Class Project .001

ENVIRONMENTAL REGULATIONS.CEE 552

Lake Tahoe erosion and stabilization

Nevada Highway 28

Larry Yenko

Student number 08602588/26/2011

Lake Tahoe Highway Right-Of-Way Erosion and Stabilization

Proposed SWPPP:

I Certifications and Approvals.

Certifications were submitted by hydraulic engineers for NDOT and not the contractor. NDOT is ultimately responsible for developing, submitting, obtaining approval, compliance and maintenance of the SWPPP (though, by contract, the contractor is responsible to maintain the terms of the SWPPP). Construction projects within the Lake Tahoe basin must also obtain a permit from TRPA1.

III Introduction and Project Description

A. General Description

The Lake Tahoe Highway right-of-way erosion and stabilization project started in May 2011. It is an upgrade to a storm water filtering systems and an upgrade to existing utilities contained in the right-of-way of the Nevada Department of Transportation (NDOT), Highway 28 from the intersection of Nevada Highway 341 to the California border in North Lake Tahoe, Nevada. For years, development of the Lake Tahoe basin remained unchecked with little or no regulation, especially to the control of storm water runoff. Beginning in the late 1960s, people in the Lake Tahoe basin became increasingly aware of the quality of life in the Lake Tahoe area, in particular, the environment. One of the most alluring attractions to the basin is that clarity of Lake Tahoe. In 1967 the clarity of the Lake was measured by lowering a circular target, 18 inches in diameter with a black cross painted on it, into the Lake. The distance was measured where the target was no longer visible. In 1967, this depth was 100 feet. The clarity of the Lake had been measured using this method of about every 10 years since then. In the late 90s, the depth at which the target was no longer visible was 67 feet. Scientists concluded that the loss of clarity was due to the increased organic matter and sediment carried by storm water over disturbed areas surrounding the Lake. To try and reverse this problem, the government formed the Tahoe Regional Planning Agency (TRPA) with the mandate to improve the environmental quality of the Tahoe basin. The most important improvement was to prevent contaminated storm water runoff that enters the Lake.

B. Receiving Waters

Lake Tahoe-California-Nevada

C. Unique Site Features and Potential Problems

The Lake Tahoe basin is unique among alpine lakes in that most of the soil surrounding the lake is deep volcanic sandy loam containing large gravel, making the soil pervious to water. Because of the deep nature of this well drained soil, storm water is filtered through this soil and enters the Lake through the groundwater minus most organic and inorganic sediment. To complement this filtration system, the conifer forest and undergrowth stabilized the topsoil so only a small amount of organic matter and sediment reached the Lake.

It is in this background that all development, whether commercial, hotels, residential or transportation (highways), are required to do their part to minimize or eliminate contaminated storm water runoff. Residential owners are required to retrofit their property with Best Management Practices (BMPs) to minimize contaminated storm water runoff. Local subdivisions and commercial property containing paved parking lots and streets are required to

1 State Route 28 Water Quality Improvement Project (EIP #1000), Washoe County, Nevada, TRPA Project Number 5601-201-00, TRPA File Number EIPC 2008-0032 (see attached)

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provide sediment vaults or like devices to control storm water pollution. State agencies including NDOT are required to provide state-of-the-art storm water pollution prevention systems as they improve highways and roads.

The choice of a utility modernization and road stabilization project makes it difficult to separate out storm water pollution prevention practices in construction phase when this is the focus of the project itself. However, options, other than those chosen by NDOT engineers are possible. Where this student agrees with the BMPs chosen, he will try and explain why he agrees with them and when this student believes other BMPs are the better choice. Another difficulty in analyzing this project is the limited area, at least in width, involved though offsite runoff considerations contain lengthy slopes to be used in runoff calculations.

D. Construction Site Estimates.

Highway right-of-way approximately 200 feet wide, Highway pavement approximately 24 feet wide, project length-2.68 miles. Disturbed soil approximately 7% of highway easement, minimal disturbance of soil within right-of-way, immediate stabilization of disturbed soil by either temporary or permanent erosion control (hydroseeding).

