Okaloosa County BOCC — April 7, 2015 — 2015-04-07 G0326 Amend 1 — reading text

neighborhoods, multi-family, commercial and industrial uses. Runoff from portions of the basin receives little or no water quality treatment before discharging downstream into Gap Creek. A stormwater master plan was prepared for the Grantee by HDR Engineering in April 2003; the Gap Creek watershed was modeled and shown to have one of the highest pollutant loading rates in Okaloosa County. In 2008, in a cooperative effort between the Northwest Florida Water Management District, the Grantee and the City of Fort Walton Beach, the three (3) agencies provided funding for a detailed water quality study of the Gap Creek watershed that was completed by HDR Engineering. The purpose of this study was to identify and prioritize stormwater Best Management Practice (BMP) opportunities for enhancing treatment and pollutant loading reduction capability within the Gap Creek watershed. Of the nineteen (19) sites within the Gap Creek watershed that the study recommended for retrofit opportunities to provide pollutant loading reduction, eight (8) also have the potential to reduce flood risk in localized areas of the watershed. The BMP structural improvements in the original Grant Work Plan were chosen for their high potential to provide both water quality improvements and flood attenuation. The original concept included a treatment train within a 126 acre sub-basin of the Gap Creek watershed known as the Lovejoy Community. The original project was comprised of modifying conveyance channels (upstream of Poplar Avenue Pond) to provide more storage and direct runoff to treatment areas, upgrading the existing County Poplar Avenue Pond to provide additional storage capacity and enhance nutrient uptake, and constructing a new stormwater facility (Echo Circle site) to provide additional treatment/attenuation and nutrient removal. The upgrades, as modeled by Spreadsheet Tool for the Estimation of Pollutant Load (STEPL), were expected to reduce nitrogen loads by 442 lbs/yr or 43.5%, phosphorus by 145 Ibs/yr or 89.5%, Biochemical Oxygen Demand (BOD) by 3,400 lbs/yr or 91.2% and suspended sediment by 23.8 Ibs/yr or 99.1%. Unfortunately, the project cannot be constructed as originally conceived thus requiring this Grant Work Plan to be amended Only a limited amount of improvement to the conveyance to Poplar Pond were found to be practical (a cross drain under Lovejoy Road is being added and the pipe on the north side of Lovejoy Road that connects the DEP Agreement No. G0326, Attachment A-1, Page 1 of 6 roadside conveyance system to the pond is being replaced with an open channel). Some minor reconstruction of the berm for the existing Poplar Pond and modification of the outfall structure will also be done in this amended Grant Work Plan to maximize retention and detention. The other planned elements of the original treatment train are being eliminated from this amended Grant Work Plan. Some of these original activities were not permittable, some were not necessary and some were simply found to be not practical during the design phase. The modeled estimated pollutant load reduction goals of the original project were very good and these results will not be achieved by the reduced scope of work. However, it is important to note that the water quality benefits of the conveyance improvements which were not part of the original modeled pollutant load reduction goals will still be achieved. By adding a culvert beneath Lovejoy Road and substantially increasing the capacity of the conveyance ditch to the existing Poplar retention basin and by replacing a pipe that was too small with an open channel a// of the stormwater runoff will be treated from the 86.9 acre watershed area up to a 25 year storm event and only 4% or less of the total annual runoff will bypass the treatment. Runoff, which used to exceed the confines of the existing ditch and culvert system, will now be properly conveyed allowing for much better treatment. This will mitigate flooding potential and dramatically improve the total volume of water treated. PROJECT LOCATION AND WATERSHED CHARACTERISTICS: Gap Creek is located in the Fort Walton Beach area of Okaloosa County. The creek has two (2) tributaries that originate in the western portion of the drainage area and flow eastward into Cinco Bayou, a Class I1I water body used heavily as a recreational area. Cinco Bayou is an embayment along the western shoreline Choctawhatchee Bay (a priority water body of the District’s Surface Water Improvement and Management (SWIM) program). The Choctawhatchee Bay has a surface area of approximately 129 square miles. The greatest source of fresh water into the bay is the Choctawhatchee River that flows into the eastern end of the bay. East Pass, located near the western end of the bay immediately west of Destin, is the only direct opening to the Gulf of Mexico. The bay also opens to Santa Rosa Sound at the western most end of the bay and the Intracoastal Waterway on the east end of the bay that winds its way to West Bay (part of the St. Andrew Bay system). The river and bay system include a diverse array of natural communities. The estuary supports sea grass beds, oyster bars, tidal marshes and unvegetated soft bottom habitats. The Choctawhatchee River and Bay system remains biologically diverse and productive and continues to support a rich ecology and provide an economic, recreational and aesthetic resource for the region. Among the environmental resources are diverse aquatic and wetland habitats, vast forests, Floridan Aquifer springs, steephead streams, and many species of flora and fauna including the endangered Okaloosa darter (Etheostoma okaloosae). Benefits provided by these natural resources include commercial and recreational fisheries, marine transportation, military uses, outdoor recreation, tourism, aesthetic qualities, and economic benefits associated with all of these activities. In a 2006 study by