State Highway Access Manual - Geotechnical Guidance

PAVEMENT AND GEOTECHNICAL REPORT GUIDELINES

The Developer shall develop and submit a Final Pavement and Geotechnical Report for the project to the Office of Materials Technology. The report shall contain the Developer’s plans for addressing all soils, rock, groundwater, existing pavement, and new pavement issues on the project impacting Administration highway property. A geotechnical engineer, who is a registered professional engineer, and who shall also seal the Final Pavement and Geotechnical Report, shall supervise the work. The Developer shall obtain all soils and pavement information necessary to properly complete the Final Pavement and Geotechnical Report, and the design and construction of the project. The Developer shall perform borings, sampling, in-situ and laboratory testing, analysis, and design required for this purpose. All subsurface investigations, including sampling and laboratory testing, shall be performed in accordance with Maryland State Highway Administration Standard Specifications for Subsurface Explorations. If a specialized test is not covered by these specifications, then testing shall be performed in accordance with the latest AASHTO Manual on Subsurface Investigations, AASHTO Standards and ASTM Standards. The existing structural capacity of all impacted shall be determined through in field non-destructive testing either a formal visual condition survey or deflection testing and/or pavement borings. Laboratory testing shall be performed in an AMRL or Maryland SHA certified laboratory. The recommendations contained in the Final Pavement and Geotechnical Report shall be incorporated into the plans and specifications developed for the project. The Developer shall be responsible for utility clearance and any traffic control required for his investigation. The appropriate District Office shall approve the Developer’s Maintenance of Traffic Plan for the subsurface and pavement investigation. Any investigative methods that pose a hazard to the general traveling public shall not be used. Any borings taken in roadway or shoulder areas shall be backfilled in kind with material before the area is re-opened to traffic.

The following shall be included and addressed in the Final Pavement and Geotechnical Report. Additionally, other items deemed important by the Developer shall also be included.

  • a. Soil, rock, soil moisture and groundwater conditions;
  • b. Existing functional and structural condition of all impacted roadway surfaces within project limits;
  • c. Traffic data used for pavement design. Including, but not limited to the following: Average daily traffic (ADT), percent FHWA Class 5 trucks or greater, directional distribution, truck weight information (truck factor), and lane distribution;
  • d. Subgrade strength used for design of pavements expressed in terms of resilient modulus, CBR values are acceptable;
  • e. Topsoil, pH adjustment and nutrient requirements that will allow vegetative growth to be established on slopes;
  • f. The existing pavement structure of all materials above subgrade and the subgrade soil classification and moisture conditions of all roadways and shoulders within the project limits. Existing roadways and shoulders considered to be impacted include the following: pavement resurfacing areas, pavement areas adjacent to widening locations, pavement reconstruction areas, and any and every pavement location subjected to traffic during construction under the maintenance of traffic plan;
  • g. Specifications for all materials to be used in embankment or as backfill;
  • h. The suitability of excavated material for re-use as embankment or trench backfill on the project;
  • i. Analysis and design of all cut slopes including methods proposed for use in controlling groundwater seepage, erosion and surficial instability;
  • j. Analysis and design of all embankments, including internal drainage design of side hill fills and methods proposed for use in controlling erosion and surficial instability;
  • k. Slope stability analyses shall be performed for all slopes in excess of 12 ft in height. Foundation soils and proposed storm water management practices shall be considered when determining the Factor of Safety. If the stability analysis for a slope results in a Factor of Safety of less than 1.3, the report shall identify modifications to the slope to provide a minimum Factor of Safety of 1.3;
  • l. The methods proposed for dealing with unstable embankment foundations;
  • m. Methods of subgrade preparation including the methods proposed for dealing with areas of unstable subgrade;
  • n. Ability of native soils to provide vertical drainage;
  • o. Proposed methods for dealing with groundwater and existing subsurface drainage systems including existing pavement edge drain (longitudinal underdrain) systems;
  • p. Geotextiles to be used in subsurface drainage, separation, and permanent erosion control applications;
  • q. If rock is encountered, proposed methods of rock excavation (ie. blasting or non-blasting) and any necessary safety requirements;
  • n. Proposed methods for dealing with unusual geologic or man-made conditions particular to the area (ie. sinkholes, contaminated soils, underground storage tanks, etc.);
  • r. Pre-rehabilitation repairs to existing roadway prior to final resurfacing, i.e. full-depth and partial-depth patching, grinding, milling, etc.;
  • s. Pavement designs for existing and new roadways. Designs shall include material selection and thickness.
  • t. Structural capacity of shoulders to support maintenance of traffic (MOT) and/or MOT pavement sections;
  • u. Proposed method for dealing with any significant change in the existing pavement cross slope or elevation;
  • v. Comments regarding pavement drainage;

The Final Pavement and Geotechnical Report for any portion of the project shall be submitted with or before construction for earthwork grading for that portion of the project.

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