ton capacities.  High vibrations coupled with the challenges of transporting long pile sections and the added cost/time for pile splicing led the design team towards a more practical solution for the urban site.  Ductile Iron Piles were selected as a more cost-effective and faster alternative to the H-piles and traditional drilled micropiles.  The Ductile Iron Pile system provided a 2:1 replacement of the H-piles with a working capacity of 50 tons.

Prior to the start of production operations, Helical Drilling, Inc. installed the 50 ton test pile (Series 118/7.5) to terminate on rock at a depth of 175 feet.  The test pile was loaded using a gravity reaction load test setup because of the costs associated with deep rock anchors for tension resistance.   Load testing of the end-bearing Ductile Iron Piles showed a deflection of 1.25 inches at the design load (100%) of 50 tons.  The load test was performed to 200% of the design load (100 tons).  The response was nearly perfectly elastic with a deflection at the maximum test load approaching 3 inches.  The deflection of the 175-ft long test pile met expectations for compression of a long micropile.  The results met the project teams expectations while also delivering foundation economy.

Ductile Iron Pile Load Tests LT


Production pile installation was performed at rates of 1,000 feet per day or more.  A total of 87 piles were installed in just over 2 weeks.  Vibration monitoring performed during installation recorded peak particle velocities of only 0.3 inches/second on the ground 2 feet away from installations.  The vibrations were reduced to 0.15 inches/second a distance of 4 feet away.  Measurements on the existing building foundations were less than 0.15 inches/second while installations were within 2 feet from the building.

Project Team Members

DIP Design/Build Partner: Helical Drilling, Inc.
Geotechnical Engineer: Briggs Engineering
General Contractor: Boston Design Construction
Structural Engineer: DM Berg Consultants, P.C.
Architect: Nunes Trabucco Architects


Peterborough Street Apartments

Pile Type



Boston, MA

Project Type





Adjacent Structures
Difficult Access
Soft Soils

Case Study File


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