CECW-PM
19 April 2002
Southwest Valley Flood Damage
Reduction Study
Albuquerque, Bernalillo
County, New Mexico
Issues Table of Contents
Formulation
Identification of NED Plan
Urban Drainage Criteria
Local Drainage Versus
Flood Control
Non-structural Alternatives
Flood Damages
Documentation of
Historic Flood Damages
Verification of Flood
Damage Model
Derivation of Flood Flows
Use of MONTE Instead of
HEC-FDA
Flood Damage Reduction Benefits
Benefits
Associated with Separable Features
Potential Flood
Insurance Cost Savings
Current Versus Future
Benefits
Structure Values
Formulation Of Ecosystem
Restoration Alternatives
Significance
and Value of Ecosystem Restoration Alternative Outputs
Scope of
Ecosystem Restoration Alternatives
Incremental Analysis
Justification and Cost
Allocation
Retention Basin Sizing
Uncertainty
Costs
Real Estate
1. BACKGROUND.
a. Location. The
study area covers approximately 180-square miles encompassing the Southwest Valley and its
contributing mesa areas of Bernalillo County and portions of Albuquerque, New Mexico. The study area
is located west of the Rio Grande and comprises three physiographic regions: the
relatively flat West Mesa, the steeply sloping “ceja” or mesa edge, and the very
flat valley proper. The West Mesa drains into
Westgate Dam or Cedar Wash. The ceja drains
into the five other dams owned by the Albuquerque Metropolitan Arroyo Flood Control
Authority (AMAFCA) or directly onto the valley. Elevations range from 6,000 feet on the West Mesa
to 4,870 feet at the Rio Grande. The study
area encompasses 177.7 square miles, including 23.5 square miles of valley area and 154.2
square miles of West Mesa and ceja area. Six
detention dams constructed by AMAFCA control 41.4 square miles of the West Mesa drainage
area. Another 17.4 square miles of mesa area
that contributes to valley flooding is uncontrolled.
The 95.4 square mile Cedar Wash drainage area discharges at the extreme southern
end of the Southwest Valley.
b. Study Authorization. The AFB document indicates that the study
is an interim response to the authorizing language in the Flood Control Act of 1941
(Public Law 228) as contained in House Resolution Number 4911, 77th Congress, 1st
Session, dated 18 August 1941. Section 4
authorized surveys for flood control in various drainage areas of the United States,
including the Rio Grande and tributaries, New Mexico.
c. Problem. Portions of the Southwest Valley are
subject to flooding from a variety of sources. The
runoff from the West Mesa is largely controlled by a series of dams, detention basins, and
diversion channels constructed by AMAFCA, Bernalillo County, and the City of Albuquerque. Most of these facilities release controlled
discharges directly or indirectly into Middle Rio Grande Conservancy District (MRGCD)
agricultural drainage facilities. Flood
damages occur when large floods overwhelm the capacity of these facilities, or the
capacity of the MRGCD drains or canals is exceeded. Some
portions of the West Mesa are directly tributary to the valley. The runoff consists of high peak and low volume
discharges that, due to the steep slopes, typically transport large quantities of
sediment.
Runoff from the
valley floor also causes flooding. A series
of irrigation canals, laterals, acequias, and drains traverse the valley; most of which
have embankments from one to three feet high. These
embankments and raised roadways divide the valley into many small subareas. Some subareas discharge into the MRGCD
agricultural drains where confining embankments are low or do not exist. Others discharge into adjacent subareas or pond
on-site, inundating residential, commercial, or agricultural land. The depth of the 1-percent chance event flood in
irrigated fields is often less than the depth of water that accumulates during routine
flood irrigation. The flows from subareas
that discharge into irrigation drains combine with the runoff from the mesa, groundwater,
and agricultural return water to exceed the capacity of the drains, inundating adjacent
lands.
The valley is
also subject to flooding from the Rio Grande. The
Albuquerque west levee, a major flood control structure, constructed by the Corps of
Engineers in 1958, protects the northern half of the Southwest Valley and has a design
discharge of 42,000 cfs. A non-engineered
spoil bank levee parallels the Rio Grande in the southern half of the valley.
