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Dist-County-Route: 07-LA-05 Post Mile Limits: 36.0 / 39.4 Type of Work: HOV Lane Construction Project ID (EA): XXXXXX Program Identification: HB5 Phase: PID PA/ED PS&E

Regional Water Quality Control Board(s): Los Angeles, Region 4

Total Disturbed Soil Area: 90 Acres PCTA: 26.0 Acres

Alternative Compliance (acres): 0.0 ATA 2 (50% Rule)? Yes No

Estimated Const. Start Date: _9/4/18 Estimated Const. Completion Date: 5/6/21

Risk Level: RL 1 RL 2 RL 3 WPCP Other:

Is MWELO applicable? Yes No

Is the Project within a TMDL watershed? Yes No

TMDL Compliance Units (acres): 0.0

Notification of ADL reuse (if yes, provide date): Yes Date:TBD in PS&E No

This Report has been prepared under the direction of the following Licensed Person. The Licensed Person attests to the technical information contained herein and the date upon which recommendations, conclusions, and decisions are based. Professional Engineer or Landscape Architect stamp required at PS&E only.

Betsy Ross, Registered Project Engineer/Landscape Architect Date

I have reviewed the stormwater quality design issues and find this report to be complete, current and accurate:

George Washington, Project Manager Date

Paul Revere, Designated Maintenance Representative Date

Horatio Gates, Designated Landscape Architect Representative Date

[Stamp Required for PS&E only) Friedrich Wilhelm von Steuben, District/Regional Design SW Coordinator or Designee

Date

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STORMWATER DATA INFORMATION 1. Project Description

At this stage of the project, the no build option, was not chosen and therefore this project will move forward into design. This project is a high occupancy vehicle (HOV) lane and roadway widening project that proposes to construct one HOV lane in each direction in the median along Interstate Route 5 (I-5) from the I-5 and State Route 170 (SR-170) interchange to the I-5 and SR-118 interchange (I-5 PM 36.0/39.4). The project consists mainly of roadway widening along northbound (NB) I-5. The project also includes the removal and reconstruction of the I-5/SR-170 interchange to provide both a mixed-flow connector ramp and a direct HOV connector to and from SR-170 and I-5. As part of the roadway widening and connector reconstruction, a total of 11 on- and off-ramps will be re-aligned or widened, 6 bridge structures will be widened, and 16 retaining walls and 11 sound walls will be constructed and/or modified. Three construction stages are expected to complete the project. The total disturbed soil area (DSA) for this project is estimated to be 90 acres. The area was estimated using limited data and includes areas for construction, access, and staging. DSA will be recalculated when the project survey is complete. The post construction treatment area (PCTA) for the project is estimated to be 26.0 acres. The area was estimated using the following project impervious areas obtained from AutoCAD using old Caltrans survey data. The PCTA will be recalculated when the project survey is complete.

PCTA Calculations

Impervious Areas Acres

Post-project impervious area1 150

Pre-project impervious area1 125

Excluded impervious areas2 0.00

NNI3 25.0

NNI to post-project impervious area 17%

RIS4 1.0

NIS5 26.0

ATA #16 0.00

ATA #27 0.00

1 within project limits (PM 36.0 to PM 39.4) 2 none (see 2017 PPDG Table 4-1) 3 NNI (Net new impervious) = Post-project impervious area - pre-project impervious area - excluded impervious areas 4 RIS (Replaced Impervious Area); includes estimated exisiting impervious areas replaced (see 2017 PPDG 4.3 Step 7) 5 NIS (New Impervious Area) = NNI + RIS 6 ATA (Additional Treated Area) #1; removed or modified existing TBMP impervious area that must be treated 7 ATA (Additional Treated Area) #2; all existing impervious area within the project limits less any RIS, but only if the percent of NNI to post-project impervious area is 50% or more

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PCTA8 26.0

Treatment BMPs will be considered to meet Permit Post Construction Treatment requirements. The treated areas will be determined at later phases of the project when more design information is available.

