1616 126TH ST SE 2025-01-29 - Laserfiche WebLink

MR4: Preservation of Natural Drainage Systems and Outfalls Same before and after MR5: On-Site Stormwater Management Stormwater management from roofs: Full dispersion is not possible due to the site already being developed. Per attached soils report, depth to water table is 18-36". My testing found ground water around 24". Next to consider is the downspout full infiltration system and the rain garden. Both are not feasible due to not being able to constructed at the required depth under each and still be a minimum above the water table. Next is downspout diversion and is the most feasible.The roof is divided into basically 6 roof draining sections. Five of the six are less than 700 sq ft.Three of them will drain onto splash blocks and then disperse onto 50+' of established lawn and the fourth onto a strip of established grass and onto an existing gravel pad.The parking pad next to the garage will be shortened so it does not extend into the 10' strip of lawn at the south end of the property.The fifth, at only 342 sq ft., will drain onto a small section of driveway, then onto an established grass strip. The sixth section, at 964 sq ft.,will require two downspouts.These will be directed into a new mulched landscape area north of the new driveway to filter the runoff. Stormwater management from driveway: We will be adding 1354 sq ft of new driveway, while removing and landscaping 370 sq ft of existing driveway. As stated previously, full dispersion is not feasible.The high water table does not allow for the proper depth for installation of either permeable pavement or a rain garden. Next to consider is sheet flow dispersion.This will be the feasible solution.There is a slight grade of the driveway away from the house. Runoff will drain onto a 10' strip of established lawn that runs the entire length of the west property line. Existing lawn will be preserved as much as possible and, if impacted,will be restored with amended material and new lawn to aid in the absorption of runoff. The new landscape area will installed using amended or imported topsoil with sufficient organic content, then planted and mulched.