Morrisville Engineering, Design, and Construction Manual - July 2016

Section 3: Earthwork 3.1 Fill Placement 3.2.1 General

Section 3: Earthwork

3.1. FILL PLACEMENT The placement of any fill material must be conducted under the observation of a qualified licensed geotechnical engineer. Upon completion of the earthwork activities, the Town must be provided with a final grading report certifying the type of fill material and its proper placement, including the corresponding compaction test results and field reports.

3.2. GRADING DESIGN

General

3.2.1.

An adequate maintainable slope must be provided to prevent standing water from collecting along any flow path.

Construction Plans must show sufficient spot elevations on the grading plan to:

1. Ensure proper drainage from the building to the curb line, from the curb line to the gutter line, and along the gutter line to the drainage inlets; 2. Ensure that stormwater does not enter waste collection areas requiring a drain connection to the sanitary sewer system;

3.

Verify Building Code compliance; and

4. Confirm compliance with Americans with Disabilities Act (ADA) requirements, including those in the State Building Code and, where applicable, the stricter limits defined in the Federal rules and regulations.

Impervious Areas

3.2.2.

The minimum allowed slope for an impervious area is 1%, except where building codes are more stringent (e.g., a minimum 2% slope away from residential structures). The maximum allowed slope for an impervious area is 10%. This maximum also applies to driveway slopes. See Section 4.7, Driveways.

Pervious Areas

3.2.3.

The minimum allowed slope for a pervious area is 2%. Refer to Section 3.2.6, Cut and Fill Slopes, for standards pertaining to slopes greater than the minimum.

Street and Other Accessway Construction

3.2.4.

Excavation of Triassic Materials

1. In instances where Triassic “shale”, “mud rock”, or other compressible immature Triassic sedimentary rock-like material is encountered and must be disturbed within the limits of the street paving section or designated fire lanes by grading of the street or installation of water, sewer, storm drainage lines, structures, or other utility service lines, that material shall be excavated and permanently removed from street rights-of-way, access easements or designated fire lanes. 2. Suitable replacement material as determined by the Geotechnical Engineer of Record shall be utilized to achieve the final section and/or backfilled ditch. 3. No such Triassic material shall be utilized as fill or backfill within the street rights-of-way, access easements, or designated fire lanes unless site specific geotechnical reports and recommendations from a certified design professional are proposed and approved as an Alternative Standard in accordance with Section 1.3.3, Alternative Standards. The certified design professional must be able to demonstrate that the un-acceptable material will not cause premature failure of the

January 2016

Morrisville, NC

Page 8

Engineering, Design, and Construction Manual