fsa excellence award for stormwater projects iii. … · 17-03-2011 · fsa excellence award for...

FSA EXCELLENCE AWARD for STORMWATER PROJECTS – III. DESCRIPTION Lee County Division of Natural Resources – Lakes Park Water Quality Restoration Project

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Lee County, FL encompasses 804 square miles, 255 square miles of which are estuaries designated

Outstanding Florida Waters with a population over 600,000 full-time residents. Lee County is an award-

winning tourist destination with over $3 billion economic impact annually. Lee County’s Division of

Natural Resources (LCNR) manages 1,041 miles of waterways through stormwater pollution/illicit

discharge prevention, hazardous waste management, water resource monitoring, hydrologic

reconnection projects and water quality restoration.

Lee County has experienced a general decline in the quality of its surface water over the last several

decades due to development, agriculture and other human activities resulting in harmful algal blooms,

negative impacts to human and wildlife health, our economy as well as limiting the use of our water

resources. In accordance with Florida Administrative Code 62-303, the Florida Department of

Environmental Protection (FDEP) adopted TMDLs and subsequently basin management action plans in

Lee County to address water quality degradation. The primary pollutant of concern in Lee County is

nutrients, particularly nitrogen.

The Lakes Park Regional Park Facility (Lakes Park) is located in the headwaters of Hendry Creek, impaired

water body, a tributary to the Estero Bay, Florida’s first Aquatic Buffer Preserve and an Outstanding

Florida Water. The total drainage area contributing to Lakes Park is 1,750 acres. The drainage basin is

comprised of high-density residential and commercial land uses, many of which were built prior to

implementation of current water quality standards.

The Lee County is currently conducting a multi-phased

retrofit of Lakes Park to improve water quality of

stormwater runoff by routing flows through a created filter

marsh system. In addition to the recent filter marsh

expansion, Lee County is actively researching bio-chemical

processes to develop a water quality treatment facility on-

site further enhancing nutrient removal.

The Lakes Park Water Quality Restoration Project consists

of 30 acres of created wetland filter marsh system that is part of a multi-

use regional park that receives approximately 500,000 visitors per year

and supports recreational and educational opportunities, wildlife habitat

and community gardens. The multi-use facilities are supported by Lee

FSA EXCELLENCE AWARD for STORMWATER PROJECTS – III. DESCRIPTION Lee County Division of Natural Resources – Lakes Park Water Quality Restoration Project

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County Parks & Recreation and the Lakes Park Enrichment Foundation. This public-private partnership

has brought in millions of dollars in funding support, adding value to the residents and visitors of Lee

County by providing educational and recreational venues and events.

The Lakes Park Water Quality Improvement Project cost is $2,829,037 with $510,000 in grant funding

through the Florida Department of Environmental Protection and $1.2 million in funding from the South

Florida Water Management District. Personnel involved in the project include the Director, Roland

Ottolini, P.E., Surface Water Program Manager, Anura Karuna-Muni, P.E., Staff Engineer, Brian Bates,

P.E., Water Quality Planner, Karen Bickford, NPDES Operations Manager, Tony Pellicer, and NPDES

Coordinator Leigh Simmons. Project design, permitting and nutrient load reduction estimates were

performed by AIM Engineering & Surveying, Inc., and Boylan Environmental Consultants.

FSA EXCELLENCE AWARD for STORMWATER PROJECTS - IV. SUPPORTING INFORMATION Lee County Division of Natural Resources – Lakes Park Water Quality Restoration Project

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Hendry Creek is a tributary to the Estero Bay, designated Outstanding Florida Waters and the first

Aquatic Preserve in the state of Florida. Located in the southwestern Lee County in southwest Florida,

approximately 3 miles south of the City of Fort Myers and 3 miles southeast of the city of Cape Coral, the

Hendry Creek has a TMDL and a BMAP for total nitrogen and fecal coliform. Estero Bay proper is a

shallow, subtropical lagoon with an area of 17.7 square miles (mi2) (11,317 acres) separated from the

Gulf of Mexico by the barrier islands. In the past, the naturally dispersed water patterns distributed

nutrients over broad areas of wetland vegetation. Increased development since the 1960s has led to

changes in the natural river systems around Estero Bay, altering freshwater inflow patterns (Florida

Department of Environmental Protection [FDEP] 2003). The headwaters of Hendry Creek are bounded

by high-density residential and commercial land uses. Much of the watershed was developed prior to

current environmental resource permitting practices and lack sufficient treatment for stormwater

runoff.

