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The Tampa Bay Mitigation Bank:
A New Option for Wetland Mitigation in the Central Florida Region

The Federal Interagency Guidelines authorized wetland mitigation banking legislatively (Federal Register 1995, Chapter 373). The Tampa Bay Mitigation Bank (TBMB) is the first mitigation bank approved in the Tampa Bay basin, and was developed in the headwaters of Cockroach Bay, Manatee County, in response to the regionally expanding need for freshwater and estuarine wetland mitigation. Recommendations established for the restoration of Tampa Bay wetland habitats in Charting the Course for Tampa Bay: The Comprehensive Conservation and Management Plan for Tampa Bay (Tampa Bay National Estuary Program 1996) included the site proposed by Tampa Bay Mitigation Bank. The TBMB consists of historically agricultural, ruderal land in southern Hillsborough County on the Cockroach Bay peninsula. Site development will be consistent with and expand on the Cockroach Bay Habitat Restoration Project, a SWIM (Surface Water Improvement) project undertaken by the Southwest Florida Water Management District and the Hillsborough County Environmental Lands Acquisition and Protection Program. The TBMB will produce 71.90 palustrine and 31.17 estuarine mitigation credits by creating and/or restoring 81.26 acres of freshwater wetlands, approximately 3.80 acres of freshwater ponds (a declining habitat required for white ibis (Eudocimus albus) reproduction), 42.16 acres of tidal marsh/mangrove wetlands, and 34.01 acres of upland and wetland hammock habitat. The TBMB plan was developed in concert with other public efforts to improve the ecological integrity of Cockroach Bay and is supported by the Cockroach Bay Restoration Alliance, Hillsborough County, and the Tampa Bay National Estuary Program. Scheduled for implementation in 2003, TBMB will restore historical habitats and provide water quality benefits to Cockroach Bay Aquatic Preserve and Tampa Bay.


INTRODUCTION
Mitigation banking regulations in Florida were promulgated in 1994 (Rule 62-342, F.A.C. (1994)). Subsequently, 32 mitigation banks have been approved throughout the state. TBMB is the first bank established in the Tampa Bay region.

The approval process for a mitigation bank is complex, and the proposal was reviewed extensively by state and federal regulatory agencies since the bank was first proposed in 1997. Numerous resource agencies also provided comments on the proposed plans. With the continued urbanization of the Tampa Bay area, appropriate mitigation for critical infrastructure projects within the watershed had been very difficult to locate. The TBMB site will provide mitigation to offset projects permitted within the watershed, and habitat restoration at TBMB will assist in meeting goals established for bay habitats in Charting the Course for Tampa Bay, the Comprehensive Conservation and Management Plan for Tampa Bay (Tampa Bay National Estuary Program 1996), including estuarine and palustrine wetlands and water quality enhancement to the Cockroach Bay Aquatic Preserve.


METHODS
The proposed mitigation bank design was determined by characterizing existing site conditions, including evaluations of habitat, hydrology, and sediments. These analyses were used to identify proposed bank conditions based on the potential to restore or create wetlands and upland habitat. Mitigation bank credits were determined based on a comparison of habitat values between the “without bank” condition and the proposed “bank” condition following the approved credit assessment procedure promulgated by the Mitigation Bank Review Team (Joint State/Federal Mitigation Bank Review Team Process for Florida - Operational Draft 1998.). The difference in pre- and post-restoration habitat value, or “lift”, was utilized to establish the number of authorized mitigation credits for the bank.

Habitat Characterization
The TBMB site consists of 161.2 acres surrounding the headwaters of Andrews Creek, on the southeast portion of the peninsula between Little Cockroach Bay and Cockroach Bay, east of the southern portion of the Southwest Florida Water Management District’s (SWFWMD) Cockroach Bay Habitat Restoration Project in southeastern Hillsborough County, Florida (Sections 22, 23, Township 32S, Range 18E) (Figure 1).

Historic habitats on the site were a mosaic of hydric hammock, swamp, pine flatwoods (both hydric and upland) and upland hammocks. Approximately forty years ago, portions of the TBMB site were converted to irrigated row crops and cattle grazing. Agricultural irrigation was achieved by channelizing the headwaters of Andrews Creek, and ditches were cut throughout the property to rapidly drain seasonally high water and storm flows.

Presently, five plant communities occur on the site: agricultural, herbaceous fallow field, shrubby old-field, disturbed upland hammock, and disturbed palustrine emergent marsh. The eastern and northern portions of the site remain in agricultural use, while the rest of the site is ruderal and dominated by Brazilian pepper (Schinus terebinthifolius) and similar undesirable herbaceous and shrub species. Drainage affecting the hydrology of the site including 3.69 acres of palustrine wetlands has encouraged the invasion of numerous Category 1 nuisance species (Florida Exotic Pest Plant Council 2003). Palustrine emergent communities occur marginally along Andrews Creek, the southwestern wetland, and two small wetlands on the eastern portion of the property. The euryhaline estuarine marsh community along the Andrews Creek channel receives freshwater inflow that supports palustrine emergent vegetation including southern cattail (Typha domingensis), interspersed with open mud flats. The southwestern marsh is dominated by Brazilian pepper, in association with canna (Canna flaccida), primrose willow (Ludwigia peruviana), cattail, and pennywort (Hydrocotyle sp.). Wildlife utilization was determined to be extremely limited due to the highly disturbed nature of the site and existing agricultural use (Figure 2).