The study area has historically been subject to nearly annual flood
events caused by localized thunderstorms. These
storms have affected primarily residential structures in the flood plain.
d. Report Findings / Tentatively Selected Plan. Due to the complexity of the drainage
system flat gradient in the study area, the routing of flows was modeled as a series of
ponds. The analyses looked at a series of
nine retention basins and nine detention schemes. Detention
alternatives simply added pumping stations to the retention plans. None of the detention schemes contributed to NED
or NER goals. Analyses of NED benefits and
costs indicated that five of the retention alternatives were economically justified, with
benefit to cost ratios ranging from 1.8 to 1.0 to 1.0 to1.0. Wetland development was considered for each of the
excavated retention pond locations and the environmental benefits were considered
sufficient to justify three of the non-economically justified retention alternatives. The recommended plan is to construct retention
basins at eight locations: the Muniz Lane/Copeland Road site; DeVita Road/Valley Road
site; Mayflower/Torres site; Bonito Drive site; Barcelona Drive site; Isleta Drain-1 site;
Isleta Drain -2 site; and Isleta Drain -30 site. The
total cost to design and construct the recommended plan is cited as $8.7 million. Bernalillo County, New Mexico, and AMAFCA are
non-Federal sponsors for the feasibility study and prospective non-Federal sponsors for
the proposed project.
2. REVIEW SUMMARY.
Primary policy review concerns involve the process employed to formulate flood
damage reduction and ecosystem restoration alternatives and related issues, compliance
with environmental policy, and real estate concerns.
3. FORMULATION OF FLOOD
DAMAGE REDUCTION ALTERNATIVES.
Comment: a. Identification of the NED Plan. No objectives specifically related to ecosystem restoration are stated in the AFB document. In the initial formulation of project alternatives, there is no mention of potential ecosystem related problems and opportunities. The future without project condition does not include a description of a degraded ecosystem that could be restored and the potential restoration outputs that could be gained. Management measures and plans are formulated for flood control. However, in certain cases, where the measures are not economically justified based on flood control benefits, ecosystem restoration measures (modified design for retention basins to create wetlands) are added to “justify” the measures. Hence, the use of ecosystem restoration benefits for alternative justification is merely an add-on and not the product of formulation. The plan formulation process followed in the study does not support the addition of these ecosystem features. Absent additional formulation analyses that demonstrate that combined flood damage reduction and ecosystem restoration features are justified, the non-economically justified flood control measures should be removed from the recommended plan.
District Response:
Concur that although formulation of restoration features is largely absent from
the report, plan formulation for wetland restoration was conducted concurrently with plan
formulation for flood control. The text on
page 6-1 notes that “An estimated 30 to 50 percent of the original wetlands…have
been lost” and the without project condition is for continued losses. The objective of wetland restoration was an a
priori assumption, however, the draft report will be revised to clearly state the
objective of ecosystem restoration is wetland restoration and articulation of the
objective will be placed in the report. The
draft report will, also, be revised to include a separate ‘problems and
opportunities’ section with historical wetland and additional wetland loss
information for the area. It will be
demonstrated here that habitat restoration is warranted based on historical information. The existing conditions section will include a
section on wetlands. A discussion on future
without project conditions for ecosystem restoration will be added to the report.
The draft
report will be revised to clarify that management measures and plan formulation for
ecosystem restoration were dependent on the plan formulation for flood control. An array of restoration measures will be presented
in the draft report, but wetland establishment in the basins will probably be
incrementally justified due to the land acquisition costs, availability of runoff, and
very limited opportunities in the study area for a continuous corridor of wetlands. Aquatic habitat is dependent on a source of
water. Plan formulation for wetland
restoration was dependent on a water source and it was determined that the main source of
water for our wetland restoration project would be storm water redirected to the basins
for flood control. A secondary source of
water for wetland restoration would be groundwater, however, plan formulation for the
location of the wetlands was dependent on the location for flood basins. Thus, wetland restoration at the basins will
probably be a least cost incrementally justified wetland restoration alternative. This information for formulation of management
measures and plan formulation for the wetland restoration will be included in the draft
report and discussed thoroughly.