The Lakes Regional Park Facility

(Lakes Park) is located in the

headwaters of Hendry Creek. The

total drainage area is 1,750 acres,

including the 329 acre Reflection

Lakes development. The upstream

portions of the watershed are

comprised of high-density

residential and commercial land

uses. The drainage basin runoff is

routed through a series of

wetlands, canals, and or weirs

before discharging into the Lakes

Park system. A public bathing

beach in the park was closed

several years ago due to poor

water quality. Lakes Park is

currently undergoing a multi-

phased retrofit to improve water

quality of flows received from

these upstream urban land uses.

Drainage basin boundaries,

system flow-through and

structures are indicated in Figure 1

(right).

The first phase of the project known as Reflection Lakes Flow Way located at the northern most in-flow

to Lakes Park is a sinuous marsh-type flow-way that creates an organic filtering system to help reduce

the quantity of surface water pollutants currently discharging into the Lakes Park from The Reflection

Figure 1


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Lakes development. Reflection Lakes Flow Way is a 10.3 acre meandering flow way constructed by back-

filling portions of the existing borrow-pit, creating peninsulas which increase the littoral area along the

flow-way, supporting native plantings for water quality improvement. Reflection Lakes is a 329.28-Acre

mixed-use development bound on the North and West by Cypress Lake Boulevard and Summerlin Road

respectively. In 1998 Engle Homes/Southwest Florida, Inc., the developer and owner at the time,

obtained permits for the Reflection Lakes Flow Way as part of the development. The flow way

construction was completed and operational in July 2000 and deeded to the County in 2006. The

Reflection Lakes Flow Way is an additional retention/filtration best management practice built by the

developer, who in return received park impact fee credits from Lee County to the offset water quality

impacts to Lakes Park.

The next phase of the water quality improvement project included improvements to circulation through

the west lake during periods of flow, and enhanced nutrient removal from the west lake by the addition

of littoral “benches”. New structures to enhance circulation within Lakes Park included an inflow

structure at the north end of the west lake (Figure 1, LPCT-1) and an outflow structure at the south end

of the west lake (Figure 1, LPCT-3). The west lake inflow and outflow structures were modified with

operable gates to achieve the overall permitted discharges and to prevent saltwater backflow through

the existing outflow structure. Three existing spoil islands near the public beach area were modified to

create littoral “benches” through the removal of excess spoil material and exotic vegetation and native

wetland plantings.

The third phase of the project utilized the “East Lake” and “West Lake” of the Lakes Park system as an

extension of the existing filter marsh (the Reflection Lakes Flow Way) to the north leading into Lakes

Park. The new filter marsh consists of a series of “peninsulas" alternating from the east and west bank of

the East Lake to create a sinuous flow path similar to the Reflection Lakes Flow Way to the north. This

sinuous path maximizes the flow distance and contact time between the lake water and the vegetative

plantings surrounding the peninsulas. The peninsulas are varying in width and height with the highest

point being less than 1.0 foot above the control elevation (2.83 ft above sea level) of the East Lake.

During high flow events, most of the peninsulas will be submerged. The peninsulas are planted with

trees, shrubs, and herbaceous vegetation native to Florida. The area surrounding the peninsulas is

underwater "littoral shelves" that extend

horizontally at a shallow slope out to a depth of 0.5

ft below sea level. The shelf supports native

herbaceous and floating plants to absorb nutrients

from the water. Beyond that point, the slope

steepens to the bottom of the lake (average depth

approximately -6.0 ft below sea level) to create a

main flow way for storm water and provide aquatic

life refugia. The West Lake filter marsh construction

included removing top material and exotic

vegetation from the spoil islands in the middle of

Lakes Park to convert those areas into shallow,


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submerged, meandering littoral shelves to support wetland vegetation plantings. Construction of the

filter marshes was completed in November 2012. Lee County estimates that the filter marsh system

alone will remove approximately 8,000 lbs/yr TN and 500 lbs/yr TP by macrophyte uptake, settling and

denitrification as well as bi-annual plant harvesting. Load reduction estimates were calculated as

follows:

Mass Removal Rate (MRR) and Annual Removal Rate (ANR) Calculations – Following the load reduction estimate includes Kadlec and Knight (1996) and the MRRs for the Lakes Park system were estimated using measured data from a project with similar environmental conditions and native vegetation as the project under consideration. The Ten Mile Canal filter marsh, located less than a mile from Lakes Park, was deemed appropriate for this purpose. Boylan Environmental Consultants (2010) first determined the MRR for Ten Mile Canal using monitoring data then adjusted these MRRs to account for the “operational” differences between the filter marsh systems. Specifically, the MRRs were adjusted to account for the fact that Lakes Park is an inline system, so losses via percolation into the surrounding soils is not expected to occur and if so, at a reduced rate compared with Ten Mile Canal. The adjustments were made by assuming that the outflow volume for Ten Mile Canal equals the inflow volume minus evapotranspiration losses. The adjusted MRRs were then used to determine the ANR for Lakes Park according to the equation: MRR (lb/acre/yr) x Filter Marsh Area (acres) = ANR (lbs/yr)