Hydrological Analysis
The channelization of Andrews Creek and ditching significantly altered site hydrology. Additionally, a 35-foot concrete wall with a 5.8-foot weir located near its center was installed c. 1950 across Andrews Creek just east of the western boundary of the site to restrict tidal influence; however, the weir no longer restricts discharges and tidal influx is minimally inhibited by the structure. Hydrological information was obtained from site topographical surveys, historic and recent aerial photographs, and weekly sampling (5-1998 to 7-1999) at seven piezometers installed across the site (Scarola Associates 1999). Typical seasonal high groundwater (SHGW) elevations were established through site specific studies, and rangefrom 0-0.33 m below the existing ground surface, declining closer to the Andrews Creek channel (PSI 1998, Scarola Associates 1999). Due to the alterations of the historic hydrologic regime and flow patterns in the vicinity of the TBMB, wetlands restoration on site will require stormwater runoff inflow from off-site basins to establish appropriate wetland hydrology across the site (Scarola Associates 1999) (Figure 3).

Sediment Analysis
Sediment samples were collected throughout the site based on topography and soil mineralogy and analyzed for pesticides and heavy metals using EPA Methods 6010 (heavy metals), 8081 (chlorinated pesticides), and 9060 (total organic carbon) to confirm that restoration of the site would not affect endemic fauna. Sediment analysis showed that heavy metals and organo-chlorines associated with sediments within the TBMB site were below probable effects level and no effects to endemic fauna are expected following restoration(MacDonald 1994).

Restoration Plan Design
The restoration plan for the TBMB was designed based on using upstream drainage for palustrine areas of the site, tidal inflow from Andrews Creek, and elevational adjustment in all areas to establish appropriate hydroperiods for wetlands communities (Figure 3). The plan was modeled after the Cockroach Bay Habitat Restoration Project to the west and northwest of the bank site.

A mosaic of tidal and palustrine wetlands will be constructed in conformance with the proposed restoration/creation plan, converting approximately 81.26 acres of uplands to palustrine emergent wetlands, varying by three hydroperiod and elevational regimes, and creating 3.80 acres of freshwater ponds for white ibis foraging habitat, which has been declining regionally through hydrologic modification. Palustrine marsh habitat will be vegetated by pickerel weed (Pontederia cordata), arrowhead (Sagittaria lancifolia), maidencane (Panicum hemitomon), sawgrass (Cladium jamiacense), and needle rush, (Juncus effusus) (Figure 4). Marsh areas closer to Andrews Creek and tidal tributaries will be planted with euryhaline species.

An important element of the TBMB is the enhancement of Andrews Creek and creation of tidal tributaries through elevational adjustment allowing tidal inundation of excavated wetland basins through Andrews Creek. Approximately 40.0 acres of low and high saltmarsh interspersed with mangroves will be established through red mangrove (Rhizophora mangle) planting and recruitment, and planting saltmarsh cordgrass (Spartina patens), saltmeadow cordgrass (Spartina alterniflora), seashore paspalum (Paspalum distichum), saltwort (Batis maritima), and glasswort (Salicornia virginica) to accelerate saltmarsh establishment (Myers and Ewel 1994).

Approximately 2.21 acres of tidal creek mangroves will be enhanced by opening the weir on the western property boundary and controlling invasive plants (S. terebinthifolius, other spp.). Mangrove and estuarine marsh habitat will be increased to 42.16 acres through wetlands enhancement and creation.

An upland buffer of live oak (Quercus virginiana), red cedar (Juniperus virginiana), and cabbage palm (Sabal palmetto) will be established on the property perimeter between the bank’s on-site wetlands and off-site disturbed lands, and bordering selected interior locations to separate wetland communities requiring different hydrologic regimes, thus increasing landscape diversity (Figure 5).

Credit Assessment
Existing and proposed site conditions were assessed for all polygons in accordance with the “Joint State / Federal Mitigation Bank Review Team Process for Florida” (Joint State/Federal Mitigation Bank Review Team Process for Florida – Operational Draft 1998.) to establish mitigation credits. For assessment areas containing freshwater, non-tidal wetlands the “Wetland Rapid Assessment Procedure (WRAP)” was used to establish credits (Miller and Gunsalus 1999). Mangrove or tidal marsh wetlands polygons were assessed using the “Estuarine Wetland Rapid Assessment Procedure” (EWRAP) (Joint State/Federal Mitigation Bank Review Team Process for Florida – Operational Draft 1998). These two procedures are very similar, and the numeric results for individual polygons are computed identically during calculation of WRAP/EWRAP variables.

