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HomeMy WebLinkAboutTab 3 - Site Utility Study• 2222 BISCAYNE BOULEVARD MAJOR USE SPECIAL PERMIT SITE UTILITY STUDY • Prepared for: Grouper Financial, Inc. Prepared by: Consulting Engineering and Science, Inc. June 30, 2006 • • • • 1. General A. Project Location and Size: The project is located along the west side of Biscayne Boulevard in the City of Miami; bounded on the north by N.B. 23rd Street; bounded on the west by N.E. 2nd Avenue; and, bounded on the south by N.E. 22nd Street. The site has a gross lot area of 223,653 square feet, or 5.13 acres; and, a net lot area of 161,885 square feet, or 3.72 acres, The site has approximately 312 feet of frontage along Biscayne Boulevard; approximately 488 feet of frontage along N.E. 23rd Street; approximately 312 feet of frontage along N.E. 2nd Avenue; and, approximately 488 feet of frontage along N.E. 22nd Street. The land on which the project is proposed consists of a single parcel of land, identified as Miami -Dade County tax folio numbers 01-3230--062-0010. A legal description of the property is as follows: A portion of Tract A of TERRANOVA BISCAYNE, according to the plat thereof, as recorded in Plat Book 150, at Page 14, of the Public Records of Miami ---Dade County, Florida. The eastern portion of the site is presently occupied by a 2-story office building (18,280 sf) and a 7-story office building (44,037 sf) interconnected by a covered breezeway; and, a 2-story parking structure. The western portion of the site is presently vacant. B. The proposed project build -out will be as follows: Office. 62,317 sf (Existing) 430,477 sf (Proposed) 492,794 sf Net Lot Area 161,885 sf, or 3.72 acres Gross Lot Area 223,653 sf, or 5.13 acres It is intended that the existing structures within the eastern portion of the site will remain; and, a new office condominium tower of 28 stories will be constructed on the western portion of the site. -1- • • • 2. Drainage Drainage Area Upon development, the site will include two (2) drainage sub - basins. The eastern sub -basin, containing 1.97 acres, will be approximately 66 per cent impervious and approximately 34 per cent pervious. The western sub -basin, containing 1.75 acres, will be approximately 80 per cent impervious and approximately 20 per cent 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: Eastern Sub -basin: 66 . 0% (impervious) X 0.90 34.0% (pervious) x 0.20 Overall coefficient Western Sub -basin: 80.0% (impervious) X 0.90 20.0% (pervious) x 0.20 Overall coefficient B. Existing Storm Drainage System 0.59 0.07 0.66 0.72 0.04 0.76 In the eastern portion of the site that is developed, runoff is currently directed to a number of catch basins located in and around the open spaces between structures from which the runoff is directed to underground seepage trench/exfiltration trenches. There are no existing drainage facilities located in the western portion of the site. 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/exfiitration 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 (DEFJ4). It is anticipated that the existing storm drainage system in the eastern portion of the site will remain. It is further anticipated that the stormwater disposal system for the western portion of the site will include four (4) 24" drainage wells. See supporting -2- • • • 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. Table 1 Preliminary Drainage Calculations Eastern Portion of the Site: Total Net Area 1.97 Acres a. Impervious Roof/Driveways/Walks 1.30 Acres 1/3 Vert. Bldg. Surface 0.14 Acres Total 1.44 Acres b. Pervious 0.67 Acres c. Adjusted Contributing Area 2.11 Acres 2. Adjusted Runoff Coefficient 1.44(0.9)-1- 0.67(0.2) 2.11 = 0.68 3. Design Storm 5 years 4. Time of Concentration 15 minutes 5. Rainfall Intensity 5.50 in/hr 6. Peak Runoff (Q) = CiA (0.68)(5.50)(2.11) 7.89 cfs Existing drainage facilities to remain. -3- • • Western Portion of the Site: €. Total Net Area 1.75 Acres a. Impervious Roof/Driveways/Walks 1.40 Acres 1/3 Vert. Bldg. Surface 3.06 Acres Total 4.46 Acres b. Pervious 0.35 Acres c. Adjusted Contributing Area 4.81 Acres 2 Adjusted Runoff Coefficient 4.46(0.9)+ 0.35(0.2) 4.81 = 0.85 3. Design Storm 5 years 4. Time of Concentration_ 15 minutes 5. Rainfall Intensity 5.50 in/hr 6. Peak Runoff (Q) = CiA (0.85)(5.50)(4.81) = 22.49 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 = 22.49 cfs = 4.03 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 22.49 cfs for 1.5 min: = 22.49 cfs x 1.5 min x 60 sec/min = 2,024 cubic feet (cf) Provide four (4) tanks (one with each well) with the following approximate interior dimensions: 4 times 6'-S" (width) x 15'-3" (length) x 5' (depth) = 2,034 cf -4- • • • Water Distribution The project is located in the water service area of the Miami - Dade Water and Sewer Department (WASD). There is an existing 16-inch water main in Biscayne Boulevard; and, existing 12- inch water mains in N.E. 23rd Street, N.E. 2nd Avenue and N. Eo 22nd Street. These existing water .mains are capable of providing the required domestic and fire flow required for this project; and, as such, it is not anticipated that WASD or the Fire Department will require off --site water system improvements to serve this project. Existing water and fire service connections to those buildings to remain shall remain as is. The water and fire service connections to the new portion of the project will be made from the adjacent existing water mains. 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 Existing Offices; 62,317 sf @ 10 gpd/100 sf .... 6,232 gpd Proposed Offices: 430,477 sf @ 10 gpd/100 sf = 43,048 gpd Total _ 49,280 gpd • • • 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 gravity sewer mains fronting the property in Biscayne Boulevard, N.E. 23rd Street and N.E. 22nd Street; and, has a 10-inch gravity sewer main fronting the property in N.E. 2nd Avenue. Thee existing sewer mains appear to have adequate capacity 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. Existing sewer laterals serving those buildings to remain shall remain as is. It is anticipated that new sewer laterals will be installed from the adjacent existing gravity sewer mains to serve the new portion of the project. Anticipated sewage flow calculations are shown below, in Table 3. Table 3 Sewage Flow Calculations Average Daily Flow (Table 2) = 49,280 gpd Average Daily Flow = 34.2 gpm Peak Flow (34,2 x 2.0) = 68.4 gpm -6- • • • 5e 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 Existing Office: Solid Waste = 62,317 sf x 3.08 lbs/sf/year 191,936 lbs/year = 96 tons/year = 526 lbs/day Proposed Office: Solid Waste = 430,477 sf x 3.08 lbs/sf/year 1,325,869 lbs/year = 663 tons/year 3,633 lbs/day Total _ 4,159 lbs/day The project is located in the water and sewer service area of the Miami Dade Water and Sewer Department (WASH). -7-