The calculated adjusted MRRs for TN and TP are 231.13 and 14.43 lb per acre per year, respectively. For purposes of estimating the ANR for the Reflections Flow Way, it was assumed that the MRRs for Reflection Lakes are the same as those calculated for West Lake and East Lake. The following table summarizes the estimated annual nutrient load reductions for each of the three project components. Component Treatment Acres MRR (lb/ac/yr) ARN (lb/yr)

East Lake 17.04

TN 231.13 3,938.5

TP 14.43 245.9

West Lake 8.95

TN 231.13 2,068.6

TP 14.43 129.1

Reflection Lakes Flow Way 10.3

TN 231.13 2,380.6

TP 14.43 148.6

Total 36.29

TN 8,387.7

TP 523.6

Because a filter marsh alone might not achieve the water quality improvement objectives for the much

more turbid West Lake, other treatment processes to reduce nutrients were proposed. The two

processes Lee County is currently considering for additional treatment includes alum injection and ultra-

violate (UV) bio-carbon treatment.

The Comprehensive Everglades Restoration Program (CERP) has helped spur investigation of various

nutrient reduction technologies as well as refining our understanding of the issues that drive nutrient

reduction in various treatment systems. An important finding from CERP is that dissolved inorganic


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nitrogen (DIN) are labile and can be treated effectively in passive treatment systems such as filter

marshes by macrophyte uptake and dentrification, whereas dissolved organic nitrogen (DON) is

recalcitrant and cannot be utilized by macrophytes nor denitrify, leading to export of nitrogen from the

system. This led to the realization that to effectively treat surface water runoff for nitrogen, we have to

convert DON to DIN to allow macrophyte uptake and anaerobic denitrification.

Aluminum Sulfate ("Alum") injection is used commonly to accomplish algae precipitation in drinking

water treatment systems. Lee County’s Olga Water Treatment Plant uses Alum (with other processes) to

make drinking water from the Caloosahatchee River. Alum has also been used extensively for sediment

control on construction projects and nutrient removal for lake restoration most prominently by the

Reedy Creek Improvement District in Orange County, Florida. While alum has been implemented with

success for stormwater treatment in other locations it has high operation and maintenance costs. The

results of Lee County’s pilot alum testing project completed in 2010 at Lakes Park for surface water

treatment were compelling; nutrient removal efficiencies of 33% for TN and 78% for TP optimized at 70

ppm alum. As indicated in the Lakes Park final alum pilot test report, the County would have to factor in

sludge processing, handling, pH management in the returning waters and removal options that would

include variations on cost, staff, and other park-affecting requirements. Taking this into consideration

Lee County is currently conducting research at Lakes Park to compare the costs and benefits of UV/bio-

carbon treatment in addition to alum treatment.

Ultra-violet/bio-carbon treatment is an emerging field of research. The lead investigator for this pilot

project, HSA Engineers & Scientists, Inc., the County’s engineering consultant, specialized in nutrient

removal optimization for CERP. To date HSA has conducted literature research finding strong evidence

from various bodies of work1 that ultra-violet light can be used to cleave organic nitrogen and that the

resulting product are labile nitrogen forms; ammonia and nitrate. Ammonia and nitrate/nitrite are

relatively easy forms of nitrogen to treat aerobically or anaerobically. Ammonia is easily converted to

nitrate by denitrifying bacteria under aerobic conditions and under anaerobic conditions nitrate in the

presence of bio-carbon is readily converted to nitrogen gas (denitrification), effectively removing it from

surface waters.

Upon conclusion of the UV/bio-carbon pilot study and comparison of Alum and UV/bio-carbon

treatment costs and benefits, Natural Resources will select the most cost effective of the two treatment

technologies and proceed to design and permit a full scale (2 MGD) treatment facility situated and

hidden from view so as not to disturb park visitors or wildlife. The facility will provide a complete

“turnover” of West Lake water twice a year. The clarified water from the treatment facility will be

returned to the headwaters of the West Lake for repeated passes through a new filter marsh for further

nutrient removal. Along the route of the recirculating line, lateral lines will be installed to allow for

additional aeration and circulation within the West Lake. It is projected that over time, the quality of

water in the Park will be restored to levels that will allow uses currently not possible, and reduce the

impact on the downstream estuarine system.

1Phase I Pilot Testing To Reduce Nitrogen Content of Surface Waters, HSA Engineers & Scientists, Inc., March 17, 2011.


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fsa excellence award for stormwater projects iii. … · 17-03-2011 · fsa excellence award for...

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