STORMWATER FIRST FLUSH TREATMENT

FOR INTERNATIONAL AIRPORT FACILITY

An innovative design was developed and implemented to divert and capture contaminated stormwater runoff from approximately 50 acres of airport aprons. The contributing runoff areas were identified and the resulting flows were determined for a variety of rainfall events. A unique headwall/diversion structure was designed for the 72” sewer to divert, capture and treat the “first flush” of stormwater (representing approximately 0.25" rainfall). The hydraulic diversion was designed to be passive and self-cleaning, not requiring any human operation or maintenance. The first flush was diverted from an impaired stream to the existing de-icing fluid treatment system. The remaining, non-contaminated, stormwater was allowed to discharge freely to the existing stormwater outfall.

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Stormwater Management and Treatment

1. Overview
   
   

2. Stormwater Management and Treatment Experience

STORMWATER TREATMENT UNIT DESIGN

A treatment unit was custom designed for a plastics extrusion company to remove fugitive pellets from stormwater. The unit was a gravity separator and screen sized based on the polymer pellet diameters and densities used at the facility. The treatment unit was designed as a below grade concrete system that operated on the existing stormwater drainage system grades. It has successfully operated for years.

DESIGN OF COMPREHENSIVE SITE DRAINAGE SYSTEM AND STORMWATER CONTAINMENT AND TREATMENT FACILITIES AT COMMERCIAL HAZARDOUS WASTE DISPOSAL FACILITY

Phoenix developed detailed design drawings and specifications for stormwater collection and management at this 1300 acre facility. The design basis was a 100-yr storm. Facilities contributing stormwater included a landfill, outdoor waste container storage, process chemical/waste loading and unloading areas, and equipment decontamination facilities. Drainage structures and stormwater conveyances were designed to minimize stormwater contamination. The physical-chemical treatment facilities consisted of grit removal, coagulation, sedimentation, filtration, and carbon adsorption. Containment facilities included secondary containment around tank farm, outdoor waste bin storage areas, and treatment facilities. The first flush (1") of stormwater from outside storage areas was also automatically collected. Phoenix performed resident engineering during construction.