Sec. 22-539. Technical requirements.
(a) Slopes. The slope of cut or fill surfaces shall be in conformance with Roadway Design and Construction Specifications, but shall be no steeper than is safe for the soil and intended use. The need for slopes steeper than allowed in this subsection shall be avoided by the installation of approved retaining walls or an approved equivalent.
(b) Preparation of ground. Ground preparation shall be in conformance with Roadway Design and Construction Specifications. The ground surface shall be prepared to receive fill by removing vegetation, noncomplying fill, topsoil and other unsuitable materials. The ground shall be scarified to provide a bond with the new fill. Unsuitable fill soils are soils which, in the opinion of the city engineer, the civil engineer, the soils engineer, or the engineering geologist, are not competent to support other soil or fill, to support structures or to satisfactorily perform the other functions for which the soil is intended.
(c) Structure fill material. Detrimental amounts of organic material shall not be permitted in structural fills. Structural fill shall be in conformance with Roadway Design and Construction Specifications. The slope of fill surfaces shall be no steeper than is safe for the intended use.
(d) Retaining walls. All retaining walls shall be designed in accordance with the IBC and with good engineering practices. Walls higher than four feet shall be designed by a professional engineer, and plans submitted to the city for approval before construction. Any wood used in retaining walls shall be pressure treated in accordance with the building code, stamped or certified by an approved testing agency at the factory. Where the drainage flow is over the top of retaining walls, adequate protection shall be provided to prevent erosion of the soil on both sides of the wall.
(e) Compaction. All fills which support foundations and slabs on grade, including but not limited to floors, patios, porches, driveways, sidewalks, and fills for utility trenches, shall be compacted to the requirements identified in Roadway Design and Construction Specifications. It is not the intent of this article to control compaction of backfill around foundations, but rather to make it the responsibility of the builder to correct substantial subsidence which occurs within one year of the date of the issuance of the final certificate of occupancy. When substantial subsidence occurs within this year, it shall be the responsibility of the owner of the property to notify the builder and to temporarily prevent any further damage into the subsided area. The builder shall correct the subsidence within 30 days of written notice by the owner.
(f) Fine grading of single-family detached dwellings and single-family duplex dwellings.
(1) Generally. Fine grading shall be constructed per good engineering standards and in accordance with the approved final drainage study and/or geotechnical soils foundation report.
(2) Slope away from the building. The slope away from the building shall have a minimum grade of five percent for the first ten feet or property line, whichever is closer to the building, then two percent until the slope reaches the swale around the building. If physical obstructions or lot lines prohibit the ten feet of horizontal distance, a five percent slope shall be provided to an alternative method of diverting water away from the foundation. Such alternative method shall be reviewed and approved by the city engineer. Swales used for this purpose shall be sloped a minimum of two percent. In no condition shall the bottom of the swale at its highest point be less than six inches below the grade at the foundation of any adjacent structure. Impervious surfaces within ten feet of the building foundation shall be sloped a minimum of two percent away from the building.
(3) Swale around the unit. The swale around the unit shall have a minimum slope of two percent, unless otherwise recommended by a professional engineer and approved by the city engineer. Where it is intended that a swale be constructed straddling the property line, both halves of the swale must be constructed at the time the first building is completed. Where one side of the swale is considerably steeper than the other, the velocity effect of the water drainage off the steep side shall be taken into account, so as to prevent carrying the water over the other side. Swales having sharp change in direction shall be constructed with adequate turn radius and depth to prevent overflow. Where there is a large difference in elevation between one rear lot and the lot immediately behind, it may be desirable to place a lot line at either the top or the bottom of the swale. In this case, with prior approval of the City, the drainage swale running parallel to the bottom of the slope may be allowed on one lot. Obstructions of swales, such as fences, berms and walls, shall not be allowed within the swale unless adequate provisions have been made to allow passage of drainage.
(4) Grade adjacent to foundations and siding. The finish grade from the top of foundation or the bottom of the exterior siding material, whichever is lower, shall be in accordance with the IRC and IBC. In the event the manufacturer of the siding being installed recommends a more restrictive separation, the recommendation shall apply. Where there is no guidance, a minimum of six inches from bottom of siding to finish grade shall be provided.
(g) Fine grading of townhouse, condominium, and apartment projects.
(1) Generally. Fine grading shall be constructed per good engineering standards and in accordance with the approved final drainage study and/or geotechnical soils foundation report.
(2) Slope away from building. The slope away from the building shall have a minimum grade of five percent for the first ten feet, then two percent until the slope reaches the swale around the building. If physical obstructions or lot lines are within ten feet of horizontal distance from the building, a five percent slope shall be provided to an alternative method of diverting water away from the foundation. Such alternative method shall be reviewed and approved by the city engineer. Swales used for this purpose shall be sloped a minimum of two percent. In no condition shall the bottom of the swale at its highest point be less than six inches below the grade at the foundation of any adjacent structure. Impervious surfaces within ten feet of the building foundation shall be sloped a minimum of two percent away from the building.
(3) Swales around units. The swales around units shall be constructed in such a fashion as to carry the 100-year developed flow through the project without inundating any units. Swales shall be piped under walks and through curb heads so as not to carry drainage collected in swales over the top of sidewalks and over the top of curbs. Sidewalks shall not be constructed in the bottom of the swale unless otherwise specified in the approved final drainage study. Where sidewalks and swales parallel, the depth of flow in the swale for the design storm shall not exceed the top of the sidewalk.
(4) Grade adjacent to foundations and siding. The finish grade from the top of foundation or the bottom of the exterior siding material, whichever is lower, shall be in accordance with the IRC and IBC. If the manufacturer of the siding being installed recommends a more restrictive separation, the recommendation shall apply. Where there is no guidance, a minimum of six inches from bottom of siding to finish grade shall be provided.
(h) Fine grading of office, industrial, and retail commercial projects.
(1) Generally. Fine grading shall be constructed per good engineering standards in accordance with the approved final drainage study and/or geotechnical soils foundation report.
(2) Slopes away from building.
a. Minimums: The slope away from the building shall have a minimum grade of five percent for the first ten feet, then two percent until the slope reaches the swale round the building. If physical obstructions or lot lines are within the ten feet of horizontal distance from the building, a five percent slope shall be provided to an approved alternative method of diverting water away from the foundation. Swales used for this purpose shall be sloped a minimum of two percent. In no condition shall the bottom of the swale at its highest point be less than six inches below the grade at the foundation of any adjacent structure. Impervious surfaces within ten feet of the building foundation shall be sloped a minimum of two percent away from the building.
b. Exception: The slopes away from the building shall be per the recommendation of the soils engineer and per good engineering judgment.
(3) Grade adjacent to foundations and siding. The finish grade from the top of foundation or the bottom of the exterior siding material, whichever is lower, shall be in accordance with the IRC and IBC. In the event the manufacturer of the siding being installed recommends a more restrictive separation, the recommendation shall apply. Where there is no guidance, a minimum of six inches from bottom of siding to finish grade shall be provided.
(i) Grading within major drainageways. Rough and fine grading within major drainageways shall be per an approved set of construction plans and per the approved final drainage study. The requirements in chapter 70 of this Code shall also apply. (Ord. No. 2014-12, § 2, 5-12-2014; Ord. No. 2006-78, § 1(Exh. A), 1-8-2007)