There are no additional right-of-way costs associated with the proposed Treatment BMPs. There are no existing Treatment BMPs within the project limits.

To accommodate this roadway widening project, properties and parcels will be affected and have been identified as residential, commercial, and industrial uses. These properties will need to be acquired for this project as fee takes, permanent footing easement, drainage easement, or temporary construction easement. A right-of-way certificate will be required for this project.

The project limits are shown on the attached vicinity map. According to the Water Quality Planning tool, the project is located within the County of Los Angeles urban MS4 area.

2. Site Data and Stormwater Quality Design Issues

Water Quality Data

A Water Quality Assessment Report (WQAR) was prepared for this project.

According to an Initial Study/Environmental Assessment (IS/EA) prepared in December 2014 and an Environmental Reevaluation Addendum dated January 23, 2016, a Regional Water Quality Control Board 401 certification and an Army Corps of Engineers 404 permit are required for this project. Applications of the required permits are in progress.

There is one high risk area identified within the project limits according to the Caltrans Stormwater Management Program District 7 Work Plan 2017/2018 dated April 1, 2017: Pacoima Spreading Grounds (PM 39.28/40.46 on I-5). The Pacoima Spreading Grounds are located on both sides of old Pacoima Wash Channel from Arleta Avenue southwest to Woodman Avenue.

The project is located in the Los Angeles River watershed and the Bull Canyon hydraulic sub-area (HSA 412.21). The project receiving waterbody is Tujunga Wash from Hansen Dam to the Los Angeles River. The Tujunga Wash crosses within the project limits just south of the I-5/SR-170 interchange at PM 36.34. The Tujunga Wash is a 2012 303(d) listed waterbody and is listed for coliform bacteria, ammonia, copper, and trash. This was determined using the California State University, Sacramento Office of Water Programs Water Quality Planning Tool (WQPT).

The Tujunga Wash crosses LA-05 within the southern project limits, and it is a direct receiving water body for the project. Tujunga Wash merges with Los Angeles River approximately 7 miles downstream of the project. Los Angeles River is tributary to San Pedro Bay approximately in 17 miles. This was determined using the WQPT.

8 PCTA (Post Construction Treatment Area) = NIS + ATA #1 + ATA #2; if less than 1 acre for highway projects (5,000 sf for non-highway) PCTA is 0. PCTA is the mandatory impervious area to be treated.

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The following total maximum daily loads (TMDLs) are within the project limits: Los Angeles River TrashTMDL, Los Angeles River Indicator Bacteria TMDL, Los Angelese River and Tributaries Metals TMDL, Los Angeles River Nitrogen Compounds and Related Effects TMDL, and Dominguez Channel and Greater Los Angeles and Long Beach Harbor Waters Toxic Pollutants TMDL. A summary of the TMDLs area as follows:

Los Angeles River

Established TMDLs

Los Angeles River Trash TMDL

The Los Angeles River Trash TMDL became effective August 28, 2002. Caltrans is proceeding with Trash TMDL Implementation Projects, which are to retrofit GSRDs at the existing drainage outfalls in the right-of-way. Table A lists those Trash TMDL Implementation Projects that are either in construction or completed. Any projects that overlap within the limits of freeway corridors listed in Table A are not required to consider GSRDs for those overlapping limits. However, Project Engineers shall consider placing infiltration basins or media filters as much as possible in lieu of GSRDs at existing and proposed drainage systems.

