UTR5_100_Specs_Rvsd_05_11_16.pdf

TECHNICAL SPECIFICATIONS

FOR

UPPER TRUCKEE RIVER REACH 5

RESTORATION PROJECT

Prepared for:

USDA – Forest Service Lake Tahoe Basin Management Unit South Lake Tahoe, CA

Prepared by:

STREAM SOLUTIONS LLC

South Lake Tahoe, CA

May 11, 2016

Upper Truckee River Reach 5 Restoration Technical Specifications

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I. Summary of Work 1

II. Dewatering and River Diversion 4

III. Clearing and Grubbing 14

IV. Grading 16

V. Excavation, Fill and Compaction 25

VI. Erosion Control and Revegetation 27

VII. Willow Planting and Roses 33

UTR 2016 Diversion Contractor Responsibilities and Relevant Information are highlighted in RED throughout this document.

If/where inconsistencies are found between the design plans and the Technical

Specifications, the Technical Specifications should be followed.

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I. SUMMARY OF WORK

PART 1 GENERAL

1.1 DESCRIPTION

A. These technical specifications cover work under the Upper Truckee River Reach 5

Channel Restoration Project to include:

1. Installing erosion control and temporary protection measures

2. Dewatering for new channel construction and seasoning

3. Installing river diversions

4. Excavating 7,416 feet of new channel and grading up to 5.6 acres of floodplain to the north. This is a maximum acreage estimate for floodplain grading, because existing vegetation within the grading limits will be protected where feasible

5. Constructing temporary access roads

6. Installing two temporary river crossings

7. Installing channel bed and bank treatments

8. Installing grade control and lateral control structures

9. Protecting existing utility lines at new river channel crossings and where the new channel gets close to utilities

10. Maintaining and irrigating new vegetation throughout all constructed channel and floodplain activities

11. Demobilizing and remobilizing temporary access road at end and beginning of each construction phase

12. Backfilling, grading and revegetating existing channel

13. Winterizing all disturbed areas

14. Seeding and revegetating all disturbed areas

1.2 PHASES AND ORDER OF WORK

Construction Phases A. New Channel Construction Phase I (Year 1) – [COMPLETED] Construct up to

4,066 linear feet (LF) of new channel on the southern (i.e. upstream of southernmost river crossing) portion of Project area. Work will likely require some dewatering during new channel construction. Work requires temporarily diverting the river to install and later remove a temporary river crossing at the low water crossing along the access road from Sunset Stables staging area.

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B. New Channel Construction Phase II (Year 2) – [COMPLETED] Construct any remaining southern portion of new channel (i.e. any length not completed in first year) and 3,650 LF of new channel on the northern portion of the Project area.

This work requires two temporary river diversions to construct and remove temporary river crossings one at the low water crossing near Sunset Stables and the other on the northern end of the Project site (per Sheet C-4). Dewatering will also be required during new channel construction. In addition to dewatering activities associated with construction, at the start of Phase II construction season, the new channel sections completed in the previous year are assumed to have standing water and will require dewatering to get and maintain surface waters in the bed of the new channel around 1’ depth or less to encourage vegetative growth and attain adequate seasoning.

C. Channel Seasoning Phase III (Year 3 and/or 4) – [YEAR 3 COMPLETED] The third phase will be focused on irrigating, seasoning and flushing the new channel sections in preparation for channel activation during Phase IV. It is anticipated that dewatering of the newly constructed channel will be required each additional year of seasoning during which revegetation success is monitored and new channel areas are checked for the need to pump down to low water levels and maintain that water depth in order to promote adequate vegetation growth. Bed and bank treatments, particularly those incorporating vegetative materials, shall be evaluated during Phase III to assess progress towards reaching full functionality for channel bed and bank stability and floodplain resistance to erosion. Local areas of treatments may require supplemental seeding or other adjustments to ensure readiness for Phase IV activation. Channel Activation under Phase IV will not commence until LTBMU Project Manager and other responsible parties agree that the conditions are adequate.

D. Channel Activation Phase IV (Year 4 or 5) – As part of the assessment to determine whether the new channel is prepared for activation, it is assumed dewatering of the previously constructed new channel may be required at the start of this phase to expose streambanks and assess seasoning and vegetation growth.

A portion of the growing season may be required prior to the next step of this phase. Once the new channel and floodplain vegetative growth is determined to be suitable to receive unregulated river flows (by the LTBMU Project Manager and other responsible parties) the final crossings, tie in areas and northern floodplain will be constructed. This effort will require two river diversions as shown on “Amended for Phase IV (2016) Plan Sheets C5 and C6”. The LTBMU’s hired Contractor (i.e. Diversion Contractor) will install, operate, and maintain the two river diversions according to the plans, specifications and permits and as directed by the LTBMU. The Diversion Contractor will cease

-3-diversion operations and remove all diversion infrastructure from the project site when directed by the LTBMU. The completed installation and operation of river diversion D-1 will allow LTBMU crews to pump the northern portion of the existing river sufficiently dry to use as an access route (eliminating the need for a second temporary crossing), and to construct the northernmost tie in, three new channel/existing river crossings, and grade the northern floodplain. While diversion D-1 is being installed, the LTBMU staff will conduct fish and mussel relocation efforts on the portion of the existing river being dewatered by the diversion.

