Updated  10/13/06

Progress Report

Tasks I through III

Phase I Long Range Dredged Material Management Plan

for the Intracoastal Waterway

in Miami-Dade County

 

May 24, 2000

 

This report summarizes the results of our work on Tasks I through III for the Phase I development of the Long Range Dredged Material Management Plan for the Intracoastal Waterway (ICWW) in Miami-Dade County, Florida (Figure 1). Specific efforts expended in the completion of these tasks, as well as results obtained from these efforts, will be reported to the project’s Technical Advisory Committee on May 24^th, the project’s Citizens’ Advisory Committee on May 30^th, the general public on June 6^th, and the FIND Board of Commissioners on June 23^rd at their regularly scheduled meeting in Brevard County.

 

            Review of Resource Materials

 

The attached tables and figures summarize the results of Tasks I through III.  Task I results reflect the analysis of information from materials collected during project Task I-A (data collection). These materials include U. S. Geological Survey (USGS) NAPP 1994 color-infrared aerials, USGS 7.5-minute series topographic quadrangle maps, and U. S. Fish and Wildlife Service National Wetland Inventory maps (all at a scale of 1:24,000) of the entire project area, 1994 Florida Inland Navigation District (FIND) blueline aerials of the 10-ft project segment of the Waterway, showing existing disposal easements and FIND-owned properties (1:2,400), Jacksonville District Corps of Engineers Real Estate and Control Data maps, 1999 Miami-Dade County Tax Assessment aerials (scale 1:3,600), and Miami-Dade County Comprehensive Plan future land use elements and maps. As part of this task, we have reviewed all relevant dredging records (plan documents, surveys, dredging summaries, OCE reports, etc.) held by the Jacksonville District Corps of Engineers (COE). We also have analyzed the comprehensive survey data from the FIND’s 1996 survey of the entire 10- and 12-ft project segments of the ICWW channel including the 10-ft project segment within Miami-Dade County. Notably, this survey did not include the ICWW channel from Government Cut southward to the Miami-Dade\Monroe County line. We have just recently (April 21^st) received data from the Jacksonville District’s recent survey of the entire ICWW channel, including data from Government Cut southward, and are now beginning its analysis. Finally, we have reviewed all available sediment data and reports from the Florida Department of Environmental Protection and South Florida Water Management District characterizing the chemistry of the Waterway sediments. We have also reviewed sediment chemistry data obtained as part of a recent Jacksonville District COE program to characterized channel sediment throughout the ICWW in Florida. However, we still await core boring logs and sediment grain-size data from that same COE program before we determine the most appropriate channel locations in which to concentrate our planned sediment sampling, not yet scheduled.

 

            Project Definition

 

The Miami-Dade County segment of the ICWW extends approximately 48 miles from the Broward/Miami-Dade County line between Hallandale and Aventura southward to the Miami-Dade/Monroe County line in Card Sound south of Biscayne Bay. Portions of two separately-authorized federal navigation projects — the 10-ft Project (Ft. Pierce to Miami) and the 7-ft Project (Miami to Key West) comprise the Intracoastal Waterway within Miami-Dade County. The 10-ft Project (Ft. Pierce to Miami) extends southward to the Port of Miami Channel (Government Cut) and includes authorized dimensions of 10 ft below Mean Low Water  (-10 ft MLW) depth and 125 ft base channel width. The 7-ft Project (Miami to Key West) extends southward from Government Cut and within Miami-Dade County includes authorized dimensions of  -7 ft MLW depth and 75 ft base channel width. For the present planning effort, the Miami-Dade County project area extends 47.92 miles from a point approximately 530 ft south of the Broward\Miami-Dade County line (ICWW mile 333.24; Cut DA-1, Station 0+00) to the Miami-Dade/Monroe County line (Figure 1). The county’s northernmost 530 ft lie within the southernmost Broward County cut (Cut BW-63) and are addressed as part of the long-range plan for the ICWW in Broward County.

