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runoff will then exit the underground system via a bubbler and continue down the curb line at a rate less than or equal to existing rates. Runoff north of the high point on the east side of Capital Drive will be collected into a proposed catch basin and underground detention tank system that will discharge into an existing drainage ditch north of the site. Runoff on the west side of Capital Drive will drain at rates and locations that match existing conditions either to the western gutter line or the adjacent neighboring properties to the west. Private Roadway The applicant has proposed three discharge locations for the runoff of the proposed private roadway. The first discharge point is for the southern portion of the private roadway, which will be collected by catch basins or a trench drain and will enter an underground detention tank. From here, the runoff will then be discharged into the eastern gutter line south of the intersection via a bubbler. The second discharge point for the private roadway is located at the bottom of the conservation area between Lots 13 and 14. Runoff for this drainage basin will be collected into various underground storage tanks that will reduce the peak discharge rate and release into the eastern conservation area west of the Ribbon Trail, via level spreaders. The third discharge point is for runoff along the northern portion of the private roadway. This runoff will be collected into a series of underground storage tanks and discharged into an existing drainage ditch north of the proposed development site. Individual Lots For the lots bound by the new roadway improvements, upon treatment and flow control, drainage disposal will discharge onto the new roadways. For the lots draining away from the roadway to the east, disposal will be into level spreaders directed toward the existing park land to the east or north. These locations are consistent with existing drainage patterns. The proposed system has been designed so that discharge will occur at locations that mimic existing conditions and at rates that are less than or equal to existing rates. The results from infiltration testing confirms that the soils (Hydrologic Groups C and D) mapped at this site are not appropriate for on-site infiltration, which is why the applicant has proposed a series of underground mechanical forms of collection, detention, treatment, and discharge. Staff confirms that the proposed detention system demonstrates conceptual compliance with this standard and EC 9.6791(3)(b)(2), subject to a more detailed review for compliance with applicable standards during subsequent permit reviews. Based on these findings, this standard is met and will be further reviewed at the time of development. EC 9.6792 Stormwater Quality In order to reduce runoff pollution and mitigate the volume, duration, time of concentration, and rate of stormwater runoff from the development, the applicant must select, size, and locate stormwater quality facilities from the Stormwater Management Manual to treat the stormwater runoff from the proposed development. As noted previously, the application includes the widening of an existing public street as well as the construction of a private street. Capital Hill PUD (PDT 17-1) February 2018 49 Page 49