Discussion: The urbanized study area limits potential
environmental restoration locations to areas also being considered for flood control. The flood control alternatives in the Southwest
Valley were analyzed to develop the NED plan using the separable and joint costs necessary
to build flood control structures that will contain damaging flood events. The separable and joint costs necessary to build
environmental restoration features were identified and used as inputs into an Incremental
Cost/Cost Effectiveness analysis to develop a supply curve of incrementally cost-effective
environmental restoration features. The
results of these two analyses are an NED plan for flood control which identifies maximum
net benefits where the B/C ratio is greater than 1:1 and the aforementioned supply curve
of incrementally cost-effective environmental restoration alternatives. The non-Federal sponsor discussed the potential of
supporting a locally preferred project that deviates from the NED plan and potential to
seek a specific Secretarial exemption from ASA(CW) for the plan. If an ASA(CW) exception is sought, the District
will need to prepare and process a request to Headquarters for coordination with ASA(CW).
Primary restoration will benefit and
provide additional habitat for migratory waterfowl.
The Rio Grande corridor is already a major flyway for migratory waterfowl. The restored areas will add to already existing
habitat.
The draft report will be revised to
clarify that management measures and plan formulation for ecosystem restoration were
independent of plan formulation for flood control. Once
the quantity of environmental restoration outputs is determined, locations that provide
flood control and environmental restoration benefits will be analyzed using the Separable
Costs/Remaining Benefits techniques prescribed in ER 1105-2-100.
The revised analysis will be provided
separate of the draft report to Tom Birchett, CECW-PC, for review and coordination.
Action
Required: The district will provide
the revised ecosystem restoration analysis to CECW-PC, for review prior to release of the
draft report. The draft report will be
revised to include appropriate discussions and documentation to support formulation and
selection of the proposed ecosystem restoration features.
Comment: b. Urban
Drainage Criteria. The measures
included in the alternatives include culverts, ditches and detention basins, which are
generally features of storm drainage systems. Further
information should be presented in the report to demonstrate that the improvements
proposed are of Federal interest in accordance with ER 1165-2-21, entitled Flood Damage
Reduction Measures in Urban Areas. Information should also be presented to show that the
affected areas satisfy the minimum flow and drainage area criteria (800 cfs / 1.5 square
mile drainage area guidance (ER 1105-2-100, Section 3-3 b.(6), page 3-12) for Federal
involvement or that a waiver has been granted.
District Response: Understood that ER 1165-2-21 (developed in the 1970s and carried forward in Section 3-3 b.(6), of the more recent ER 1105-2-100) is intended to lay out fair and consistent “criteria to distinguish between improvements accomplished by the Corps…and storm sewer systems to be accomplished by local interests.” And concur that the Proposed Federal Project consists of measures that are generally considered storm drainage features. However, one should note that ER 1165-2-21 refers to “storm sewer systems,” and ER 1105-2-100 refers to “basic drainage system(s).” The measures as part of the South West Valley Project are neither “storm sewer systems” nor “basic drainage system(s).” Precise nomenclature is important, because the underlying intent and application of the policy is critical. Rather than being a storm sewer system, the measures are an integral part of the Federal Project as floodwater conveyance features, since they are the only practicable measures available to convey the floodwaters to the retention basins and ultimately to the Rio Grande. The valley floor is squeezed between the West Mesa and the perched Rio Grande River Channel to the East, and there is little elevation change from the South to the North making evacuation of floodwaters by gravity infeasible. In addition, high groundwater compounds the problems of evacuating the flows.
Furthermore, the model used for development of the criteria is based on conditions predominate in the Midwest and East. The model assumes a well-defined natural channel that conveys additive flow from a series of tributaries draining small independent sub-basins. This model is not reflective of the conditions in the arid Southwest. Ill-defined channels, alluvial fan sheet flow, ponding, and numerous instances of dis-tributary flow characterize flow conditions in the Southwest.
Finally, it is
clearly the intent of the regulations that once the criteria are met, then the areas
downstream are part of the Federal Project. The
drainage basin and minimum flow criteria were met at a point well upstream of the proposed
measures. In the AFB documentation package,
starting on page 2-30, it states, ”Based upon preliminary hydrologic data available
at the time of the reconnaissance study, BERNCO and AMAFCA requested and obtained a
Congressional legislative waiver of the 1,800 cubic feet per second (cfs) 1 percent chance
flow criterion—commonly referred to as the “800 cfs rule”—via the
Water Resources Development Act (WRDA) of 2000. Since
that time, more detailed hydrologic analysis identified the location where the 800-cfs
criterion is fully met. The upstream most
point where the 800-cfs discharge for the 10 percent chance event is met is at Amole Dam. Thus, all the areas downstream of this point meet
the minimum flow criteria.”
