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Home My WebLink AboutIII. - Tab 3 - Site Utility Study• • • • 1770 NORTH BAYSHORE DRIVE MAJOR USE SPECIAL PERMIT SITE UTILITY STUDY Prepared for: On the Park Properties, LLC Prepared by: Consulting Engineering and Science, Inc, May 15, 2006 • • • 1. General A. Protect Location and Size: The project is located along the west side of North Bayshore Drive in the City of Miami; bounded on the north by N.E. 18th Street; bounded on the west by N.E. 4th Avenue; and, bounded on the south by privately held property. An existing 10-foot wide public alley runs through the site in a north -south direction. The site has a gross lot area of 117,663 square feet, or 2.70 acres; and, a net lot area of 56,641 square feet, or 1.30 acres. The site has approximately 190 feet of frontage along North Bayshore Drive; approximately 391 feet of frontage along N.E. 18th Street; and, approximately 96 feet of frontage along N.E. 4th Avenue. The land on which the project is proposed consists of four (4) parcels, identified as Miami -Dade County tax folio numbers 01-3231- 003-0560/0620/0630/0640. A legal description of the property is as follows: Lot 1, 2, 3 and 4, Block 8, of MIRAMAR, according to the plat thereof, as recorded in Plat Book 5, at Page 4, of the Public Records of Miami -Dade County, Florida. The site is presently occupied by four (4) multi -story residential buildings containing a total of 114 residential living units. B. The proposed project build -out will be as follows: Residential: Retail: 648 units 10,000 sf Net Lot Area 56,641 sf, or 1.30 acres Gross Lot Area 117,663 sf, or 2.70 acres Construction will consist of two (2) residential towers of 43 and 47 floors, including interior parking and ground level retail. -1- • • • • 2. Drainage A. Drainage Area Upon development, approximately 90 per cent of the site will be impervious and approximately 10 per cent of the site will be pervious. Stormwater runoff will consist of rainfall from the building roofs, driveways, walkways, landscape areas and one-third of the vertical building surfaces. The coefficient of runoff is calculated as follows: 90.0% (impervious) X 0.90 + 10.0% (pervious) x 0.20 Overall coefficient 0.81 0.02 0.83 B. Existing Storm Drainage System In the four parcels that make up this project site, runoff is currently directed to a number of catch basins located in and around the existing at -grade parking areas from which the runoff is directed to underground seepage trench/exfiltration trenches. C. Proposed Storm Drainage System The storm drainage system to serve this project will be designed to direct the 5-year 1-day storm event to on -site retention/exfiltration systems and to contain the 25-year 3- day storm event on -site, as required to comply with the applicable requirements of the Miami -Dade County Department of Environmental Resources Management (DERM). While exfiltration trenches will be reviewed for feasibility at this location, it is anticipated that the stormwater disposal system will include four (4) 24" drainage wells. See supporting calculations in Table 1. Runoff will be collected through a system of catch basins and conveyed by pipes to the well locations. Runoff from driving surfaces such as driveways and walkways will be diverted through baffled pollution control structures which will capture the oils and greases prior to flowing into the wells. -2- • • Table 1 Preliminary Drainage Calculations 1. Total Net Area 1.30 Acres a. Impervious Roof/Driveways/Walks 1.17 Acres 1/3 Vert. Bldg. Surface 2.74 Acres Total 3.91 Acres b. Pervious 0.13 Acres c. Adjusted Contributing Area 4.04 Acres 2. Adjusted Runoff Coefficient 3. 91. (0.9)+ 0.13(0.2) 4.04 0.88 3. Design Storm 5 years 4. Time of Concentration 1.5 minutes 5. Rainfall Intensity 5.50 in/hr 6. Peak Runoff (Q) = CiA (0.88)(5.50)(4.04) = 19.55 cfs Assume each 24-inch diameter drainage well has a capacity of 1,000 gpm per foot of head; and, using 2.5 feet of available head: Well Capacity = 1,000 gpm x 2.5 feet = 2,500 gpm per well 5.57 cfs per well No. Wells = Peak Runoff = 19.55 cfs = 3.50 wells Well Capacity 5.57 cfs Provide four (4) - 24" diameter Drainage Wells Detention Tanks: Provide 1.5 minutes of detention time of storage in detention tanks: Volume of tanks required to handle 19.55 cfs for 1.5 min: 19.55 cfs x 1.5 min x 60 sec/min = 1,760 cubic feet (cf) Provide four (4) tanks (one with each well) with the following approximate interior dimensions: 4 times 6' -8" (width) x 13'-3" (length) x 5' (depth) = 1,768 cf -3- • • • • 3 Water Distribution The project is located in the water service area of the Miami - Dade Water and Sewer Department (WASD). There is an existing 8-inch water main in North Bayshore Drive, an existing 6-inch water main in N.E. 18th Street and an existing 4-inch water main in the alley that runs through the site. A 12-inch water main has been proposed by another developer for a portion of N.E. 18th Street. These existing water mains are not capable of providing the required domestic and fire flow required for this project. As such, it is anticipated that WASD and the Fire Department will require off -site water system improvements to provide water service and fire protection to this project. In addition, WASD will require the removal of the existing 4-inch water main in the alley. The water and fire service connections to this project will be made from those new water main improvements. The connections will consist of domestic water services, fire line services and cooling tower/irrigation water service, as applicable. No on -site water wells are planned for this project. The calculations for anticipated water usage required for this project are shown below, in Table 2. Table 2 Water Usage Residential Condominiums: 648 units @ 200 gpd/unit = Retail: 10,000 sf @ 5 gpd/100 sf = 129,600 gpd 500 gpd Total = 130,100 gpd 4- • • • • 4. Sanitary Sewer The project is located in the sewer service area of the Miami - Dade Water and Sewer Department (WASD) . WASD currently has 8- inch and 12-inch gravity sewer mains located in the adjacent streets on the west and north sides, respectively, which appear to have adequate capacity to serve this project. It is anticipated that new sewer laterals will need to be installed from those existing sewer mains to serve this project. Flow from this project will be directed to WASD pump station PS-02 which currently has sufficient available capacity to serve this project. Therefore, it is anticipated that no new pump station will be required to serve this project. Anticipated sewage flow calculations are shown below, in Table 3. Table 3 Sewage Flow Calculations Average Daily Flow (Table 2) = 130,100 gpd Average Daily Flow - 90.3 gpm Peak Flow (90.3 x 2.0) - 180.6 gpm -5- • • • 5 Solid Waste Generation Solid waste generated by this project will be collected in standardized on -site containers for refuse and recyclable waste. Regular service will be provided by either private hauling companies and/or the City of Miami Solid Waste Department. Both will transport the waste to Miami -Dade County's Disposal or Recycling facilities. The projected daily volumes of solid waste generation are shown below, in Table 4. Table 4 Solid Waste Generation Residential Units: Solid Waste Retail: Solid Waste 648 units x 1.42 tons/unit/year 921 tons/year 2.52 tons/day 5,046 lbs/day 10,000 sf x 3.08 lbs/sf/year 30,800 lbs/year 85 lbs/day Total = 5,131 lbs/day The project is located in the water and sewer service area of the Miami Dade Water and Sewer Department (WASD). -6-