This project provides the Silver Spring community with a new library located within the Central Business District (CBD). The new library is approximately 90,000 gross SF in size and is intended to meet the unique requirements of an increasingly urban, ethnically and culturally diverse residential and business community. The building is five floors plus a basement. The footprint of the first floor is split by the right-of-way for the future Purple Line light rail resulting in a main building to the west of the ROW and the “Pavilion” to the right. The project also includes an art gallery and is a LEED Silver building.
Geotechnical Engineering: During the design stage Balter performed geotechnical evaluations to prepare a comprehensive geotechnical report. Extensive evaluations of multiple foundation options, including both shallow and deep, were performed. Because of the varability of the existing undocumented fills, residual soils, decomposed and highly weathered rock, and rock, shallow foundations were not suitable for this site. As a result, most of the evaluations consisted of selecting the appropriate deep foundation design, which included Micropiles and Caissons. The report provided the appropriate parameters for each foundation type, including skin friction and end bearing parameters. Recommendations also included detailed seismic design parameters in accordance with the 2006 IBC, as well as slab on-grade, earth pressures, underground retaining structures, design recommendations related to construction tying into the light rail, and earthwork.
Geotechnical Consulting continued through the design phase with project specifications, review of alternate design considerations, and WMATA design requests. During construction, geotechnical support was involved with excavation and sheeting and shoring/tie-back installations, foundation construction, and utility relocations and installations.
Special Inspections: Balter provided Special Inspections and laboratory materials testing services in our WACEL, CCRL, and AASHTO-certified laboratory facility in accordance with Montgomery County Special Inspections requirements for this project. Primary building components include shoring, tie-backs, formwork systems; soils, earthwork, deep foundations; reinforcing steel, cast-in-place concrete, structural steel framing, metal decking, light gauge framing, fireproofing and structural masonry, utilities, WSSC water and sewer lines, and pavements. Heavy structural steel beam features which cantilever the Purple Line required additional measures of fabrication shop and on-site inspection and NDT testing. All inspection documentation and engineering submittals included daily reports and test data, tracking non-compliance logs, in accordance with MCDPS requirements and permitted plans and specifications.
Balter’s field inspectors, managers and engineers worked closely with the County to anticipate and prevent construction defects. Our significant experience resulted in a high level of inspections, whereas we observed potential construction deficiencies, and worked with the County and the general contractor to change procedures and/or materials to prevent non-compliances. Balter’s engineers and managers worked closely with the County when construction issues were encountered to propose cost effective and timely solutions which included incorrect control joints, concrete, severe honeycombing, and incorrect lagging boards on the temporary sheet pile walls. As the geotechnical engineer of record, we were able to seamlessly with our field representatives to provide real-time modifications to the design during drilled shaft construction. Balter continuously updated a non-compliance log and maintained communication with the design team, owner and contractor to track and resolve the non-compliances.