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I I 27th AVENUE STORMWATER RETROFIT PROJECT MONITORING IHIGHLIGHTS: ■ Innovative BMP development • Grant funding-319(h)EPA • Construction document preparation • Multi-BMP approach I C • Environmental Resource Permit • Water quality monitoring and analysis c. • Construction administration ■ Circulation study of receiving water IThe 27th Avenue stormwater retrofit project was construct- t tilt, l;'W.r j. s. • _ . ed to treat stormwater from a 20-acre urban/ residential ar- rIlif ; ,�,c d i:_ li e9.itrA I '.' ea along 27th Avenue in New Smyrna Beach, Florida. His- rill i; l�' ?`4 19 1`i xu „t, °d — 11 r 1 torically, stormwater from the area discharged directly into 4 )Er 4- ---la ' 'c:. .x;4;; ` '�} the Indian River Lagoon (IRL). To reduce pollutant load- " - ings of suspended solids and nutrients to the IRL, the city ! -i contracted ECT to design the stormwater retrofit project in 7 H a I- ;:..,t,„:1 `=y 2006. ECT used innovative methods to deal with the high- !_ 'i i,s i _ water table, low ground surface elevations, and tidal condi- i ,,S.,.-1111 r I I. t 1 I tions in the receiving water body. The primary objective = tt—z : was to reduce non-point source pollution to the IRL by re- . , r ;ifacaaa•-` ° taining stormwater in the upland zone, immobilizing con- 1 taminates, allowing suspended solids to settle out. This A typical sampler setup in 27th Avenue maximized infiltration, thereby mimicking the natural hy- stormwater monitorino site drologic path of rainfall to groundwater, and ultimately to the estuary through seepage. I The retrofit project was composed of two components, a sediment pond with a trash collection screen and a bermed offline retention area. Floating debris and trash are collected by the trash screen and sed- I iment is captured in the pond. When the water level in the pond reaches an elevation of 4.0 ft, water overflows to the bermed offline retention area through an inlet control structure and a 15-inch HDPE pipe. A flap gate was installed to prevent backflow to the sediment pond. The pipe is buried under a I multi-use trail that separates the pond and the retention area. The bermed retention area was designed to take advantage of the existing site topography, minimize clearing, and preserve as much natural hab- itat as possible. IAfter construction, ECT assisted the city with the quality assurance project plan (QAPP) and per- formed water quality monitoring. ECT used ISCO®Avalanche Automatic Samplers to collect samples at the inflow and outflow pipes. The samplers were enabled by a rain event greater than 0.25 inch. A I total of seven storm events were sampled between 2007-2008. For each storm event, composite sam- ples were collected for a period of 2 hours. The samples were analyzed by a NELAC-certified analyti- cal laboratory. Results showed that the treatment efficiency of the system was 89 percent. I I IEC/EC7 PROJECT PROFILE e) Y.^FIPOISCIPW2lWATfliWROFIIFSUIWSB-3JIHAVE DOC-030912