E. Construction Activity Schedule.

Construction is to begin May 1 and shut down October 15. Winterization and stabilization plan submitted by October 1. Construction to be suspended July-August and for America's Most Beautiful Bike Ride, Celebrity Golf Tournament, Hot August Nights, Street Vibrations and Tour de Tahoe. Hours of work 8 AM-6:30 PM daily, Monday through Thursday, 8 AM to 12 PM Fridays. Work areas shall be 500 feet maximum, complete each zone prior to starting an next work zone. Service construction equipment during working hours only. Deliver working materials only during working hours. Do not work on Nevada state holidays. Two weeks prior to construction schedule a pre-grade meeting, this requirement to be scheduled every year until completion of the project.

F. Potential Pollution Sources.

Unvegetated-disturbed soil areas, sediment on highway, soil on equipment, soil exposed on trenches, asbestos concrete pipe, soil from removed pipe and culverts, demolition of utilities being replaced, replaced aggregate, petroleum products used on or with equipment including maintenance and fluid changes, sewer waste, toxic adhesives used on plastic sewer pipe, air pollution from diesel fuel, concrete residue from washing out trucks and welding materials. Potential sediment pollution from water wells dewatering (private wells and/or wells dug for the purpose of this contract).

G. Endangered Species Certification.

Swallow and other nesting birds nests not to be disturbed. Compliance with the Endangered Species Act.

H. History Preservation.

Required certification that no his story structures are within the state easement.

I. Archaeological Sites.

No archaeological sites have been identified, however, exposure of any historic or archaeological site must be reported to appropriate agency.

J. Applicable federal, state, tribal, and local programs.

Comply with additional TRPA rules and regulations.

K. Responsible Party Obligations and Contact Information.

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Special Provisions, Proposal, Contract and Bond2

NDOT, Headquarter Buildings, Room 101, 1263 S. Stewart St., Carson City, NV 897123

IV Documents Incorporated by Reference-see Appendix B

Construction Site Best Management Practices (BMPs) Manual.

TRPA Best Management Practices

Special Provisions, Proposal, Contract and Bond, Project Number: MS-0028 (005)

Construction Plans Project Number: MS-0028 (005)

Soil Survey Of the Tahoe Basin Area, California and Nevada.

Western US Precipitation Frequency Map, NOAA Atlas 2, Nevada.

State Route 28 Water Quality Improvement Project (TRPA permit) page numbers.

Hydraulic Information Computation.

Drainage areas Highway 28 project .

Vegetative communities for off-site watersheds

Hydraulic information calculations (runoff coefficients).

Design report.

V Plan Details.

A. SWPPP objectives-substantially reduce or eliminate organic material and inorganic sediment from storm water runoff.

B. Vicinity maps-see attached

1. Soils map of North Lake Tahoe (project 28 junction of Nevada 341 and Nevada 28 to the California state line (Appendix B).

2. Sheet number 1 of project plans (Appendix B).

3. Sheet number D2 and D3 project plans-area chosen as focus of student analysis (appendix C).

C. Pollution source identification.

1. Existing (preconstruction) conditions-roadway without curb and gutter, stabilized soil and stabilized drainage formations, weathered asphalt, including patches, petroleum pollution deposited on existing roadway (oil drips etc. from passing cars), underground utilities and asbestos concrete pipe, inadequate storm sewer and asphalt turnouts.

2. See III F

3. Characteristics of site soils-

2 see special provisions ( attached)3 see special provisions (attached)

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Off-site soil characteristics. Soil characteristics are indicated for off-site subbasins approximately 200 feet long to 10,000 feet long.

-Cagwin rock outcrop complex 5 to 15% slopes.

-Inville stony course sandy loam, 9 to 15%. Slope.

-Jorge-Tahoma very stony sandy loam 30 to 50% slopes.

-Meiss cobbly loam 30 to 50% slopes.

-Rock outcrop-Cagwin complex 30 to 50% slopes.

-Rock outcrop and rumble land.

-Umpa very stony sandy loam 515% slopes.