Once D-1 is installed and fully operational, the Contractor will install the impermeable barrier fence (or approved equivalent) at the downslope boundary of Upland Dewater Basin North and Dewater Irrigation Cell 6 to accommodate further dewatering of diverted sections of the stream channel by the LTBMU. The Contractor will provide the materials for the LTBMU to install and secure sprinkler heads at the end of each dewatering pipe within the upland dewater basins and irrigation cells.

Upon LTBMU’s direction the second diversion, D-2 will be installed as shown on the amended plans to divert flows around the southern portion of the existing channel. Again, fish and mussel salvage and relocation efforts will be completed by the LTBMU while the Contractor is installing diversion D-2. D-2 will be configured to divert flows to the new channel at approximate Station 39+50 IF the new channel in this area is sufficiently flushed and has been authorized for activation. If that isn’t the case, D-2 will be configured to divert flows to the “WYE” connection at the D-1 diversion pipe to essentially divert around the entire existing river in the project reach and allow for an extended period for the northern portion to be flushed and ultimately receive activation authorization.

E. Utility Relocation Phase – [COMPLETED] This phase will be constructed under a separate contract and will require coordination with the new channel construction phases. Because it requires a temporary river crossing on the north end to access the utility line work, it should be implemented concurrently with Phase II channel work. Localized dewatering would be needed for excavated sections to lower and reposition pipes, and will be the responsibility of the Utility Relocation construction contractor.

F. A recommended order of work is presented in Section IV.

PART 2 PRODUCTS

Not Used

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PART 3 EXECUTION

END OF SECTION

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II. DEWATERING AND RIVER DIVERSION

PART I GENERAL

1 .1 DESCRIPTION

A. The work of this section consists of the following:

1. Providing water diversion structures during work within any sections of the active river.

2. Dewatering areas with standing water prior to and during backfilling and grading activities.

1.2 DEWATERING DURING CONSTRUCTION PHASES

A. New Channel Construction Phase I (Year 1) – [COMPLETED] As stated in Section I this phase would construct up to 4,066 linear feet (LF) of new channel on the southern portion of the Project area. Work may require dewatering up to

1.4 million gallons during construction of the entire 4,066 feet of new channel and continued dewatering as excavation of the deeper pool features continues to receive groundwater seepage. The dewatering approach will be to pump from sections of the 4,066 LF of constructed new channel and spray irrigate the decant to separate meadow areas, or Dewater Irrigation Cells 1 through 4 as shown on Sheet C-5 that are approximately 1 to 2 acres in size. Pumps will be placed at the low spots (i.e. pools) and used to pump approximately 150 to 350 gpm of decant water to the center of each dewater cell for spray irrigation. The direction of pumping will be down valley or northward to minimize re-infiltration of water into work areas.

While actively pumping, the dewater irrigation cells and adjacent new channel sections will be monitored periodically throughout the day in order to ensure that no surface runoff is being created and there is no accelerated groundwater recharge into the new channel sections downstream of the dewater irrigation cells.

At no time will pumping be allowed to continue to these areas if there is danger of surface runoff entering the existing river, drainage ways or new channel. If necessary a coir log could be staked around the perimeter of each of these dewater irrigation cells to provide added protection against any potential surface runoff.

As new channel construction progresses through the project area, water pumped from construction areas may be used to irrigate newly planted vegetation along constructed channel banks, which would reduce the volume of water going to the

-6-dewater irrigation cells and basins. This would only continue as long as water does not pond in the new channel and result in additional dewatering needs.

As a key contingency measure and in order to prepare for the channel seasoning efforts in the next year, the materials for the 7.5 acre-feet Upland Dewater Basin Central will be mobilized and ready for installation in the Ponca Pit area to the southeast (Sheet C-5). When needed, the basin will be constructed by installing a 4 feet water-filled berm around the basin perimeter with overlapping impermeable liner extending into the basin approximately 10 feet. The water-filled berm will be enclosed with a chain link fence and coir log or straw wattle perimeter to prevent vandalism and protect water quality in the event of a leak or partial failure of the water-filled berm. As an additional back-up to Upland Dewater Basin Central, there is the option to mobilize for and install when needed the additional 12 acre-feet Upland Dewater Basin South near the southern end of the Project (Sheet C- 6). Upland Dewater Basin Central and South would only be utilized during Phase I if and when the dewater cells within the meadow were not able to accommodate the volume of water pumped from the new channel excavation.

When in use the upland dewater basins will also be monitored on a daily basis to ensure the water-filled berms are intact and functioning and that there is sufficient freeboard to prevent overtopping.

Any upland dewater basins activated during this construction phase, if still holding water, will be drained in a controlled manner per the approved SWPPP and demobilized prior to the onset of winter, or the water filled berm and chain link fence with coir log would remain in place over the winter, and would be available for the Phase II construction activities.

B. New Channel Construction Phase II (Year 2) – [COMPLETED] This phase would construct the remainder of the 4,066 LF of new channel not completed during Phase I and 3,650 LF of new channel on the northern portion of the Project area.

