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~ 1 RIBIYNi AND ASSOCIATES INC. EHGIH!ERS - PLAIIoWlS - SURVEYORS Robayna and Associates, Inc. City of Sunny Isles Beach RFQ No. 11-11-02 F 1 , ) grade rework is needed must be defined to quantify the necessary roadway material quantities needed during construction to repair the road properly. While preparing plans for the roadway coordination will be made with Miami-Dade Public Works and Waste Management Department Highway Division as needed and FDOT and the City to define any requirements which may be needed so that permitting goes smoothly. Roadway design will follow ASSHTO, FDOT and Miami-Dade County Standards. r I It may be the intent of the City to upgrade its traffic calming method at the speed bumps to speed cushions or a table. This would be discussed with the City at the appropriate time in the design. r 1 J D,'aina{!e Approach I r 1 I I I 1'1 I Robayna and Associates Inc. will provide stormwater management design services for l741h Street. An exhaustive project approach is crucial in successfully designing and implementing upgrades for the storm water management systems. . . Given the as-built information provided by the City and the information collected in the field a preliminary model will be developed for the roadway and contributing areas. Given the roadway profile collected in the topographic survey the usefulness of each existing drainage inlet will be determined. At this time it would be necessary to determine whether the use of exfiltration trench, drainage wells, or a combination of them would be appropriate. For an explanation of each method please read the following subsections. With the treatment system decided upon that best serves the City and the Residents we would continue to develop the design plans and drainage computer model. ~ l , I During analysis we will define for the 5-year design storm if any elements need to be upgraded or kept. Reusing elements within the existing drainage system is crucial for the project due to the substantial savings that it can provide. , I Water Quality: The FDEP, SFWMD,PERA and the City of Sunny Isles Beach require that all projects meet state water quality standards, as set forth in Chapter 17-302, Florida Administrative Code CF AC). Because it has been well documented that the first inch of runoff generated by a storm event, also known as the first flush, contains over 90 percent of the total pollutants conveyed by stormwater runoff. Approximately 90 percent of the annual storm events in South Florida are less than one inch of rainfall. The state water quality standards are presumed to be met if the volume from the first flush is retained in the storm water management system. Projects within the PERA jurisdiction are required to retain 100 percent of the first one inch of runoff from the drainage basin within the stormwater management system. The methodology for estimating this volume is outlined in PERA's "Policy for Design of Drainage Structures." All projects in Miami-Dade County are required to retain the larger of the water quality volume as determined by either the SFWMD or PERA criteria. However, PERA's criteria typically generates larger volumes than SFWMD. French Drains: In Miami-Dade County, French drains, or exfiItration trenches, are the most widely used, when in- situ soil hydraulic conductivity and/or hydraulic head is sufficient to promote exfiItration of the required storm water quality volume. As required by SFWMD, PERA and FDOT, French drains must be designed in accordance with the following design criteria and parameters: 56