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 Study Design         I. Lawn Fertilizer Experiment             II. Real-time Creek Monitoring
Purpose
This study has been designed to assess the potential to reduce phosphorus levels in residential runoff by restricting the use of lawn fertilizer containing phosphorus.

Planned Monitoring Period
Spring 2001 - Fall 2002


Study Design I.
Lawn Fertilizer Experiment

Study Design II.
Real-time Creek Monitoring

Maple Grove #2 Maple Grove #3 Maple Grove #1 Plymouth #1 Plymouth #2 Plymouth #3
Maple Grove map legend
Plymouth Map legend

fertilizer application Study Design I. The Lawn Fertilizer Experiment
Six small watersheds have been selected as study sites. Three of these watersheds are located in Plymouth where the use of fertilizers that contain phosphorus is restricted, and three are located in Maple Grove, where there are no such restrictions. These watersheds were carefully selected to include one newly developed area, one middle-aged, and one older neighborhood within each of the cities. All of these watersheds are located within 6 miles of each other to minimize differences in precipitation patterns, soil types, and aerial loading of phosphorus.


In each of these watersheds, runoff flows to a single outlet pipe. Automated sampling equipment was installed at each of these outlet points to collect detailed flow information and flow-weighted composite water samples. By determining the mean phosphorus concentration and the total flow volume for each rain event, we will be able to calculate the total phosphorus load from each watershed during the monitored period. If restricting the use of fertilizers containing phosphorus reduces the amount of phosphorus in residential runoff, we should see significantly lower phosphorus loading from the Plymouth watersheds when compared to runoff from the Maple Grove watersheds.

Additional information has been collected to assess the potential role of other variables in leading to differences in phosphorus loading between Maple Grove and Plymouth. Each city has provided lot size information and percent impervious area for the watersheds, and surveys will be administered to all homes within each watershed to determine lawn-care practices including fertilizer application, watering, mowing, and aeration. The watersheds in Plymouth were surveyed in the spring of 2001, but Maple Grove residents will not be surveyed until the fall of 2002 to prevent any changes in lawn-care practices during the planned monitoring period. To maximize the number of Plymouth residents using phosphorus-free fertilizer, Hennepin Parks has offered a free bag of phosphorus-free fertilizer to a select group of homes that indicated that they had been using fertilizer with phosphorus or that did not respond to the survey.


stream

Study Design II. Real-time monitoring of Plymouth and Ridgedale creeks
Two of the major tribuatry streams that flow into Medicine Lake, Plymouth Creek and Ridgedale Creek, are being monitored. Both monitoring sites were equipped with ISCO 6712 automated samplers with area-velocity flow modules and communication modems for remote access. These samplers were programmed to begin sample collection ata trigger water level and then collect additional samples based upon the flow in the stream. Flow data were downloaded weekly and water samples were retrieved within 24 hours of each flow event. In addition, the Plymouth Creek site was also equipped with a YSI

multiprobe sonde to collect DO, temperature, pH and conductivity data. All water samples were analyzed for total and dissolved phosphorus, total nitrogen, suspended solids, and in some cases, ammmonia, nitrate, and total solids.
Equipment
ISCO GLS Automated Water Samplers
ISCO 6712 Automated Water Samplers
ISCO 4120 Submerged Probe Flowloggers
ISCO 4150 Area/Velocity Probe Flowloggers
ISCOISCO 6712ISCO 4120ISCO 4150

Quality Assurance and Quality Control

Samples analyzed under same QA/QC protocol as Hennepin Parks lake samples. Blanks, replicates, duplicates, recovery of known additions, as recommended in Standard Methods 1020 and 1030

 

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