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Table A PM

Status EA Route From To xxxxxx 405 30.31 36.15 completed xxxxxx 60 2.7 6.6

completed 710 22.5 23.8

xxxxxx 5 27.62 28.15

completed 10 9.02 13.82 90 1.84 2.70

xxxxxx 10 5.59 8.80

completed 91 10.25 13.88 105 8.25 13.15 110 21.65 23.61

xxxxxx

2 15.40 21.46

completed 101 7.21 7.21 170 14.78 19.92

134/710 13.34 13.34 210 22.73 23.88 405 25.46 29.41

xxxxxx 5 16.35 16.35

completed 101 12.70 26.50 134 0.00 9.86

Los Angeles River Nitrogen Compounds and Related Effects TMDL

The Los Angeles River Nitrogen Compounds and Related Effects TMDL became effective March 23, 2004. The TMDL requires the Storm Water NPDES Permittees to submit a Monitoring Work Plan by March 23, 2005 to estimate nitrogen loadings associated with runoff from the storm drain systems. County of Los Angeles has submitted the Monitoring Work Plan as required on behalf of Caltrans and other Storm Water NPDES Co-Permittees in the watershed. Targeted pollutants are Total ammonia as nitrogen (NH3-N), Nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N), and Nitrate nitrogen plus nitrite-nitrogen (NO3-N + NO2-N).The Department's monitoring data depicts Caltrans discharges to be below the TMDL limits, thus no additional measures are needed to be considered for meeting the conditions of the Nitrogen TMDL.

Los Angeles River and Tributaries Metals TMDL

The Los Angeles River and Tributaries Metals TMDL became effective on January 11, 2006. Caltrans will work with 5 groups of Responsible Agencies toward compliance of the TMDL. Targeted pollutants are total Cu, Pb, Zn, Cd, and Se. Project Engineers shall consider treatment controls for the project and consult with the District NPDES Storm Water Coordinator.

Total Maximum Daily Loads for Indicator Bacteria in the Los Angeles River

The Total Maximum Daily Loads for Indicator Bacteria in the Los Angeles River became effective on March 23, 2012. The TMDL requires the Responsible Agencies, including Caltrans, to reduce number of exceedance days of bacteria concentrations in the Los Angeles River and achieve waste load allocations in 25 years. Caltrans will be working with groups of Responsible Agencies to jointly comply with the TMDL. Project Engineer shall consider treatment controls for the project and consult with the District NPDES Storm Water Coordinator.

Dominguez Channel and Greater Los Angeles and Long Beach Harbor Waters Toxic Pollutants TMDL

Dominguez Channel and Greater Los Angeles and Long Beach Harbor Waters Toxic Pollutants TMDL became effective on March 23, 2012. Targeted pollutants are copper, lead, zinc, PAH, DDT, PCBs, Benzopyrene and Dieldrin for water column in the channel and harbors, and for sediments in the

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harbors. The TMDL requires the dischargers of the Los Angeles River and the San Gabriel River to monitor water quality at the mouth of each River. Caltrans will participate in groups of agencies to jointly comply with the TMDL. Project engineers shall consider treatment controls for the project and consult with the District NPDES Storm Water Coordinator.

Aerially deposited lead (ADL) is anticipated during the construction of the project. An Aerially Deposited Lead Investigation Report dated June 29, 2015 indicates that ADL exists at depths ranging from 6 inches to 5 feet below ground surface and within 30 feet from the edge of pavement. Handling of ADL material will also be required beyond the 30 feet along the retaining wall and sound wall layout lines. The June 2015 report recommends the reuse of certain ADL contaminated soils within Caltrans right-of-way in conformance with the conditions set forth by the Soil Management Agreement. Potential pollutant sources include the cut and fill slopes.

Geotechnical Data

The existing soil type within the project limits is Soil Hydrologic Group B per the geotechnical report. The infiltration rate for the site has been determined by the Geotechnical Engineer to be 0.5 in/hr.

Topographic Data

The United States Geological Survey (USGS) topography map of the area shows the elevation of the project area ranging from roughly 800 ft to 980 feet above sea level. Topography within the project limits is relatively level.

Hydraulic Data

The depth to ground water is 35 feet per the project’s geotechnical report. Flow based Treatment BMPs will be designed using the water quality flow (WQF) for the project area, 0.2 inches per hour. Likewise volume based Treatment BMPs will be designed using the water quality volume (WQV) based on the 85th percentile 24-hour storm event, 0.75 inches. Both these values were obtained from Caltrans Basin Sizer program (Ver. 1.47).

