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Environmental assessment and nationwide section 4(f) evaluation Canyon Ferry Road : STPS 430-1(5)1; CN 4480, Lewis and Clark County, Montana (Volume 2003) online

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In accordance witli 7-22-2152 and 60-2-208, M.C.A., MDT would also reestablish a permanent
desirable vegetation coniinunity along all areas distuibed by the proposed highway construction.
MDT would develop a set of revegetation gmdelines tliat must be followed by the contiactor.

CUMULATIVE IMPACTS. The proposed reconstmction of Canyon Ferry Road would not cause
any notable cumulative effects on the topography, geologic conditions or soils withm the project
area.

IMPACTS OF THE NO ACTION ALTERNATIVE. MDT's maintenance actions liave the
potential to cause minor disturbances to surface or subsurface materials vvdthin the Canyon Ferry
Road project area.

Mitigating Measures (Geology and Soils impacts)

The following measmes will be implemented to minimize project-related effects on the local
topography and geological conditions.

■ Clearing and grubbing operations will be restricted to the minimum area
necessary to accommodate the planned reconstruction activities and
improvements.

■ To stabilize slopes and to minimize the visual effects of highway construction,
roadside slopes and disturbed areas will be revegetated as soon as practicable.

■ A Storm Water Pollution Prevention Plan (SWPPP) employing Best Management
Practices for controlling erosion and sediment transport will be implemented in
the project area.



2. IMPACTS TO IMPORTANT FARMLAND



Existing Conditions. The Lewis & Clark Conservation District was contacted in August 2001
to identify important soils that may be affected by the reconstmction of Canyon Ferry Road. The
Farmland Policy Protection Act (FVP A) (7 U.S.C. 4201 et. seq.) requires special consideration
be given to soils that considered as prime farmland, unique farmland, or farmland of statewide or
local importance by the U.S. Department of Agriculture Natural Resources
Conservation Services (NRCS).

The Conservation Distiict identified ten soils crossed by Canyon Feiiy Road as "Statewide
Importance," ''Prime Importance," "Otlier Importance," "Prime and Statewide Importance" and
"Local Importance." For the pmposes of this EA, these soils are considered togetlier and
identified as "Important Farmland."

The following soils (listed by soil number and name) withm the Canyon Feny Road project

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Environmental Assessment



corridor were identified by the NRCS as being Important Farmland:



33B Sappington-Amesha loams (1-4% slopes)

33C Sappington-Amesha loams (4-8% slopes)

137B Musselshell-Crago Complex (2-8% slopes)

218A Meadowcreek- Fairway loams

306A Nippt-Attewan complex (0-4% slopes)

406A Nippt gravelly loam {0-2% slopes)

413A Attewan loam {0-2% slopes)

513A Attewan-Nippt complex (0-2% slopes)

533B Sappington -Musselshell gravelly loams

569A Amesha-Attewan loams



Prime Importance

Statewide Importance

Local Importance

Statewide Importance

Other Importance

Other Importance

Prime and Statewide Importance

Statewide Importance

Statewide Importance

Statewide Importance



IMPACTS OF THE PREFERRED ACTION. Of importance under the FPPA are the areas of
direct and indirect conversion of Important Farmland. Direct conversions occiu' when soils meeting
the definition of farmland are included in the proposed liighway right-of-way. Indirect conversions
of farmland occur whentiie areas remaining in a tiact of land partially taken for iight-of-way: 1)
would no longer be capable of being fanned due to access restrictions; or (2) would likely be
converted to a non-farm use due to the accessibility of the liighway.

The information provided by NRCS and preliminary right-of-way plans for the proposed
improvements were reviewed to determine the area of Important Farmland that would be
affected by the Canyon Ferry Road project. Based on the information presented above, tire
constinction of tire proposed project would directly convert about 1 7.7 hectares (ha), oi 43.8 acres,
of soils meeting the designation of Important Farmland. The proposed project would mdiiectiy
convert about 0.35 ha (0.9 acres) of important familand due to the reconfiguration of tiie Canyon
Feiiy Road/Spokane Creek Road intersection.

A Farmland Conservation Impact Rating form (#AD-1006) was processed for the proposed
liighway improvement project in accordance witii the FPPA. The NRCS completed Parts II, IV,
and V of the form and assigned a relative value of 65 for tiie farmland to be converted. MDT's
consultant assigned points for the site assessment criteria in Part VI of the form and arrived at a
total score of 69. The ro/a/Pom/sfortheproject inPart VII of the form was calculated to be
1 34. Since tins total is less tiian 260 pomts, no fmtiiei consideiation for protection is necessary
and no additional Important Farmland evaluations are required. The completed form was not
submitted to the NRCS but a copy is provided m APPENDIX B.