Discussion: The
recommended plan is the result of a formulation process that addressed a comprehensive
valley-wide solution. Several alternatives
were formulated and analyzed; some costing as much as $100 million. The more costly alternatives were found to be not
economically justified. The results of
formulation indicated that the recommended plan was the most cost-effective solution for
comprehensive flooding on the valley floor. The
non-Federal Sponsor had hoped that the Corps would be able to implement a much larger
comprehensive plan, and will continue to pursue a total solution to the flooding problem.
Alluvial flood
flows enter the valley floor from numerous locations along the western escarpment. Approximately 60 square miles of the West
Mesa drains into the valley area, of which about 17.5 is uncontrolled and about 42.5 is
control by six detention dams built by AMAFCA. It
is important to note, however, all floodwaters controlled by these six dams must be
released by AMAFCA within 96 hours. Consequently,
peak flood discharge onto the valley floor is effected while total volume of flood flows
is not.
The District
explained that under existing conditions flows exceed the 1800 cfs criteria at the
North-South Coors Pond, located at the intersection of Bridge Boulevard and Coors
Boulevard. The existing conditions 100-year
flow at this point is 1,834 cfs, future 100-year conditions flow is 3515 cfs, and the
drainage area is 3.84 square miles. Once the
flood flows from the North-South Coors Pond area and remaining West Mesa area reach the
valley floor the flows attenuate and spread broadly across the floodplains. The resultant flooding is characterized by
stationary ponding on the flat valley floor. There
is no method for flood flows to enter into the Rio Grande, as the river is perched higher
than the valley floor. Additionally, the flow
gradient is away from the river. Evaporation
and transpiration are the main means by which floodwaters are dissipated. The resultant structural alternatives consist of
retention basins located in the areas of heaviest floodwater concentrations. While these solutions appear to mimic local storm
drainage features; however, due to the lack of relief on the valley floor, there is no
other way to intercept flood flows. The
Division, District, and non-Federal sponsors strongly feel that the flow criteria of ER
1165-2-21 have been met and the project warrants full Federal participation for the
reasons described above.
Action Required:
John Lucyshyn will coordinate with the OASA(CW) concerning policy concerns and the
Federal interest in flood control. The
District will provide Mr. Lucyshyn with additional mapping indicating magnitude and
location of flows greater that 800cfs, an overlay of the proposed Corps plan, and affected
sub-basins for each alternative.
Follow-up Actions to the AFB: On 14 February 2002 Headquarters staff briefed Mr. Jim Smyth,
OASA(CW), on the Southwest Valley project and concerns related to consistency with policy
related to flood damage reduction measures in urban areas.
Due to the complex nature of flood flow movement in the valley area and the need to
have a clear understanding of the flooding problem and source of floodwaters a decision on
consistency with the policy was held in abeyance until a detailed briefing by the
district. As a result, on 28 February 2002,
representatives from the District, Bernalillo County and Albuquerque Metropolitan Arroyo
Flood Control Authority (non-Federal sponsors), and Headquarters briefed Mr. Smyth on the
Southwest Valley flood problem. The
district provided a detailed description of the watershed and explained the complex nature
of flood flow movement on the valley floor. The
district discussed the operation of local flood control channels and detention basins. They explained how these projects, while providing
significant flood damage reduction benefits in the valley, are required by water
agreements to release flows from the detention basins to the valley area within 96 hours. In addition, due to existing physical constraints,
the valley area drainage system is defined and delimited by irrigation canals, acequias,
agricultural drains and numerous roadways. Because
many of the larger irrigation canals and major roadways are constructed several feet above
the surrounding grade they function as drainage divides controlling flow movement and
creating a waffle effect.
The minimum
flow criteria of the ER 1165-2-21 was discussed, as well as, the need to be able to
distinguish between problems related to urban drainage and urban flood control. It was recognized that regulated and
unregulated flood flows from a number of sources were reaching the valley but because
there is no defined stream in the valley there was no point where the District could
demonstrate that the minimum flow criteria was met in the traditional sense. Consequently, an alternative approach was taken to
identify the total amount of Mesa flood flows entering the valley area across a cross
section, in this case Coors Boulevard. The
district determined that if all Mesa area flood flows flowing across Coors Boulevard were
considered, flows entering the valley area would exceed the 1800 cfs criteria for the
1-percent flood and that the study area is consistent with the urban drainage criteria. However, after considerable discussion the
following conclusions were reached:
1). Meeting
the flow criteria by adding flows across Coors Boulevard (weir concept) was not
acceptable. The intent of ER 1165-2-21 is
clear; the discharge criteria must be met at a point. Totaling all flood flows flowing across Coors
Boulevard does not constitute a point.