-Umpa very stony sandy loam 30 to 50% slopes.

-Cagwin-Rock outcrop complex 30 to 50% slopes.

-Inville stony course sandy loam 15 to 30% slopes.

-Jorge-Tahoma very stony sandy loam, it's 15 to 30% slopes.

-Rockland

-Rock outcrop-Tome complex 30 to 50% slopes.

-Tahoma stony sandy loam to to 15% slopes.

-Umpa very stony sandy loam 15 to 30% slopes.

-Waca cobbly course sandy loam nine 230% slopes.

On-site/offsite soil characteristics chosen for analysis (subbasins 5, 6 and 7). See soils map appendix B.

-subbasin 5-100% inville stony course sandy loam 9 to 15% slopes.

-Subbasin 6-100% inville stony course sandy loam 9 to 15% slopes.

-Subbasin 7-23% inville stony course sandy loam 9 to 15% slopes.

D. Soils Analysis.

Soil profile, subbasin 5, 6, and 7-A-topsoil (mineral soil and considerable organics).

Hydraulic analysis, subbasin5, 6 and 7.

The flow rate (see appendix A).

Volume (see appendix A).

Topographic analysis.

Subbasin 5 -off-site slope and length -15% 300 feet long.

on-site-25% 200 feet long.

Subbasin 6-off-site slope and length-15% 300 feet long.

on-site-10% 200 feet long.

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Subbasin 7 -off-site slope and length-15% 2400 feet long.

on-site 3% 300 feet long.

Slopes are North to South.

Potential erosion analysis-Revised Universal Soil Loss Equalization (RUSLE) Y(s) = R x K x LS x C x P x A

Subbasin 5 -off-site R = 504*K = .19 (sandy loam + >4% organics5*LS (15% slope, 300 feet long = 4.4*C = .30 (forests + residential + cover )*P = 1 (no

mechanical treatment)*A = 1.31 acres = 16.4274 tons/year.

Subbasin 5-on-site R = 50*K = .19 (sandy loam + >4% organics6)*LS (25% slope, 200 feet long = 8.1*C = .517 (cover + bare ground + asphalt pavement)*P

= 1 (no mechanical treatment)*A = .8 acres = 31.3956 tons/year.

Subbasin 6 -off-site. R = 50*K = .19 (sandy loam + >4% organics8)*LS (15% slope, 300 feet long) = 4.0*C =.33 (forest, residential, cover)*P = 1 (no

mechanical treatment)*A = 2.43 = 30.4722 tons/year.

Subbasin 6-on-site R = 50*K = .19 (sandy loam + >4% organics9)*LS (10% slope 200 feet long) = 2.0*C = .2610*(cover + bare ground + asphalt

pavement)*P = 1 (no mechanical treatment)*A = .8 acres = 3.952 tons/year.

Subbasin 7-off-site R = 50*K = .19 (sandy loam + >4% organics11)*LS (15% slope, 2400 feet long) 11.0*C = .34 (forest + residential + cover)*P = 1 (no

mechanical treatment)*A = 96.34 = 3423 tons/year.

Subbasin 7-on-site R = 50*K = .19 (sandy loam + >4% organics12)*LS (3% slope, 300 feet long) = .35*C = .2613 (cover + bare ground + asphalt

pavement)*P = 1 (no mechanical treatment)*A = .8 acres = .6916 10/acres.

E. Best Management Practices.

Construction Management Practices.

Scheduling- Work may be performed between 8 AM and 6:30 PM Monday through Thursday and 8 AM to 12 PM on Fridays. Work can commence on May 1 and cease October 15 of each year. Work is to be suspended the months of July and August and the designated events per contract (see attached). Work shall be limited to 500 feet at a time, to be completed before the next 500 feet. Winterizing plans for the construction site to be submitted by October 1 of each year. Material-material to the ordered and placed at construction site only when needed. Construction site to be cleaned at the end of each day. Monitor weather daily.

