17.18.050 Slope Special Requirements

In order to appropriately evaluate and protect against any potential impacts to adjacent properties and city infrastructure and services, the following special requirements apply to all development in the city. 1. Based on a contour map at intervals no greater than ten (10) feet, a slope calculation is required for the average slope of the site, subdivision, or sub-area prior to any grading, utilizing the following formula: S = .00229 (I) (L) / A Where: S is the average slope I is the contour interval in feet L is the summation in length in feet of all contour lines A is the total number of acres Alternate methods of calculation may be approved by the City Engineer. 2. If the calculation results in an average slope exceeding 15%, then additional standards and evaluations shall be placed on the subdivision including: a. As overall slope increases, density shall decrease. i. Slopes greater than 15% and up to and including 20% shall have no more than one (1) unit per acre. ii. Slopes greater than 20% and up to and including 25% shall have no more than one (1) unit for every two (2) acres. iii. Slopes greater than 25% and up to and including 30% shall have no more than one (1) unit for every five (5) acres. iv. No development is allowed on slopes greater than 30%. b. As slope increases, allowable impermeable surfaces shall decrease. i. For lots with slopes greater than 15% and up to and including 20%, not more than 25% of the lot shall be impermeable surfaces. ii. For lots with slopes greater than 20% and up to and including 25%, not more than 15% of the lot shall be impermeable surfaces. iii. For lots with slopes of greater than 25% and up to and including 30%, not more than 7.5% of the lot shall be impermeable surfaces. c. Either by natural topography or mass grading, all lots having an average slope exceeding 15% shall have a reasonable building area (defined as land with a slope less than 15%) of at least 7,500 square feet with a minimum dimension of fifty (50) feet. d. Additional fire safety/emergency vehicle related reviews may be required including but not limited to, access, fire hydrants, driveway (grades, lengths, and widths), road surfacing, turnarounds, building distances from the street, and so on. e. Spark arresters shall be installed on all indoor and outdoor fireplaces. f. A grading and drainage plan shall be submitted with the subdivision improvement drawings. The plan shall clearly identify how the developer intends on grading each lot to ensure that storm water runoff is either directed to the fronting or intersection roadways or collected and conveyed in such a manner that it will not have an adverse effect on adjacent or neighboring properties. Building areas and elevations, cuts and fills, drainage swales, slopes, and proposed drainage easements shall be minimum design elements and shall assure reasonable access and safety. g. Existing vegetation shall be preserved to the greatest extent possible. A map of areas to be disturbed shall be submitted. Disturbed areas shall be revegetated within two months, in accordance with an approved re-vegetation plan. Rock outcropping shall be avoided. 3. For any portions of one-half (1/2) acre or greater of the subdivision that have slopes over 15%, the appropriate design and safety provisions above (2b thru g) shall apply to the development of sub-areas within the subdivision where such slopes are found. (Ord.2026-10, dated 5/12/26; prior code: Ord.2008-5, dated 4/8/08)