222 W CASINO RD 2020-05-06 - Laserfiche WebLink

• Horizon Elementary School — Classroom Portable Installation NI II Construction SWPPP Narrative May 10, 2019 engineering p e origination point within this designated on-site wetland area. Along the eastern property boundary there is a steep slope with a rockery at the base of the slope located on the adjacent multifamily residential property. 6. SOILS According to USDA Natural Resources Conservation Service Web Soil Survey,the site consists of Alderwood-Urban land complex, 2 to 8 percent slopes. Hydrologically,this soil type is typically considered moderately well drained yielding suitable infiltration rates. The site is located in the Merrill &Ring Creek drainage basin,which ultimately discharges into Port Gardner Bay in the Puget Sound. 7.POTENTIAL EROSION PROBLEM AREAS The site is not within an erosion hazard or channel migration area, so there are not expected to be any significant erosion problems. Per the proposed contract documents,the contractor is to provide protection for soils to limit the exposure to erosion. The limitation of disturbance, adequate cover practices, seasonal work limitation, and runoff control are the most effective methods for reduction of turbidity in stormwater runoff. Any runoff that does occur will be directed to the existing storm facilities with installed inlet protection which then discharges to the existing detention pond. Areas that have not been permanently stabilized will be addressed using DOE-approved BMPs,per the construction documents. 8.CONSTRUCTION PHASING At this time, it is not expected that the project will be formally phased. The contractor is responsible for coordinating work of all subcontractors to keep the duration of site disturbance limited to the maximum extent possible. 9.CONSTRUCTION SCHEDULE Construction is expected to begin in July 2019 and be completed by September 2019. Construction is not expected to take place in the wet season, October 1st to April 30th. Should any wet weather conditions occur during construction,the contractor shall implement the de-watering procedures outlined in this SWPPP and applicable BMPs including,but not limited to C123, Plastic Covering; C121, Mulching; C122,Nets and Blankets; C126,Polyacrylamide for Soil Erosion Protection; C130, Surface Roughening. I 0.FINANCIAL/OWNERSHIP RESPONSIBILITIES This property is owned by Mukilteo School District. The accepted low bidder on the project will be responsible for posting a performance and payment bond with Everett School District, and thus will be the responsible party for any liability associated with erosion and sedimentation impact. I I.ENGINEERING CALCULATIONS A copy of any calculations performed during design of the project and relevant storm drainage modeling discussions is included in the project's Stormwater Drainage Report. Page 4