This will require dewatering of approximately 1.3 million gallons initially followed by continued dewatering from recharge into low lying areas. The 3,650 LF of new channel will be dewatered into a single 4-acre Dewater Irrigation Cell Number 5 between the airport and new channel construction with the option to utilize Dewater Irrigation Cell Number 6 in the more upland area to the northeast (Sheet C-5) by installing a water-filled berm along its western edge to prevent any potential surface water runoff from degrading the adjacent drainages. Similar to Phase I, the water will be pumped from the deeper pools in the work area and conveyed at approximately 150- to 350 gpm to spray irrigate the designated meadow area.

These meadow areas will be monitored periodically throughout the day for any evidence of pooling or standing water with the potential to become runoff. The existing river channel and any newly constructed channel sections down gradient

-7-of the dewater cells will also be monitored to ensure sediment laden water is not being released via increased groundwater seepage. If excessive ponding or surface water is observed in the dewater cell areas or any dirty water piping downgradient, spray irrigation will be immediately suspended in those areas and another dewater cell or upland dewater basin will be brought on line and monitored closely to accommodate the construction water decant. All active upland dewater basins will also be inspected on a daily basis and repairs will be made immediately upon observation of any damages to the water-filled berm.

Any pumping to the damaged basin will be immediately halted if the water-filled berm is leaking or overtopping.

Water pumped from the construction areas may be used to irrigate newly planted vegetation along channel banks (in the previous year’s constructed channel areas, and in those areas already constructed as part of this phase), which would reduce the volume of water going to the dewater irrigation cells and basins. This would only continue as long as water does not pond in the new channel and result in additional dewatering needs.

An additional 1.8-acre Dewater Irrigation Cell 6 adjacent to Upland Dewater Basin North will be on standby to spray additional decant waters to if needed or desired. As a contingency measure, Dewater Basin North (3.4-acres) will be mobilized to be ready to accept an initial volume of 10.3 acre-feet or 3.3 million gallons, 2.5 times the assumed initial volume of new channel excavation.

There is the option to begin work on the left bank of the downstream transition area prior to Phase IV, if time allows during this phase, by partially isolating flows (i.e. moving them to the other side of the channel via a water-filled berm or sheet piling). This would increase the dewatering volume being pumped to Dewater Cell 4 in the meadow slightly while these bank improvements were being installed.

In addition to dewatering activities associated with construction, at the start of the season, the new channel sections constructed in the previous Phase I year are assumed to have standing water and require targeted dewatering down to 1’ depth or less to facilitate vegetative growth and ensure seasoning. This is a potential volume of up to 13-acre feet that would be accommodated via the 7.5-acre feet Upland Detention Basin Central and adjacent dewater cells. Dewatering of the new channel is required only to improve vegetation growth during the summer season therefore it can be done in a very purposeful and measured manner by conveying to the 7.5 acre-feet or 2.4 million gallon capacity Dewater Basin Central and if dry conditions allow also spray application to the adjacent 5 acres of Dewater Cells 1 through 4. If spray application is unable to be used to accommodate the additional new channel decant during seasoning, 3.2 million gallon capacity Upland Dewater Basin South will be brought on line to provide the additional 1.8 million gallons of capacity needed to adequately lower the new channel water levels for vegetation growth leaving an additional 1.4 million gallon capacity available for continued channel drawdown.

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Similar to Phase I, as a contingency measure in the event Dewater Irrigation Cell Number 5 in the meadow is not able to keep up with demand or begins to infiltrate back into the new channel work and in preparation for the next year’s channel seasoning when almost the entirety of the new channel will require draining and seasoning, a 10.5 acre-feet Upland Dewater Basin North will be mobilized if needed during this phase to the northeast (Sheet C-5). It would only be constructed and activated during Phase II if and when the meadow dewater cells were not able to accommodate the volume of water pumped from the new channel excavation. Any upland dewater basins activated during the construction phases, if still holding water, will be drained in a controlled manner per the approved SWPPP and demobilized prior to the onset of winter or the water filled berm and chain link fence with coir log would remain in place over the winter, and would be available for the Phase III dewatering needs.

C. New Channel Seasoning Phase III (Year 3 and/or 4) [Year 3 COMPLETED] Dewatering of the new channel will likely be required each additional year of seasoning. During these times revegetation success will be monitored and new channel areas will be checked for the need to pump down to low water levels in order to promote adequate vegetation growth. It is conservatively assumed that the entire volume of the new channel constructed during the first two years would need to be pumped and contained at the start of each summer season, resulting in a total volume of 24 acre-feet or 8 million gallons. Upland Dewater Basins North, Central and South with a combined initial capacity of roughly 9 million gallons would be used to accept this initial decant under a controlled manner and with infiltration are expected to keep up with continued dewatering demand. Since pumping for channel seasoning is a proactive approach and wouldn’t necessarily require complete immediate removal, another option would be to rely on the meadow dewater irrigation cells for pumping and spray irrigating in order to lower the new channel water surface elevation during seasoning and only use the upland dewater basins if capacity in the meadow areas becomes exceeded.