Climate The climate is mild with average temperatures ranging from 49 to 78 degrees Fahrenheit. The average annual rainfall in the area is 18 inches. The rainy season for the project is October 1 to May 1. Since vegetated stormwater measures are being considered, preliminary consultation with the District Landscape Architect (DLA) indicates the area’s climate is favorable for long-term vegetation establishment.

3. Construction Site BMPs to be used on Project

Project specific BMP measures will be specified and quantified during the design phase. Temporay construction BMPs have been estimated at 2.00% of the total project cost ($120,000,000) in accordance with the Project Initiation Cost Estimate Method, Appendix F.3.1, 2017 PPDG.

Risk Assessment

This project was determined to be Risk Level 2 based on Method 1, GIS Map Method, Appendix 1, 2009 CGP. The Risk Level documentation is attached to this report.

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Construction Site BMP Strategy

The construction of the project will be completed in phases to account potential conflicts including, but not limited to, traffic handling and consideration of rainy seasons. Erosion control and BMPs will be incorporated as part of this project to reduce storm water impacts.

This project will disturb 1 acre or more of soil and therefore, the preparation of a Storm Water Pollution Prevention Plan (SWPPP) is required.

DSA will be protected in accordance with the project’s approved SWPPP. The BMP categories suitable for controlling potential pollutants to be considered for this project will be detailed during later phases and include:

Soil Stabilization Sediment Control Tracking Control Wind Erosion Control Non-storm Water Management Waste Management and Materials Pollution Control

Dewatering may be required during the construction of this project; however, a separate dewatering permit is not anticipated. This is a Risk Level 2 project and required to perform stormwater sampling at all discharge locations. A meeting with the Caltrans Construction Storm Water Coordinator, William Alexander was held in September 18, 2017. The Construction unit concurs with the Construction Site BMP strategy and development for this stage of the project. Project specific BMP measures will be specified and quantified during the design phase.

4. Maintenance BMPs

A meeting was held on 9/1/17 to coordinate the maintenance BMPs and concerns for this project with the District Maintenance Stormwater Coordinator (MSWC) Paul Revere. Topics discussed included protection of existing inlets, drain inlet stenciling, and the permanent erosion control strategy for the site. Drain inlet stenciling is not required for this project because there is no pedestrian access to the inlets. At this time, Mr. Revere is in agreement with the project maintenance strategy. Final concurrence on implementation of the strategy will be obtained during PS&E.

5. Other Water Quality Requirements and Agreements

A meeting was held by District NPDES Stormwater Coordinator, Nathanael Greene, on 9/1/17 with the Los Angeles RWQCB. There are no anticipated negotiated understandings or agreements between Caltrans and the RWQCB for this project.

6. Permanent BMPs

Rapid Stream Assessment (RSA)

This project requires RSAs based on the algorithm (items 1-4 below) provided in Section 2 of Caltrans Hydromodification Guidance dated February 2015.

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This project includes stream crossings. This project does include 1 acre or more of net new impervious (NNI) surface. The NNI is within the stream threshold drainage areas. Stream crossings are “Water of the US” as defined by Army Corps of Engineers latest

guidance on determination of jurisdiction for CWA section 404. RSAs have been completed by the District Hydraulics Unit and included as an attachment. The overall Hydromodification Susceptibility scores range from xx-xx. This implies that the channel upstream and downstream of each of the crossings displays excellent vertical and lateral stability.

Design Pollution Prevention (DPP) BMP Strategy

The District’s Landscape Architect, Jolene Turk, has indicated landscape irrigation (greater than 2,500 sf) will be rehabilitated with this project and the Maximum Applied Water Allowance (MAWA) and Estimated Total Water Use (ETWU) for this project will be provided at PS&E.

Design Pollution Prevention BMPs will be incorporated into the project where appropriate in order to minimize impacts to water quality by preventing downstream erosion and stabilizing disturbed soil areas. The following is a general overview of BMPs that may be incorporated into the project.