4 NDOT, Appendix D, Water Quality Analysis, page 5, C:\Users\Larry Yenko\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.IE5\CUN17ZK1\Appendix_D[1].pdf5 Soil Survey of the Tahoe Basin Area, California and Nevada, page 21846 id7 NDOT, Appendix D, Water Quality Analysis, page 7, C:\Users\Larry Yenko\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.IE5\CUN17ZK1\Appendix_D[1].pdf8 Soil Survey of the Lake Tahoe Basin Area, California and Nevada, page 21849 id10 NDOT, Appendix D, Water Quality Analysis, page 7, C:\Users\Larry Yenko\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.IE5\CUN17ZK1\Appendix_D[1].pdf11 Soil Survey of the Lake Tahoe Basin Area, California and Nevada, page 218412 id13 NDOT, Appendix D, Water Quality Analysis, page 7, , C:\Users\Larry Yenko\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.IE5\CUN17ZK1\Appendix_D[1].pdf

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Stockpiles of material shall be located off-site, cleaned and stabilized of noxious weeds. Asphalt and concrete cement plants to be located off-site and comply with all environmental regulation. All equipment, parking and staging areas to be located off-site with landowner agreements for such activities.

Erosion control practices.

Off-site practices.

-Based on the above RUSLE calculations, the potential for a large amount of sediment from subbasin 7 should be addressed if it is within

NDOT or TRPA authority.

-Insured that all residential property owners have complied with TRPA retrofit BMPs.

-In stall willow wattlings on public land horizontal to the flow of water directing the runoff to the existing swale.

-ensure all slope stabilizations are installed and maintained (generally this would not be a burden to the contractor, however, NDOT is a public

agency and therefore entire soil stabilization, even beyond their easement is good public policy).

On-site erosion control.

-preservation of existing vegetation, including grass, shrubs and trees. Temporary fencing to be installed to protect areas from soil

disturbance in the construction process and to provide easy identification of preserved areas. Fencing around trees and tree drip area (7 feet from trunk of a tree) shall be installed. Temporary fencing to protect vegetation to be removed last after completion of construction.

-immediate hydroseeding of all disturbed soil not covered by asphalt. Hydroseeding with native grasses, shrubs and trees (vegetation

seeds obtained from suppliers of Sierra native seeds from vegetation 6200 feet to 10,000 feet) to include mulch and tackifier in a two step process (see being first application, mulch second application. Hydroseeded soil to be irrigated until grasses, shrubs, and trees are sustainable without irrigation. Areas of less than 80% germination and growth to be re- hydroseeded. Hydroseeded area to be stabilize/winterized prior to October 1 of each year. Re-hydroseed areas with less than 80% growth the following May 1. Hydroseed with fertilizer approved by project engineer. Hydroseeding equipment to be cleaned off-site outside the Tahoe basin.

-stabilize slopes with riprap per plan design (manual placement of rock), top soil integrated into the riprap. Hydroseeding and mulch

applied after top soil placement. Organic (coconut woven mulch blanket) blanket complied two areas of greater than 4:1 slopes or hydroseeding at the end of the growing season.

Runoff control practices.

Off-site.

-sediment logs, made of organic fibers rolled tightly and fixed to the slopes perpendicular to water flow to reduce velocity and

dissipate water flow to sheet flow on long slopes. Sediment logs are placed in a small swale and anchored by stakes or staples. Sediment logs can be left in place permanently. They should be placed above the NDOT right away, but not on residential property.

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On-site.

-because the construction site is narrow, most sediment control consists of placement of silt fences. Silt fence placement is indicated on

the project plans however, I believe additional silt fences should be placed near the southern boundary of the NDOT right away (near existing

residential homes) to avoid sediment particles reaching existing residents and the lake less than 100 yards from the NDOT right-of-way. Silt fence should be tied 2, fabric with wire mesh backing, secured by metal T posts, 8 foot on center. Bottom of the fabric shall be placed in a trench 6 inches deep dug by handrefilled and tamped. Silt removal when silt reaches 1/3 of fence height.

-storm drain protection type III gravel bag placed around drain inlet with bags interlocking to a height above the curb.

Tracking practices.

