Grading and Drainage Requirements

This page outlines general requirements for grading and drainage on residential lots and explains how to demonstrate compliance with these requirements on building plans.

IS A GRADING AND DRAINAGE PLAN REQUIRED?

A grading and drainage plan must be submitted with each building permit application. Demonstration of compliance is required for permit approval.

Before construction can begin, a site must be graded to guide the surface water runoff away from the building(s) on the site. Grading and drainage plans demonstrate how runoff will be captured, redirected, and removed from the site, and can also influence how building heights are calculated. It is important that this aspect of site design is factored into rebuilding during the initial design stages to address the unique conditions of each site.

WHAT ARE THE GENERAL REQUIREMENTS FOR GRADING AND DRAINAGE?

• A minimum 10% slope away from the building is required within first 5’ of the foundation, with minimum 2% slope required beyond 5’.
• A minimum 2% slope is required in swales.
• Drainage plans must conform to existing grading in adjacent lots ( already developed).
• Drainage may not be directed over adjacent sidewalks. If necessary, chase drains may be required to avoid adverse impacts on public improvements and ensure compliance with Section 11-1-40 (c) of the Town Code.
• Driveway slope may not exceed 10%.

WHAT ARE THE PLAN REQUIREMENTS FOR GRADING AND DRAINAGE?

A site-specific plan for each house is required. Drawings shall be based on engineer’s scale (1” = 10’, 20’, 30’, etc.) and include:

• Existing and proposed corner grade elevations, grade high points, swales, and flow arrows with slope percentages
• Foundation elevation
• Top of slab for garages and walkouts
• Back of curb or sidewalk elevation
• Grading and drainage may be included on the plot plan or provided separately.

The following illustrations on the following pages represent a range of grading types for different site conditions