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

December 2010

Risk Level Determination (RLD) for theConstruction General Permit (CGP)

December 7, 2010

December 2010Webinar 1: Risk Level Determination

Agenda

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Meet the Presenters

Facilitator: Jeff Bold

Presenter: Tim Sobelman

Q&A Panel: Tim Sobelman

Robert Schott

Mike Marti

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Agenda

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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.

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Agenda

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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)

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Risk Level Determination

Today’s presentation will:

1) Discuss what Risk Levels mean to a Caltrans Construction Sites2) Describe the site-specific data that is needed to conduct a RL

Determination 3) Discuss the programs/websites that are available to obtain the site

data4) Go over two Methods of conducting a RL Determination 5) Answer questions related to calculating a project Risk Level

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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

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Risk Level Determination Factors

Completed for pre-construction conditions Only two factors determine Risk Level:

– Sediment– Receiving Water

3 possible Risk Levels

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Combined Risk Level

For each project sediment and receiving water risks are combined

Combined Risk Levels: 1 2 3 low medium high

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What does Risk Level 1 mean?

Level 1 SWPPP Requirements for a QSD/QSP Visual monitoring Annual reports


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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

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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 eventsConduct bioassessment testing on sites > 30 acres

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RLD – Where to start…

http://www.swrcb.ca.gov/water_issues/programs/stormwater/constpermits.shtml

Appendix 1 - Risk Determination Worksheet (select ‘Excel’)

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Open SWRCB Excel fileGIS Map Method

Use GIS Map Method to determine: Step 1) Sediment RiskStep 2) Receiving Water RiskStep 3) Combined Risk Level

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GIS Method is used at each phase (PID, PAED, PS&E). Document in the Storm Water Data Report.


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 erodibilityL = length of slope S = slopeC = coverP = practices

C and P are assumed to be constant; no data needed for risk calculation

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Step 1 - Sediment Risk

1) Locate site2) Obtain KLS3) Calculate R4) Sediment Risk = R • KLS

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Truckee Bypass

Project located adjacent to the Truckee River

39°20’23.44” N; 120°10’16.20” W 19


Rainfall Erosivity (R)

Enter site name, project duration

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http://cfpub.epa.gov/npdes/stormwater/LEW/lewCalculator.cfm



Enter site location (latitude/longitude)

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For a 13 month job:

R = 10.34

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Sediment Risk - KLS GIS Map

1) Locate site2) Obtain KLS

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Sediment Risk - KLS GIS Map

KLS = 1.6

Truckee Bypass Project

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Calculate Sediment Risk

Sediment Risk = R • KLS

= 10.34 • 1.6

= 16.54

Low: <15 tons/acreMedium: ≥15 to <75 tons/acreHigh: ≥75 tons/acre

Medium Sediment Risk

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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 Sediment Risk

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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 riskIf Yes to either – High RW risk

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Water Quality Planning Tool

http://www.owp.csus.edu/research/stormwater/tools/wqpt.htm

Locates site, watershed by Post-Miles

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Water Quality Planning Tool

TMDL & 303(d)listed waterbodies

Receiving Water located in Truckee River Watershed

Truckee River TMDL listed forsediment

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Water Quality Planning Tool – Truckee River

Spawn

Migratory

Cold

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Receiving Water Risk Estimate – Truckee River

TMDL sediment – Yes Cold+Spawn+Migratory – YesReceiving Water = High Risk

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Combined Risk Level

Sediment Risk = Low

Receiving Water Risk = High

Combined Risk = Level 2

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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.

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Individual vs GIS Map Methods

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Individual Method - Sediment Risk Factor Worksheet

R Factor

K Factor

LS Factor

Sediment Risk

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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/

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Soil Erodibility (K)

http://soils.USDA.gov

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Soil Erodibility (K)

Find specific K factor for area of influence (AOI)

K = 0.24

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Slope Length and Steepness (LS)

Example: weighted average for project area are:L = 50 feet, S = 50%

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LS= 5.16



Sediment Risk was reduced from:

15.54 tons/acre (Med) (GIS MAP Method)

to

12.81 tons/acre (Low)(Individual Method)

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Receiving Water Risk

Same as GIS Method

RW Risk = High

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RLD Truckee Bypass

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Sediment Risk = Low(Individual Method)

Receiving Water Risk = High

Combined Risk Level 2


Alternative Rainfall Erosivity (R)

For a 5 year, 4 month job:

R = 49.74

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Calculate Sediment Risk – GIS Map Method


= 49.74 x 1.6

= 79.58 (High Sediment Risk)


Risk Level 3

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Calculate Sediment Risk – Individual Method


= 49.74 x 1.24

= 61.68 (Medium Sediment Risk)


Risk Level 2

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Medium


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

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Caltrans District 8 GIS

On Caltrans website: http://sv08arcgis/cgp2009/

latitude and longitude

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Caltrans District 8 GIS - Imagery

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K Factor - Caltrans District 8 GIS

K= 0.24

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Caltrans District 8 GIS – Planning Watershed Boundaries

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Summary

Which RLD method?– Start with GIS Map Method PID and PAED

• Simple, fast, conservative – Individual Method (optional) PS&E

• More detailed• Use when GIS method results in borderline

sediment risk

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Where to go for more information?

This site contains: RLD Guidance RUSLE2 8-hour training course A recording of this presentation A copy of the Q&A Session

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http://www.dot.ca.gov/hq/oppd/stormwtr/index.htm


Agenda

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

Documents

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