D. Channel Activation Phase IV (Year 4 or 5) – It is assumed dewatering of the previously constructed new channel may be required at the start of this phase in order to continue to promote adequate seasoning and vegetation growth. Again it is conservatively assumed that the entire volume of the new channel constructed during the first two years, up to 8 million gallons would need to be pumped and contained at the start of the summer season. As stated under Phase III, another option might be to rely on the meadow dewater cells for pumping and spray irrigating, particularly if the meadow is dry at the time of pumping, in order to lower the new channel water surface elevation during seasoning and only use the upland dewater basins if capacity in the meadow areas becomes exceeded.

The majority of river diversion activities will take place under Phase IV in order to construct the three existing river crossings and upstream and downstream tie-

-9-ins. The river diversion approach is described under section 1.3 below. During river diversion, dewatering of the work area between the coffer dams at each of the two river diversions, Diversion 1 (D-1) and Diversion 2 (D-2) due to porosity of the dams and groundwater influence is assumed to be accommodated by spray discharging to the nearest Dewater Irrigation Cells in the meadow and if necessary the Upland Dewater Basins. All diversions would remain in place until the new channel sections are deemed ready for activation by the LTBMU, TRPA, and Lahontan RWQCB.

Once the new channel is activated, 7,312 LF of the existing channel will need to be backfilled.

Assuming a third of the total volume of the existing channel would need to be dewatered following installation of both diversions would result in around 11 acre-feet or 3.6 million gallons initially plus continued dewatering as groundwater moves in. Initially, and until the majority of the water is drained from the existing channel, this water while meeting all surface discharge requirements would be diverted around the construction area, and directly into the existing channel downstream of the disturbance area. When the water level drops to near the riffle elevations or when the decant is no longer able to meet surface discharge requirements, the existing channel flow will be dewatered as described below rather than diverted around the construction area. It is anticipated that there will be sufficient time lapsed for the Upland Dewater Basins Central, South and North with continued infiltration to have drained sufficiently from the channel seasoning to accommodate the initial and continued decant as groundwater is likely to continue to move into the existing channel during backfilling operations.

Decommissioning of the upland Dewater Basins will also be a part of this final phase of the Project.

E. Utility Relocation Phase – [COMPLETED] This phase will be constructed under a separate contract and will require coordination with the new channel construction phases. Because it requires a temporary river crossing to access the utility line work, it is expected to be implemented concurrently with Phase II channel work. Localized dewatering would be needed for excavated sections to lower and reposition pipes, and will be the responsibility of the Utility Relocation construction contractor.

F. Dewatering Methods

a. Design pump intakes and outlets to minimize turbidity and the potential to wash contaminants into adjacent creeks or wetlands. Use an energy dissipater to prevent erosion at the outlet. Screen pump intakes with wire mesh, sized and approved by the LTBMU Project Manager, to prevent fish and amphibians from entering the pump system. Check intake periodically to ensure screen is functioning properly.

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b. Any turbid water pumped from the work site will be disposed of in the approved Dewater Irrigation Cell and Upland Dewater Basin locations shown on Revised Sheets C-5 and C-6.

c. Refuel pumps in areas a safe distance from stream channels and wetlands and where approved by the LTBMU Project Manager. Place fuel absorbent mats or leak free tray under pump while refueling.

1.3 RIVER DIVERSION DURING CONSTRUCTION PHASES

A. New Channel Construction Phase I (Year 1) [COMPLETED]

A temporary river diversion using water-filled berms as coffer dams per the plans will be needed to construct the temporary river crossing at the low water crossing along the access road from the Sunset Stables staging area (D-1 on Plan Sheet C- 6). Installation of the Temporary River Crossing is described below.

a. Installation of Temporary River Crossings A maximum of two temporary crossings will be utilized per plan sheets.

Because this work will occur in late summer, flows are expected to be low.

Following temporary river diversion (refer to Detail 2 on sheet D-9), the temporary crossings will be installed as outlined below:

Following successful river diversion with the water-filled berm coffer dams, pumps will be used to dewater the area and convey to a nearby dewater irrigation cell or upland dewater basin as needed. Once adequately dewatered, the geotextile fabric will be placed in the bed of the channel to cover the full extent of the crossing plus 10’ in each direction and at least 20’ beyond the top of each bank to accommodate the approaches. A single 1-foot layer of clean straw will be added to the fabric layer. Then a layer of clean gravel will be applied and the main culvert will be positioned horizontally in the lower point of the bed on the fabric/straw/gravel layer. An additional layer of gravel will be applied and then the second two culverts will be positioned horizontally and slightly higher than the main culvert. Clean gravel will be backfilled in-between and on all sides of the culverts until it is at least level with the top of the lowest culvert. 3” minus coarse aggregate will be used to backfill the remainder to bring the crossing at grade with the banks on either side.

b. Removal of temporary crossing At the end of each construction season all temporary crossings will be removed. The steps to be followed at each temporary crossing are outlined below.

The 3” coarse aggregate and 1” clean gravel fill culvert bedding material will be removed and transported to the stockpile area. The gravel will be removed using an excavator until the straw layer is encountered and the final material will be removed with hand tools in order to preserve the integrity of the

-11-geotextile fabric. The culverts will be removed and stored in the staging area for use the following year or transported off-site to an existing LTBMU storage facility. The fabric will be removed in a manner that avoids spillage of sediment into the stream channel.