-eliminate tracking of sediment off-site from construction vehicles or equipment. Install construction entrance pad consisting of rock 1 inch in diameter, 6 feet

wide and 6 inches deep, draining to a sediment entrapment device. Install wheel cleaning equipment, sweep and vacuum entrance to pavement.

Wind erosion control practices.

-since soil stabilization by hydroseeding should command immediately after soil disturbance and contouring and all construction should take place on

asphalt pavement, no dust depression is anticipated, however, if the need arises, care should be taken for dust suppression by watering dusty areas so that this method does not contribute to sediment runoff. Dust suppression chemicals are inappropriate for the Lake Tahoe basin.

Non-storm water control practices.

-the project calls for installation of curb and gutters with street drains to a newly designed storm water drain system. Upgrades to existing utilities are

included. This requires placement of concrete, finishing of the concrete, rinsing out ready- mix concrete trucks, removal of some existing utilities, removal of asbestos concrete pipes, converts, steel piping and re-pavement or patching of existing asphalt pavement. Concrete truck clean the areas must be installed (off-site), concrete and asphalt batch plants must be set up and maintain (off-site) and aggregate for backfill and pavement must be supplied (cleaned and stored off- site).

Dewatering control practices.

-water used in courts of construction, cutting existing piping (including asbestos concrete pipes) is to be separated and prevented from moving off-site.

Practices for control of other construction site pollutions.

-asbestos removal and free conscience per statute.

-materials to be used on the project shall be stored off-site including aggregate.

-staging areas-off-site.

-wash out areas (see above).

-vehicle staging, storage and maintenance off-site as per statute.

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-spill prevention and cleanup plan, must be reviewed and approved prior to beginning construction.

Maps (referred to Appendix C-plans).

Out of bounds fencing, South side of road-referred to plans-TPC 2 and TPC3-out of bounds fencing, starting from left of plan South of Highway 10 feet

proceeding West perpendicular to road, around drip line of existing trees, West, parallel to Highway at the toe of the slope at plan marker 195 W. to tree drip line at 195.5 W. to proposed shoulder turn out (197) West 10 feet from proposed shoulder to plan marker 200 W. to proposed slope modification (Southside) West to second slope modification (203.5) West to tree drip line (204.5) West to tree drip line at to 206.5 West parallel (10 feet) to Highway plan marker 210. (Out of bounds fencing continuous from start of project to end of project)

Out of bounds fencing, north side of the road-referred to plans-TPC 2 and TPC 3 starting at the edge of plans 10 feet from Highway, West to plan marker

198 around existing riprap velocity berms, West to tree drip line (199.5), West to tree drip line at 200.5 West 10 feet from Highway to plan marker 210.

Silt fences-South side of Highway placed at the toe of slope plan marker 194-195.5, surrounding shoulder 197-200. Additional silt fences 10 feet below proposed shoulder, silt fence in swale at 200.5, from toe of modified

slopes plan marker 201-203.5, toe of slope 204.5-206.

Silt fences-north side of Highway-above riprap velocity controls 198-198.5, above the storm drain 199.5, from 205-210 (based on off-site runoff

volume).

Storm drain protection-the Southside of Highway 201.5, 205.5, 209.5, north side of highway 199.5.

Sediment logs-off-site subbasin 7 as described above.

Pollution control budget-unavailable.

BMP, inspection and maintenance-all BMPs to be inspected weekly by NDOT personnel and after every rain fall event greater than .5 inches. A check list to be supplied for each inspection to include all BMPs. Check list plus maintenance to be recorded.

Training

-contractor training-topics, purpose and need of SWPPP, spell response procedures, review of past spells, review of good housekeeping

procedures, proper material handling procedures, proper disposal or recycling of material, location of cleaning materials and spill kit, reviewed material storage systems, familiarize employees with drainage routes of storm water.

-subcontractor framing same ads general contractor training for those subcontractors that will deal with SWPPP.

