Agenda Item Name:
Title
Mill Creek Sink Water Quality Improvement Project, Countywide Wetland Protection Code Application
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Presenter:
Stephen Hofstetter, 352-264-6811
Description:
The Mill Creek project (12-acre site, property owned by City of Alachua) has proposed to provide pre-treatment water quality improvements of contributing storm and surface waters currently draining into the Mill Creek Swallet and adjacent Mill Creek Sinkhole. The applicant is requesting a wetland buffer impact of 0.66-acre with mitigation. Proposed mitigation for the buffer encroachment will include preservation of an expanded 1.1-acres of buffer habitat beyond the required 75 ft. limits for the eastern wetland, combined with the 1.2-acres of created wetland habitat within the treatment wetland The applicant is requesting approval from the Board for these wetland buffer impacts with mitigation.
Recommended Action:
Recommended Action
Approve the proposed wetland buffer encroachment and associated mitigation as compensation for the encroachment.
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Prior Board Motions:
N/A
Fiscal Consideration:
Fiscal Consideration
N/A
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Background:
During the last few years, the proposed project site has been under evaluation for land acquisition, technical assessment and water quality improvement design by the City of Alachua (COA) and their consultant (Wood Environmental & Infrastructure Solutions, Inc.). The SRWMD has also committed efforts as well as funding for the construction-related activities. Post-construction operation, maintenance and management activities of the project will be conducted through the COA. The primary goal of the proposed project is to reduce nitrogen loading to the Santa Fe River watershed basin, which is listed as impaired for nitrate-nitrogen. The project is also intended to remove other pollutants such as heavy metals, hydrocarbons, and suspended solids. In addition to the referenced habitat improvements associated with wetland and associated buffer preservation and from the constructed treatment wetland, the design evaluation determined the project will result in a reduction range of 54-77% for total nitrogen and 84-91% for total phosphorus compared to existing conditions.
The Mill Creek project (12-acre site, property owned by City of Alachua) is proposed to provide pre-treatment water quality improvements of contributing storm and surface waters currently draining into the Mill Creek Swallet and adjacent Mill Creek Sinkhole. Design features include the excavation of two pre-treatment basins, treatment wetland and containment berm. The proposed design was able to avoid encroachment within the 2.7-acres of wetland within the property. However, due to site and design constraints, it was determined necessary for some encroachment within the 75-ft. wetland buffer. Buffer encroachment has been minimized to a total 0.66-acre. To mitigate for the encroachment, the design has incorporated the preservation of an additional 1.1-acres of expanded wetland buffer beyond the required 75-ft. limits for the remaining wetland area, as well as the construction, vegetative planting and management of the 1.2-acre treatment wetland. Staff believe the proposed 0.66-acre of buffer encroachment is justified due to the site constraints, and the total 2.3-acres of proposed mitigation is appropriate to compensate for the encroachment and finds the project consistent with the Chapter 77, Countywide Wetland Code.