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J110.4 Modification of Slope Location. The building official may approve alternate setbacks. The building official may require an investigation and recommendation by a qualified engineer or engineering geologist to demonstrate that the intent of this section has been satisfied. SECTION J111-DRAINAGE AND TERRACING J111.1 General. Unless otherwise indicated on the approved grading plan, drainage facilities and terracing shall conform to the provisions of this section for cut or fill slopes steeper than 1 unit vertical in 3 units horizontal (33.3% slope). Storm water shall meet the requirements of the California Regional Water Quality Control Board San Francisco Bay Region Alameda Countywide National Pollution Discharge Elimination System (NPDES) Municipal Stormwater Permit Order R2-2003-0021 and the latest City of Pleasanton stormwater ordinance in effect at time of plan submittal. J111.2 Terrace. Terraces at least 6 feet (1829mm) in width shall be established at not more than 30-foot (9144 mm) vertical intervals on all cut or fill slopes to control surface drainage and debris except that where only one terrace is required, it shall be at midheight. For cut or fill slopes greater than 60 feet (18 288 mm) and up to 120 feet (36 576 mm) in vertical height, one terrace at approximately midheight shall be 12 feet (3658 mm) in width. Terrace widths and spacing for cut and fill slopes greater than 120 feet (36 576 mm) in height shall be designed by the civil engineer and approved by the building official. Suitable access shall be provided to permit proper cleaning and maintenance. Swales or ditches on terraces shall have a minimum gradient of 5 percent and must be paved with reinforced concrete not less than 3 inches (76 mm) in thickness or an approved equal paving. They shall have a minimum depth at the deepest point of 1 foot (305 mm) and a minimum paved width of 5 feet (1524 mm). A single run of swale or ditch shall not collect runoff from a tributary area exceeding 13,500 square feet (1254.2 m2) (projected) without discharging into a down drain. J111.3 Subsurface Drainage. Cut and fill slopes shall be provided with subsurface drainage as necessary for stability. J111.4 Disposal. All drainage facilities shall be designed to carry waters to the nearest practicable drainage way approved by the building official or other appropriate jurisdiction as a safe place to deposit such waters. Erosion of ground in the area of discharge shall be prevented by installation of non-erosive down- drains or other devices. 65