B08 Attach 1 Red Mountain Road SOW 2021 0217.pdf

Red Mountain Road Upgrade Phase II Statement of Work (SOW)

With Additive Line Items

Bureau of Land Management (BLM)

Arcata Field Office

TABLE OF CONTENTS

1.0 Background

2.0 Scope

3.0 Objectives

4.0 Requirements

5.0 Delivery

6.0 Government-Furnished Property

7.0 Place of Performance

8.0 Period of Performance

Appendix A. Schematics for Typical Treatments

Appendix B. Best Management Practices

1.0 Background

The Bureau of Land Management (BLM) Arcata Field office requires work that will entail repairs, upgrades and reconstruction of road drainage sites along 12 miles of Red Mountain Road, a rural dirt and aggregate-surfaced road in Mendocino County, California near the community of Piercy (Maps 1 and 2). The road provides access to both public and private lands. The work is being done to replace aging infrastructure (e.g., culverts), comply with Clean Water Act requirements for reducing road-related erosion, and enhancing safe vehicular access along the road. Specific actions include culvert replacements, rolling dip construction, aggregate base installation, road reshaping, and rock armoring of vulnerable fill slopes.

The work will conform to various specifications and Best Management Practices:

(a) Typical diagrams describing the various treatment types are provided as

Appendix A of this Statement of Work (SOW).

(b) Best Management Practices for protection of water quality are provided in

Appendix B of this SOW.

2.0 Scope

Road upgrading work shall be implemented along 12 miles of Red Mountain Road. The road is a rural, dirt and aggregate-surfaced road in a steep, mountainous setting. Broadly, the work includes:

• Surface drainage restoration along the entire 12 miles of Red Mountain Road, including ditch clearing, restoration of road surface drainage “lead-outs” and rolling dips,

• Site-specific upgrades at 10 sites along the road, treatments shall include:

o Eight (8) culvert replacement or installation sites (note that one site entails two (2) pipe installations o Installation of a minimum of 27 rocked drivable rolling dips and critical dips

(see Appendix A for diagrams) o Rock armoring of fill slope, inlet areas and/or ditch lines at 6 of the sites o In addition to rock at rolling and critical dips, rock will also be applied over

100 feet at one site as described in the treatments table.

• The contractor shall provide photographic documentation of all treatment sites.

Prior to the start of work, the BLM will stake and/or flag the start and finish points for the 12 miles of general treatments. Similarly, the BLM will stake and/or flag the individual treatment sites prior to work.

2.1 Additive Line Items.

Three (3) additional sites are listed as additive line items. If awarded, these sites will conform to all requirements contained herein this SOW. These three sites are listed at the end of the Treatments Table below. These sites include:

1. Two culvert installation sites with associated rock armoring, critical dip and rolling dip installation.

2. A road segment to improve for vehicle accessibility and road drainage which includes road rocking over 475’ and installation of rolling dips.

3.0 Objectives

The objectives of the project are to:

• Improve road surface drainage

• Replace aging and failing culverts

• Improve vehicle access conditions

• Reduce the amount of sediment delivering to watercourses from the road.

4.0 Requirements

Requirements are listed here in two general categories: general road treatments that will occur over the entire 12-mile road segment, and more intensive, site-specific treatments.

Each of these is described below.

The Contractor shall perform all of the general road treatments and site-specific treatments. The contractor shall be responsible for purchasing and providing all materials for the project.

Road Closures.

The contractor shall post notice along road notifying users of upcoming road closures, anticipated duration and contact information. Any anticipated road closures in excess of 24 hours will require the approval of the COR.

General Road Grading and Drainage Treatments. The Contractor shall clear plugged ditches and restore road surface drainage features (i.e., rolling dips, lead-outs and areas of water ponding on road surface) along the 12 miles of Red Mountain Road beginning at Milepost 1.9 and extending to Milepost 14. Where ditch clearing generates excess material, spoils sites will be identified in coordination with the BLM representative and will be in stable areas away from watercourses. No side-casting of excess material off the edge of the fill slope will occur. Excess material will be properly disposed of off-site, or as directed by the Contracting Officer’s Representative (COR).

Site Specific Treatments. The Contractor will implement specific treatments at 10 sites identified for upgrading. The Site-Specific Treatments Table below provides the list of sites, milepost location, treatments and the identified problem at the site as background.