If at any time during the removal of the crossing turbidity in excess of what is deemed allowable under the Lahontan and TRPA permits is generated or the project manager determines that there is a risk of sediment release to the stream, water will be pumped from the first pool upstream of the crossing and diverted around the crossing installation areas, and the water within the crossing installation area will be conveyed to a nearby dewater irrigation cell and/or upland dewater basin to dewater the area until removal is complete.

B. New Channel Construction Phase II (Year 2) [COMPLETED]

This work requires a temporary river diversion using water-filled berms as the coffer dams to construct a temporary river crossing near the northern end of the project area (D-2 on Plan Sheet C-5) as shown in the plans in addition to the river crossing that would be needed again near Sunset Stables (D-1 on Plan Sheet C-6) for constructing the remaining new channel length to the north. For diversion approach, see 1.3.D.a and for temporary river crossing installation see 1.3.A.a.

C. New Channel Seasoning Phase III (Year 3 and/or 4) [YEAR 3 COMPLETED]

It is not expected that the temporary river crossings at Sunset Staging area and the northern end will need to be constructed for Phase III dewatering and irrigating operations.

D. New Channel Activation Phase IV (Years 4 or 5)

River Diversion during Phase IV Channel Activation Phase IV requires diverting the river around three existing channel crossings and upstream and downstream transition reaches to construct improvements where the new channel intersects or ties in prior to activating the new channel. Given the need to install the stream diversions early enough to complete Phase IV work within the grading season (May 1 to October 15), the two pumped diversions, D-1 and D-2 will be required to accommodate flows of up to 30 cubic feet per second (cfs) or 13,465 gallons per minute (gpm) and 15 cfs or 6,732 gpm respectively. In order to collect and divert the river flow around these construction areas, coffer dams of visquene encapsulated sand bags (Detail 2, Sheet D-9) or an approved equivalent would be installed at either end of diversions D-1 and D-2 and screened pump intakes would collect and convey the flow. The downstream coffer dams for both diversions would be smaller, constructed to a minimum 3 ft height.

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Both diversions would be fed by pumps if flows are below 30 cfs in the UTR at the time of diversion installation. If flows greater than 30 cfs exist in the UTR when the first diversion (D-1) is installed, a gravity diversion option would be used. This gravity diversion option for D-1 would consist of the LTBMU constructing a ditch along the temporary access road, and the Contractor installing a series of pipes in the ditch to carry the UTR flows by gravity to the downstream end of the project area. The alignment of the gravity diversion option, the coffer dams, and the inlet and outlet location would be the same as that for the pump diversion option at D-1. This gravity diversion option would be designed to accommodate flows of up to 100 cfs, in the event of a summer precipitation event.

The Diversion Contractor shall be equipped with additional pumps for each pumped diversion to accommodate a potential precipitation event and the resulting increase in river flows up to 30% of the original diversion amount. The Diversion Contractor and LTBMU will monitor weather on a daily basis in order to plan for any forecasted large precipitation events and a contingency plan will be developed as part of the SWPPP to address potential overtopping of the coffer dams in the event of a rainstorm that increases flows to over 30% of the original diversion amount.

Note: In the event of higher stream flows and installation of the gravity diversion option for D-1, the Diversion Contractor would only be responsible for installation of the coffer dams and the gravity flow pipes in the ditch, and not the pumped diversion.

D-1 will be installed first concurrent and in coordination with fish and mussel relocation efforts by the LTBMU staff in order to dewater the northern portion of the existing river. Once sufficiently dewatered LTBMU crews will be able to access the downstream tie in, the three locations where the new channel crosses the existing channel, and the northern floodplain to complete the restoration construction of those areas.

Upon assessment of the construction progress on the northern portion of the site, the LTBMU will direct the Diversion Contractor to install the second diversion, D-2. IF the northern portion of the new channel has been completed, sufficiently flushed, and authorized for activation by the LTBMU, TRPA, and Lahontan RWQCB diversion D-2 will be installed to divert flows from the intake upstream of the tie in at Station 84+16 and release them into the new channel at approximate Station 39+50. IF the northern portion of the new channel has not been authorized for activation then D-2 will be installed to tie into a “Wye” fitting at D-1 and flows will be diverted around the entire existing river reach within the Project area. Both diversions will remain in place for the period it takes to complete all bed and bank treatments and adequate flushing associated with the upstream and downstream tie-ins and three river crossings. D-1 will be installed starting July 11th and both D-1 and D-2 may remain until vegetation is adequately

-13-seasoned, channel bed and banks are deemed sufficiently stable for active flows, and channel flushing is complete.

Upon direction by the LTBMU the following will be the general Order of Work for the Diversion Contractor per Amended for Phase IV (2016) Plan Sheets C-5 and C-6.

Starting with D-1 just U/S of the new channel crossing at Station 41+50 install a coffer dam of visquene covered sand bags (or approved equivalent) in the existing channel. Install a second coffer dam of similar construction just beyond the limit of construction, but smaller height (min 3 ft) at the D-1 D/S tie-in (at approx.

Station 10+00). Given the critical nature of this most downstream tie-in, a redundant coffer dam constructed of water-filled berm of a minimum 3 ft height (or approved equivalent) will be installed just D/S of the D/S sand bag coffer dam, but still within the Project Boundary (around Station 9+85). Once this river bypass is operational it enables construction of the more critical D/S tie-in and the crossings earliest in the season in order to have some beneficial growing season.

