780 CMR 18.00 FOUNDATIONS AND RETAINING WALLS

780 CMR 18.00FOUNDATIONS AND RETAINING WALLS780 CMR 1801.0 GENERAL1801.1 Scope. The provisions of 780 CMR 18.00shall govern the design and construction offoundations and retaining walls.1801.2 Design. Foundations shall be designed toprovide adequate load bearing capacity whilelimiting settlement, heave and lateral movement totolerable levels. Allowable bearing pressures,allowable stresses and design formulas provided in780 CMR 18.00 shall be used with the allowablestress design load combinations specified in780 CMR 1605.3. The quality and design ofstructural materials shall conform to therequirements specified in 780 CMR 16.00, 19.00,21.00, 22.00 and 23.00. Excavations and fills shallalso comply with 780 CMR 33.00.1801.3 Foundation Types Not Covered by CodeProvisions. Types of foundations not specificallycovered by the provisions of 780 CMR, and groundmodification treatments to improve soils withinadequate load bearing capacity or settlementcharacteristics, may be permitted subject to approvalby the building official. A report shall be submittedto the building official that identifies the foundationas a type not covered by existing code provisions,and contains sufficient data and analyses tosubstantiate the adequacy of the proposed foundation. The report shall be prepared by a registereddesign professional who is knowledgeable in thedesign of the proposed type of foundation or groundmodification. The building official may require thatan independent peer review be performed to evaluatethe adequacy of the proposed design.1801.4 Qualifications of Registered DesignProfessional. Where the services of a registereddesign professional are required by the provisions of780 CMR 18.00, the registered design professionalshall be knowledgeable in the field of geotechnicalengineering and shall be qualified by appropriatetraining and experience to provide the specificservices required by the code provisions.780 CMR 1802.0 FOUNDATION ANDSOILS INVESTIGATIONS1802.1General.Foundation and soilsinvestigations shall be conducted in conformancewith 780 CMR 1802.2 through 1802.6. The scope ofthe investigation shall be determined by a registereddesign professional. The registered design professional shall oversee the performance of theinvestigation and prepare a report containing theresults of the investigation.8/22/08 (Effective 9/1/08)1802.2 Where Required. Foundation and soilinvestigations shall be required for all newstructures, and for alterations of existing structuresthat result in increased foundation loads or decreasedload resistance, except as noted below. Where thereis sufficient local experience that indicatessatisfactory performance of similar structures in thevicinity of the proposed structure, the followingtypes of structures do not require a foundation andsoils investigation, unless specifically required bythe building official:1. one- and two-family dwellings and theiraccessory buildings;2. unoccupied structures that do not pose asignificant risk to public safety in the event offailure; or3. structures used for agricultural purposes.1802.3 Soil and Rock Classification. Classification of soil materials shall be done in accordancewith ASTM D 2487. Refer to commentary in780 CMR 120.R for guidelines regardingdetermination of soil and rock Material Classes andConsistency in Place for use with Table 1804.3 andrelated provisions.1802.4 Investigation. The investigation shallconsist of subsurface explorations and engineeringstudies. The borings, test pits or other subsurfaceexplorations shall be adequate in number and depthand so located to accurately define the nature of thesubsurface materials necessary for the support of thestructure. When it is proposed to support thestructure directly on bedrock, the building officialshall require core borings to be made into the rock;or shall require adequate information from othersources to define the nature and quality of thebedrock. The results of previous subsurface explorations may be utilized where deemed to be adequateby the registered design professional. Engineeringstudies shall be made as necessary to identifysuitable bearing strata and evaluate soil strength,compressibility, bearing capacity, settlement,liquefaction potential, lateral earth pressures, slopestability and impacts of groundwater.1802.4.1 Groundwater Table. The investigationshall determine the location of the groundwaterlevel relative to the proposed structures andevaluate the potential groundwater impacts. Theevaluation shall consider both the impacts ofgroundwater on the structures and the potentialimpacts of the structures on the local groundwaterlevels.780 CMR - Seventh Edition429

780 CMR: STATE BOARD OF BUILDING REGULATIONS AND STANDARDSTHE MASSACHUSETTS STATE BUILDING CODE1802.4.2 Pile and Pier Foundations. Where pieror pile foundations are used, the investigationshall include the following:1.Recommended pier or pile types,dimensions and installed capacities.2. Recommended center-to-center spacing ofpiles or piers.3. Driving criteria.4. Installation procedures.5. Field inspection and reporting proced-ures(to include procedures for verification of theinstalled bearing capacity where required).6. Pier or pile load test requirements.7. Durability of pier or pile materials.8. Designation of bearing stratum or strata.9.Reductions for group action, wherenecessary.10.Evaluation of conditions that mightpromote deterioration of pile or pier foundations, in order to satisfy the requirements of780 CMR 1808.2.17.1802.4.3 Rock Foundations. Where sub-surfaceexplorations at the project site indicate variationsor doubtful characteristics in the structure of therock upon which foundations are to beconstructed, a sufficient number of borings shallbe made to a depth of not less than ten feet belowthe level of the foundations to provide assuranceof the soundness of the foundation stratum and itsbearing capacity.1802.4.4 Liquefaction Potential. Where thefoundation investigation indicates subsoils ofMaterial Classes 8 or 9, as defined in Table1804.3, the investigation shall include anevaluation of the potential for earthquake-inducedliquefaction in accordance with 780 CMR 1804.6.1802.5 Borings, Sampling and Testing. The scopeof the subsurface exploration, including the numberand types of borings, soundings or test pits, theequipment used to drill and sample, the in-situtesting equipment and the laboratory testingprogram, shall be determined by a registered designprofessional. The boring and sampling procedureand apparatus shall be in accordance with generallyaccepted engineering practice. The registered designprofessional shall have a qualified representative onthe site during the subsurface exploration and shallperform suitable checks to verify the adequacy ofinformation obtained from others.1802.6 Reports. The design bearing strata andload-bearing capacity shall be shown on theconstruction document. The written report of theinvestigation shall include, but need not be limitedto, the following information:1. A plot showing the locations of the subsurfaceexplorations.2.Logs or other suitable records of thesubsurface explorations.4303. An interpretative description of the subsurfaceprofile.4. Elevation and/or depth of the water table, ifencountered, and an evaluation of groundwaterimpacts in accordance with 780 CMR 1802.4.1.5. Results of in-situ testing and/or laboratorytesting, if performed.6. Recommendations for foundation type anddesign criteria.7.Evaluation of earthquake liquefactionpotential8. Expected total and differential settlement.9.Pile and pier foundation information inaccordance with 780 CMR 1802.4.210.Compacted fill material properties andtesting in accordance with 780 CMR 1803.5.11. Lateral earth pressures on foundation wallsand retaining walls.780 CMR 1803.0 EXCAVATION,GRADING AND FILL1803.1 Excavations near Footings or Foundations. Excavations for any purpose shall not removevertical or lateral support from any footing orfoundation without first

minimum distance of ten feet (3048 mm) measured perpendicular to the face of the wall or an alternate method of di verting water awa y from the f oundation shall be used. The procedure used to establish the final ground level adjacent to the foundation shall account for potential settlement of the backfill. 1803.4 Compacted Structural Fill .