Downstream Effects Related to Potentially Increased Flow, Checklist DPP-1, Parts 1 and 2

The proposed improvement will increase the impervious area to accommodate the widening which will increase velocity and volume of flow within the project limits. This increase has been accounted for in the project design and mitigated through the use of BMPs. Per the project Drainage Report, the design matches the pre-project runoff curve number and time of concentration and controls erosive velocities in accordance with the HDM. Because the design has accounted for the increased velocity and volume of flow, the project should have a negligible impact on downstream flow. Additional mitigation includes attempting to infiltrate the water quality volume generated from the 85th percentile 24-hour storm event. The water quality volume will be based on the PCTA of the project.

This project will not discharge to unlined channels or encroach, cross, realign, or cause other hydraulic changes that may affect downstream channel stability. Rock slope protection will be used to dissipate energy at culvert outlets to prevent scour. All transitions between culvert outlets, headwalls, wing walls, and channels will be smooth to reduce turbulence and scour.

Slope/Surface Protection Systems, Checklist DPP-1, Parts 1 and 3

Cut and fill requirements are expected to be minimal. There will be an embankment slope for approximately 1,000 feet along SR-170. Benching and slope rounding will be considered to reduce concentrated flows on this slope. Existing slopes at the project site are 2:1 (H:V) or flatter, stable, and vegetated. New slopes will be 2:1 (H:V) or flatter.

The existing vegetated surface consists of trees and ground cover. Once substantially complete, all disturbed slopes will be revegetated in accordance with Caltrans Landscape policy and procedures. All vegetated surfaces will be identified on the project plans. Hard surfaces are not anticipated on this project.

Methodology for obtaining the CGP NOT will be decided by the PDT during the PSE phase.Concentrated Flow Conveyance Systems, Checklist DPP-1, Parts 1 and 4

New inlets and pipes will be designed to intercept runoff created by the new impervious areas. The conveyance system will direct the runoff to new treatment BMPs. The existing system will

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continue to intercept and discharge the remainder of the project runoff. Scouring and gulling is not anticipated as the runoff is collected in asphalt concrete dikes. Rock slope protection will be added to existing outfalls as needed to prevent scour.

Preservation of Existing Vegetation, Checklist DPP-1, Parts 1 and 5

Clearing and grubbing is required in specific locations to facilitate construction of the new interchanges, travel lanes, retaining walls, sound walls, and treatment devices. Preservation of existing vegetation will be maximized, and the locations of clearing and grubbing will be clearly defined on the contract plans.

All areas that will be off limits to the contractor (i.e. environmentally sensitive areas and areas of landscape preservation) will be delineated on the plans during the PS&E phase. The project design will consider minimizing the footprint of new construction where possible. Existing grade will be matched as close as possible to preserve existing vegetation.

Treatment BMP Strategy

This project is required to consider treatment BMPs and will be in accordance with the July 2017 Project Planning and Design Guide (PPDG).

The proposed Treatment BMP strategy for this project will utilize Treatment BMPs to limit the amount of pollutants discharged to the Tujunga Wash. The goal of the design is to treat 26.0 Acres of impervious surface within the project limits prior to infiltrating or discharging to the Tujunga Wash.

Treatment BMPs have been considered using the I-5 North Corridor Storm Water Quality Master Plan, Volume 1 Final Report dated June 2007.

At this time the project survey data is not complete. The geotechnical report is available. The T-1 checklist is being used to select appropriate Treatment BMPs.

The following table includes proposed Treatment BMPs and impervious areas treated with this project to date.

Recommended Treatment BMPs1 

Site No.