The “lift” or delta between existing and proposed conditions was determined and the delay in establishing a functionally mature system was taken into consideration by application of a temporal lag factor. The credit assessment was reviewed and modified by the federal Mitigation Bank Review Team (MBRT), which included the U.S. Army Corps of Engineers, U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service, and U. S. National Marine Fisheries Service.


RESULTS
Credits and Credit Release Schedule

Approximately 103 mitigation credits were established for the TBMB through the MBRT process. Table 1 provides the number of permit mitigation credits approved for each habitat type and the credit release schedule for the bank.

TBMB credits will be released pursuant to the federally approved credit release schedule, which differs from the schedule approved by SWFWMD. State rules specify that freshwater credits may not be released until “success” or compliance with all permit conditions has been reached (Rule 62-342, F.A.C. 1994).

Long-term management will be provided in perpetuity by the TBMB through establishment of a management trust fund. A public, or approved private entity, may assume responsibility for management of the bank upon determination of success with conveyance of the management trust fund. Monitoring will be conducted quarterly for the first year and annually for the subsequent two years to confirm establishment of the targeted communities and adequate hydrology.

Mitigation Service Area
The bank’s approved Mitigation Service Area (MSA) includes the Tampa Bay basin as depicted in the SWFWMD’s ERP Manual (Figure 1). The MSA for TBMB is consistent with SWFWMD’s defined drainage basins and the bank’s ability to offset environmental impacts in the region. To utilize the bank, an applicant must ensure that the nature of proposed impacts will be offset by participation in the bank and be within the MSA, unless exempted by rule.


CONCLUSIONS

Tampa Bay Mitigation Bank, the first mitigation bank approved in the Tampa Bay basin, will provide an approved regulatory option for mitigating estuarine and palustrine wetland impacts within the watershed. Its proximity to other sites chosen for restoration and preservation leverages the benefits of the bank itself and other public efforts, and the location of the bank was selected to enhance the restoration efforts already underway proximal to the bank. The TBMB concept was determined to be appropriate for establishment of a mitigation bank based on evaluation of the bank site location, the mitigation plan, long-term operational sustainability, and the proposed methods for determining “lift” between “with” and “without” bank scenarios. Approximately 103 total credits were established for the bank through the federal MBRT review process.


LITERATURE CITED

Birkitt Environmental Services, Inc., Caloosa Shell Corporation, and Scarola Associates. 2002. Tampa Bay Mitigation Bank: Final Mitigation Banking Instrument. Tampa, FL.

Federal Register. 1995. Federal Interagency Guidelines for Mitigation Banking.

Florida Administrative Code. 1994. Rule 62.342, Mitigation Bank Rule.

Florida Exotic Pest Plant Council. 2003 List of Invasive Species. http://www.leppc.org/plantlist/03list.htm. Accessed 21 October 2003.

Lewis, R.L. and D. Robison. 1995. Setting Priorities for Tampa Bay Habitat Protection and Restoration: Restoring the Balance. Technical Publication #11-95 of the Tampa Bay National Estuary Program. St. Petersburg, Florida.

MacDonald, D.D. 1994. Approach to the Assessment of Sediment Quality in Florida Coastal Waters: Volume 1 – Development and Evaluation of Sediment Quality Assessment Guidelines. Florida Department of Environmental Protection Office of Water Policy, Tallahassee, Florida.

Miller, R.E., and B.E. Gunsalus. 1997. Wetland Rapid Assessment Procedure (WRAP) Technical Publication REG-001. South Florida Water Management District, Natural Resource Management Division,West Palm Beach, FL.

Myers, R.L. and J.J. Ewel, Editors, 1990. Ecosystems of Florida. University Presses of Florida. 1990.

PSI. 1998. Results of the shallow subsurface investigation seasonal high groundwater table determination, Tampa Bay Mitigation Bank, L.L.C. Site, Ruskin, Florida.

Scarola Associates. 1999. Drainage Report for Tampa Bay Mitigation Bank, Section 22 & 23, Township 32 S, Range 18E, Hillsborough County, Florida

Tampa Bay National Estuary Program. 1996. Charting the Course for Tampa Bay. Tampa Bay National Estuary Program in cooperation with the U.S. Environmental Protection Agency, St. Petersburg, Florida.

U.S. Army, Corps of Engineers. 1998. Joint State/Federal Mitigation Bank Review Team Process for Florida - Operational Draft. Jacksonville, FL.

U.S. Department of Agriculture Soil Conservation Service (NRCS), in cooperation with University of Florida Agricultural Experiment Stations. 1989. Soil Survey of Hillsborough County, Florida.

 

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