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1 <br /> 1 <br /> i Addendum to Storm Drainage Report <br /> ' 5. Storm Drain/Roof Drain System: This design proposes that all <br /> rooftop drainage be modified to directly connect to the new <br /> proposed storm drain conveyance system. Construction of the <br /> new storm drain along the west (low) side of the building will <br /> ' cause re-paving of the driveway.Porous pavement will NOT be <br /> replaced above the new storm drain system. Instead,typical <br /> ' impervious pavement will be placed above the new storm drain <br /> system. Drainage from this area will be directed to the new <br /> conveyance system along the west half of the site, then to the <br /> infiltration trench on the north side of the building. The storm <br /> ' pipe size and slope was sized using the full developed <br /> condition basin area. <br /> 6. Roof Drains: As stated, WHPacific recommends all rooftop <br /> ' drainage be directed to the new storm drain conveyance <br /> system. The roof drains along the front should be re-connected <br /> to a roof drain system along the front of the building and <br /> ' directed to the new storm drain system. The roof drain at the <br /> NE corner of the building should outfall onto the parking lot <br /> pavement instead of in the landscaped island. The center roof <br /> drains on the north side of the building that currently outfall <br /> ' onto the impervious pavement may be left in their present <br /> condition. The two roof drains at the extreme west side of the <br /> building that outfall onto the porous pavement should be <br /> ' directed to the storm drain system. <br /> 7. The east side porous pavement will have to be re-paved or <br /> sealed to eliminate its infiltrating characteristics. <br /> ' 8. Irrigation lines on the west side and immediately adjacent to <br /> the building should be disconnected and drought tolerant <br /> species should be replaced <br /> Maintenance and WHPacific recommends that the maintenance for the pre-settling <br /> Operation tank and infiltration trench should be the same as a detention vault <br /> Requirementsand infiltration trench. All erosion and sediment features will be <br /> inspected regularly throughout construction and will be repaired, <br /> ' maintained or supplemented with further erosion control items as <br /> needed. <br /> 1 <br /> Seaway Center Lot 2A—Storm Drainage Addendum P:iErotic Tool Weldi g103S1231DesigoiReporut35123-storm ADDENDUW.doc <br /> WHPac/Ic,Inc. December 2,2009/Page 3 <br />