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Risk Level Determination (RLD) for the Construction General Permit (CGP)

Risk Level Determination (RLD) for the Construction General Permit (CGP). December 7, 2010. Agenda. Introductions. Meet the Presenters. Facilitator : Jeff Bold Presenter : Tim Sobelman Q&A Panel : Tim Sobelman Robert Schott Mike Marti. Agenda.

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Risk Level Determination (RLD) for the Construction General Permit (CGP)

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  1. Risk Level Determination (RLD) for theConstruction General Permit (CGP) December 7, 2010

  2. Agenda Introductions

  3. Meet the Presenters Facilitator: Jeff Bold Presenter: Tim Sobelman Q&A Panel: Tim Sobelman Robert Schott Mike Marti

  4. Agenda Webinar logistics:phones, how to submit questions, how Q&Q will run, etc

  5. Communication During Webinar • Your phone is automatically muted. • Please submit your questions electronically on the Q/A portion of your screen. • Questions will be addressed after the presentation is completed.

  6. Agenda CGP Risk Level Determination

  7. Caltrans CGP Guidance • Division of Environmental Analysis • Webinars, Water Quality Dispatch, etc. http://www.dot.ca.gov/hq/env/stormwater/cgp/index.htm • Division of Construction • CPD/CPB, SWPPP Preparation Manual, etc. http://www.dot.ca.gov/hq/construc/stormwater/stormwater1.htm • Division of Design • Risk Level Determination Guidance, CGP Cost Estimating, Specifications, etc. • Risk Level Determination (RLD) Webinar • RUSLE2 Training (RL Determination module)

  8. Risk Level Determination • Today’s presentation will: • Discuss what Risk Levels mean to a Caltrans Construction Sites • Describe the site-specific data that is needed to conduct a RL Determination • Discuss the programs/websites that are available to obtain the site data • Go over two Methods of conducting a RL Determination • Answer questions related to calculating a project Risk Level

  9. Caltrans Project RLD Guidance http://www.dot.ca.gov/hq/oppd/stormwtr/index.htm • Goals: • Determine appropriate Risk Level for each site: • Accurate Slope Length and Steepness values • Construction during dry seasons could reduce sediment risk • GIS Map / Individual Method

  10. Risk Level Determination Factors • Completed for pre-construction conditions • Only two factors determine Risk Level: • Sediment • Receiving Water • 3 possible Risk Levels

  11. Combined Risk Level For each project sediment and receiving water risks are combined Combined Risk Levels: 1  2  3 low medium high

  12. What does Risk Level 1 mean? Level 1 • SWPPP • Requirements for a QSD/QSP • Visual monitoring • Annual reports Combined Risk Levels: 1  2  3 low medium high

  13. What does Risk Level 2 mean? Combined Risk Levels: 1  2  3 lowmedium high • Level 2 = Level 1 requirements plus: • Rain Event Action Plan (REAP) • Numeric Action Level (NAL) • pH 6.5-8.5, • turbidity < 250 NTU • Storm water sampling during rain events

  14. What does Risk Level 3 mean? Combined Risk Levels: 1  2  3 low medium high • Level 3 = Level 1 + Level 2 requirements plus: • Numeric Effluent Limits (NEL) • - pH 6.0 – 9.0 • - turbidity < 500 NTU • Receiving water sampling during rain events • Conduct bioassessment testing on sites > 30 acres

  15. RLD – Where to start… Appendix 1 - Risk Determination Worksheet (select ‘Excel’) • http://www.swrcb.ca.gov/water_issues/programs/stormwater/constpermits.shtml

  16. Open SWRCB Excel fileGIS Map Method Use GIS Map Method to determine: Step 1) Sediment Risk Step 2) Receiving Water Risk Step 3) Combined Risk Level GIS Method is used at each phase (PID, PAED, PS&E). Document in the Storm Water Data Report.

  17. Sediment Risk Factors • Based on Revised Universal Soil Loss Equation (RUSLE) • Soil loss (tons/acre/year) = R • K • L • S • C • P R = rainfall erosivity (EPA website) K = soil erodibility L = length of slope S = slope C = cover P = practices C and P are assumed to be constant; no data needed for risk calculation

  18. Step 1 - Sediment Risk • Locate site • Obtain KLS • Calculate R • Sediment Risk = R • KLS

  19. Truckee Bypass Project located adjacent to the Truckee River 39°20’23.44” N; 120°10’16.20” W

  20. Rainfall Erosivity (R) • http://cfpub.epa.gov/npdes/stormwater/LEW/lewCalculator.cfm Enter site name, project duration

