#13 - Landscaping Requirements Top Soil - New Text Color

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Chapter 153 Water Resource Management Adopted 6/28/2022 Page 20 of 34 improvements as updated from time to time. The treatment achieved by these projects will offset the treatment that was not achieved on the permitted development. (3)Credit Banking. Water quality treatment credit and volume reduction credit provided in excess of the treatment requirement may be banked for use on another project. Excess banked credit amounts shall not exceed stormwater credit awarded for the BMP by the county. The county must review and approve all banking credits generated. (E)Rate control standard. (1)Peak rates. The peak rates shall not increase from existing conditions for the 2-, 10-, 100-year storm events, and the 100-year, 10-day snowmelt event. Peak rates shall be calculated using Atlas 14 precipitation depths and storm distributions. (2)Conveyance System. At a minimum, the storm sewer conveyance system shall be designed for a 10- year, 24-hour storm event. The pond and pond outlet structure shall handle the 100-year, 24-hour storm event. (F)Water quality standard. (1)Total Phosphorus (TP) Removal Standards. The stormwater management plan must remove 90% of the TP generated by the site under developed conditions. (2)Total Suspended Solids (TSS) Removal Standards. The stormwater management plan must remove 90% of the TSS generated by the site under developed conditions. (3)BMP Sizing. Treatment areas must be sized appropriately for the area draining to the feature. (G)Volume Control Standards (1)Volume Control Standard. The stormwater management plan must provide volume control for: (a)1.0 inches from the impervious surface for unconstrained sites. (b)0.5 inches from the impervious surface for constrained sites. (2)BMP Sizing. Volume control areas must be sized appropriately for the area draining to the feature. (3)Volume Control Standard for Constrained Sites. Specific site conditions may make volume control difficult, undesirable, or impossible. If these conditions are present, the site may qualify as “constrained,” subject to county review and determination. Some of these conditions are listed in Table 1. The applicant may also submit a request to the County for Constrained Site eligibility for site conditions not listed below. All requests for constrained site eligibility shall indicate the specific site conditions present and include a grading plan, utility plan and the submittal requirement listed in Table 1. Table 1. Constrained Site Conditions Type Specific Site Condition Volume Reduction Limitation Submittal Requirement Potential Potential stormwater Infiltration