CUMULATIVE IMPACTS. The Preferred Action, togetiier witii otiier ongoing and fiitijie
development activities on rural lands withm the Helena Valley, will continue to incrementally
convert mmoi amounts of faiinland to otiiei uses. Commeicial and residential development of
tins area contmues to increase at a steady rate. Building a higher quality road may contiibute to
conversion of faiinland by attiactmg residential and commercial development to an improved
transportation facility. Over time, these cumulative conversions could represent a notable loss of
Important Farmland in the county.

IMPACTS OF THE NO ACTION ALTERNATIVE. The No Action Altemative would not
dnectiy or indirectiy convert any additional Important Farmland in tiie Canyon Ferry Road
com dor.



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Canyon Ferry Road; STPS 430-1(5) 1



Environmental Assessment



Mitigating Measures (Important Farmland)

No mitigating measures are necessary or proposed since the Total Points for tlie project is less
tlianthethieshold of 260 points on form #AD-1006.



3. IMPACTS TO WATER RESOURCES AND QUALITY



Existing Conditions - Surface Water. As indicated previously, the major surface waters
witlim tlie project area include Prickly Pear Creek (located west of the project corrrdor) and its
tributaries and Spokane Creek and its associated mmor trrbutaries. Streams originatir^ in the
Elkliom Mountains to tlie south of the Helena Valley and from the Spokane Hills to the east of
the Valley flow fiom south to north toward Lake Helena. Many of these streams pass beneath
Canyon Feny Road through culverts or under brrdges as they flow towards Lake Helena and
ultimately the Missourr Rrver.

The Helena Valley Irrigation District utilizes the Helena Valley Canal system for drstrrbuting
water &om Canyon Ferry Reservoir to agricultiual and otlier users. The Helena Valley Canal
parallels and crosses Canyon Ferry Road at various locations throughout the project corridor.
Two different sections of the Helena Valley Canal are located wrthin the project conidor.

There are also several other active and abandoned irrigatron facilities existing along the entiie
lengtli of tliis project. Many of the facilities (irrigatron ditches) have been combined over the
years to improve their efficiency. Hence, the number of ditches has been reduced over tlie years.
These facilities mclude bridges, ditches, culverts, siphon culverts, flow splitters, weirs, pmnps,
and sprinklers. With tiie exception of larger diameter inrgation siphons for the Helena Valley
Canal, irrrgation/drainage culverts typically range fiom 750 to 1 ,200 millimeters (mm), or 30 to
48 inches, in diameter. Culvert types are corxugated steel pipe (CSP) or reinforced concrete pipe
(RCP) in fair to good condition.

FIGURE 7 shows existing surface waters, major irrigation features, bridges and inigation
crossings along Canyon Feny Road.

Surface water quality is typically assessed according to the amount and kind of substances
present in water, by the water's ability to support beneflcral uses such as uiigation and
recreation, and by the overall health of the aquatrc ecosystem. The health of stieams and
wetiands (and other surface waters) is assessed based on the constrtiients dissolved in the water,
tiie condition of tiie banks and associated riparian zone, and the types and numbers of plants and
animals living m the water.

The Montana Department of Environmental Quality (MDEQ) has the responsibility under
Section 401 of tiie federal Clean Water Act(33 U.S.C. 1251-1376) and the Montana Water
Quality Act (75-5-101 M.C.A., et seq.) to monitor and assess tiie quality of Montana surface
waters and to rdentify impaued or tiireatened stieani segments and lakes. The MDEQ sets limits,
known as Total Maximum Daily Loads (TMDLs), for each pollutant entering a body of water.



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Canyon Ferry Road; STPS 430-1(5) 1 Environmental Assessment

TMDLs are established for streams or lakes that fail to meet certain standards for water quality
and describe the amount of each pollutant a water body can receive without violating water
quality standards. The legislatively mandated TMDL process determines the concentiation of
pollutants in water bodies and stipulates controls needed to improve water quality in order to
support designated uses.

Prickly Pear Creek is the only surface water in the project area to be evaluated by tlie MDEQ for
TMDL purposes. MDEQ concluded that the stream's uses (aquatic life support, cold water
fishery and recreation) ai'e impaiied by nutiients, suspended solids and tiieimal modifications
caused by iirigated crop production, placer mining, rangeland activities, resource extiaction and
various industiial activities. However, Prickly Peai" Creek was assigned a lower priority for
development of a TMDL than another stieam in the Helena Valley — Tenmile Creek.