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Appendix A

Peak Flow Rate and Volume

Section 5-100% inville stony course sandy loam 9 to 15% slopes. *[(.21*1.31*.80) +

(.23*1.31*20)]/(1.31) +.07 = [(.22) +

(.06)]/(1.31) +.07= .30

Section 6-100% inville stony course sandy loam 9 to 15% slopes. *[(.21*2.43*.50) +

(.26*2.43*.50)]/(2.43) +.07 =

[(.25) + (.31)]/(2.43) +.07 = .32

Section 7-23% inville stony course sandy loam 9 to 15% slopes. [(.21*96.34*.70) +

(.27*96.34*.30)]/(96.34) +.07 = [(14.16) + (7.80)]/(96.34)

+07 = .34

54% inville stony course sandy loam 15 to 30% slopes

22% Jorge-Tahoma very stony sandy loam 15 to 30% slopes.

1% Umpa very stony sandy loam 30 to 50% slopes.

Summation = [ (.30*1.31) + (.32*2.43) + (.34*96.34)]/(1.31+2.43+96.34) = .339

*[(Base C*Nonresidential Area) + (Residential C*Residential Area)]/(WS Area) + Slope Adjustment.

On-site subbasin 5 , 6, and 7 runoff coefficient .21 (per chart hydraulic information-see appendix B).

Peak flow rate: QR = C IR A

Volume: VR = C PR A ([43560 ft2/acre]/[12 inches/ft])

where,

QR = peak flow (cfs) for a storm of return frequency R;

C = estimated runoff coefficient;

IR = peak rainfall intensity (inches/hour) for a storm of return frequency R;

A = drainage catchment area (acres); and

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VR = runoff volume in ft3.

IR Values:

The peak rainfall intensity IR for the specified return frequency R design storm is determined using a unit peak rainfall intensity factor iR for a given return frequency R design storm using the following equation:

IR = (PR)(iR)

where,

PR = the total precipitation at the project site for the 24-hour duration storm event at the given return frequency, from the isopluvial map;

iR = (a)(Tc) -b, the unit peak rainfall intensity factor;

Tc = time of concentration (minutes), calculated using the method described below; and

a, b = coefficients from the Table of Coefficients.

Tt = L/60V

where,Tt = travel time (minutes)

( Note: Tt through an open water body (such as a pond) should be assumed to be zero with this method. );

L = the distance of flow across a given segment (feet);

V = average velocity (ft/sec) across the land cover = kR(so)0.5;

kR = time of concentration velocity factor (ft/sec; see Velocity Factor Table);

so = slope of flow path (ft/ft)

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Off-site subbasin 5-1.31 acres of Forest with floor vegetation C = .30 velocity factor KR = 2.5, slope 15 %, 300 feet long.

On-site subbasin-5 .8 acres impervious asphalt + bare ground + cover C = .53, KR = 17.0 slope 25%, 200 feet long.

Cc = ((C1 x A1) + (C2 x A2) = ((0.30 x 1.31 acre) + (0.53 x .8 acres))/2.11 acres = .817

IR = (PR)(iR) PR = 2. 8 inches (per isupluvial map, http://www.wrcc.dri.edu/pcpnfreq/nv10y24.gif ) iR = (a)(Tc) -b

a = 2.44) b = 0.64

Forest: kR = 2.5V = kR(so)0.5 = 2.5(0.15)0.5 = .155 ft/sec

T1 = L/60V = 300 ft/(60)(0.155) = 32.25 min

right-of-way kR = 17.0 (impervious + bare + cover)V = kR(so)0.5 = 17.0(0. 25)0.5 = 8.5 ft/sec

T2 = L/60V = 200 ft/(60)(8.5) = .39 min

Tc = 32.25 + .39 = 32.64 min

iR = (2.44)(32.64) (-0.64) = 0.26

IR = (2.8)(0.26) = 0.728 inch/hour

QR = (0.817)(0.728)(3) = 1.35 cfs

VR = C PR A ([43560 ft2/acre]/[12 inches/ft]) = (.871)(2.8)(2.11)(43560)/12 = 18679 ft3.