The minimum required materials for each site are listed in the table below.

Installation methods and finished sites will conform to the typical drawings provided in Appendix A. Specific treatment types such as various rolling dip types, critical dips and culvert installations will adhere to the construction techniques provided in the typical drawings in this SOW. These include such measures as soils compaction, finished grades and mulching. The Contractor shall be responsible for reviewing and familiarizing themselves with the required treatment designs. Best Management Practices (BMP) for water quality protection are provided as Appendix B and are to be implemented in the appropriate circumstances as described for the specific BMP.

Each treatment site has the following minimum requirements:

• Contractor shall use angular road base material at all stream crossing culvert sites.

A minimum of 20 yards will be applied.

• Contractor shall use angular road base material at all ditch relief culvert sites. A minimum of 10 yards will be applied.

• Contractor shall install angular road base material at all rolling dip installations. A minimum of 10 yards will be applied.

• Contractor will apply straw mulch over all disturbed ground within 100 feet of a watercourse.

• Contractor shall utilize Aluminized, Type 2 corrugated metal pipe for all culvert sites. All culverts 42" or smaller shall be 12 gauge aluminized corrugated metal pipe. All culverts 48" and larger shall be 10 gauge aluminized corrugated metal pipe.

• Contractor shall take photos of all sites prior to and after treatment to document compliance with applicable BMPs. At the conclusion of the project, Contractor shall submit all photos in digital format clearly labeled with site number and date. A minimum of two photos per site shall be taken capturing salient features of the treatment. Photos will be used for annual permit reporting requirements.

• Replaced culverts shall be transported and disposed legally offsite.

Site Specific Treatments Table Milepost Site # Treatment Comments

2.1 77 Rolling dip installations.

1. Rolling dip installs (3):

- Install 1 rocked rolling dip at intersection of old road (above Red Mountain Road) ~ 35' left of DRC.

- Install 1 rocked rolling dip just down road of gully coming off driveway (see sketch).

- Install 1 rocked rolling dip further up the left road.

18" ditch relief culvert (DRC) with extensive active gully below outlet running down to lower private spur road and ultimately into headwall swale with assumed delivery. Gully varies from 1’ wide x 0.5' deep to 6'wide x 4' deep and is still active though rate of erosion may be much lower now than in past. Problem appears to emanate from private property above Red Mountain Road. Someone's driveway or private access road appears to capture flow from a near origin stream or at least a headwall swale plus some unknown length of road. Not fully investigated upslope due to private property and “No Trespassing” signs.

4.0 63 New culvert installation and rolling dips.

1. Culvert Install. Install an 18" x 60' L DRC at site location. Additionally, install a 25* angle elbow coupler to DRC outlet and install an 18" x 60' L full‐round downspout to elbow with anchoring appropriate for the site.

2. Rolling dip installs. Install 2 Type 2 rocked rolling dips up left road, connected to the cutbank. Breach the berm on the outboard side of the road.

3. Excavate and restore function to buried cross-drain inlet approximately 200 yards up the road.

285' of bermed left road features a rill and gully system developed along the road surface, discharging at road bend along headwall swale leading downslope into Holohan Gulch.

4.6 60.1 Rolling dips and coarse road rock installation.

1. Rolling dip installs (9):

- Install 3 rocked rolling dips to left road. Shape road to drain to one side or another for 750'.

- Install 6 rocked rolling dips up right road over 1,400'.

2. Road rock install. Install minimum 15 yards of 3” diameter angular rock to harden and raise low spot in road

Maintenance site only. Long segments of uncontrolled road meet at a low spot along the saddle of this mountain ridge. This location was used recently to spoil from summer 2019 work along Red Mountain Road.

Spoils are covered with straw. An 8'w x 3'd x 25'L "out" has been excavated at the low spot to breach the through-cut.

However, road shaping is poor and water ponds on the surface making road soft and muddy. No sediment delivery to watercourses.

Milepost Site # Treatment Comments

7.0 52 Culvert replacement.

1. Culvert install. Excavate from top of crossing (TOP) to base of fill (BOT) and replace existing culvert with a 48" x 50'L culvert set at the natural stream grade with the outlet at the base of the outboard fill (OBF).