 

To provide a project framework, Table 1 lists all of the Miami-Dade County channel cuts (i.e., the straight line channel segments) within the 10-ft Project, across the Port of Miami turning basin, and within the 7-ft Project; the length of each cut; and the corresponding mileages measured from three starting points: the northern boundary of the Miami-Dade County project area, the northern end of the Intracoastal Waterway at the St. Johns River in Jacksonville (specifically, the southern edge of the Jacksonville Harbor Project, designated ICWW mile 0.0), and the northern end of the Atlantic Intracoastal Waterway within Florida near the Florida/Georgia border (specifically, the southern edge of the Fernandina Harbor Project, designated AIWW mile 0.0).

 

            Projected Dredging and Material Storage Requirements

 

To project future dredging and material storage requirements for the Miami-Dade County project area, we first compiled and reviewed all available Jacksonville District, U.S. Army Corps of Engineers’ (COE) archival dredging records and channel surveys, as stated above. By this process, we determined that within the 10-ft Project segment, eight separate maintenance dredging operations have been performed since this segment of the channel was deepened to its presently authorized depth in 1965. As shown in Table 2, all took place within a 0.5-mile reach extending from ICWW mile 339.26 (Cut DA-9, sta 22+00) to ICWW mile 339.75 (Cut DA-9, sta 48+00) immediately opposite Baker’s Haulover. These eight operations removed a total volume of over 323,000 cubic yards (cy), or an average of over 40,000 cy per operation. The FIND’s December 1996 three line survey of the entire ICWW south to Government Cut, and the only recent comprehensive survey of the Miami-Dade County 10-ft Project segment, documented an additional 12,400 cy of shoaling found primarily in a 1.2-mile reach centered about the 79^th Street Causeway (ICWW mile 343.12 to mile 344.28). From these data, we then projected for the 10-ft project segment within Miami-Dade County a 50-year dredging requirement of 508,230 cy, and a 50-year projected material storage requirement of 1,092,6954 cy, based on an assumed bulking plus overdredging factor of 2.15. Notably, 96% of this projected requirement reflects shoaling immediately opposite Baker’s Haulover. Although sufficient to guide our initial identification and evaluation of candidate sites, this projected material storage requirement will be refined based on the results of the Jacksonville District’s recently completed three line survey of the entire ICWW, including the Miami-Dade County segment.

 

The Jacksonville District’s archives contain little information about historic dredging within the Intracoastal Waterway southward from Government Cut (i.e., within the Intracoastal Waterway 7-ft Project, Miami to Key West). The records indicate that the authorized channel was constructed to Cross Bank near Plantation Key in Monroe County, but do not specify when the dredging took place. Examination of nautical charts (the only presently available source of bathymetric information within this segment of the Miami-Dade County project area) suggests that construction of this portion of the project required only minimal dredging through a limited number of shoals, or banks. The remainder of the authorized channel appears to have been naturally at or below the 7-ft project depth. No record of maintenance dredging since the channel’s original construction was found. Ongoing analysis of data recently received from the Jacksonville District will provide the only available comprehensive update of the channel’s condition and will form the basis from which to project present and future dredging and material storage requirement (Figure 2).

            Inventory of Existing Sites

 