At this location the river is to be diverted by pumping at the U/S coffer dam (or gravity fed in a previously constructed ditch if flows are greater than 30 cfs) and conveyed along the western edge of the Project site near the airport fence and released to an energy dissipater downstream of the coffer dam and redundant water-filled berm (or approved equivalent) near the north Project boundary.

Once D-1 is installed and fully operational, the Contractor will install the impermeable barrier fence (or approved equivalent) at the downhill boundary of Upland Dewater Basin North and Dewater Irrigation Cell 6 and if needed Upland Dewater Basin Central to accommodate further dewatering of diverted sections of the stream channel by the LTBMU.

In general, while diversion D-1 is in place and the crossings and D/S tie-in are being constructed, nearby and previously completed sections of new channel that hadn’t already been adequately flushed during the previous construction seasons, will be flushed and tested while they are still offline. Until water flows clear, the flushing flows will be intercepted at the downstream constructed coffer dam and pumped to Upland Dewater Basin North. Once the D/S tie-in section is completed, metered flows will be introduced into both the section previously constructed and seasoned and the tie-in section. Until water flows clear and meets discharge requirements identified in the approved SWPPP, the flushing flows would be intercepted at the most D/S pool just past the constructed tie-in by leaving the two most downstream coffer dams (i.e. one sandbag and the second water-filled berm (or approved equivalent)) in place and sent to the Upland Dewater Basin North and/or Irrigation Cell 6 for infiltration.

Similar to the D/S tie in section, while D-1 is still in operation and as soon as each of the river crossings are constructed (i.e. between approximate Stations 19+00 to

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21+00, 26+00 to 29+00, and 40+00 to 43+00) the LTBMU will begin to flush these sections until they run clear and meet the Lahontan RWQCB permit requirements. Once approved, flow will be metered through the entire northern section of the new channel.

The second river diversion D-2 would be installed once the LTBMU determines that either the northern portion of the new channel is completed and ready for metered flows or there is a pressing need for the second diversion in order to allow for sufficient time for construction to be completed within the grading season. The D-2 bypass will initiate via a similar coffer dam installation just U/S of the southern tie-in at approximate Station 84+00. The D-2 bypass will either be configured to outlet into the new channel at approximate Station 39+50 IF that portion of channel has been authorized for activation or tied into the “Wye” diversion pipe fitting at D-1. Once the entire new channel is running clear and meets the Lahontan RWQCB permit requirements, the U/S diversion will be removed and the entire channel flushed and tested with any sediment-laden water still being captured at the two most downstream coffer dams (i.e. approximate Station 10+00 and 9+85) and pumped to Upland Dewater Basin North and Irrigation Cell 6. The two most downstream coffer dams would only be removed once the water runs clear and consistently meets the Lahontan RWQCB permit conditions.

After both diversions have been removed and the LTBMU gives the Contractor authorization to remove the dewatering infrastructure, the impermeable barrier fence (or approved equivalent) at Upland Dewater Basin North, Dewater Irrigation Cell 6 and possibly Dewater Basin Central will be demobilized and all materials removed from the site.

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III. CLEARING AND GRUBBING

Not used

PART 2 PRODUCTS

2.1 TOPSOIL

A. Soil and other organic material salvaged during grubbing activities shall be stockpiled for reapplication following grading. The top 12 inches of soil in the new channel may be stockpiled in the immediate work vicinity if re-used within 3 to 4 days by placing on plastic sheeting or a construction mat (i.e. Duradeck or equivalent) and re-applied as a top-dressing on the new channel banks and top of banks. Subsoil from the new channel (i.e. all soil below the initial 12” layer) shall be removed and stockpiled separately at the Sunset Stables staging area for use to backfill the existing channel during Phase IV. Within 30 days following placement of all stockpiles that are no longer being added to, revegetate with seed Mix 1 and stabilize with hydromulch.

A redundant sediment control system of combined orange/coir log fence along the edge of the aggregate base pad on the down-gradient side of the staging area perimeter and 100% biodegradable sediment logs (preferred) or straw wattles encircling the immediate stockpile(s) will be installed at the Sunset Stables staging area. Where fencing or straw logs are used on the AB staging area pad, they would be held in place with sand bags or tubes. At the end of each construction phase the large stockpile should be winterized by seeding and applying a mulch and tackifier or bonded fiber matrix to control erosion.

2.2 SOD

A. Salvaged Sod. In addition to sod material salvaged within the new channel disturbance area, there are additional proposed meadow sod harvest areas. These areas are shown on Sheet C-1 and total approximately one acre (i.e. 43,575 ft²).

Additional sod harvest areas may be identified in the field by the LTBMU Project Manager. Sod shall be removed in as large a unit as practicable, resulting in clean, vertical edges to the extent feasible. Sod may require moistening through the root zone before harvest. Sod shall be scalped from the original ground surface to a depth of no less than six inches, as measured from the root crown.