  21. Rainfall Erosivity (R) Enter site location (latitude/ longitude)

  22. Rainfall Erosivity (R) For a 13 month job: R = 10.34

  23. Sediment Risk - KLS GIS Map • Locate site • Obtain KLS

  24. Sediment Risk - KLS GIS Map Truckee Bypass Project KLS = 1.6

  25. Calculate Sediment Risk Sediment Risk = R • KLS = 10.34 • 1.6 = 16.54 Low: <15 tons/acre Medium: ≥15 to <75 tons/acre High: ≥75 tons/acre  Medium Sediment Risk

  26. Sediment Risk Change from a 13 month project to a 12 month project R declines from 10.34 to 9.03 = 9.03 • 1.6 = 14.45 Low: <15 tons/acre Medium: ≥15 to <75 tons/acre High: ≥75 tons/acre  LOW Sediment Risk

  27. Step 2 - Receiving Water (RW) Risk Locate watershed and identify receiving water body • TMDL and/or 303(d) listed for sediment? OR • Designated Beneficial Uses? • Spawn and • Cold and • Migratory If No to both – Low RW risk If Yes to either – High RW risk

  28. Water Quality Planning Tool http://www.owp.csus.edu/research/stormwater/tools/wqpt.htm Locates site, watershed by Post-Miles

  29. Water Quality Planning Tool Receiving Water located in Truckee River Watershed TMDL & 303(d) listed waterbodies Truckee River TMDL listed for sediment

  30. Water Quality Planning Tool – Truckee River Cold Migratory Spawn

  31. Receiving Water Risk Estimate – Truckee River TMDL sediment – Yes Cold+Spawn+Migratory – Yes Receiving Water = High Risk

  32. Combined Risk Level Sediment Risk = Low Receiving Water Risk = High Combined Risk = Level 2

  33. Sediment Risk – Individual Method Use when detailed analysis may produce more favorable RLD Consider Individual Method at PS&E (unless detailed project information is available earlier). Document in the Storm Water Data Report.

  34. Individual vs GIS Map Methods

  35. Sediment Risk – Individual Method

  36. Individual Method - Sediment Risk Factor Worksheet R Factor K Factor LS Factor Sediment Risk

  37. How do we get the data? • R, K factors require latitude/longitude • Sources for latitude/longitude: 1) Web Browser Post Mile Query Tool (Caltrans website) 2) Google Earth 3) Caltrans District 8 GIS website: http://sv08arcgis/cgp2009/

  38. Soil Erodibility (K) http://soils.USDA.gov

  39. Soil Erodibility (K) Find specific K factor for area of influence (AOI) K = 0.24

  40. Slope Length and Steepness (LS) Example: weighted average for project area are: L = 50 feet, S = 50% LS= 5.16

  41. Sediment Risk – Individual Method Sediment Risk was reduced from: 15.54 tons/acre (Med) (GIS MAP Method) to 12.81 tons/acre (Low) (Individual Method)

  42. Receiving Water Risk Same as GIS Method RW Risk = High

  43. RLD Truckee Bypass Sediment Risk = Low (Individual Method) Receiving Water Risk = High Combined Risk Level 2

  44. Alternative Rainfall Erosivity (R) For a 5 year, 4 month job: R = 49.74

  45. Calculate Sediment Risk – GIS Map Method Sediment Risk = R • KLS = 49.74 x 1.6 = 79.58 (High Sediment Risk) Low: <15 tons/acre Medium: ≥15 to <75 tons/acre High: ≥75 tons/acre  Risk Level 3

  46. Calculate Sediment Risk – Individual Method Sediment Risk = R • KLS = 49.74 x 1.24 = 61.68 (Medium Sediment Risk) Low: <15 tons/acre Medium: ≥15 to <75 tons/acre High: ≥75 tons/acre  Risk Level 2 Medium

  47. Caltrans D8 GIS • District 8 has compiled a unique GIS http://sv08arcgis/cgp2009/ • This GIS integrates many data sources to provide the user: • Street and aerial photography location information • Sediment Risk – Latitude/Longitude (R), GIS map method (KLS), individual method (K, R, topographic info) • Receiving Water Risk – draft SWRCB GIS • How to use D8 GIS described in Caltrans RLD Guidance

  48. Caltrans District 8 GIS On Caltrans website: http://sv08arcgis/cgp2009/ latitude and longitude

  49. Caltrans District 8 GIS - Imagery

  50. K Factor - Caltrans District 8 GIS K= 0.24

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