MDEQ also issues permits to industiies, agencies and others to discharge effluent into storm
water and surface waters. Five Montana Pollution Discharge Elimination System (MPDES)
permits have been issued by MDEQ for discliarges mto Prickly Pear Creek.

Existing Conditions - Groundwater. Groundwater has become an important source of
water m tlie project area, given tire limited supply of surface water in the aiea and concerns about
its quality for certain uses. In general, gioundwater quality m the project area is considered
good, yet some cases of contamination liave occuixed.

The Helena Valley aquifer is comprised of discontinuous, heterogeneous alluvial and lacustrine
deposits, with isolated clay and silt lenses that are continuously saturated from the water table to
a deptii of at least 150 m (about 500 feet).

This aquifer is tire sole source of drinking water for nearly 28,000 citizens — approximately 55
percent of tire population in tire Helena Valley. Drinking water is supplied to tiiese residents
fiom over 5,000 domestic wells and 60 pubhc water supply systems.

Groundwater infonnation from tiie Montana Bureau of Mines and Geology was obtained
fiom the Internet (www.nris.state.mt.us) to identify the depth of groundwater at water wells
drilled m the project area. Well data was retrieved for 25 properties abutting tire project witiim
the area of interest with the dates of well installations ranging fiom 1970 to 2001 . Static water
levels recorded at tire time ofinstallation ranged fiom tiie most shallow at 4.6 m (15 feet) to the
deepest at 2 1 . 3 m (70 feet) . Average static water elevation from the well data is 1 3 . 1 m (43 feet)
at the time of well installation.

IMPACTS OF THE PREFERRED ACTION ON SURFACE WATERS. Erosion and
sedimentation dming constiiiction and surface ninoff after constiiiction would be the prmciple
ways that water quality could be affected by tiie proposed liighway reconstiuction project.
Unless preventative measures are taken, erosion and sedimentation and liighway runoff have the
potential to affect water quality and aquatic resources.



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Canyon Ferry Road; STPS 430-1(5) 1



Environmental Assessment




Figure 7:

Irrigation Crossings & Bridges

Along Canyon Ferry Road



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Canyon Ferry Road; STPS 430-1(5) 1 Environmental Assessment

As indicated earlier, vegetation clearing and grading for the proposed highway and bridge
constmction would increase tlie potential for soil erosion and sediment tiansport. Additionally,
lengtliening or replacing culverts and reconstnicting adjacent roadway approaches would expose
soils and increase tlie potential foi erosion. Although erosion occuis naturally to some extent,
tlie erosion of areas disturbed by the constiiiction could contnbute additional sediments to
suiface waters. Increased sediment loads, paiticulaily for a long duration, may alter downstream
deposition patterns, cause water temperatures and turbidity levels of the watei to rise, mcrease
the level of nutrients (nitiates and phosphorus), and promote the growth of algae.

Because MDT's Stoim Water Pollution Pievention Plan (SWPPP) would be implemented to control
erosion and sediment transport during and after the proposed project, the proposed
reconstruction of Canyon Feixy Road would not cause notable adverse effects on surface water
quality. Because the aieaof soil distiirbancesfor tins project would exceed 0.4 ha (1.0 acre), a
NPDES storm watei permit administered by the MDEQ would be required. MDT would
develop a SWPPP for this project to meet permit requuements.

Potential water quality impacts can also occiu' due to highway runoff during the operational life
of tlie road improvement project. The primary constihients m highway iiinoff include suspended
sediments (pavement wear and dirt), lead (gasoline, tire filler), zinc (tire filler, motor oil
stabilizers), copper (metal platings, brake linings), and petioleuin (gasoline, antifieeze, hydraulic
fluids). Salting and sanding practices, for example, may leave concentrations of chloride,
sodiuiu, and calciuiu on the loadway surface. Impeivious road surfaces produce runoff amounts
proportional to the pavement area. Rural roadways with gravel shoulders and ditches tend to
slow runoff through absorption into adjacent vegetation and soils.

During the mid-1980s, the FHWA conducted extensive nationvvide studies to determine highway
runoff constituents, aiuounts relative to roadway types and traffic conditions, and the potential
impacts to surface water resouices (Pollutant Loadings and Impacts from Highway Stormwater
Runoff, Volume I, FHWA, April 1990). FHWA's lesearch concluded that pollutants in liighway
nmoff are not present in amounts sufficient to threaten surface or groundwater where Average
Daily Traffic (ADT) volumes are below 30,000. Since tiaffic volmnes in tire Canyon Ferry Road
corridor are expected to be variable within the conidor and range fi'om 3,200 to 12,900 vehicles
per day by flie design year (2024), it can be reasonably concluded that runoff from tiie liighway
would not cause significant degradation of surface or groundwater in the project area.

