12815 19TH AVE SE 2022-05-06 - Laserfiche WebLink

A summary of the Project Drainage Area (PDA) is as shown in Table 1 below: TABLE 1 -- TOTAL PROJECT DRAINAGE AREA Area Description Proposed Surface ID SF Ac Existing School Property Area New NW Parking Lot Access from 127th PL SE & New & Replaced New Entry from SR-527 Surface/Grading 'A 71,683 1.65 Restriping, Sidewalk & Curbing in West & Remaining School Property Area Excluding Area B3 South Parking Lots C 412,003 9.46 483,686 11.10 Area Outside Lot 7 Property Lines & within School New & Replaced Property Surface/Grading B3 2,276 1 0.05 485,962 11.16 Future Lot 7 Area Lot 7 To Be Acquired by EPS for Access from 129th Place SE New & Replaced B 10,131 0.23 Area Outside Lot 7 Property Lines w/in ROW New & Replaced B2 1,509 0.03 11,640 0.27 Total Project Drainage Area (PDA) 497,602 11.42 1. Per Area Takeoff Calculations 11/25/02 Existing Offsite and Site Discharges ❖ Offsite — Offsite flows from upstream areas to the south pass through the School Property via an existing 12-inch pipe under the playfields to the North. See Section 3 — Upstream Analysis for detailed description of these conditions. ❖ Northwest — The western half of the School Property site discharges via catch basins and sheet flow into the SR-527 conveyance system. See Section 4 — Downstream Analysis ❖ Northeast — The eastern half of the School Property and Lot 7 Area discharges via catch basins, sheet flow and subdrainage to a 12-inch pipe at the north property'line that extends through the Hershclip subdivision to an existing detention pond. Targeted Drainage Report for Everett Public Schools Section 2 — Risk & Erosion Control Silver Lake Elementary Parking Lot Expansion January 6, 2003 By: Perteet Engineering Page 3 of 7