In the sod harvest areas as shown on Sheet C-1 sod shall be removed in strips approximately equal to one bucket width (i.e. 6’ to 8’) perpendicular to the main valley axis or slope when observable. Backfill sod removal areas with salvaged

-16-topsoil to within 0.2’ of the pre-salvage grade. If removed strips are greater than 50’ in length, willow wattles or coir logs will be installed spaced every 40’ or so to prevent rilling/gullying of the exposed area. Plant harvested sod plugs (Carex nebrascensis, Juncus balticus, and additionally (not in lieu of) Carex praegracilis) 2-foot on centers. Apply Revegetation Seed Mix 2, hydromulch and irrigate per Section VI.

Duration of sod storage shall be minimized by re-planting as soon as grading is completed. If stored, sod shall be placed roots down with edges snugly adjoining adjacent sections. Stored sod shall not be stacked. Stored sod will be kept moist by irrigating so that live vegetation is not allowed to dry out during the interim storage period.

2.3 NATIVE HAY

Prior to excavating new channel and/or harvesting sod, mow material and where possible re-use native hay on the project within the season of harvest. Native hay can be used in lieu of wood chips or pine needles.

3.1 PROTECTION OF TREES AND VEGETATION

A. Activities shall not disturb trees and vegetation outside the grading limits, unless specified for removal in Plans or directed by the LTBMU Project Manager. All trees outside of the grading area but within the work limit shall be protected to avoid damage to woody material or foliage from operation of construction equipment.

3.2 CLEARING

A. Remove all brush and vegetation from areas designated for new construction. No trees should be removed without prior approval of the LTBMU Project Manager.

3.3 GRUBBING

A. Remove all stumps, roots, and debris a minimum of 8 inches below original ground. Fill stump and root holes with native material, compact with two passes of heavy equipment to the level of the adjacent ground. Grubbed material shall be salvaged and stockpiled for re-application within the project area.

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IV. GRADING

A. Phase I restoration activities, will include but not be limited to; delineating the 14 feet access road and 28 feet turnouts with orange boundary fencing and coir logs, constructing sections of encapsulated access road, protecting utility line crossings (all utility relocations shall be done during Phase II under a separate Project), installing temporary erosion control measures including orange fencing and coir log, installing dewatering measures including Upland Dewater Basin Central (if needed), installing and removing the temporary river crossing near Sunset Stables, salvaging native materials in the area of Phase I disturbance for incorporation into new channel banks and floodplain, excavating and grading the new channel sections in the southern portion of the site (up to 4, 066 LF of new channel), stockpiling and stabilizing the excess fill in the staging area for later use, installing bank and bed treatment measures, installing cobble riffle grade controls and demobilizing the haul road installations and winterizing the site.

Phase II will be similar to Phase I, including re-installation of the haul road, temporary river crossing and encapsulated road sections, installation of additional dewater measures including Upland Dewater Basin North (and Central if not installed during Phase I), and continued salvaging and re-application of native materials, excavation and grading of the new channel, finishing any remaining portion of the Phase I 4,066 LF length and continuing with 3,650 LF of new channel towards the north. Phase II will also include installation of a second temporary river crossing on the northern end in order to access the new channel sections west of the existing Upper Truckee River. Similar to the first phase, Phase II will install bed and bank treatments and cobble riffle grade controls, demobilize the temporary haul road and winterize the site.

Phase III will be focused on new channel seasoning and flushing, and revegetation monitoring therefore will not require active earthwork.

Phase IV will consist of, but not be limited to remobilizing the haul road and one of the temporary river crossings from Phase II, continued seasoning and flushing of new channel sections completed during Phase I and II, installing river diversions in the locations shown on Revised Sheet C-5 in order to construct the new channel sections and install the bed and bank treatment controls where they cross and tie into the existing Upper Truckee River, installing impermeable barrier fences along the Upland Dewatering Basins, excavating, grading and stabilizing the northern inset floodplain, backfilling, grading and stabilizing the existing channel with a combination of new channel borrow, imported material, salvaged organic matter, and seed and winterizing and completely demobilizing the site.

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The total amount of new channel excavation will be approximately 37,900 cubic yards. All of that amount will be reused onsite either as topsoil re-integrated into the channel banks and floodplain or as backfill in the existing channel during Phase IV.

1.2 FIELD MEASUREMENTS

A. LTBMU will verify that survey benchmarks and intended elevations for layout of the work are as indicated on the plans. If discrepancies are discovered the LTBMU Project Manager will immediately notify the Engineer, the party responsible for grade staking, to correct the problem or determine the alternate course of action.

B. The following is provided as information only regarding survey monuments near the Project site to assist in project layout and grade staking. All points provided are to be verified by the party responsible for survey control and grade staking.

Benchmark at Lake Tahoe Airport (Source: National Geodetic Survey)

38 53 38.46581 (N) 119 59 45.34350 (W) NAD 83

6252.72 (El) NGVD 29

Caltrans Monuments (Source Caltrans October 1998 Survey Request Form)

25-366, Set CDOT BR DSC 2IN PIPE, Pt No. 366

446172.437 (N) 2568082.108 (E) NAD 27

6271.230 (El) NGVD 29

25-367, Set CDOT BR DSC 2IN IP, Pt No 367

446945.008 (N) 2568100.833 (E) NAD 27

6270.687 (El) NGVD 29

1.3. EARTHWORK TOLERANCES

Construction Survey and Staking Tolerances are as follows.

