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Home My WebLink About2009 10 26 Informational 101 Informing About The Oak Forest Lake Treatment ProgramCOMMISSION AGENDA ITEM 101 October 26, 2009 Meeting CONSENT INFORMATIONAL X PUBLIC HEARING REGULAR vIGR ,, , /DEPT /~ij Authorization REQUEST: The Public Works Department / Stormwater Division Informing the City Commission About the Oak Forest Lake Treatment Program PURPOSE: The purpose of this agenda item is to provide the City Commission with a summary of the planned activities for the Oak Forest Lake Treatment Program. OAK FOREST LAKE TREATMENT PROGRAM SUMMARY: • Staff is recommending a two phase update of the Oak Forest Lake Treatment Program. The first phase consists of spatterdock removal through application of Sonar chemical treatment starting in November 2009. The second phase is to implement water quality improvements consisting of the re-installation of littoral zone aquatic plantings along the east shoreline, and the installation of two high-capacity curb inlet filtration baskets at the two storm inlet structures located at Oak Forest Drive and Chokecherry Court. To prevent fish from consuming the aquatic plantings, a temporary underwater barrier will be installed to isolate the plantings from the fish. The purpose of the filter baskets is to provide treatment of stormwater run-off through the removal of pollutants (and trash) before they enter the lake. The second phase is planned for implementation in early 2010. • The following is a summary of the lake treatment program to date and the options considered for the current treatment program. Staff intends to utilize our experiences with the Oak Forest Lake Treatment Program to improve water quality management activities throughout the City. This agenda item is being distributed to all residents surrounding Oak Forest Lake along with a request for their input. CONSIDERATIONS: • spatterdock (also known as yellow water lily) is a rooted aquatic plant with large floating leaves common to lakes and ponds in Florida. Oak Forest Lake experienced a spatterdock bloom in 2006 that became difficult for the City to manage and it was unsightly for the lakefront residents. While spatterdock is beneficial to water quality, wildlife habitat, and it can be an important part of a lake ecosystem, it can also be difficult and costly to control its growth. Most lakefront residents felt the spatterdock was unsightly, especially at the extent it was covering the lake in September, 2006. Informational Agenda Item #101 October 26, 2009 Page 2 of 9 After meeting with the surrounding residents in 2006 to discuss lake treatment options, the lake was treated several times with an herbicide called "Sonar." Sonar is highly effective at removing spatterdock, but it can also damage lawns and therefore the lake could not be used for irrigation during the treatment period. The surrounding residents were highly cooperative with the Sonar treatment program and they complied with the temporary irrigation restriction during the treatment period. • The photo below is from October 2006 in the pre-treatment conditions, followed by a photo of the post-treatment conditions in February, 2007. The Sonar treatment program substantially eliminated the spatterdock. After the Sonar treatment was complete, Staff met at the lake with Amy Giannotti, a scientist from the Fish and Wildlife Conservation Commission -Invasive Plant Management Section. Ms. Giannotti observed the lake and confirmed the success of the Sonar treatment but she also noted that in several years we may see the spatterdock start to return. • In July 2009 it was observed that the spatterdock had indeed started to return to the lake, although not nearly to the extent of coverage in 2006. October 16, 2006 -Pre-treatment Condition Informational Agenda Item #101 October 26, 2009 Page 3 of 9 PLANNED OAK FOREST TREATMENT PROGRAM FOR 2009 - 2010: PHASE 1- SPATTERDOCK CONTROL • The planned first phase of the lake treatment program is to manage /control the spread and growth of the spatterdock. Staff has directed Lake Masters Aquatic Weed Control Inc, the City's aquatic weed control contractor, to implement the application of Sonar beginning on November 9, 2009 with periodic treatments as needed for approximately 45 to 60 days. The application of the Sonar treatment at Oak Forest Lake is included in the contract agreement with Lake Masters Aquatic Weed Control Inc. During the Sonar treatment period the lake water should not be used for irrigation. Staff will send out notices to lakefront residents advising them about the temporary irrigation restriction prior to the Sonar treatment. PHASE 2 -IMPROVE WATER QUALITY • The planned second phase of the lake treatment program is to address the water quality in the lake with the implementation of project(s) that will provide long term benefits to the lake. Staff explored and researched several lake water quality options, as described in the following pages. WATER QUALITY OPTIONS: 1. Install aquatic plantings in the lake and along the shore lines (littoral zone). The littoral zone is an area of aquatic plantings near the shoreline that provides many benefits including stormwater pollutant removal, bank stabilization, and wildlife habitat. Littoral zone plantings were installed at Oak Forest Lake in early 2007. Unfortunately, the littoral planting zone did not flourish as planned primarily due to the presence of weed eating Triploid Grass Carp in the lake. Oak Forest Lake has an abundant Grass Carp population and with almost no other vegetation available within the lake the Grass Carp quickly consumed the new plantings. August 17, 2009 -Current Condition Informational Agenda Item #101 October 26, 2009 Page 4 of 9 2. Install floating plant mats at one or more locations. Floating plant mats provide the benefits of vegetated littoral shelves without having to deal with the problems associated with changing water levels. Floating plant mats use interlocking mats, combined with aquatic plants