2). To
meet the intent of the 800 cfs criteria, the District would need to demonstrate the
criteria is met at a point. In order to
define a point the District was asked to look at modeling the Mesa and intervening valley
flows for existing and future conditions (conditions expected to prevail during the period
of analysis) in a non-attenuated hydrograph with the irrigation base flows being added to
the flow amount in Isleta Drain. In other
words remove the impact of physical constraints in the valley and hypothetically allow
flood flows to enter into the Isleta Drain without any obstructions and collect flows, in
effect creating a stream where point discharges could be determined. The additional flows from the Armijo Drain can
also be added to the total in Isleta Drain where it confluences just above Rio Bravo
Boulevard.
3). The
locations where concentrated future flood flows reach the Q10 of 800 cfs or the
Q100 of 1,800 cfs within the system would then be used as a basis to support
how, where, and why the urban drainage discharge criteria is met for the Southwest Valley
investigation. To document the analysis, the
District will prepare a position paper to be sent to the Division and upon review and
support will be forwarded to Headquarters. The
position paper will provide the rationale to support compliance with the urban drainage
area criteria. If the 800-cfs criteria is not
met but the 1800-cfs criteria can be met, a waiver from the Division will accompany the
position paper to Headquarters. Headquarters
staff will coordinate the results of the analysis and position paper with OASA(CW) staff.
Action Required: The District will prepare a position paper
to be sent to the Division and upon review and support will be forwarded to Headquarters. The position paper will provide the rationale to
support compliance with the urban drainage area criteria.
If the 800-cfs criteria is not met but the 1800-cfs criteria can be met, a waiver
from the Division will accompany the position paper to Headquarters. This concern will need to be resolved prior to
release of the draft report.
Comment: c. Local
Drainage versus Flood Control. Tables
in the AFB document suggest that a large portion of the damages cited would be associated
with frequent events. Page 2-6 states the
following: “… areas along Isleta
Boulevard, Arenal Road, Central Avenue, the Adobe Acre subdivision, … experience
frequent flooding with flood damages starting between the 50-percent and 20-percent chance
events.” This suggests that basic local
drainage facilities may be inadequate. The
tables in the report should be extended to include damages associated with the 50-percent
and 20-percent chance events. Non-damaging
flood frequencies should be identified for the various alternatives.
District Response:
Paragraph 1.a. above states “The West Mesa drains into Westgate Dam or Cedar
Wash. The ceja drains into the five other
dams owned by the Albuquerque Metropolitan Arroyo Flood Control Authority (AMAFCA) or
directly onto the valley.” Thus, the
local sponsor has built seven dams to contain runoff from the west side of the valley. These structures substantially reduce offsite
flows into the valley. Concerns are expressed
about minimum flow criteria in comment b, above. AMAFCA
has been very conscientious in its attempts to control the flooding in the Southwest
Valley and they should not be penalized for these efforts.
The flooding from frequent events is due to a combination of factors including: a
perched river channel; high groundwater; minimal topographic elevation change; absence of
natural channels; and numerous obstacles to overland flow.
For these reasons, few conveyance structures have been constructed because there
has been nowhere to convey the storm water.
The drainage
area on the valley floor is very flat and experiences area-wide non-localized flooding. The local sponsors have expended a great deal of
effort and money over the years to reduce flood damage as evidenced by the many large
upstream detention basins and diversion channels to protect the valley from offsite flows. Yet, valley flooding continues because a regional
drainage improvement scheme of this nature on the valley floor has not been undertaken
until now. The approach to this plan will
collect the non-localized area-wide flooding into the regional retention basins to provide
an area wide flood damage reduction system.
Historically,
the valley was developed without regard to flood control.
The land use in the Southwest Valley has historically been predominantly
agricultural. Prior to the 1930s, the valley
floor was part of the meandering riverbed of the Rio Grande. In the 1930s, the U.S. Bureau of Reclamation
developed the acequia/drain system to flood croplands in the Southwest Valley. More recently, the land use has undergone a
transition from agricultural use to urban use. Unfortunately,
the land continues to flood as designed for the agricultural usage. As this transition from agricultural to urban
usage continues, the need for a flood control system has increased.
