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Stormwater and Existing Development

Stormwater and Existing Development. Subcommittee Update. Our Process. Initial Meeting 9/27/2011 Agreed to Purpose “Characterizing nutrient sources from existing developed lands” Set General Goals & Objectives Loading from various uses (residential, industrial, etc)

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Stormwater and Existing Development

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  1. Stormwater and Existing Development Subcommittee Update

  2. Our Process • Initial Meeting 9/27/2011 • Agreed to Purpose • “Characterizing nutrient sources from existing developed lands” • Set General Goals & Objectives • Loading from various uses (residential, industrial, etc) • “First Flush” vs remaining storm loading • Fate transport impacts on loading • Loading from specific sources (golf courses, pavement, roof tops (atmospheric), etc • Forms of N&P to measure (dissolved/organic) • Effectiveness of post construction BMP’s

  3. Our Process (con’t) • 2nd meeting 11/4/2012 • Discussed various sources of loading • Considered variables that impact loading • Developed list of characteristics that influence nutrient loading (next slide) • Realized that some variables already studied • Loading from various land uses (NURP/NPDES)

  4. Our Process (con’t) • List of Characteristics that affect loading • Land use • First flush effect • Fate transport • Form of nutrient • Age of development • Style of development (LID vs conventional) • Condition of streams (stable or eroding?) • Site preparation effect (mass grading?) • Type/size of storm • applied regulations (water supply watershed?) • BMP design changes over time • Landscape and BMP maintenance

  5. Our Process (con’t) • 3rd Meeting 11/30/2012 • Goal - reduce list to 2-3 top monitoring needs and begin developing monitoring plans for each based on outline provided • Parameters • N&P (all forms) • Methods (decided to hold off) • Looked at land use as first variable • Came up with 8 categories

  6. Our Process (con’t) • Land use categories • Industrial • Commercial • Institutional • High density res • Med density res • Low density res • Very low density res • Undeveloped

  7. Our Process (con’t) • Realized there were sub categories to many of these • Sewered vs septic vs package plant? • Spray vs low pressure vs direct discharge? • Curb & gutter vs road ditch? • Age of development? • Water supply or non-water supply? • Post construction BMP’s required or not?

  8. Our Process (con’t) • The closer we looked, the more variables we identified that could influence results • First flush vs remainder of storm • How long to sample storm? • Watershed size and average slope • Age of watershed • Condition of streams • Was top soil removed • What was pre-existing condition (agriculture?) • How to make results applicable • Repeat in all impacted counties or try to keep watersheds close together? • Look for homogeneous watersheds or do paired studies?

  9. Our Process (con’t) • Discussed other monitoring variables • Where should samples be collected • At pipe vs in stream / single vs multiple points • Only sites with similar geology and geography? • Days of dry weather between storms • Intensity and duration of storm • Wind direction (atmospheric deposition) • Include extreme events or throw out?

  10. Issues • Run into overlap with BMP Subcommittee • Are we just looking at land uses without BMP’s or also those where BMP’s have been required? • There appears to be existing monitoring data for some objectives (NURP) • Due to range of storm frequency, duration, and intensity….data has high variability which necessitates many data points for statistical significance and takes long time to see trends • Lots of variables that are difficult to control

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