Survey and Staking of Horizontal Vertical Permanent Reference Points 0.05 feet 0.05 feet

Excavation and Earthwork at riffle crests 0.20 feet 0.20 feet

1.4 EARTHWORK STAGING and SCHEDULE

A. The following work items and order of work for Phase I (2013) are recommended:

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PHASE I ORDER OF WORK

WORK ITEM 1: DELINEATION OF TEMPORARY HAUL ROAD AND

STAGING AREAS AND INSTALLATION OF TEMPORARY EROSION

CONTROL MEASURES

Prior to any active earthwork all temporary erosion control measures will be implemented and approved by the LTBMU Project Manager and Lahontan RWQCB and TRPA representatives during the Pre-Grade Inspection. The temporary haul road will be delineated with orange boundary fencing installed 7’ from centerline on both sides, with the west side fence combined with coir logs in order to protect water quality in the Upper Truckee River (Sheet C-4). All staging areas will have orange boundary fencing combined with coir logs on the down-gradient side and upland dewater basins (as needed) will have orange fencing and chain link fence combined with coir logs or straw wattles around the perimeter when active, with signage to restrict the public from entry. Where haul road crosses or impinges upon underground utility lines steel plates will be used to protect those facilities. Where the road impinges upon above-ground manholes orange fencing will be placed around those features to protect them. Where the haul road crosses saturated soil or areas where ground water is less than 2’ below ground surface, an encapsulated road section will be used (Sheet C-4 and D-7).

In addition to the haul road measures, construction mats (i.e. Duradeck or similar) will be placed in any meadow areas that heavy construction equipment will need to access, for example along the new channel banks. A temporary river crossing (Sheet D-11) will be installed at the low water crossing east of the Sunset Stables staging area and water diversion will be needed to protect water quality during crossing installation.

Upland Dewater Basin Central will be constructed using a 4 feet water-filled berm (Sheet C-5 and D-7). The Sunset Stables staging area will be delineated with orange and coir log combination fencing. If it is determined by LTBMU that Cheatgrass is still persistent in the Sunset Stables staging area following removal and treatment measures being implemented by the California Tahoe Conservancy in 2011, additional measures will be installed to isolate disturbance from the invasive weed base. These measures include installation of a 6” thick aggregate base staging pad with graded swales conveying runoff to large infiltration basins or dry wells.

WORK ITEM 2: EXCAVATION AND GRADING OF NEW CHANNEL

Once the haul road, temporary crossing and erosion control measures are installed and have met LTBMU Project Manager approval, the southern sections of the new channel will be excavated and graded (up to 4,066LF). When not on the designated haul road, heavy equipment will be positioned on construction mats to protect the meadow surface.

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1. Mark the new channel limits and identify the staking layout and the area mowed.

2. If any willow or other woody vegetation resources are within the new channel limits, harvest and/or salvage and temporarily stockpile. If there is viable sod material, remove and temporarily stockpile for immediate reapplication as described in Section VI.

3. Using an excavator bucket or similar, excavate the top 12 inches of soil for a manageable channel length (i.e. up to a 100 feet section rounded to the nearest treatment unit boundary) and temporarily stockpile in the immediate vicinity on construction mat or alternative for incorporation into the new channel banks.

4. Haul excavated material that is not immediately reused to the Sunset Stables staging area for stockpiling.

WORK ITEM 3: INSTALLATION OF BED AND BANK TREATMENTS

Once rough grading has been completed for each channel section, install the prescribed bed and bank treatments. The project engineer and/or senior hydrologist from the consultant design team will be on-site to work with the LTBMU Project Manager and operator during the initial installation of each treatment type to ensure all parties are clear on the installation approach and field placement and configuration. In areas where additional elements will be placed that raise grade, such as with 12 inch riffle cobble material on the channel bed and 8 to 12 inch sod material on the banks, the subgrade will be below the finish grade to the same depth as the prescribed material thickness in order to be at finished grade once treatment has been added.

WORK ITEM 4: IRRIGATION AND SEEDING

A temporary above ground irrigation system will be installed and operated following installation of various vegetation treatments to promote growth during the summer and early fall. In addition to channel bank treatments any disturbed areas along the tops of new channel banks or adjacent floodplain that are not protected by construction mats will be scarified and seeded prior to demobilizing.

WORK ITEM 5: PHASE I WINTERIZATION AND DEMOBILIZATION

Following completion of new channel construction and prior to the end of grading season, likely October 15, 2013 all disturbed areas will be winterized, the water-filled berm and double coir log features will be installed in the floodplain locations that are adjacent and/or near the newly constructed channel sections to slow and redirect overbank flows while the construction site remains inactive during winter and spring and the haul road demobilized and disturbed footprint winterized per Sheet C-4. At the completion of the Project or in the event that the revegetation work is not completed prior to the onset of winter conditions, or as directed by the LTBMU Project Manager, all exposed soils will be stabilized with hydromulch.

B. The following work items and order of work for Phase II are recommended:

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PHASE II ORDER OF WORK

WORK ITEM 1: REMOBILIZATION AND DELINEATION OF TEMPORARY

HAUL ROAD. REPAIR AND MAINTENANCE OF STAGING AREAS,

INSTALLATION OF…