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TRANSCRIPT
FSA Stormwater Seminar 2017
TARGETED WATER QUALITY MONITORING
Agenda
Discuss City of Lakeland’s Approach1. List of Prioritized TMDL Lakes2. Targeted Water Quality Approach on Initial Lakes3. Revised Targeted Water Quality Approach for Future
City of Lakeland’s TMDL Prioritization List
PRIORITY WBID
SEGMENT NAME CO-PERMITTEES
1 Lake Hunter Major FDOT highways cross basin
2 Lake Bonny Major FDOT highway bisects basin
3 Crystal Lake
Approximately ½ of MS4 Contribution is County; #3 on County’s List; Some FDOT contribution.
4 Lake ParkerSome County MS4; #15 on County’s List; 3 Major FDOT highways cross basin
5 Lake Hollingsworth
Lake Hunter Targeted Monitoring- Watershed
Summary of Lake Hunter Targeted Monitoring # Monitoring Element Sampling Description Takeaways from Sampling
1
Lake to Lake Discharge (From Lake Beulah)
-No Beulah discharge- Storm Event sampling observed for local (MFR) drainage
- EMCMFR for TN much higher than State average- Provides limited information relative to Beulah discharge contributions to Lake Hunter-Pollutant load estimate in model should be adjusted down
2Lake to Lake Discharge (From Lake Wire) - Storm Event sampling
-Monthly BaseflowSamples
-EMC of the mixed landuse was well below State averages of the contributing land uses.-Frequent street sweeping was theorized as driver for lower EMC-Pollutant load estimate in model should be adjusted down-Nutrient loads from a combination of base and storm flows remains a significant load to the Lake
3High Load Outfall from Mostly Single Family Residential Land - Storm Event sampling
- EMCSFR for TN and TP is higher than State average- Tree cover and alleys may be driver for higher EMCs- Pollutant load estimate in model should be adjusted down
4
Single Family Residential Outfall (EMC purposes) - Storm Event sampling
- EMCSFR for TN and TP is significantly higher than State average- Tree cover and alleys may be driver for higher EMCs- Pollutant load estimate in model should be adjusted down
5 Lake Sediments-Bathymetric Survey-Characterize TP in sediments
- 288,000 cy muck of 5.5’ avg. depth- 22,000± lbs. of TP in sediment considered to have high to medium-high potential for release (point of reference: 500± lbs. TP from MS4)
Lake Hunter Targeted Monitoring- Impact on Load Reduction Targets
Pollutant Load Estimates for Non-point Sources (Landuse-Based)
TN (Lbs/Yr) TP (Lbs/Yr)
TMDL 5,259 769
Previous Landuse-Based Model (for Year 3 Annual Report) 3,194 478
Landuse-Based Adjusted by Targeted Monitoring 2,833 431
•Priority outfalls did not change from modeled to monitored condition.•The 80% TMDL reduction for TN and TP will be applied to that portion of the Non-point source load that is discharged through MS4 outfalls.
Lake Bonny Targeted Monitoring- Watershed
Summary of Lake Bonny Targeted Monitoring
# Monitoring Element Sampling Description Takeaways from Sampling
1
High Load Outfall from Mixed: Med. & High Density Res., Comm, Light Ind, & Major Highway Landuse
- Storm Eventsampling
- EMC for TN and TP were much higher than State average for all but high density residential
- Pollutant load estimate in model had to be adjusted up by 10% for TP and 16% for TN
2
High Load Outfall from Mostly Commercial, Med. Density Res., and Major Highway Landuse
- Storm Event sampling
- EMC for TN and TP were much higher than State average for all landuses
- Pollutant load estimate in model had to be adjusted down by 140±% for TP and TN
- Outfall remains a high nutrient load generator
3High Load Outfall from Mostly (>90%) Low Int. Commercial Land
- Storm Event sampling
- EMC for TN and TP is 50% higher than Stateaverage for Low Int. Commercial
- Pollutant load estimate in model must be adjusted up due to high actual EMC
4 Lake Sediments-Bathymetric Survey-Characterize TP in sediments
- 533,000± cy of unconsolidated sediments up to 10 feet deep
- 16,300± lbs. of TP in sediment considered to have high to medium-high potential for release (point of reference:1,070± lbs. TP from MS4)
Lake Bonny Targeted Monitoring- Impact on Load Reduction Targets
Pollutant Load Estimates for Non-point Sources (Landuse-Based)
TN (Lbs/Yr) TP (Lbs/Yr)
TMDL (expressed as lake concentration) N/A N/A
Previous Landuse-Based Model (for Year 3 Annual Report) 6,530 1,149
City of Lakeland Landuse-Based Adjusted by Targeted Monitoring 6,000± 1,070±
•Priority outfalls did not change from modeled to monitored condition•The 60% TMDL reduction for TN and 64% reduction for TP will be applied to that portion of the Non-point source load that is discharged through MS4 outfalls.
