Johnson Engineering provides a variety of monitoring and program guidance to assist our clients with satisfying the conditions of their National Pollutant Discharge Elimination System (NPDES) permits. The primary objective of this monitoring program is to identify potential water quality problem areas related to stormwater runoff that can be targeted for corrective action, retrofits, or non-structural Best Management Practices (BMP). A secondary objective is to indicate, refine and document land-use-specific pollutant loadings for specific watersheds or outfall areas. At the Southwest Florida International Airport, Johnson Engineering performs inspections of Lee County Port Authority (LCPA) operated facilities to determine the effectiveness of the storm water pollution prevention plan (SWPPP). Johnson Engineering also designed the pollution prevention training program, which includes topics such as spill response, good housekeeping, material management practices, preventive maintenance, spill prevention, source reduction, runoff management, sediment and erosion control, and record keeping.
As part of a stormwater research partnership between the Florida Department of Environmental Protection (FDEP) and Bonita Bay Group, a golf course maintenance building at the Shadow Wood Preserve development was selected as southwest Florida’s green roof pilot project. Johnson Engineering outfitted the roof with sensors above and below the plants to monitor temperature, heat flow, moisture content, rainfall and runoff. We also provided data collection and monitoring of the green roof system.
Refrigerated, automated samplers were installed to collect flow composite storm event runoff water quality samples from each of the green roof plots. The samples were laboratory analyzed for total suspended solids, nutrients and metals. Results from the green roof runoff were compared to the quantity and quality of runoff from more traditional roof types to evaluate the environmental benefits of this best management practice (BMP).
Amidst growing concern over upcoming Total Maximum Daily Loads (TMDL) limiting the amounts of particular pollutants allowable in impaired water bodies, The City of Bonita Springs decided to take a pro-active approach by developing a water quality monitoring program to characterize water quality upstream and downstream of commercial and industrial areas located within the city limits. The surface water quality monitoring program was implemented by Johnson Engineering on June 28, 2006. This monitoring enables a snapshot view of water quality entering, flowing through and discharging from the City of Bonita Springs. The primary conveyances for surface water runoff from the City of Bonita Springs into Estero Bay are Spring Creek and the Imperial River, which have been listed by The Florida Department of Environmental Protection (FDEP) as impaired water bodies. The water quality program monitors the parameters of concern listed, as well others. Nine surface water quality sample locations were approved by the City of Bonita Springs; including three inflow locations where surface water enters the city, and six interior commercial and industrial locations. Water quality samples, flow measurements and ambient field measurements are collected by Johnson Engineering on a monthly basis.
In 2004, the Lee County Division of Natural Resources commissioned a study to investigate the pollutant removal efficiencies of stormwater Better Management Practices (BMP) in Lee County, Florida. This study, designed by Johnson Engineering, identifies, prioritizes, and recommends the most effective BMPs to identify that post-development pollutant discharge does not exceed pre-development loading rates. Three wet detention systems in three different land use categories were selected as the representative project areas. These areas include a residential/golf course community, residential only community and large commercial development. Surface water runoff and discharge from each of the wet detention systems was monitored.
All three sites are representative of conditions generally found in developing areas in Southwest Florida such as soil types, drainage, and environmental conditions. The specific project sites were selected based on willingness of the owners to participate, the layout of the wet detention system, site security and access. Beginning May 3, 2006, we installed water monitoring equipment including automated samplers, tipping bucket style rain gauges, submerged probe flow meters and water level dataloggers. We programmed the automated samplers to enable during a rainfall event when pre-set rainfall and stage conditions were met. Upon enabling, the samplers notified us by telephone and collected composite samples based on flow detected by the submerged flow probe. Our team proceeded to the project site, collected the refrigerated samples in laboratory containers, placed them on ice and delivered them to a state certified laboratory.
Each water quality sample collected during a qualifying rain event was analyzed for nutrients, chlorophyll-a, total suspended solids, dissolved metals and total metals. These parameters have been identified as pollutants of great concern in southwest Florida water bodies and were chosen because of their relevance in the BMP selection process.