2. Rock armor fillslope. Install 20 yd. of 0.5' - 2' diameter rock armor to the OBF.

3. Ditch excavation and rock armor. Cut and armor a 2.5’ wide ditch to carry flow from Site #53 (located ~35’ left) to the new culvert inlet.

Ensure ditch has a straight-line grade and cut deep enough to capture all flow where it meets the road, even during high runoff periods.

4. Critical dip install. Install a rocked critical dip on the right hinge line of the crossing. See typicals in Appendix A for critical dip and hinge line descriptions.

Undersized 18" dia. aluminum pipe set high in the outboard fill (OBF), Plunge ~ 6' vertically from outlet to channel and is causing active, though slow scour of the base of the OBF beneath the culvert outlet. Pipe inlet is offset ~ 8' from the axis of the stream above the road.

Fresh spoils next to the inlet indicates recent cleaning of the pipe inlet. Sediment accumulation at inlet appears to be a chronic maintenance issue due to off-set pipe and sharp change of grade when it hits the ditch. Pipe also receives flow from crossing #53, flowing down the inboard ditch from ~35' to the left. Though there is a diversion potential to right, most flow will exit road near right hinge which has been armored with rock and appears to convey flow on an annual basis.

Flow from Site #53 spills partially out of ditch at high runoff periods due to sediment aggradation. Gully downslope of rocked area on right hinge is rocky and stable. There is also strong flow contribution from left ditch from source beyond Site #53.

8.3 42 Culvert replacement.

1. Culvert install. Replace current culvert with 84" x 70' L culvert set at natural stream grade with outlet set at base of OBF.

2. Reduce road width to ~18' wide. End-haul excess spoils to stable disposal site.

3. Rock armor fillslope. Install ~ 80 yd. of 0.5' x 2' dia. Rock on OBF of rebuilt crossing.

4. Rolling dip install. Install 1 rocked rolling dip up left road.

Right road described in site #41.1 comments. CULVERT installed short/high in the fill. Bedrock looks like fissile turbidite material exposed in cutbank to right of site.

Road cut has induced or aggravated ongoing landslide along very steep right road.

Colluvium buries stream channel below road and any upgrade at site location should minimize excavation to avoid undercutting unstable hillslope. 4" x 8" collapse hole (x2) within surface of left road fill near OBF. Right road and this site will always be a maintenance issue and cutbank continues to fail and deposit material onto road. Stream channel fairly rowdy above road transports 1' minus cobble and woody debris. Size pipe appropriately and consider a trash rack. Large rock and potential for Humboldt logs within fill (collapse holes) raise complexity.

10.4 30 Culvert replacement and installation (Note: Do not undercut toe of slide).

1. Culvert installs (2):

- Replace existing 24" DRC with an 18" x 40' L pipe

- Install 18" x 40' DRC near end of throughcut to help disconnect road.

2. Ditch excavation. Excavate 3' wide channel with 2:1 side slopes where possible in inboard ditch for ~ 270' (or at least up to active spring ‐ see sketch ‐ Move IBD inward ~20' there.)

3. Rock armor channel above. Rock line excavated channel bottom and banks up to 1' high with 4" ‐ 8" dia. rock armor (~ 50 yd3).

3. Rock armor channel below. Armor small head cut just below outlet with another 1 yd of 0.5' ‐ 1' dia. rock.

4. Clean inlet area of culvert.

5. Rolling dip Installs. Install 1 rocked rolling dip within 50' of the crossing and three (3) rocked rolling dips up left road. (May only dip out outer 1/2 of road due to 20% grade).

This normally wouldn't be considered a stream crossing as it could be considered a DRC with delivery, but flow originates within a large deep-seated slide ~ 200'‐300' up the left (steep) road approach. Inboard ditch is incised and is actively eroding into the inboard side of the road. Though flow is diverted down the ditch out of its natural watershed, it flows downslope of the outlet and joins a large Class II stream and appears very stable. The natural watershed below the slide appears to be a large earthflow, so the current set up is preferable to re‐establishing flow into the earthflow.

Main problems are the incising ditch, long steep undrained left road surface runoff and the potential for the toe of the slide to slump and plug the inboard ditch, which would force flow onto the road. Climbing up on slide above road, it looked like there could have been a small drainage leading into the slide, but if so, flow path is deranged and dispersed.