The start of damages event for all locations for purposes of the economic analysis was the 20 percent-chance event, so the values requested would be zero. The draft report will clarify the start of damages condition.
Discussion: The
recommend plan consists of several flood retention structures spread across the valley
floor. Although these structures might be
construed to be local drainage features they are simply the most cost-effective solution
to regional flooding problems given the physical, engineering, and unique geographical
considerations in the Southwest valley.
Action Required:
See action required for comment c above.
Comment: d. Non-structural
Alternatives. As noted on page
3-5 of the text NEPA guidelines require the evaluation of structural and non-structural
measures. Paragraph 2-3.c.(5) on page 2-5 of
ER 1105-2-100 indicates that equal consideration should be given to structural and
non-structural measures in the planning process. The
formulation presentation provides little discussion on the applicability of any
alternatives other than storm water retention and detention. Additional information should be presented in the
report on other alternatives such as flood proofing, which have potential to economically
address the flooding problem in the study area.
District Response:
Concur. In formulating
alternatives, the District considered non-structural alternatives including floodproofing,
elevating properties, and ring levees. However,
none were considered practicable. Floodproofing
was dropped from further consideration because the valley is so flat and flooding is
shallow. Therefore, flood depths would not
reach the windows nor do most structures have basements.
In addition, floodproofing measures applied to adobe and older structures would
damage the structures and be cost prohibitive. Elevating
structures and ring levees were also dropped from further consideration. Because the floodplain is so flat and the area is
largely developed, these measures would transfer the flood problem to neighboring
properties.
Discussion: District response resolves the concern.
Action
Required: The draft report will be
revised to discuss non-structural alternatives considered and explain why they were
dropped from further consideration.
4. FLOOD DAMAGES.
Comment: a. Documentation
of Historic Flood Damages. The
flood history on pages 2-3 and 2-4 has little information on the value of flood damages or
the magnitude of the historic events except for rainfall amounts. In the 35 years of flood history presented in the
text, only one numerical damage estimate is provided for $10,000 in damage to a county
road in 1965. Most of the historic damage is
described as flooded streets and relatively minor flooding to a small number of houses,
apartments, or businesses. Additional
information should be provided on the magnitude of historic events and the resultant
damages in order to support the estimates of existing and future flood damages in
accordance with the evaluation procedure for NED flood damage reduction projects outlined
in Section 3-3.c.(5)on pages 3-15 to 3-17 and Section E-19 of ER 1105-2-100.
District
Response: The evaluation procedures are
understood, but there is not additional historical flood damage documentation readily
available. In the arid Southwest, major
storms are very infrequent and the valley was developed without regard for flood control. It is statistically probable that no major flood
events have occurred in the last 35 years, yet there is still a potential for significant
damages. The magnitudes of the storms cited
in the report predominantly range from two-year to five-year events in the Southwest
Valley. The localized storm of 25 and 26 June
1988 with 2.5 inches would be in the magnitude of a 100-year event had it occurred
area-wide.
The flood history given on pages 2-3 and
2-4 were given as examples of the damages incurred over the years and were not intended to
be all-inclusive. In public meetings and
discussions with local officials it is apparent that much damage has taken place
historically that has gone unreported. Additionally,
over the past 5 years the Southwest Valley has experienced approximately a 3.6% growth
rate. Growth has impacted damages in two
different ways—first, growth in the basin has increased damaging flows; and second,
the quantity of damageable property has increased. Therefore,
it is expected that if the flood events that occurred historically were to occur today,
the amount of damage would be considerably greater, given the increase in the amount and
extent of property development. This will be
discussed further in the draft report.
Action Required:
The district will include the historical flood photographs and other applicable
historic flood information in the draft report.