Crystal Lake Targeted Monitoring- Watershed
Summary of Crystal Lake Targeted Monitoring
# Monitoring Element Sampling Description Takeaways from Sampling
1
Major Outfall from Mixed: PrimarilySFR and MFR with some Commercial and Open Space
-Storm Events sampling
- EMC for TN was much higher than State average for residential land uses
- Pollutant load estimate in model had to be adjusted up by 50%± for TN
2High Load Outfall from Primarily SFR Land Use
-Storm Events sampling
- EMC for TN and TP were much higher than State averages.
- EMCSFR for TP is higher than for other City lake basins and for TN is consistent with the EMC from other City lake basins
3 Lake Sediments-Bathymetric Survey-Characterize TP in sediments
- 33,700 cy unconsolidated sediments with 2 discernible deep pockets
- 5,500± lbs. of TP in sediment considered to be bioavailable (reference to: 123± lbs. TP from MS4)
Summary of Crystal Lake Targeted Monitoring (cont’d) •An improved estimate of the potential impact from lake sediments looking at TP flux from the unconsolidated sediments was desired
•First approximation was based on TP incubation test work done in Pinellas County where the flux was related to the mean sediment TP concentration:
•Crystal Lake had a laboratory-based TP estimate of 7,480 mg TP/kg in the sediments
•This resulted in an estimated TP flux of 4,781 kg P/km2/yr (nominal) to 56,873 kg P/km2/yr (mean) and subsequently a range of 1,200± to 14,000±Lbs TP (net internal load)
Crystal Lake Targeted Monitoring- Impact on Load Reduction Targets
•MS4 nutrient contribution estimates: • 843 Lbs TN & 123 Lbs TP
•Potential TP contribution to the water column ranges:• 1,200 Lbs (nominal) to 14,000 Lbs (mean)
•The TMDL requires a 51.3% reduction in TN and a 79.2% reduction in TP from contributing MS4 discharges. It also requires a 75% TP reduction from benthic (e.g. unconsolidated sediment) flux
•Current Action Plan: City and County want to move forward with looking at alternatives for controlling the lake sediment nutrient source.
Lake Parker Targeted
Monitoring-Watershed
Initiation of Lake Parker Targeted Monitoring # Monitoring Element Sampling Description
1 Lake to Lake Discharge (From Lake Crago) - Monthly grab sampling
2
Major Outfall at the SW Corner of the Lake- This outfall was retrofitted with relatively small sediment sump and vegetated linear wet pond.
- Storm Event sampling of BMP inflow & discharge- Monthly Baseflow Samples
3Lake Parker Canal- This major conveyance was retrofitted with an offline wet detention pond.
- Storm Event sampling of BMP inflow & discharge- Monthly Baseflow Samples
4 FWC Teneroc Preserve - Monthly Baseflow Samples
5 Major Outfall- TBD - Storm Event sampling of BMP inflow & discharge
6 Lake Sediments
- Bathymetric Survey- Characterize TP in sediments- Conduct sediment flux core tests under aerobic and anoxic
conditions
7 Lake Ambient Sampling- Expanded to include vertical water column profile of monthly
DO, pH, T°, Cond. to document conditions above sediment through year
In the Future: Lake Hollingsworth
•This lake was dredged in the 1990’s
•A whole lake alum treatment has been performed since then
•Retrofits to date include: 2 stormwater ponds, 5 skimmer boxes, 11 baffle boxes, 34 inlet baskets
•Public education including the annual cardboard boat race is held on this lake
Yet……….
In 2015, FDEP established a nutrient TMDL for a 52% reduction in TN and a 57% reduction in TP. The work continues.
Example Sampling Station Monitoring Station Dashboard
Utility of an In-place Monitoring Station - Hurricane Irma!
Utility of an In-place Monitoring Station - Hurricane Irma!