the Haas Center for Business Research that was commissioned by CBA, it was estimated that the total economic effects in the region related to the Bay include: 36,030 jobs, 2.4 billion in gross regional production and 2.3 billion in personal income. The report also concluded that improved water quality in the Bay will have a direct positive effect on the economy including increased tourist/recreational expenditures as more visitors come to the Bay. While the Choctawhatchee River and Bay watershed continues to support outstanding resources, it has also experienced many of the impacts that are common to Florida estuaries. These include urban stormwater runoff and other nonpoint sources of pollution, widespread sedimentation and habitat loss and degradation. Cumulatively, these impacts have degraded the productivity of the river and bay system and diminished the benefits it provides. Effective control of nonpoint source pollution can help to preserve and restore the natural resources and human benefits provided by the Choctawhatchee River and Bay system and limit the need for more expensive and difficult solutions in the future. Watershed Name: Choctawhatchee Bay Hydrologic Unit Code (HUC): 3140102 Sub-Basin Name: 86.9 Acre Industrial Sub-basin, Gap Creek Watershed Latitude: 30.42600 DEP Agreement No. G0326, Attachment A-1, Page 2 of 6 Longitude: 86.65674 86.9 Acre Lovejoy Industrial Sub-basin Land Use Land Use Acres Percent RESIDENTIAL HIGH DENSITY 1/8 AC OR 11.0 13 LESS COMMERCIAL AND BUSINESS 65.2 75 WETLAND FORESTED MIXED 256 3 OPEN SPACE FAIR CONDITION 8.12 9 Land Use Totals (Acreage and %) 86.9 100 POLLUTION REDUCTION STRATEGY: The Grantee completed a Stormwater Master Plan in 2003 to provide a comprehensive evaluation of stormwater infrastructure needs including analysis of water quality and flooding issues. The master plan included a comparative pollutant loading analysis of watersheds for total nitrogen, total phosphorous, total suspended solids and BOD. The analysis showed that the Gap Creek watershed had one of the highest loading rates for these pollutants in Okaloosa County. Based on the analysis of the Stormwater Master Plan, the Gap Creek Watershed Water Quality Improvements study (November 2008) was funded to identify specific stormwater retrofit alternatives for improving water quality and reduce flooding in the watershed. The City of Fort Walton Beach and the Grantee have identified the Gap Creek watershed as an area of need for stormwater improvement projects to reduce the loading of nonpoint source pollutants into Gap Creek, Cinco Bayou and ultimately Choctawhatchee Bay. This project is also consistent with the 2002 update of the District’s SWIM Plan for the Choctawhatchee River and Bay system. Recommendations in the SWIM plan include the assessment and abatement of non-point source pollution with an emphasis on urban stormwater runoff and implementation of urban BMP demonstration projects that include monitoring to demonstrate the applicability of BMP’s implemented. PROJECT DESCRIPTION: The Grantee will design (or cause to be designed) and implement the improvements to conveyance to the County Poplar Avenue Pond and minor pond modifications. The District will work with the Grantee to provide technical . assistance on the project and help manage the grant including review and comment on structural designs, quarterly and final project reporting, and assessment of BMP effectiveness. CBA will provide public outreach and educational press releases about the project. At least one volunteer event will be coordinated by CBA during the project for volunteers to participate with helping plant vegetation at the pond and/or provide trash cleanup around the project site and in the watershed. Catch basin markers will be installed to educate the public about their role in reducing non-point pollution that impacts the recreational water resources in their community. ESTIMATED POLLUTANT LOAD REDUCTION: Analysis shows that for the existing condition, the annual total runoff for the 86.9 acre Poplar Pond watershed is 291.9 ac-fi. Flooding occurs above mean annual event, and about 32 ac-ft or 11 % of the annual total runoff is bypassed. After the improvements are made, flooding only occurs for events above the 25 year event. Only 4% of the total runoff will be bypassed, or 11.6 ac-ft. Therefore, 20.6 ac-ft of runoff untreated in existing condition will be treated in the proposed condition. Using 1.2 mg/I TN, 0.26 mg/I TP and 65.2 mg/l TSS which are accepted as the EMCs for light industrial land use, the 20.6 acre feet being treated, and assuming 100% effectiveness for retention — approximately 66 Ibs/yr, 14 Ibs/yr and 3593 Ibs/yr will be removed for TN, TP and TSS, respectively. LAND OWNERSHIP STATUS: The drainage easement along Lovejoy Road where the cross drain is going to be installed is owned by the Grantee. The Poplar Pond site is also owned by the Grantee. No property will be purchased to implement this project. DEP Agreement No. G0326, Attachment A-1, Page 3 of 6 TASKS and DELIVERABLES: Task 1 Name: Execution of Agreement Description: Participate in refinement of the Grant Work Plan and the process to initiate and execute this Agreement with the Department to proceed with the project. Deliverables: Final scope of work and executed agreement. Performance Standard: The Department’s Grant Manager will review the Grant Work Plan and contract documents to verify that all of the information is correct prior to forwarding the Agreement for execution. Timeline: Start is prior to Agreement execution - completion is upon Agreement execution. Deliverables are due upon completion of the task. Task 2 Name: Construction Plans, Design and Permitting Description: The Grantee shall have the system improvements designed, which includes a cross drain under Lovejoy Road, the open channel conveyance improvements on the north side of Lovejoy Road, and minor upgrades of the existing County Poplar Pond and outfall structure.