10.8 26 Culvert replacement

1. Culvert install. Replace existing pipe with new 54" x 50' culvert.

2. Rock armor stream bank. Place 20 yd3 of 0.5' ‐ 1.5' diameter rock armor against the left bank to contain flow below outlet.

3. Rolling dip installs. Install 3 rocked rolling dips up the left road and 1 rocked rolling dip up the right road.

24" culvert drains broad springy ponded marsh area on large flat. Inlet shows bottom of culvert has rusted through. OBF has serious active erosion associated with separated pipe segment as well as road surface drainage gully. Boulders below old outlet are getting flanked and whole left bank has been scoured to and below BOT. Large boulder downstream of BOT provides grade control though potential exists for it to get flanked in future.

11.4 --

Quarry site.

This is not a treatment site. Previously stockpiled rock here may be used for project. There is ~20 yds of material available. Only existing stockpiled material may be used. No new excavation of the quarry is permitted.

Coordinates:

Latitude: 39.951746° Longitude: -123.648710°

12.95 8 Culvert replacement.

1. Culvert install. Install 42" x 40' L culvert placed with outlet at base of OBF. (Oversized pipe to account for bad spot to install critical dip).

2. Rock armor fill slope. Armor OBF with ~10 yd3 of 0.5' ‐ 1.5' diameter rock.

Slightly undersized culvert on small Class III stream in earthflow zone. Gully like channel upslope. Both inlet and outlet have rusted out holes in bottom of culvert.

Flow drops out of bottom of outlet causing ~ 1' head cut back into OBF from outlet. Diversion potential to left, though dip ~ 50' left will capture any diversion. It does not drain back towards natural drainage, but entire area is large earthflow feature. Large berm was constructed above inlet to help prevent overtopping and funnel right inboard ditch to inlet. Outlet slightly high in OBF. Minor sloughing of OBG may be associated with road surface runoff or could be from flow dropping out of bottom of culvert near outlet. (Raised treatment immediacy due solely to rusted out culvert only).

13.0 7 Culvert replacement.

1. Culvert install. Install new 54" x 50' L culvert set with outlet at base of fill slope. May need to cut pipe ~5' shorter due to stream channel turn immediately below crossing.

2. Critical dip install. Rebuild rocked critical dip similar to current one.

3. Rock armor stream banks. Armor left and right banks below new outlet with ~ 5 yd3 of 1' dia. rock.

4. Rock armor fill slope. Armor outboard fill slope (OBF) with ~15 yd3 of 0.5’ ‐ 1.5' dia. rock. Armor OBF all the way up to the outlet of the critical dip.

culvert crossing on HM energy Class II. Nice past installation with critical dip and culvert size. Outlet slightly high in fill. Main problem is bottom of culvert is worn out in outer 5' near outlet. Flow drops out through bottom of pipe and is eroding the outboard fill slope. Higher energy stream raises immediacy. No road surface issues connected to site.

13.09 5 Culvert replacement.

1. Culvert install. Replace culvert with new 30" x 50' L culvert with outlet set at top of existing rock apron.

2. Critical dip install. Install rocked critical dip on left hinge line of crossing.

3. Rolling dip install. Install 1 rocked rolling dip up right road.

Undersized culvert on gully‐like Class III stream. culvert shallow with outlet high in the OBF and has 10' full round downspout down to a heavily armored rock apron. Diversion potential down left inboard ditch.

Rock berm along top of inboard fill slope may have been placed to keep stream in ditch in case of plugging.

Main issue is advanced rust with holes at inlet and head cut below joint between outlet and downspout. Most likely due to holes in bottom of culvert near outlet (not visible) or less likely, could be that flow passes under bottom of pipe from holes closer to inlet.

Additive Line Item Sites

7.1 51 Culvert replacement.

1. Culvert install. Replace existing pipe with new 48" x 60' L culvert set with outlet at the base of the OBF.

2. Critical dip install. Install a rocked critical dip on the right hinge-line of the crossing.

3. Rolling dip install. Install 1 rocked rolling dip up the left road. Do not connect to the ditch.

4. Rock armor fillslope. Armor OBF with ~ 30 yd3 of 0.5' ‐ 2' dia. rock.

Gully-like stream channel with low-moderate stream power. Recently installed plastic culvert set short and high in the OBF. Inlet recently cleaned out but still ½ plugged. Crossing looks very stable with not much erosion at outlet. Stream has diverted in the past, causing lots of erosion in the ditch leading to DRC site #50. Channel below road is covered in duff.