in perforated pots, to suspend a simulated shallow water environment. This not only takes care of fluctuating water levels, but also produces oxygen, takes nutrients and pesticides out of the water, and provides habitat for wildlife utilization. The floating plant mat consists of puzzle cut mats held together by nylon connectors. After the mats are connected, plants are inserted into pre-cut holes. The plants may be any species of emergent aquatics. The mats can be attached to anchors or shoreline stakes. Littoral Zone Planting (Photo of a city maintained pond) Floating Plant Mat at Lake Eola Informational Agenda Item #101 October 26, 2009 Page 5 of 9 3. Installation of Bioretention filters at stormwater inlets surrounding the lake. Bioretention filters are stormwater treatment structures located immediately upstream and adjacent to the existing curb inlets. Stormwater runoffdrains directly from the street through an inlet filtration structure in a concrete box and flows through filter media consisting of mulch, plants, and soil. Treated water flows out of the system via anunder-drain connected to the adjacent curb inlet (see diagram below). The main benefit of bioretention filters is that they treat runoff and remove pollutants before they reach a water body. filrerra~ 17+Rnry Mab YwwiW ~. 4. Installation high-capacity curb inlet filtration baskets at stormwater inlets adjacent to Oak Forest Lake. Filtration baskets consist of a shelf /holder fastened inside the existing storm inlet structure where the removable filter basket will be placed. The filter baskets perform as amulti-stage filtration system when capturing the sediment, foliage, phosphates, litter, hydrocarbons and other types of pollutants that flow to the lake. For maintenance, the filter baskets may be removed from the shelf /holder for manual cleaning or direct removal of the basket contents. _~~~,.. M.v,wrbai~p cw« e cwe~wa.ur~ca rbnw«Mavn.c.gw. aan.w.~.a ~.enasP.tlaew,rsf, co.ae»a.c.r f nm4tiaa~un.p new, f ~w.,u,+~..a.~a.k f Typical Bioretention Filter Informational Agenda Item #101 October 26, 2009 Page 6 of 9 Hiah Caaacity Curb Inlet Filtration Baskets ~~ ~ ~: ~~~ ,. a,~:m~~K :.~ ~, ~_ .., ,,,,_ ~y'.~:_~M: :~Y' Typical Filtration Basket 5. Install Floc-Logs at various lake inflow locations. Floc-Logs by Applied Polymer Systems, Inc. are blocks made of a semi- hydrated polycrylamide blend that when placed within turbid water flows will remove fine particles and reduce turbidity. Floc-Logs can be placed directly in stormwater pipes or in storm structures. Floc-Logs have recently been installed on a trial basis by Seminole County at a pond in Central Winds Park and there has been a noticeable improvement in pond water quality. -, ,;y ;i ` Filtration Basket Schematic Basket Removed for Cleaning Floc-Logs Typical Curb Inlet Informational Agenda Item #101 October 26, 2009 Page 7 of 9 Oak Forest Lake Treatment Options Summary OAK FOREST LAKE -Water Quality Treatment Options No. Description of Treatment Area /Quantity Unit Cost Total Cost Review -Evaluation (Pros or Cons) 1 Aquatic f~it#t~ at t~ttora! Zont S,fl[~ ~' =1,26Q piat~ $0.55 / $693.110 ~"+a- - ~ overa~ +iv~ar ~ beneRts ait io~ur cost - Tea-poran- e4 crier soa Lf $J..~a / kF . - t>~., caw, - i1~5c pro~c~ect frava ~t ptior- t ,~ . 2 Aquatic Planting in Floating Mats 1,008 SF $7.80 / SF $7,862.40 Pro -Attractive, beneficial to water quality Barrier Nets 1,008 SF $0.85 / SF $856.80 Con -Plants will need replacement routinely and continue to Recommended Water Sampling LS $500.00 500.00 need funding every replacement (High $) Total $9,219.20 3 Bioretention Filter 1 unit -Storm Structure $9,450.00 $9,450.00 Pro -treats run-off before pollutants enter lake Con -Not practical for the area to be put in + High $ 4 High Capacity Curb Inlet Basket 2 units -Filter baskets $995.00 ea $1,990.00 Pro - Proven to be effective and economical Con -Requires periodic maintenance 5 i~ac:~.~d 0~ 7~ i.oc~ions t 1 AO $~-,~.Qii lt~~" Torts taiE`het~xe~Ler lake Informational Agenda Item #101 October 26, 2009 Page 8 of 9 RECOMMENDED WATER QUALITY PLAN: After review and evaluation of the benefits and costs of the available options, the following water quality improvement activities are recommended for Oak Forest Lake: o The replenishment of the aquatic plantings at the littoral zone area is beneficial to water quality and cost effective to implement. The designated littoral zone is the uninhabited shoreline area along the lake's east side. A variety of beneficial plant species will be provided, and a temporary barrier will be installed to prevent the weed eating Triploid Grass Carps from consuming the plants. The temporary fish barrier will be a wire fabric fence that will extend along the length of the planting area at a depth from just above the water surface to the lake bottom. The City has permits issued by the Fish and Wildlife Commission to stock lakes and ponds with triploid Grass Carps as a biological means to treat the lakes and ponds to reduce dependence on the herbicide applications. The aquatic plantings are scheduled to be imalemented January/February 2010. The estimated cost for installation of a 5,000 square foot littoral zone area including the temporary fish barrier is $1,443.00. City Pond Before Littoral Planting City Pond After Littoral Planting o The installation of Hiah Caaacity Curb Inlet Filtration Baskets at the two storm inlet - structures located at Oak Forest Drive and Chokecherry Ct. will provide treatment of stormwater run-off, the removal of the pollutants before they enter the lake, and trash collection. The City currently has curb inlet filtration baskets installed on seven (7) storm structures located on the west side of the City. The total cost for two (2) units of high capacity curb inlet filtration baskets is $1,990.00. These two units are scheduled to be installed in January/February 2010. Informational Agenda Item #101 October 26, 2009 Page 9 of 9 FUNDING: None RECOMMENDATION: N/A ATTACHMENTS: None COMMISSION ACTION: