Record of Decision for the Santa Margarita River Flood Control Project and Basilone Road Bridge Replacement Project at Marine Corps Base Camp Pendleton, California

DEPARTMENT OF DEFENSE

Department of the Navy

Record of Decision for the Santa Margarita River Flood Control

Project and Basilone Road Bridge Replacement Project at Marine Corps

Base Camp Pendleton, California

AGENCY: Department of the Navy, DOD.

ACTION: Notice of record of decision.

-----------------------------------------------------------------------

SUMMARY: Pursuant to section 102(c) of the National Environmental

Policy Act (NEPA) of 1969, and the Council on Environmental Quality

Regulations (40 CFR parts 1500-1508), the Department of the Navy

announces its decision to construct a 14,500 foot-long levee and a

2,300 foot floodwall combination and associated stormwater management

system and a replacement Basilone Road Bridge at Marine Corps Base

(MCB) Camp Pendleton, California. The Environmental Impact Statement

(EIS) for these projects was prepared jointly by the Department of the

Navy and Army Corps of Engineers. In addition, the U.S. Fish and

Wildlife Service and the San Diego Regional Water Quality Control Board

served as cooperating agencies during the analysis of potential impacts

to the environment that may occur during construction, operation and

maintenance of these projects.

FOR FURTHER INFORMATION CONTACT: Mr. Lupe Armas, Assistant Chief of

Staff, Environmental Security, Marine Corps Base, Camp Pendleton,

California, 92055, telephone (760) 725-3561.

SUPPLEMENTARY INFORMATION: Pursuant to section 102(c) of the National

Environmental Policy Act (NEPA) of 1969, and the Council on

Environmental Quality Regulations (40 CFR parts 1500-1508), the

Department of the Navy announces its decision to construct a 14,500

foot-long levee and a 2,300 foot

[[Page 7132]]

floodwall combination and associated stormwater management system and a

replacement Basilone Road Bridge at Marine Corps Base (MCB) Camp

Pendleton, California. The Environmental Impact Statement (EIS) for

these projects was prepared jointly by the Department of the Navy and

Army Corps of Engineers. In addition, the U.S. Fish and Wildlife

Service and the San Diego Regional Water Quality Control Board served

as cooperating agencies during the analysis of potential impacts to the

environment that may occur during construction, operation and

maintenance of these projects.

Proposed Action

The Proposed Action consists of construction of a flood control

structure (a levee) at MCB Camp Pendleton to provide protection to

Marine Corps Air Station (MCAS) Camp Pendleton, the Chappo Area, Sewage

Treatment Plant (STP) 3, and the Santa Margarita Ranch House complex

from a flood event of up to 100 years in magnitude; a stormwater

management system to direct runoff from MCAS Camp Pendleton and the

Chappo Area into the Santa Margarita River without creating a flood

hazard; and replacement of a north-south circulation route across the

Santa Margarita River at or in the vicinity of Basilone Road and

Vandegrift Boulevard. The flood control structure would consist of a

14,500-foot-long levee and a 2,300-foot floodwall combination extending

from STP 3 to just upstream of the Santa Margarita Ranch House complex.

With this alignment, minimum airfield safety distances along the length

of MCAS Camp Pendleton would be maintained. The alignment would

transition sharply to run parallel to Vandegrift Boulevard downstream

of the airfield for approximately 2,300 feet, and finally would be

aligned to bulge out and around STP 3. The structure type would change

from earthen levee to a floodwall along the 2,300-foot run parallel to

Vandegrift Boulevard. This alignment would also include an upstream

guide vane to the main levee. This vane would improve the hydraulics of

the levee structure with respect to the impinging flow, and

significantly reduce scour depths at the upstream end of the levee and

the need for revetment protection.

The stormwater management system would drain surface runoff that

becomes trapped behind the flood control structure. The system would

have the capacity to manage runoff from approximately 2,100 acres,

including MCAS Camp Pendleton and the Chappo Area. The collected

stormwater would be pumped back into the river. The system would be

designed to manage a storm event with a duration of up to 24 hours and

a recurrence interval of up to 100 years.

The Basilone Road Bridge replacement project would involve

construction of a 1,155 foot long, two-lane bridge over the Santa

Margarita River. The bridge would be constructed to meet engineering

standards for transporting military loads, as well as providing surface

transportation for other users. The new bridge would allow water flow

to pass safely underneath the bridge during a 100-year flood event.

Rifle Range Road would be used for temporary access during project

construction. In preparation for this use, a ten foot corridor on

either side of the road would be maintained free of vegetation and the

road would be resurfaced. Upon completion of project construction,

Rifle Range Road would be removed and the area restored to the natural

river condition.

Purpose and Need

The basic project purposes for the proposed action are:

1. To provide protection for all U.S. Marine Corps assets within

the limit of the 100-year floodplain of the Santa Margarita River,

including the entire MCAS Camp Pendleton.

2. To provide a permanent, all-weather crossing over the Santa

Margarita River in the southeast portion of MCB Camp Pendleton.

MCB Camp Pendleton and MCAS Camp Pendleton maintain and operate

facilities and provide services to support operations of aviation

activities and units of operational forces of the Marine Corps. MCB

Camp Pendleton is the only west coast Marine Corps installation where a

comprehensive air, sea, and ground assault training scenario can be

executed; therefore, its ability to operate is considered to be of

paramount importance to national security. Facilities and operations in

the portion of MCB Camp Pendleton adjacent to the Santa Margarita River

are located in the 100-year floodplain for the river.

Heavy rainfall in 1993 resulted in the flooding of MCAS Camp

Pendleton, portions of MCB Camp Pendleton, and destruction of the

Basilone Road Bridge. The readiness and ability to support the missions

of MCB Camp Pendleton and MCAS Camp Pendleton were seriously

jeopardized because of the flooding and resulting damage. The flood

damage caused operations to cease in the flood damaged areas and

reduced the ability of the installation to perform the required

missions for a period of seven months. The flooding also damaged

structures and facilities, including buildings in the historic Santa

Margarita Ranch House complex, structures in the Chappo Area, and STP

3. A temporary bridge was erected on the site of the destroyed bridge

to reestablish the north-south road network.

To prevent future damage to property and the disruption of

essential operations, construction of flood control facilities is

required. These facilities would protect Marine Corps assets within the

100-year floodplain of the Santa Margarita River. In addition,

replacement of the temporary Basilone Road Bridge is required in order

to provide reliable north-south access across the Santa Margarita River

in the southeast portion of MCB Camp Pendleton. The bridge must

withstand a 100-year flood event.

Alternatives Considered

In preparing the EIS for the projects, an alternatives screening

analysis was performed. The selection criteria were based on the need

to optimize hydraulic control, sediment control, channel maintenance,

channel width, military mission, air station flight operations,

timeliness, project cost, water resources and biological resources.

These criteria are discussed in detail in Appendix C of the Final EIS.

A screening analysis of flood control options for the Santa

Margarita River evaluated an in-stream levee, an upland levee,

relocation of the air station, a concrete-lined channel, a soft bottom

channel, and an on-base detention dam. A previous evaluation of an off-

base dam/reservoir on De Luz Creek was also reconsidered. The concrete-

lined channel, soft-bottom channel, upland levee, on-base detention and

off-base detention alternatives, and the relocation of MCAS Camp

Pendleton were eliminated.

Camp Pendleton Alternatives Eliminated

1. Upland Levee

An upland levee would have to be adjacent to the runways at the air

station. This would violate air safety criteria and preclude routine

air station operations.

2. Concrete-Lined Channel

The height of levees on a concrete channel would intrude into the

flight path and violate airfield safety criteria and this alternative

would result in significant adverse environmental impacts.

3. Soft-Bottom Channel

The soft-bottom channel would not eliminate the need for routine

channel

[[Page 7133]]

maintenance and would result in significantly adverse environmental

impacts.

4. On-Base Detention Basins

Construction of on-Base basins would take an extensive amount of

time to design and permit, delaying flood protection for the air

station for an extended period of time. In addition, a basin would

reduce downstream groundwater recharge and would adversely affect

biological resources from both construction and inundation by water

held in the dam.

5. Relocation of MCAS

The possibility of off-site alternatives on MCB Camp Pendleton was

eliminated as infeasible based on the requirement that any relocation

of MCAS Camp Pendleton must successfully accommodate safe air

operations while minimizing impacts on the environment, local

communities, military operations, and military and civilian airspace.

The proposed flood control project would protect approximately 800

developed acres that include numerous buildings and facilities,

including MCAS Camp Pendleton. To relocate these facilities would

require the dedication of 800 acres of land either on or off base.

There would be potential significant impacts to listed species and

habitat in this 800 acres. In comparison, the proposed project would

permanently impact only 14.5 acres of habitat and 2.6 acres of

jurisdictional wetlands. The proposed project would have much less

impacts than relocating the facilities it would protect.

MCB Camp Pendleton operational siting constraints include potential

interference with ordnance impact areas, ranges and ground training,

amphibious, and aviation training activities. Important considerations

include the air safety restrictions associated with proximity to

training ranges. The locations of these ranges would cause approach,

departure, and pattern flight tracks to traverse restricted or

hazardous airspace.

There are 33 training areas at MCB Camp Pendleton that are used for

tactical exercise and field training, including cantonments, ordnance

impact areas (41,850 acres), and maneuver training areas. A deficiency

of live-fire ranges exists at MCB Camp Pendleton as addressed in the

Land and Training Area Requirements for MCB Camp Pendleton.

MCB Camp Pendleton is the only location on the west coast where

Marine Corps amphibious training operations can be combined with

elements of aviation activities to develop, evaluate, and exercise the

full range of combat techniques. Functions provided by the aviation

combat element include air reconnaissance, anti-air warfare, assault

support, offensive air support, electronic warfare, and control of

aircraft and missiles. Training for all of these functions is supported

by the restricted airspace and Military Operating Areas of MCB Camp

Pendleton.

Air Installation Compatible Use Zone requirements are another major

factor affecting the siting of MCAS Camp Pendleton. This program

includes analyses of Airfield Accident Potential Zones, Noise Zone

impacts, and Imaginary Surface obstructions. Underlying land uses must

be compatible with these restrictions and requirements.

Other geographic restriction criteria exclude relocation of these

facilities. There are limited areas of sufficient topography to

accommodate relocating this facility. Other constraints include

earthquake faults and steep topography. Direct seismic effects include

ground shaking and ground rupture, while indirect effects include

dynamic settlement, rock falls, and slope instability. Large areas in

excess of five-percent slope are also a constraint in locating an

alternative site for MCAS Camp Pendleton.

The Detailed Inventory of Naval Shore Facilities Report for MCAS

Camp Pendleton reflects the Current Plant Value (the return for selling

a particular building) as of September 30, 1995. The listed figure of

$235,213,000 was adjusted to $336,213,000 to include construction

between 1995 and 1999 which is underway. The costs to cover site

preparation, utility infrastructure to the site and environmental

mitigation was estimated at $64,000,000. This total estimate of

$400,000,000 covers only the 410 acres of the airfield area and does

not cover the almost 400 acres of billeting, personnel support,

maintenance, storage, office spaces and equipment parking located in

the surrounding areas of Camp Pendleton which support the 3d Marine

Aircraft Wing units that utilize the airfield. Current construction

costs at MCAS Camp Pendleton and MCAS Miramar for the same type

buildings shows that replacement costs would be significantly greater

then the Current Plant Value used to evaluate this alternative. In

comparison, the estimated cost of construction, mitigation, and

maintenance of the flood control project is $21.3 million. Permanent

all weather crossing of the Santa Margarita River would be required

regardless of the location of MCAS Camp Pendleton. The total cost of

relocating MCAS Camp Pendleton would be over 20 times the cost of the

proposed projects.

Off Camp Pendleton Alternatives Eliminated

1. Off-Base Dam/Detention Basin

An off-Base detention dam would lengthen the time required to

approve and construct flood protection, leaving MCB and MCAS Camp

Pendleton unprotected for a longer period of time. In addition, the

off-Base detention dam would reduce downstream groundwater recharge and

would adversely affect biological resources from both construction and

inundation by water held in the dam.

2. Relocation of MCAS

Off-Base relocation would include acquisition of property,

personnel requirements, infrastructure requirements, and base operating

costs. Relocating MCAS Camp Pendleton would include recreating the

facilities needed for the 3,100 personnel and 160 helicopters currently

assigned to MCAS Camp Pendleton. Additionally, as a result of the

implementation of decisions by the Base Realignment and Closure (BRAC)

Commission, two helicopter squadrons from MCAS Tustin and two

helicopter squadrons from MCAS El Toro will be relocated to MCAS/MCB

Camp Pendleton in 1999.

Marine Corps Bases/Air Stations are geographically positioned into

interdependent complexes of supporting installations on the East Coast,

West Coast, and in the Pacific. The major ground operational/tactical

base on the West Coast is MCB Camp Pendleton. MCAS Camp Pendleton lies

completely within the boundaries of MCB Camp Pendleton and allows for

intense helicopter operations without the requirement for excessive

transit time or flight within civil air space.

Other air stations within 200 air miles (near the upper-most range

limits for the CH-46 helicopters) of MCAS/MCB Camp Pendleton are MCAS

Miramar, Naval Air Facility (NAF) El Centro, Naval Air Station (NAS)

North Island, and March Air Force Base (AFB).

In accordance with the approved recommendations of the Base

Realignment and Closure Commission, MCAS Miramar will receive four

additional helicopter squadrons and associated support operations. MCAS

Miramar does not have the operational capacity or facilities to receive

MCAS Camp Pendleton's existing 3,100 personnel, 160 rotary-wing

aircraft with

[[Page 7134]]

associated maintenance and administration support resources in six

helicopter squadrons, and the four additional helicopter squadrons

mandated by BRAC.

The primary purpose of NAF El Centro is to support transient

aircraft using nearby ranges. However, the base was built in 1943 and

has severely deteriorated; the hangars are substandard, maintenance

facilities are insufficient, only one runway is operational, and the

remaining runways are closed due to their deteriorated condition.

Additionally, the distance, although less than 200 miles, is at the

upper limits for the range of CH-46 helicopters, thus requiring

refueling at Camp Pendleton to conduct operations and training in Camp

Pendleton airspace. Utilization of this facility would require huge

financial expenditures.

NAS North Island is located approximately one mile from Lindbergh

Field (the major commercial airport in San Diego, California) and is

adjacent to downtown San Diego. NAS North Island is considered fully

utilized at present with almost no expansion capability. Further,

training events such as helicopter touch and go and Ground Control

Approach (GCA) could not be efficiently conducted.

March AFB is in the process of being converted to an Air Force

Reserve Base and joint civilian use facility in accordance with the

1993 BRAC Commission's recommendations. The facilities are insufficient

and could not facilitate Marine Corps operational requirements.

Relocation to March AFB would require increased infrastructure, costs,

manpower needs, and delays in training.

Discussion of these other alternative air station facilities that

were considered but eliminated is contained in the Realignment to MCAS/

MCB Camp Pendleton EIS (BRAC EIS) which is referenced in the Final EIS

for the current flood control and bridge replacement projects.

In addition to the infrastructure costs associated with relocating

the MCAS on Camp Pendleton (if even possible), the relocation costs

off-Base would include land acquisition. This would include replacing

the approximately 800 acres, as well as other required replacements

such as additional family housing, recreational facilities,

commissaries and exchanges at the new location.

Proposed Levee Alternatives

The results of the screening analysis identified a levee and

associated stormwater management system as the most feasible and least

environmentally damaging flood control method. Three alternative levee

alignments were identified and analyzed in detail in the Final EIS.

Levee Alignment 3, the preferred alternative, is a 14,500 foot-long

levee and a 2,300 foot floodwall combination extending from STP 3 to

just upstream of the Santa Margarita Ranch House Complex. With this

alignment, minimum airfield safety distances along the length of MCAS

Camp Pendleton would be maintained. The alignment would transition

sharply toward and then run parallel to Vandegrift Boulevard downstream

of the airfield for approximately 2,300 feet, and finally would be

aligned to bulge out and around STP 3. The structure type would change

from earthen levee to a floodwall along the 2,300 foot run parallel to

Vandegrift Boulevard. This alignment would also include an upstream

guide vane to the main levee. This vane would improve the hydraulics of

the levee structure with respect to the impinging flow, and

significantly reduce scour depths at the upstream end of the levee and

the need for revetment protection. The guide vane would be constructed

in the same manner as the levee and would result in a significantly

smaller cumulative footprint and less potential impacts to riparian

habitat than the training structures proposed with levee alignments 1

and 2.

Levee Alignment 1 is a 16,585 foot-long levee extending from STP 3

north to approximately 1,000 feet upstream of the Santa Margarita Ranch

House Complex. This alternative would include three upstream flow

training structures and shaving of the hillside upstream of Basilone

Road Bridge. Minimum airfield safety distances along the length of the

MCAS Camp Pendleton airfield would be maintained. This levee alignment

would be a smooth line between the west end of the airfield and STP 3.

Levee Alignment 2 is a 15,200 foot-long levee extending from STP 3

to just upstream of the Santa Margarita Ranch House Complex. This

alternative would not include hillside shaving, but would incorporate

six river training structures upstream of Basilone Road Bridge and

several similar structures downstream of Basilone Road. This alignment

would be identical to Levee Alignment 1 from STP 3 to the downstream

side of Basilone Road. Minimum airfield safety distances along the

length of the MCAS Camp Pendleton airfield would be maintained.

Construction of a levee would require a stormwater management

system to drain surface runoff that becomes trapped behind the flood

control structure. The system would need the capacity to manage runoff

generated from approximately 2,100 acres during a 100-year storm event

with a 24 hour duration. The stormwater system would collect stormwater

and pump it back into the Santa Margarita River. Two alternative

stormwater management systems to accommodate surface runoff

requirements associated with each levee alignment were analyzed in the

Final EIS. For Levee Alignment 3, the preferred alternative, an

existing inundation area would be used for temporary management and

removal of stormwater through existing culverts under, and an earthen

ditch parallel to Vandegrift Boulevard, and then discharge into the

Santa Margarita River. The Stormwater Management System for levee

alignments 1 and 2 would use the same existing inundation area as Levee

Alignment 3, but an additional inundation area would be created behind

the levee and used to manage stormwater runoff. The inundation areas

used to manage stormwater for levee alignments 1 and 2 would

necessitate smaller emergency pumps than those required for Levee

Alignment 3.

Proposed Bridge Replacement Alternatives

A Camp Pendleton transportation planning analysis identified five

alternatives for the replacement of Basilone Road Bridge. Construction

of a suspension bridge was eliminated because it would violate airfield

safety criteria and compromise the operational readiness of the air

station. Construction of a new bridge at Hospital Road was eliminated

because it would bisect critical training areas and would not be

consistent with the operational requirements of the base. The remaining

three alternatives involve various alignments along Basilone Road. Each

of these three alternatives is summarized below as bridge alignments A,

B, and C.

Bridge Alignment A, the preferred alternative, will follow the

existing alignment. With this alternative, the temporary Basilone Road

Bridge will be replaced in its existing alignment providing a river

channel width of approximately 1,155 feet over the newly constructed

levee. The height of the new bridge will not cause an encroachment into

the runway approach-departure clearance zone of the MCAS Camp Pendleton

airfield; however, certain high profile vehicles (e.g., tractor-trailer

trucks), will intrude into the approach-departure clearance zone.

Traffic lights will be installed, which will be operated by the MCAS

control tower, to control the flow of traffic on the bridge to

[[Page 7135]]

prevent this encroachment during landings and take-offs of aircraft.

Bridge Alignment B is an east curve alignment. This alignment would

begin at the existing Basilone Road alignment on the north bank of the

river and curve to the east to avoid runway approach-departure

clearance zone encroachment from traffic on the bridge. Bridge

Alignment B would be slightly longer at 1,375 feet.

Bridge Alignment C, the Rattlesnake Canyon Road alignment, would

construct a new roadway and bridge alignment. The bridge would be

created about 1,200 feet northeast of the existing alignment and

southwest of the existing intersection of Rattlesnake Canyon Road and

Vandegrift Boulevard. With this alternative, a 2,000 foot-long bridge

would be constructed and 2,500 feet of new roadway would be required on

the north bank of the river.

A comparison of the three levee alternatives, three bridge

alternatives, and two stormwater management alternatives is provided in

Table 1.

Table 1.--Comparison of Alternatives

------------------------------------------------------------------------

Levee alignment 3 stormwater management:

pumphouse

-----------------------------------------

Influencing factor Bridge Bridge Bridge

alignment alignment alignment C--

A--existing B--east Rattlesnake

alignment curve Canyon

------------------------------------------------------------------------

Ground Disturbance--Permanent

(acres)...................... 25 25 27

Levee A................... 18 18 18

Spur Dikes/Silt Fences.... 0 0 0

Bridge Approaches (North &

South, feet)............. 3,150 3,150 8,650

Ground Disturbance--Temporary

(acres)...................... 66 66 85

Levee..................... 51 51 51

Spur Dikes/Silt Fences.... 0 0 0

Bridge and Roadway

Approaches............... 15 15 34

(2) Levee alignment 1

stormwater management:

pumphouse

Ground Disturbance--Permanent

(acres)...................... 67 67 69

Levee A................... 51 51 51

Spur Dikes/Silt Fences.... 9 9 9

Bridge Approaches (North &

South, feet)............. 3,150 3,150 8,650

Ground Disturbance--Temporary

(acres)...................... 76 76 95

Levee..................... 50 50 50

Spur Dikes/Silt Fences.... 11 11 11

Bridge and Roadway

Approaches............... 15 15 34

(2) Levee alignment 2

stormwater management:

pumphouse

Ground Disturbance--Permanent

(acres)...................... 41 41 43

Levee A................... 16 16 16

Spur Dikes/Silt Fences.... 18 18 18

Bridge Approaches (North &

South, ft.).............. 3,150 3,150 8,650

Ground Disturbance--

Temporary (acres)........ 75 75 94

Levee..................... 44 44 44

Spur Dikes/Silt Fences.... 16 16 16

Bridge and Roadway

Approaches............... 15 15 34

------------------------------------------------------------------------

AIncludes earthen levee, floodwall, guide vanes, roadway realignments,

and hillside grading as they apply to each conceptual project

alternative.

Rationale for the Preferred Alternative

The three alternative levee alignments and three alternative

Basilone Road Bridge Replacement alignments were combined to provide

nine project alternatives, which were evaluated in the Final EIS. The

no action alternative was also evaluated. The preferred alternative

(3A) combines Levee Alignment 3 and associated stormwater management

system, and Bridge Alignment A.

Hydraulic and Sediment Transport Analyses, conducted in February

1997, at the request of the Army Corps of Engineers, U.S. Environmental

Protection Agency, and U.S. Fish and Wildlife Service, concluded that

the proposed projects would not significantly alter the system-wide

geomorphology and river mechanics of the Santa Margarita River. Project

effects on flow depth, velocity, and sediment transport capacity would

be minimal and predominantly confined to three areas within the project

limits. Hydraulic and sediment transport effects upstream and

downstream of the project area would be negligible.

Although levee Alignments 1 and 2 would have more favorable cost

and engineering factors, Alignment 3 is the least damaging from an

environmental perspective. The design of alternative 3 avoids and

minimizes impacts to riverine habitats to the maximum extent practical.

Differences between Alignment 3 and the other levee alternatives

include elimination of proposed spur dikes and reconfiguration of the

downstream portion of the levee to a floodwall along Vandegrift

Boulevard. The preferred alternative represents a reduction of impacts

to riverine habitat when compared with the other levee alternative

alignments of 20 acres less direct permanent impact, 8.4 acres less

direct temporary impact, and 48 acres less indirect impacts due to

isolation of habitat. The preferred alternative has resulted in a

reduced impact to Corps jurisdictional waters of the U.S. and wetlands

by 7.8 acres less permanent impact, 4.2 acres less temporary impact,

and 30.9 acres less

[[Page 7136]]

impact associated with isolation of habitat.

Tables 2 and 3, respectively, show the permanent, temporary and

isolation impacts of the levee and bridge alternatives. In all cases,

levee Alignment 3 and Bridge Alternative A would result in lower

impacts to habitat and wetlands than the other alternatives considered.

The lower impacts to riparian habitat will translate to less impacts to

Federally-listed endangered species and other riparian dependent

species. Therefore, the preferred alternative would be consistent with

the requirements of NEPA and the Clean Water Act, is the least

environmentally damaging, and is determined to be the environmentally

preferred alternative.

Table 2.--Comparison of Habitat and Wetland Impacts Associated With Alternative Levee Alignments

----------------------------------------------------------------------------------------------------------------

Permanent impacts (acres) Temporary impacts Isolated acreage

--------------------------- (acres) --------------------------

Levee alternative --------------------------

Total Wetlands Total Total Wetlands

habitat habitat Wetlands habitat

----------------------------------------------------------------------------------------------------------------

1............................... 70.1 13.8 116.3 16.2 148 45.5

2............................... 29.6 10.1 37.5 14.9 129 42.3

3............................... 13 2.8 34.6 10.7 78.8 11.4

----------------------------------------------------------------------------------------------------------------

Acreage of wetland impacts is a subset of the acreage of total habitat impacts.

Table 3.--Comparison of Habitat and Wetland Impacts Associated With Alternative Bridge Alignments

----------------------------------------------------------------------------------------------------------------

Permanent impacts Temporary impacts (acres)

(acres) ---------------------------

Bridge alternative --------------------------

Total Total Wetlands

habitat Wetlands habitat

----------------------------------------------------------------------------------------------------------------

A......................................................... 1.5 0.3 2.1 0.6

B......................................................... 3.7 0.8 4 1.3

C......................................................... 5.8 1.2 7.5 3

----------------------------------------------------------------------------------------------------------------

Acreage of wetland impacts is a subset of the acreage of total habitat impacts.

Mitigation

The lower Santa Margarita River is an intact riparian corridor

ranging from 1,000 to 2,000 feet wide. The river corridor contains a

mosaic of riparian and freshwater marsh habitats, but suffers from

infestation by invasive, exotic weeds, primarily Arundo donax. The full

suite of hydrologic, biogeochemical, and biologic riverine functions

are performed at a level at or above most other rivers in southern

California. The Santa Margarita River supports some of the largest

known populations of the federally-listed endangered least Bell's

vireo, southwestern willow flycatcher, and southwestern arroyo toad.

Survey data from 1996 indicate the Santa Margarita River supports about

492 breeding pairs of vireo and 10 breeding pairs of flycatcher.

Because the proposed project will be built in the floodplain of the

Santa Margarita River, it will result in significant impacts to

wetlands, riparian habitat and endangered species. The following

provides a discussion of how these impacts will be mitigated.

Impacts to Corps jurisdictional waters of the United States and

wetlands (Table 4) would be mitigated by restoration of wetlands and

riparian habitat at Ysidora Flats. This 90 acre area is within the

floodplain of the Santa Margarita River, downstream of the proposed

project site. Ysidora Flats were historically separated from the river

by a series of berms and used for percolation and groundwater recharge.

The percolation ponds were damaged during the flooding of 1993 and

subsequently discontinued. The Marine Corps has removed the berms,

restoring the hydrologic connection between the area previously

encompassing the ponds and the river. The area has been recontoured,

and will be subject to ongoing invasive weed control and revegetation

with native riparian species. It is expected that most of Ysidora Flats

will become Corps jurisdictional wetlands and the remainder will become

non-jurisdictional floodplain riparian habitat. This area is being used

to mitigate the impacts of the previously authorized air station

expansion as well as the proposed project.

Table 4.--Mitigation for Impacts to Corps Jurisdictional Waters of the U.S. and Wetlands

--------------------------------------------------------------------------------------------------------------------------------------------------------

Mitigation at Ysidora On-site revegetation Exotic weed control (per

Acreage of ------------------------------------------------------ BO)

Type of impact impact --------------------------

Ratio Acres Ratio Acres Ratio Acres

--------------------------------------------------------------------------------------------------------------------------------------------------------

All Permanent Impacts.................................... 2.6 3:1 7.8 0:1 0 10:1 26

Temporary Impacts to Freshwater Marsh.................... 5.2 1:1 5.2 a 1:1 5.2 1.13:1 5.9

Temporary Impacts to Riparian Woodland................... 5.1 1:1 5.1 b 1:1 5.1 2:1 10.2

Temporary Impacts to Unvegetated Waters of U.S........... 1 1:1 1 c 1:1 1 0:1 0

Full Isolation Behind Levee (all habitat types).......... 4.5 1.5:1 6.8 0:1 0 0:1 0

Partial Isolation Behind Guide Vane...................... 6.9

(5)Monitored until after the first 10-year event. If

impacts occur, mitigation would be 3:1 at Ysidora. If

impacts do not occur, no mitigation would be required.

[[Page 7137]]

Total................................................ 25.3 ........... 25.9 ........... 11.3 ........... 42.1

--------------------------------------------------------------------------------------------------------------------------------------------------------

a Revegetation would occur via natural recruitment.

b Revegetation would occur via active planting.

c Area would be recontoured to pre-construction conditions.

All temporarily impacted areas, including wildlife habitat,

wetlands and waters of the U.S., will be kept free of invasive exotic

plant species for five years to allow natural revegetation. This

mitigation scheme is based on the Final Wetland Mitigation Plan for

BRAC Projects at the MCAS Camp Pendleton, which was published on

September 8, 1997. Monitoring concerning wetlands mitigation will be in

accordance with the provision of this Plan. Consultation shall take

place, prior to construction, with the Regional Water Quality Control

Board to determine any necessary changes in the National Pollution

Discharge Elimination System/Section 401 general permit.

Mitigation ratios for impacts to Army Corps of Engineers

jurisdictional areas are summarized in Table 4. The Marine Corps would

mitigate for indirect impacts to non-Clean Water Act jurisdictional

floodplain riparian habitat which would be isolated behind the levee by

either restoring jurisdictional wetlands at Ysidora Flats at a 0.33:1

ratio or by restoring non-wetland riparian habitat at Ysidora Flats at

a 0.5:1 ratio. This would translate, respectively, to 29 or 41 acres of

restoration at Ysidora Flats to compensate for loss of function

associated with floodplain isolation.

In addition to the mitigation required by the Army Corps of

Engineers, the U.S. Fish and Wildlife Service Biological Opinion (BO)

1-6-95-F-02 of October 30, 1995, requires that permanent impacts to all

habitat types (including Army Corps of Engineers jurisdictional areas)

be mitigated by removal of invasive weeds from the Santa Margarita

River at a 10:1 ratio. Temporary impacts must be mitigated by removal

of invasive weeds at ratios ranging from 0.5:1 to 2:1 depending on the

sensitivity of the habitat type being temporarily impacted. This BO

fulfills compliance requirements under Section 7 of the Endangered

Species Act. Monitoring for this mitigation will be accomplished as

provided for in the BO.

Sensitive habitats will be properly delineated to determine

construction zones and access roads. Lay-down areas will be located in

disturbed or developed areas, and shall be fenced when adjacent to

sensitive habitats. A qualified biologist shall monitor construction to

insure there are no inadvertent impacts to sensitive species. To

minimize impacts to arroyo southwestern toads during construction,

exclosure fencing will be constructed around the footprint to a height

minimum of 12 inches. In addition, surveys for this species and

monitoring will be conducted. No habitat will be cleared during the

breeding season of the least Bell's vireo and the southwestern willow

flycatcher (March 15-August 31).

The Santa Margarita River Estuary will be monitored for

sedimentation from construction activities. However, extensive

hydrogeomorphic modeling performed for this project indicates that

there should not be adverse downstream sedimentation effects. An

erosion and sedimentation control plan will be prepared prior to

construction.

Pre-construction surveys of biological resources and monitoring

plans will be provided to the U.S. Fish and Wildlife Service. Pre-

construction meetings with the U.S. Fish and Wildlife Service and the

Army Corps of Engineers will be conducted relating to biological

resources and to cultural resources. An upstream guide vane to mitigate

the potential for turbulent flow conditions and associated erosion

potential at the upstream end of the levee will be constructed as part

of the preferred alternative. Monitoring of the jurisdictional wetlands

and waters of the United States, partially isolated behind the guide

vane, will be conducted for a minimum of five years, which must include

a 10-year storm event.

Construction of the preferred alternative will require the

disturbance of an archeological site eligible for listing on the

National Register of Historic Places, and construction near the Santa

Margarita Ranch House Complex which is listed on the National Register.

Per 37 CFR 800.6(a), a Memorandum of Agreement, executed on February 5,

1998, among the U.S. Marine Corps, California State Historic

Preservation Office, Advisory Council on Historic Preservation, and the

Pechanga and Pauma bands of the Luiseno Mission Indian Tribe has been

implemented. This agreement provides for the preparation of an Historic

Properties Treatment Plan to specify the treatment for each historic

property, including archaeological sites and buildings, within the Area

of Potential Effect. This Agreement completes Section 106 requirements

of the National Historic Preservation Act.

Public Involvement

Preparation of the EIS began with a public scoping process to

identify issues that should be addressed in the document. Involvement

in scoping was offered through a combination of public announcements

and meetings with federal and state regulatory agencies. A Notice of

Intent (NOI) to prepare an EIS was published in the Federal Register on

January 9, 1996. In addition, copies of the NOI and Notice of the

Public Scoping Meeting were sent to federal, state, and local agencies,

as well as other interested parties; to radio, television, and print

media; and to libraries in the vicinity of MCB Camp Pendleton.

Advertisements announcing the scoping meeting were placed in several

local and regional newspapers and posted on the community calendars of

local cable television companies. The scoping period was from January 9

to March 10, 1996. A public scoping meeting was held on January 25,

1996 to solicit comments and concerns on the proposed action from the

general public. Comments received on the scoping process focused on

alternatives to the proposed action, alternative designs of the levee,

wetlands, water quality, biological resources, cultural resources, air

quality, and hazardous material handling during construction. The

Notice of Availability of the Draft EIS was published in the Federal

Register on July 18, 1997. The review and comment period for the Draft

EIS was from July 18, 1997, through September 5, 1997. A public hearing

regarding the Draft EIS was conducted on August 13, 1997. Comments were

received from 18 agencies and organizations that

[[Page 7138]]

identified the following major concerns; relocation of facilities out

of the floodplain, range and depth of alternatives, species and habitat

types impacted, potential effects to archaeological sites, river

hydrology and water quality, and wetlands. The Final EIS addressed

issues raised in comments to the Draft EIS. The Notice of Availability

of the Final EIS was published in the Federal Register on December 19,

1997. The Final EIS was distributed to federal, state, and local

agencies, interested parties, and public libraries on December 19,

1997, and the comment period closed on January 19, 1998.

Agency Decision

On behalf of the Department of the Navy and the U.S. Marine Corps,

I have decided to implement the proposed action through the preferred

alternative, Alternative 3A, (Levee Alignment 3--A 14,500 foot-long

levee and a 2,300 foot floodwall combination and Bridge Alignment A--

Existing Alignment). The requirements of applicable Executive Orders

have been considered. Specifically, the following determinations are

made with respect to these Executive Orders:

Executive Order 11988, ``Floodplain Management''. I have determined

that implementation of the Santa Margarita Flood Control Project is the

only practicable alternative, consistent with law and policy, to avoid

the potential severe consequences posed by potential significant flood

events to existing multi-million dollar facilities at MCB Camp

Pendleton and MCAS Camp Pendleton. All practicable means to avoid or

minimize harm to the floodplain are included within those mitigation

measures associated with the preferred alternative for this project.

Executive Order 11990, ``Protection of Wetlands''. I have

determined that the preferred alternative is the least environmental

damaging practicable alternative for the implementation of the Santa

Margarita Flood Control Project. I have further determined that the

preferred alternative incorporates all practicable measures to avoid or

minimize adverse impacts to wetlands which may result from this

project. In addition, all practicable mitigation measures to offset

wetland impacts will be implemented. This determination includes

consideration of, among other factors, the economic consequences and

the potential impact upon the national security missions of MCB Camp

Pendleton and MCAS Camp Pendleton posed by significant flood events

within the Santa Margarita River.

Executive Order 12898, ``Federal Actions to Address Environmental

Justice in Minority Populations and Low-Income Populations''. The

proposed action has been evaluated with respect to environmental and

social impacts, as well as access to public information and an

opportunity for public participation in the NEPA process as required by

this Executive Order. The project is consistent with the goals and

provisions of this Executive Order and no disproportionate impacts to

minority or low-income populations will occur.

I have determined that the preferred alternative is the least

environmentally damaging practical alternative for the implementation

of the Santa Margarita flood control and bridge replacement projects.

The Department of the Navy believes there are no remaining issues to be

resolved with respect to these projects. Questions regarding the Final

EIS prepared for this action may be directed to Mr. Lupe Armas,

Assistant Chief of Staff, Environmental Security, Marine Corps Base,

Camp Pendleton, California, 92055, telephone (760) 725-3561.

Dated: February 8, 1998.

Duncan Holaday,

Deputy Assistant Secretary of the Navy (Installations and Facilities).

[FR Doc. 98-3614 Filed 2-11-98; 8:45 am]

BILLING CODE 3810-FF-P