PM Nearest Cross-Street Tributary

Area2 (acres)

TABLE 6-1 Infiltration Devices

36 38.54 On-ramp loop at Van Nuys Boulevard 2.63 

41 37.99 Off-ramp loop N/B at Terra Bella Street 1.89 

4.52 TABLE 6-2 Media Filters and Detention Devices

102 39.21 900 feet north of Paxton Street 5.03 

37 38.54 Off-ramp N/B at Van Nuys Blvd 2.35 

42 37.50 200 feet north of Osborne Street 2.02 

47 36.35 1500 feet north of Sheldon Street 3.27 

49 36.16 600 feet north of Sheldon Street 6.14 

18.81 TABLE 6-3 Biofiltration Strips and Swales

36 38.54 On-ramp loop at Van Nuys 2.63 

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37 38.54 Off-ramp loop N/B at Van Nuys 2.35 

38 38.46 Off-ramp N/B at Van Nuys Boulevard 1.25 

44 37.40 On-ramp loop N/B at Osborne Street 1.32 

         7.55 

      Totals 30.88 

Based on the I-5 North Corridor Storm Water Quality Master Plan, Volume 1 Final Report dated June 2007 the total estimated treatment BMP cost is $xxx,xxx. At PS&E phase, the project engineer will examine other storm water treatment opportunities to compensate for BMPs eliminated as a result of various design issues and/or site constraint.

Required Attachments

Vicinity Map

Evaluation Documentation Form

Risk Level Determination Documentation

Supplemental Attachments

SWDR Summary Spreadsheets

Deviation of BMP from the Corridor Study Recommendation

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Vicinity Map

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Evaluation Documentation Form

DATE: 09-23-17_______________________ Project ID (EA): XXXXXX_______________________

No. Criteria Yes

No

Supplemental Information for Evaluation

1. Begin Project evaluation regarding requirement for implementation of Treatment BMPs

See Figure 4-1, Project Evaluation Process for Consideration of Treatment BMPs. Continue to 2.

2. Is the scope of the Project to install Treatment BMPs (e.g., Alternative Compliance or TMDL Compliance Units)?

If Yes, go to 8.

If No, continue to 3.

3. Is there a direct or indirect discharge to surface waters? If Yes, continue to 4.

If No, go to 9.

4. As defined in the WQAR or ED, does the project:

a. discharge to areas of Special Biological Significance (ASBS), or

b. discharge to a TMDL watershed where Caltrans is named stakeholder, or

c. have other pollution control requirements for surface waters within the project limits?

If Yes to any, contact the District/Regional Design Stormwater Coordinator or District/Regional NPDES Coordinator to discuss the Department’s obligations, go to 8 or 5.

(Dist./Reg. Coordinator initials)

If No to all, continue to 5.

5. Are any existing Treatment BMPs partially or completely removed?

(ATA condition #1, Section 4.4.1)

If Yes, go to 8 AND continue to 6.

If No, continue to 6.

6. Is this a Routine Maintenance Project? If Yes, go to 9.

If No, continue to 7.

7. Does the project result in an increase of one acre or more of new impervious surface (NIS)?

If Yes, go to 8.

If No, go to 9.

8. Project is required to implement Treatment BMPs. Complete Checklist T-1, Part 1.

9. Project is not required to implement Treatment BMPs.

______(Dist./Reg. Design SW Coord. Initials)

______(Project Engineer Initials)

(Date)

Document for Project Files by completing this form and attaching it to the SWDR.

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Risk Level Determination Documentation

Figure 1 . R Factor (Value=159.86) Source: < https://www.epa.gov/npdes/rainfall-erosivity-factor-calculator-small-construction-sites>

https://www.epa.gov/sites/production/files/2015-10/documents/fact3-1.pdf

(EI) Zone = 25

Annual R value = 50

R = (EI)% x Annual R value

Constr Date (EI) %

Annual 

R 

Value

R

Begin 9/4/2018 63.65 50 31.82

2019 100.00 50 50.00

2020 100.00 50 50.00

End 5/6/2021 56.08 50 28.04

Total 159.86

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Figure 2 . K Factor from GIS Map (Value=0.24)

Figure 3 . LS Factor from GIS Map (Value=0.96)

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Figure 4: Receiving Water Risk GIS Map

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Figure 5 . Sediment Risk Factor Worksheet