11.7 17 Culvert replacement.

1. Culvert install. Replace existing pipe with new 84" x 60' L culvert set with outlet at the base of the OBF.

2. Rolling dip installs. Install 2 rocked rolling dips up the right road and 1 rocked rolling dip up the left road. (Note: The rolling dip up the left road should be upgradient of the hillslope gully at the edge of the raveling cutbank).

3. Rock armor fillslope. Armor OBF with ~ 25 yd3 of 0.5' ‐ 2' dia. rock and armor the IBF with ~ 5 yd3 of similar sized rock.

Rowdy Class II stream with 5.5' diameter culvert.

Bottom of pipe is rusted through with flow dropping out partly ~ 1/2 way into culvert and remainder dropping out before outlet. Rocks in OBF help lower rate of headcut back into OBF though will continue to get worse. A secondary, though relatively minor, issue is road surface runoff that discharges onto OBF near left hinge of crossing, which has created ~ 3' x 1' gully down the OBF. Rate of erosion at present is relatively low with no catastrophic implications to crossing.

Lastly, note ravelling tall cutbank near left hinge has active hillslope rills and a gully that run into the springy inboard ditch which then drains towards the inlet of crossing.

12.9 9 Access and drainage improvements.

1. Maintain DRC in present location.

2. Rolling dip installs. Re‐grade the road from Site #8 to Site #10. Install 3 rocked rolling dips, connected to the ditch.

3. Road rock install. Re‐rock the road for ~ 475' L using ~65 yd3 road rock.

~ 475' of road winds across spring earthflow. Road is shaped poorly for "drivability" but is not a significant source of erosion or sediment delivery to watercourses below road. Spring flow passes through DRC @ site location and delivers chronic sediment to streams downslope. See sketch for details.

Environmental Controls. Federal and state permitting requirements have mandated project start and end dates from May 15 through October 15. The Best Management Practices (BMPs) listed in Appendix B are required to satisfy Clean Water Act requirements for Non-point source pollution. The presence of archaeological resources, sensitive soils and private lands within the project area requires that all vehicles and equipment operate on the existing roadway and up to 50 feet from the road centerline as required to complete work at designated sites. Only previously stock-piled and disturbed rock may be used with the quarry site (see Government Furnished Property Section below)

Site Use Plan. All vehicle and equipment use shall be restricted to the existing roadway.

Equipment work may occur within 50 feet of the road centerline. Equipment operations on areas beyond 50 feet require approval from the Contracting Officer (CO) or the COR. Existing pull-outs may be used for equipment staging and materials storage. Other sites may be utilized for staging, storage or disposal of excess soils subject to the Contracting Officer or the COR’s approval. The quarry site at milepost 11.4 may be utilized for materials storage and staging. At the conclusion of work, all storage and staging areas shall be restored to a free-draining condition and be free of any inorganic debris. All excess soils will be groomed to match existing topography as feasible. No hazardous materials or fuels shall be stored within 150 feet of a watercourse. Contractor shall provide a Site usage plan to be approved by the COR/CO prior to the Notice to Proceed. Plan details shall include but not limited to: equipment storage locations, camping locations, materials stockpile/staging areas.

Warranties. Any warranties provided by the contractor will be considered.

5.0 Delivery

The Contractor shall complete all treatments within 100 calendar days after notice to proceed.

Due to permitting requirements for the protection of water quality and federally listed species, all work must occur between May 15 and October 15.

Within 15 calendar days of the conclusion of work completed, the Contractor shall provide all site-specific photographs of the treatment sites reflecting the before and after conditions and clearly labeled with site number and date(s). The photos shall be submitted to the BLM in digital format clearly organized, labeled and stored either on a compact disc, USB thumb drive, or retrievable from an online repository.

Final Inspection and Acceptance. The COR will review all work. At the conclusion of the work, the CO, or their representative, will inspect all sites for conformance with the specifications and requirements. Any deficiencies noted during the inspection will be corrected prior to release of final payment. Prior to final payment the Contractor will have properly disposed of all waste materials including culverts, completed site mulching and grooming of staging and storage areas, and submitted project photographs.

