10725 19TH AVE SE 2023-04-07 - Laserfiche WebLink

3. Downspout Dispersion Systems in accordance with BMP T5.10B—This BMP is not feasible due to not meeting the minimum requirement of 25 feet of flowpath. 4. Perforated Stub-out Connections in accordance with BMP T5.10C—This BMP was considered not feasible as well due to site constrains. The connection from the stub- out to catch basins it constrained and it is not preferable to add ground water in the vicinity of detention facility. Other Hard Surfaces: 1. Full Dispersion in accordance with BMP T5.30—This BMP is considered not feasible on this project due to site limitation and soils conditions. 2. Permeable pavement in accordance with BMP T5.15—This BMP is considered to be not feasible due site limitation, setbacks from structures and underground utilities and due to low permeable layer would create saturated conditions within one foot of the bottom of the lowest gravel base course. See project Soil Report. 3. Bioretention - This BMP was considered not feasible due the the measured native soil infiltration rate of less than 0.3 in/hour, site constrains and limited space availability to construct such a facility. 4. Sheet Flow Dispersion in accordance with BMP T5.12 or Concentrated Flow Dispersion in accordance with BMP T5.11 - BMPs T5.11 is considered not feasible due to the required vegetated flow path of 25 feet or more cannot be provided and BMPs T5.12 is not considered feasible due to the required 10-foot flow path per every 20 feet of contributing surface flow path cannot be provided. Small amount of permeable pavers will be used as a voluntary measure and will be modeled as landscape. BMP T5.13 Post-Construction Soil Quality and Depth is achieved by implementing best management practice. Soils that have been disturbed, will be amended according to the following procedures: a. Scarify subsoil to a depth of one foot. b. In planting beds, will place three inches of compost and till in to an eight-inch depth. c. In turf areas, will place two inches of compost and till in to an eight-inch depth. d. Apply two to four inches of arborist wood chip, coarse bark mulch, or compost mulch to planting beds after final planting. Undisturbed soils will be protected from compaction during construction. Preserve native soils by stockpiling site duff and topsoils and reapply after grading and construction. Stormwater from driveway and walkways will sheet flow toward catch basins and connect the runoff to an onsite detention facility. Pipe drains will collect the downspout runoff from the new structures and connect the runoff to an onsite detention facility. The location and types of BMPs selected are shown in the project site/drainage plans.