Source: State Water Resources Control Board spreadsheet

Entry

159.86

0.24

0.96

Watershed Erosion Estimate (=RxKxLS) in tons/acre

Site Sediment Risk FactorLow Sediment Risk: < 15 tons/acre

Medium Sediment Risk: >=15 and <75 tons/acreHigh Sediment Risk: >= 75 tons/acre

K Factor Value

LS Factor Value

Medium

C) LS Factor (weighted average, by area, for all slopes)

The soil-erodibility factor K represents: (1) susceptibility of soil or surface material to erosion, (2) transportability of the sediment, and (3) the amount and rate of runoff given a particular rainfall input, as measured under a standard condition. Fine-textured soils that are high in clay have low K values (about 0.05 to 0.15) because the particles are resistant to detachment. Coarse-textured soils, such as sandy soils, also have low K values (about 0.05 to 0.2) because of high infiltration resulting in low runoff even though these particles are easily detached. Medium-textured soils, such as a silt loam, have moderate K values (about 0.25 to 0.45) because they are moderately susceptible to particle detachment and they produce runoff at moderate rates. Soils having a high silt content are especially susceptible to erosion and have high K values, which can exceed 0.45 and can be as large as 0.65. Silt-size particles are easily detached and tend to crust, producing high rates and large volumes of runoff. Use Site-specific data must be submitted.

The effect of topography on erosion is accounted for by the LS factor, which combines the effects of a hillslope-length factor, L, and a hillslope-gradient factor, S. Generally speaking, as hillslope length and/or hillslope gradient increase, soil loss increases. As hillslope length increases, total soil loss and soil loss per unit area increase due to the progressive accumulation of runoff in the downslope direction. As the hillslope gradient increases, the velocity and erosivity of runoff increases. Use the LS table located in separate tab of this spreadsheet to determine LS factors. Estimate the weighted LS for the site prior to construction.

36.831744

Site-specific K factor guidance

LS Table

Sediment Risk Factor Worksheet

A) R Factor

R Factor Value

B) K Factor (weighted average, by area, for all site soils)

Analyses of data indicated that when factors other than rainfall are held constant, soil loss is directly proportional to a rainfall factor composed of total storm kinetic energy (E) times the maximum 30-min intensity (I30) (Wischmeier and Smith, 1958). The numerical value of R is the average annual sum of EI30 for storm events during a rainfall record of at least 22 years. "Isoerodent" maps were developed based on R values calculated for more than 1000 locations in the Western U.S. Refer to the link below to determine the R factor for the project site.

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

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Figure 6 . Risk Level Determination (Value=Risk Level 2)

Source: State Water Resources Control Board spreadsheet

Low Medium High

Low Level 1

High Level 3

Project Sediment Risk: Medium 2

Project RW Risk: Low 1

Project Combined Risk: Level 2

Combined Risk Level Matrix

Sediment Risk

Re

ceiv

ing

Wa

ter

Ris

k

Level 2

Level 2

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SWDR Summary Spreadsheets

SWDR

SWDR Signed Date

District EA/Project ID County Route Beg_PM End_PMProject

DescriptionProject Phase

Long SWDR

Risk Level

DSA (ac)

TMDL Waterbody

9/23/2017 7 xxxxxx LA 5 36.00 39.40HOV Lane 

ConstructionPAED Yes RL2 90.0 Yes

Biofiltration Strips and

SwalesDetention

Infiltration Devices

GSRD TST MedFilter DPPIA SA Other BMPEst.

Const_StartEst. Const

_Comp

0 0 0 0 0 0 0 0 0 9/4/2018 5/6/2021

Net New Impervious area

(NNI)

Replaced Impervious

Surface (RIS)

Additional Treatment Area

(ATA)

Post Const

Treatment Area (ac)

Treated Impervious Area (ac)

Treated Impervious

Area Balance (ac)

Treated Pervious Area (ac)

Stabilized Area (ac)

MWELO RSASW

Comment

25.00 1.00 26.00 0.00 -26.00 0.00 0.00 Yes Yes

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Deviation of BMP from the Corridor Study Recommendation