6.0 Government-Furnished Property

The government may furnish up to 20 cubic yards of unprocessed quarry rock from a quarry site at approximately mile 11.4 along Red Mountain Road. Coordinates for the quarry are:

Latitude: 39.951746°

Longitude: -123.648710°

The BLM will stake and flag the site prior to work. The Contractor shall be responsible for processing and hauling this material to the treatment site(s). Materials may only be used for treatment sites along Red Mountain Road. Unused materials shall be left onsite and the site groomed to restore a more natural appearance, by piling unused materials against the quarry wall. Any excess rock from the project may be staged and stored here. Only previously worked and disturbed materials may be utilized. No excavation of the intact bedrock is permitted.

7.0 Place of Performance

The work shall occur on Red Mountain Road in Mendocino County, California near the community of Piercy. See Maps 1 and 2. Work will commence at approximately milepost 1.9 and extend to mile 14. The BLM will mark these start and endpoints prior to work.

Coordinates for these points are:

• Intersection of Red Mountain Road and State Highway 271 o Latitude: 39.946792° o Longitude: -123.779338°

• Start of 12 mile treatment segment at mile 1.9 o Latitude: 39.951553° o Longitude: -123.757409°

• End of 12 mile treatment segment at mile 14 o Latitude: 39.919714° o Longitude: -123.644183°

Red Mountain Road is located in northernmost Mendocino County near the community of Piercy. The road is accessed at exit 625 off of Highway 101.

Coming from the north on Highway 101, exit 625 is approximately 13.5 miles south of Garberville and 1.5 south of the Piercy exit. At the exit, turn left and proceed 0.2 miles to the Red Mountain Road intersection which is signed.

Coming from the south on Highway 101, exit 625 is approximately 13 miles north of Leggett and 2 miles north of the Confusion Hill roadside park. At the exit, turn right and proceed 0.1 miles to the Red Mountain Road intersection.

Red Mountain Road traverses approximately 14 miles of private and public lands. Moderate to high clearance vehicles are recommended for traveling the road. All milepost figures for treatment sites are referenced from the intersection of Red Mountain Road and Highway 271 (“from the pavement”).

8.0 Period of Performance

The period of performance will extend 100 calendar days from the Notice to Proceed date.

Due to permitting requirements for the protection of water quality and federally listed species, all work must occur between May 15 and October 15.

Map 1. Red Mountain Road General Location

Map 2. Red Mountain Road Treatment Site Locations

Appendix A

Schematics for Typical Treatments Specified in the Scope of Work and detailed in the Site-Specific Treatments Table.

Appendix B

Best Management Practices For the Protection of Water Quality

To maintain compliance with federal Clean Water Act Requirements, Contractor is responsible for adhering to Best Management Practices. The following list of Best Management Practices (BMPs) will be employed at treatment sites depending on the nature of treatments and the applicability of a given BMP for the site.

Construction and reconstruction BMPs:

1. Minimize fill volumes at stream crossings by restricting width and height of fill to amounts needed for safe travel and adequate cover for culverts. For deep fills (generally greater than 15 feet deep), incorporate additional design criteria (e.g., rock blankets, buttressing, bioengineering techniques) to reduce the susceptibility of fill failures.

2. Place sediment-trapping materials or structures such as straw bales, jute netting, or sediment basins at the base of newly constructed fill or side slopes where sediment could be transported to waters of the State. Keep materials away from culvert inlets or outlets.

3. Construct road fills to prevent fill failure using inorganic material, compaction, buttressing, sub-surface drainage, rock facing, or other effective means.

4. Locate waste disposal areas outside wetlands, Riparian Reserve, floodplains, and unstable areas to minimize risk of sediment delivery to waters of the State. Apply surface erosion control prior to the wet season. Prevent overloading areas, which may become unstable.

5. Design stream crossings to minimize diversion potential in the event that the crossing is blocked by debris during storm events. This protection could include hardening crossings, armoring fills, dipping grades, oversizing culverts, hardening inlets and outlets, constructing critical dips, and lowering the fill height.

6. Design stream crossings to prevent diversion of water from streams into downgrade road ditches or down road surfaces.

7. On new construction, install culverts at the natural stream grade, unless a lessor gradient is required for fish passage.