Off-site subbasin 6-2.43 acres of forest with floor vegetation C = .33, kR = 2.5, slope 15% 300 feet long.

On-site subbasin 6-.8 acres (impervious + bare + cover) C = .59, kR = 17.0, slope (6340-6320 = 20 feet, difference in elevation/horizontal distance, 20/200, see plan sheet D2) 10%, 200 feet long.

Cc = ((C1 x A1) + (C2 x A2) = ((0.33 x 2.43 acre) + (0. 59 x .8 acres))/3.23 acres = 1.27

IR = (PR)(iR) PR = 2.6 inches iR = (a)(Tc) -b

a = 2.44) b = 0.64

Forest kR = 2.5 V = kR(so)0.5 = 2.5 (0.10)0.5 = .79 ft/sec

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T1 = L/60V = 300 ft/(60)(.79) = 6.33 min

Right-of-way: kR = 17.0 V = kR(so)0.5 = 17.0(0.10)0.5 = 5.38 ft/sec

T2 = L/60V = 200 ft/(60)(5.38) = .62 min

Tc = 6.33 + .62 = 6.95 min

iR = (2.44)(6.95) (-0.64) = 0.71

IR = (2.8)(0.71) = 1.97 inch/hour

QR = (1.27)(1.97)(3.23) = 8.10 cfs

VR = C PR A ([43560 ft2/acre]/[12 inches/ft]) = (1.27)(2.8)(3.23)(43560)/12 = 41694 ft3.

Off-site subbasin 7-96.34 acres of forest with floor vegetation C = .34, kR = 2.5, slope 15% 2400 feet long.

On-site subbasin 7-1.2 acres of forest with floor vegetation C = .59, kR = 17, slope (6310-6300 = 10 feet, difference in elevation/horizontal distance 10/300, see plan sheet D3) 3% 300 feet long.

Cc = ((C1 x A1) + (C2 x A2) = ((0.34 x 96.34 acre) + (0.59 x 1.2 acres))/97.54 acres = 32.08

IR = (PR)(iR) PR = 2.8 inches iR = (a)(Tc) -b

a = 2.44) b = 0.64

Forest: kR = 2.5 V = kR(so)0.5 = 2.5 (0.15)0.5 = .97 ft/sec

T1 = L/60V = 2400 ft/(60)(.97) = 41.24 min

Right-of-way: kR = 17.0 V = kR(so)0.5 = 17.0 (0.03)0.5 = 2.94 ft/sec

T2 = L/60V = 300 ft/(60)(2.94) = 1.70 min

Tc = 41.24 + 1.70 = 42.94 min

iR = (2.44)(42.94) (-0.64) = .22

IR = (2.8)(0.22) = .62 inch/hour

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QR = (0.43)(0.62)(3) = 0.80 cfs

VR = C PR A ([43560 ft2/acre]/[12 inches/ft]) = (32.08)(2.8)(97.54)(43560)/12 = 31804002 ft3

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Appendix B

Construction Site Best Management Practices (BMPs) Manual.

http://www.nevadadot.com/uploadedFiles/NDOT/About_NDOT/NDOT_Divisions/Engineering/Hydraulics/2006_Storm_Water_Quality_BMP_Manual.pdf

TRPA Best Management Practices.

http://www.tahoebmp.org/Documents/BMP_Contractors_Notes.pdf

Special Provisions, Proposal, Contract and Bond, Project Number: MS-0028 (005)

Construction Plans Project Number: MS-0028 (005)

Soil Survey Of the Tahoe Basin Area, California and Nevada.

http://soildatamart.nrcs.usda.gov/Manuscripts/CA693/0/Tahoe_CA.pdf

Western US Precipitation Frequency Map, NOAA Atlas 2, Nevada.

http://www.wrcc.dri.edu/pcpnfreq.html

State Route 28 Water Quality Improvement Project (TRPA permit).

Drainage areas Highway 28 project (figure 2-1)

Vegetative communities for off-site watersheds (figure 3).

Hydraulic information calculations (runoff coefficients).

Design report.

ftp://ftp.nevadadot.com/Public/Yenko/

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