Sec. 7-40. – LOT DRAINAGE PLAN
Sec. 7-40-1. – Purpose
The purpose of this section is to ensure that development on individual residential lots created prior to the adoption of stormwater regulations does not result in adverse stormwater impacts, such as flooding, erosion, or nuisance drainage, and that proper grading and drainage infrastructure are incorporated into site design. Stormwater runoff shall not be increased, or in a manner that causes flooding or erosion, and the alteration of existing drainage patterns shall not obstruct drainage flow.
Sec. 7-40-2. – Applicability
A drainage plan shall be required for all new single-family & two-family residential construction on standalone lots, and for projects on residentially zoned lots that introduce more than 400 square feet of new impervious surface.
For purposes of this section, a standalone lot is a lot of record that is not covered by an approved stormwater management plan and is not subject to State or County stormwater permitting requirements. The issuance of an Erosion and Sediment Control permit alone shall not be construed to exempt a lot from the requirement to submit a lot drainage plan under this section.
Sec. 7-40-3. – Plan Submission Requirements
A drainage plan, to be approved by the City’s Stormwater Department, shall be submitted as part of the building permit application. An engineered drainage plan shall not be required unless the City’s Stormwater Engineer determines that site specific conditions warrant preparation of a plan by a licensed professional engineer. Drainage plans shall include the following information:
(A) .Site Information
a. Lot address and parcel ID number;
b. Property lines, easements, and setback lines;
c. Location and footprint of proposed and existing structures;
d. Location and dimensions of driveways, walkways, patios, and other impervious areas;
e. North arrow and scale;
f. Total square footage and percentage of site comprised of impervious surfaces;
g. Existing and proposed ground elevations, shown via spot elevations or contour lines at 2-foot intervals.
(B) Drainage Features
a. Existing and proposed stormwater flow directions;
b. Location, dimensions, and invert(s) of proposed drainage infrastructure, including:
i. Graded swales;
ii. Culverts;
iii. Ditches;
iv. Inlets, where applicable;
c. Points of discharge or tie-in to public or natural drainage systems;
d. Location and spot elevation(s) of any low points or areas of potential water ponding.
(C) Erosion and Sediment Control
a. Temporary erosion control measures shall be installed and maintained during construction, including but not limited to:
i. Silt fencing: Shall be installed at the perimeter of construction sites, around disturbed slopes and stockpiles, and at all existing and proposed stormwater features to capture sediment before it can leave the site. Installation shall happen before major soil disturbance occurs and shall continue until the site is permanently stabilized. Install silt fence on contour, 18 to 24 inches in height, trenched six (6) inches wide by six (6) inches deep and posts set at six (6) feet on center (4 feet on center without wire backing). Maintain regularly and remove sediment when it reaches one-third the height of the fence.
ii. Inlet protection: Provide inlet protection at all new or existing drains using pine bags, gravel bags, block and gravel, or approved inserts with overflow. Maintain regularly and clean when sediment reaches one-third of capacity.
iii. Construction entrance stabilization: Construct stabilized entrance a minimum of 20 feet long by 10 feet wide with 6 inches thick of 2 to 3 inch washed stone placed over geotextile fabric. Sweep streets daily or as needed to remove tracked sediment (do not wash into inlets).