Laboratory analysis results from each site are used to calculate flow composite event mean concentrations (EMC) for each monitored parameter. Pollutant removal efficiencies for each parameter of interest are calculated and compared to typical efficiencies of wet detention systems, as well as other types of stormwater management systems. Flow data recorded at each site will then be combined with EMC data to assist in quantifying the annual reduction in pollutant loading provided by each of the three monitored stormwater BMP areas.
A water quality monitoring program requested by Lee County Department of Natural Resources (LCDNR) for the Ten Mile Filter Marsh was executed by Johnson Engineering on February 27, 2007. The objective of the program is to implement a long-term water study to document and track the effects of the Ten Mile Filter Marsh system in accordance with the provisions of specific conditions within the Florida Department of Environmental Protection (FDEP) Environmental Resource Permit (ERP). Attention was particularly focused on the mass pollutant load removal efficiency of the system. As part of this objective, Johnson Engineering installed automated samplers and water level dataloggers in the first and last of the four cells that make up the filter marsh system. We record monthly stage levels shown on our gauges in each of the four cells within the filter marsh as well as the areas immediately upstream and downstream of the filter marsh area. In addition, we downloads digital stage data from the continuous recording dataloggers. The water level data is used to estimate flows through the system, which coupled with the laboratory analytical data, provides a monthly efficiency analysis of the overall system. Flow entering and exiting the filter marsh system is also verified using a flow probe.
Water quality samples are collected quarterly from the intake and outfall of the filter marsh system. These quarterly samples are collected in conjunction with specific rainfall event intensities and increases in stage. Following notification from the automated samplers via text message, we mobilize our team to the project site and collect the composite samples and record ambient water and weather conditions. Grab samples are also collected at each sample location. The samples are laboratory analyzed for nutrients, metals, bacteria and total suspended solids. The first year of monitoring will be completed in December 2007. Reports summarizing the water quality results, stage and flow data, and pollutant removal efficiency of the filter marsh system are prepared and submitted to LCDNR quarterly.
Johnson Engineering was contracted by the Florida Department of Transportation (FDOT) in June of 2004 to evaluate stormwater runoff pollutants and nutrient loadings from four state roadways and associated wet detention ponds within FDOT District One in southwest Florida, which extends from Manatee County southward to Collier County along the gulf and eastward to Lake Okeechobee. The water quality ponds were selected from Lee, Collier and Hendry counties based on various levels of service or average annual daily traffic (AADT) counts on the associated roadways.
In addition to characterizing the quality of stormwater runoff from the roadways, pond pollutant removal efficiencies were evaluated using the summation of loads (SOL) technique, which compares mass loads entering the ponds versus leaving the ponds. Flow data was combined with the laboratory analyzed water quality concentrations to calculate these mass loads.
Refrigerated, automated, programmable samplers were used to collect water quality samples, record water levels and monitor flow in each pond. A tipping bucket style rain gauge was also installed at each of the wet detention ponds to record rainfall. In addition to the rain gauge, a rainfall collection device was also installed at each wet detention pond.
Ten storm event samples were collected at each of the wet detention ponds over a period of one year. The samples were collected from four locations at each monitored wet detention pond and associated roadway: a roadway inlet in front of the pond, the pond inlet pipe, the pond outfall structure and a rainfall collection device. Each of the storm event sample sets collected at the inlet locations were triggered by rainfall intensities and flow. Event samples collected at the pond outfall locations were triggered by pond levels at the outfall structure that produced discharge. During each monitored storm event, the automated samplers collected sample aliquots over the course of the event based on the amount of flow detected. Following remote notification via telephone, our team drove to the sample and collected the samples in accordance with Florida Department of Environmental Protection (FDEP) Standard Operating Procedures (SOP).
The storm event samples were laboratory analyzed for parameters including total suspended solids, nutrients and metals. Results obtained from these samples were compared to other water quality studies of state roadways in Florida and to state water quality standards.