8. Place instream grade control structures above or below the crossing structure, if necessary, to prevent stream head cutting, culvert undermining and downstream sedimentation. Employ bioengineering measures to protect the stability of the streambed and banks.

9. Prevent culvert plugging and failure in areas of active debris movement with measures such as beveled culvert inlets, flared inlets, wingwalls, over-sized culverts, trash racks, or slotted risers.

10. Utilize stream diversion and isolation techniques when installing stream crossings.

Evaluate the physical characteristics of the site, volume of water flowing through the project area and the risk of erosion and sedimentation when selecting the proper techniques.

11. Disconnect road runoff to the stream channel by outsloping the road approach. If outsloping is not possible, use runoff control, erosion control and sediment containment measures. These may include using additional cross drain culverts, ditch lining, and catchment basins. Prevent or reduce ditch flow conveyance to the stream through cross drain placement above the stream crossing.

Surface Drainage BMPs:

1. Effectively drain the road surface by using crowning, insloping or outsloping, grade reversals (rolling dips), and waterbars or a combination of these methods. Avoid concentrated discharge onto fill slopes unless the fill slopes are stable and erosion-proofed.

2. Consider using broad-based drainage dips or leadoff ditches in lieu of cross drains for low volume roads. Locate these drainage features where they will not drain into wetlands, floodplains, and waters of the State.

3. Avoid use of outside road berms unless designed to protect road fills from runoff. If road berms are used, breach to accommodate drainage where fill slopes are stable.

4. Design roads crossing low-lying areas so that water does not pond on the upslope side of the road. Provide cross drains at short intervals to ensure free drainage.

5. Divert road and landing runoff water away from headwalls, slide areas, high landslide hazard locations, or steep erodible fill slopes.

Cross Drain BMPs:

1. Locate cross drains to prevent or minimize runoff and sediment conveyance to waters of the State. Implement sediment reduction techniques such as settling basins, brush filters, sediment fences, and check dams to prevent or minimize sediment conveyance. Locate cross drains to route ditch flow onto vegetated and undisturbed slopes.

2. Choose cross drain culvert diameter and type according to predicted ditch flow, debris and bedload passage expected from the ditch. Minimum diameter is 18.”

3. Locate surface water drainage features (e.g., cross drain culverts, rolling dips, and water bars) where water flow will be released on convex slopes or other stable and non-erosive areas that will absorb road drainage and prevent sediment flows from reaching wetlands, floodplains, and waters of the State. Where possible, locate surface water drainage structures above road segments with steeper downhill grade.

Locate cross drains at least 50 feet from the nearest stream crossing and allow for a sufficient non-compacted soil and vegetative filter.

4. Armor surface drainage structures (e.g., broad based dips, and leadoff ditches) to maintain functionality in areas of erosive and low-strength soils.

5. Discharge cross drain culverts at ground level on non-erodible material. Install downspout structures or energy dissipaters at cross drain outlets or drivable dips where alternatives to discharging water onto loose material, erodible soils, fills, or steep slopes are not available.

6. Cut protruding ‘shotgun’ culverts at the fill surface or existing ground. Install downspout or energy dissipaters to prevent erosion.

7. Skew cross drain culverts 45–60 degrees from the ditch line and provide pipe gradient slightly greater than ditch gradient to reduce erosion at cross drain inlet.

8. Provide for unobstructed flow at culvert inlets and within ditch lines during and upon completion of road construction prior to the wet season.

9. Install critical dips down-grade of cross drain culverts to accommodate overtopping flows. Where road grades are too adverse for critical dip construction, provide for appropriate routing of overtopping flows across road tread or into adjacent, suitably-sized drainage structure.

General Erosion Control BMPs:

1. Where sediment could be transported to waters of the State, place sediment-trapping materials or structures such as straw bales, jute netting, or sediment basins at the base of newly constructed fill or side slopes. Keep materials away from culvert inlets or outlets.

2. Suspend ground-disturbing activity if projected forecasted rain will saturate soils to the extent that there is potential for movement of sediment from the road to wetlands, floodplains, and waters of the State. Cover or temporarily stabilize exposed soils during work suspension. Upon completion of ground-disturbing activities, immediately stabilize fill material over stream crossing structures. Measures could include but not limited to erosion control blankets and mats, soil binders, soil tackifiers, or placement of slash.