Fill placement and associated drainage installation work within stieam channels may be needed
at the liighway ciossings of No Name Spring Creek and Spokane Creek for tiie installation of
culverts. Road reconstiiiction would also encroach on a section of No Name Spring Creek (RP
8.68) that parallels the south (right) side of the new highway. This liighway encroacliment would
require rerouting a section of the stieaiu. Work in or near streams mthe project area would
reqime 124SPA Stieam Protection Permits from the Montana Department of Fish, Wildlife
& Parks (MDFWP). Likewise, the placement of any fill material in suiface waters or wetiands
would be subject to the issuance of Section 404 permits by tiie U.S. Army Corps of Engineers
(COE). These and other peimit reqimements are discussed at tiie end of this Part.

IMPACTS OF THE PREFERRED ACTION ON GROUNDWATER. The storm water
infiltration system proposed for the commercial/residential section where curbs and gutters

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Canyon Ferry Road; STPS 430-1(5) 1 Environmental Assessment

would be installed coiild potentially affect groundwater hydrology in the area . Lewis and Clark
County's records of septic tank installations and groundwater mformation &oin the Montana
Bureau of Mines and Geology reviewed for tliis EA suggests that tlie mstallation of this
systeiu would adliere to MDEQ guidelines for offsets to septic diainfields and wellheads. The
infiltration systems would also be buried to a depth at least 1.525 m (5 feet) above groundwater
levelsinthe vicinity of the installations. Additional work must be accomplished during the
design of the project to estabhsh tlie locations of drainfields and wells m the areas where
infiltration systems are proposed and to determine the depth to groundwater in nearby wells.

Groundwater hydrology in tlie remaining project areas would be unaffected by tlie proposed
liighway improvements since necessary excavation would not e:^ose or affect the groundwater
table. The rural portion of the proposed project would have no duect adverse impacts to
groundwater or public or private drmkmg water supplies derived fiom groundwater sources.

CUMULATIVE IMPACTS. The proposed improvements to Canyon Ferry Road, together wi\h
the impacts of present and reasonably foreseeable flitiue developments m the area, would not cause
any notable cumulative effects on the quahty or quantity of surface or groundwater m the project
area. MDT's engineered road design and the application of upland best management practices
(BMPs) would avoid or mitigate potential water quahty impacts in tlie general vicinity of this
project.

IMPACTS OF THE NO ACTION ALTERNATIVE. The No Action Alternative would not
cause any new effects on suiface water or groundwater m tlie project area.

MitiqatinQ Measures (Surface and Groundwater Resources)

The foUovvdng measures will be implemented to mmiiuize water quality impacts m the Canyon
Ferry Road project area.

■ A Storrit Water Pollution Prevention Plan (SWPPP) employing Best Managetnent
Practices for controlling erosion and sediment transport will be implemented in
the project area.

■ Any restrictions on work near streams or in wetlands will be specified as terms of
water-related permits obtained from the MDEQ, MDFWP, and the CoE.

■ Development of a revegetation plan, erosion control plan, and storm water
pollution prevention plan will be coordinated with appropriate permitting and
resources agencies.

■ Installation of the storm water infiltration system in the project's curb and gutter
section would follow MDEQ guidelines for offset to septic drainfields and well
heads.



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Canyon Ferry Road; STPS 430-1(5) 1 Environmental Assessment



4. FLOODPLAIN IMPACTS



Existing Conditions. Executive Order No. 1 1988 and FHWA's floodplain regulations (23
CFR 650 , Subpart A) reqiuie that tlie proposed action be evaluated to detenuine the effects of
any encroachments on tlie "base" floodplain. The base floodplain is the area covered by water
fiom the 1 00-year flood. The 1 00-year flood represents a flood event that has a 1 percent chance
of being equaled 01 exceeded in any given year. The Executive Order requires that federal
agencies, in carrying out their proposed projects, provide leadership and take action to reduce the
risk of flood loss; niiniinize the impacts of floods on human safety, health, andwelfaie; and
restore and preserve tlie natural and beneficial values served by floodplams.

Large floods in Lewis and Clark County are typically the result of heavy rainfall combined with
snowmelt, although m some areas rainfall or snovraielt alone can be the cause of flooding.
Historic records show tliat widespread flooding occurred on most major streams in the County,
including Piickly Pear Creek, durmg 1908, 1964, 1975, and 1981. Rapid snovraielt events in
1982, 1985, 1996, and 2003 also caused flooding problems at various locations along Canyon
Eeny Road.