We also inventoried all existing disposal easements within the Miami-Dade County project area, based on review of relevant COE Real Estate maps and Control Data sheets for the Intracoastal Waterway, Jacksonville to Miami (10-ft Project), FIND Maps of Proposed Right-of-Way and Maintenance Spoil Areas along the Intracoastal Waterway from the Dodge Island Seaport southerly to the Miami-Dade-Monroe County Line in Miami-Dade County (1970), and 1994 FIND blueline aerials We then derived preliminary estimates of site parameters (e.g., upland acreage, capacity, pipeline access, etc.) from the above described resource materials. A complete inventory of all existing easements and the results of the preliminary easement evaluation process are summarized in Table 3 and Figure 3. By this process, we determined that only two existing easements  — a portion of Sandspur Island opposite Baker’s Haulover and a portion of Legion Picnic Island Park south of the 79^th St. Causeway — possess any realistic potential for development as dredged material management areas and thus merit further evaluation. Notably, these two sites are located near the two documented shoal areas.  However, the total storage capacity of these two properties, estimated as over 72,000 cy, represent less than 7% of the projected 50-year storage requirement of the 10-ft Project segment within Miami-Dade County. Moreover, use of these sites may not represent the most cost-effective or operationally efficient means of meeting these long-term needs of the Waterway within Miami-Dade County. We are now refining these preliminary estimates of useable site acreage and potential site capacity within these two sites based on field inspections and detailed site mapping as discussed below.

 

           Dredged Material Management Concepts

 

Based on the results of Task I and review of the overall physical, environmental, and demographic characteristics of the coastal areas of the county, we then preliminarily identified the most appropriate material management strategy for the requirements of 10-ft Project segment of the Miami-Dade County project area. Given the concentration of shoaling around Baker’s Haulover, and the likely presence of beach-quality channel sediments in this segment of the Waterway, beach placement, supplemented by an nearby upland staging and material transfer area, appears to be the most appropriate management strategy for this channel segment. However, the presence of beach-quality channel sediment must be demonstrated by sediment data soon to be to be received from the Jacksonville District COE, and confirmed by additional sediment sampling based on this data. For the remainder of the 10-ft Project segment, the use of confined upland placement in a limited number of centralized material management areas appears the most appropriate material management strategy.

The environmental sensitivity and protected status of much the area through which the 7-ft Project passes clearly imposes unique demands on designating an appropriate dredged material management strategy for this segment of the Miami-Dade County project area. Because the designation of an appropriate management strategy and the associated delineation of operational channel reaches largely reflects the quantity and distribution of shoaling as well as the quality of the channel sediment, these tasks must necessarily await analysis of the recent survey data and the receipt of sediment data from the Jacksonville District.

 

           Candidate Site Identification and Field Inspection

 

Although not yet final, the results of Task I and the preliminary definition of appropriate management concepts for the 10-ft Project segment of the Miami-Dade County project area then guided the identification of 63 additional candidate sites based on an office review of 1994 NAPP color-IR aerial photography, USGS 7.5-minute topographic quadrangle maps, Comprehensive Plan Future Land Use maps and U.S. Department of the Interior wetland inventory maps. To update each candidate site’s present land use, we then obtained current (1999) Miami-Dade County tax aerials for each area identified. Through review of these aerials, we eliminated 11 candidate sites with obvious land use conflicts (i.e., recent development) not shown in the 1994 aerials, and thereby reduced the number of required candidate site inspections. Field inspection of the remaining candidate sites (Figure 4-1, Figure 4-2 and Table 4), as well as the two existing sites that show some potential for development as dredged material management areas, was conducted the weeks of April 10^th and April 24^th. A team consisting of one engineer and one biologist inspected each existing and newly-identified candidate site not presently available to the FIND to determine existing land uses on and adjacent to each site, to characterize and preliminarily quantify on-site vegetation communities and associated environmental liabilities, and to assess the general suitability of each site for development as permanent dredged material management facilities.

 

In Task IV, each candidate site will be further evaluated under the full standard set of engineering, operational, environmental, socioeconomic, and land-use criteria. We are now mapping land use and vegetation communities on each site to Level 3 of the Florida Land-Use and Cover and Forms Classification System (FLUCS) (FDOT, 1985), based on the 1999 Miami-Dade County aerials. When completed, these maps will guide a refined estimate of each site’s dredged material storage capacity, based on realistic containment basin geometries, field-verified environmental constraints, and appropriate setback considerations.  The resulting site capacities, acreage requirements, and basin geometries, as well as each site’s associated reach requirements and land-use parameters, will be outlined in a Site Data Summary Sheet to accompanying each candidate site map.