The Eederal Emergency Management Agency (FEMA) piepaied detailed floodplain maps
for Lewis and Clark Comity in 1981 and revised them in 1985. The 1985 revisions were updated
on June 1 7, 2002 to incorporate new approximate flood hazard information for Prickly Pear
Creek Oveiflow, Silver Creek, Spokane Creek, and Trout Creek. The revised Flood Insmance
Rate Maps (FlRM's) desciibed Spokane Creek and Prickly Pear Creek 100-year and 500-year
floodplains. FIRM panels #1570, #1575, #1544, #1542, and #1541 identify dehneated
floodplains witliin the project corridor. FIGURE 8 shows floodplains in the Canyon Ferry Road
project area fromitsbegmningof tlie project to just east of Valley Drive.

The FIRM'S identify three overflow branches of Prickly Peai' Creek floodplain crossing Canyon
Eeny Road between tlie beginning of the project and Lake Helena Drive. These branches are
identified as the East Branch of Prickly Pear Creek, the North Overflow of Pnckly Pear Creek,
and the Valley Drive Branch of Prickly Pear Creek. A 100-year floodplain, known as the Lake
Helena Drive Branch, crosses the existing liighway aligmiient just east of Lake Helena Drive.

The East Branch, North Overflow, Valley Drive Branch and Lake Helena Drive Branch of the
Prickly Peai' Creek floodplain flow noitheily, inteisecting tiie Helena Valley Canal prior to
crossing the proposed aUgnment. Field reviews of the Helena Valley Canal revealed siphons
beneath the canal, concrete drainage chutes into the canal, a concrete overchute, and headgates
botiimto and out of the canal.

Canyon Eeny Road crosses the Spokane Creek floodplain, delineated by approxunate methods,
neai' the east end of flie project.

IMPACTS OF THE PREFERRED ACTION. The existing floodplain situation within the
Canyon Eeny Road between tiie project's beginning and Lake Helena Drive is extiemely
complex due to the level terrain, the presence of existing commercial and residential

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Canyon Ferry Road; STPS 430-1(5) 1 Environmental Assessment

development, and the fact that this area is subject to sheet flow type flooding. The Helena Valley
Canal also presently functrons as botli a barxier to flood flows and as a relief channel for
transporting floodwater out of this portion of the project area. These conditions pose serious
design constraints for the new highway and its associated drainage features.

This proposed project would result in ti'ansverse encroachments on delineated floodplains at four
locations and longitudmal encroacliments at tliiee locations. The Preferred Action would replace
existing drainage features at or near their present locations to ensure that floodwater is
accommodated and managed without major charges that could adversely impact nearby
residents and uses. Where possible, the proposed project would attempt to enhance existing
diainage conditions.

The Preferred Achon would place fill and require work within the stream channel for the
installation of new dramage culverts at No Name Spring Creek and witliin tire delineated
floodplain of Spokane Creek. However, tiie new culverts would be appropriately sized to handle
the anticipated flood flows wifliout interruption to public tiansportation due to flood damage to
the roadway. MDT standard procedures and specifications would be employed to ensure that the
required floodplain encroachment meets FHWA guidelines.

A floodplam permit fiom Lewis and Clark Comity would be required prior to construction in
designated floodplains in tiie Canyon Ferry Road project area.

Between Wyhe Drive and Lake Helena Drive, the project comdoi consists of residential build-
up with some commercial developments. Widening Canyon Ferry Road m this area would
eliminate the existing roadside ditches in tliis area. Although they are steep and do not meet
current safety and design criteria, the roadside ditches provide storm runoff storage and assist
witii minor flood control. Few natiual outfalls exist to transport storm water runoff in the
commercial/residential sectron of flie corridor and tire existing natuial outfalls are shallow wifli
shght rolling grades. Storage capacity appears limited and extensive work would be reqmred far
outside the project limrts to get diainage chamiels to adequately diain.

Two possible remedies for the lack of adequate outfalls have been considered. Detention ponds
could be developed to hold stonnwater or burred mfiltiatron galleries could be incorporated to
satisfy storm design runoff storage needs. Detention ponds would likely require the acquisition
of easements and development/maintenance withm resrdentral properties. Due to the greater
right-of-way acquisition needs, potential aesthetic problems, and safety concerns posed by
detention ponds, the recommendation has been made to incorporate a subsurface infiltiation
system to satisfy liighway storm water runoff management needs in the commercral/residential


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Online LibraryRobert Peccia & AssociatesEnvironmental assessment and nationwide section 4(f) evaluation Canyon Ferry Road : STPS 430-1(5)1; CN 4480, Lewis and Clark County, Montana (Volume 2003) → online text (page 7 of 19)