Comment: b. Verification
of Flood Damage Model. Paragraph
3-3.c.(5)(f), page 3-16, ER 1105-2-100 states that the basis for the determination of
existing damages is losses actually sustained in historical floods supplemented by
appraisals, application of depth-damage curves and an inventory of capital investment in
the floodplain. Information presented in the
text is not sufficient to verify that the overall damage-frequency relationship predicted
by the model is representative of flooding problems and damages that have actually
occurred. The information presented in the
text is not sufficient to correlate the estimates of damage during hypothetical events
with historical flooding events. Table 2-15
indicates that a 10-year event would damage 839 residences, commercial, and public
structures. Table 2-16 shows that flood
damage from the 10-year event is estimated to be about $8.7 million. However, contrary to what is described for
historic events, this estimate apparently assumes no damages to streets, roads or
utilities. The average annual damage is shown
in Table 2-17 as $2 million. This is not
supported by the history of flood damages presented in the AFB document. Damages
associated with all of the flood events chronicled in paragraph 2.03, spanning 35 years of
flooding history, do not appear to total 2 million dollars.
The document discusses the rainfall data for the historic storms but
includes only limited discussion of damaged structures during the events. One would expect that in the approximately 35-year
period from 1965 to the present, the study area would have experienced several significant
flood events. The
damage model suggests that such events would have produced significant associated damages. What is the
actual statistical risk of approximately 2.0 million dollars in average annual flood
damages to structures and contents set forth in paragraph 2.08.3? What are the assumptions made in establishing that
risk? The text should be modified to
include information that confirms that damages predicted by the model are reasonable
considering documented damages from historic events.
District Response: Concur that historical damages must verify
and substantiate model results. And the chronicled historical record spanning 35 years does not total $2 million, yet the model
results are much higher. The divergence of
the historical record documentation (see District response to comment 4a above) and the
model results can be explained by: Strong
local cultural preference for independent action and verbal records, therefore, most
damage is unwritten and unreported; Study area has experienced intense growth and today
damages would be much higher; statistically we have been “lucky;” and finally, sponsors
have recently provided historic records of cleanup and repair to public facilities, roads,
and utilities. The divergence between the
historical record and the model will be explained during the AFB and documented in the
draft report.
In the arid Southwest, major storms are
very infrequent and the valley was developed without regard for flood control. It is statistically probable that no major flood
events have occurred in the last 35 years. However,
there is evidence in the available record that damaging events have occurred and, given
the increased level of development in this area, damage would be more significant in the
future.
The flood
history given on pages 2-3 and 2-4 were given as examples of the damages incurred over the
years and were not intended to be all-inclusive. For
example, the AFB documentation did not mention a storm that occurred in the Southwest
Valley on July 31, 1974 in which $123,200 in damages ($81,000 in crop damages) was
documented. These damages came at a time when
the area was much more rural than it is today.
In public meetings and discussions with local officials it is apparent that much
damage has taken place historically that has gone unreported. Additionally, over the past 5 years the southwest
valley has experienced approximately a 3.6% growth rate.
Growth has impacted damages in two different ways—first, growth in the basin
has increased damaging flows; and second, the quantity of damageable property has
increased. Therefore, it is expected that if
the flood events that occurred historically were to occur today, the amount of damage
would be considerably greater, given the increase in the amount and extent of property
development. This will be discussed further
in the draft report.
Concur that
Table 2-15 did not include damages to streets, roads, and utilities. The corrected table follows:
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SINGLE
OCCURRENCE DAMAGES |
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PREPROJECT
CONDITIONS |
|
||||||
|
SOUTHWEST
VALLEY FLOODPLAIN |
|
||||||
|
(x
$1,000 September, 2001 price level) |
|
||||||
|
|
|||||||
|
EVENT |
|||||||
Land
Use Category |
|
|
|
|
||||
10% |
4% |
1% |
0.20% |
|||||
|
|
|
|
|
|
|
|
|
|
Mean |
SD |
Mean |
SD |
Mean |
SD |
Mean |
SD |
|
|
|
|
|
|
|
|
|
Residential |
5,179,393 |
97,432 |
6,932,934 |
108,270 |
11,234,540 |
135,370 |
17,059,610 |
149,870 |
|
|
|
|
|
|
|
|
|
Res.
Content |
3,170,771 |
60,543 |
4,175,784 |
66,052 |
6,313,251 |
78,495 |
9,409,575 |
94,633 |
|
|
|
|
|
|
|
|
|
Commercial |
92,520 |
30,172 |
252,564 |
28,721 |
336,076 |
29,358 |
481,008 |
35,391 |
|
|
|
|
|
|
|
|
|
Comm.
Content |
63,522 |
30,562 |
292,058 |
77,940 |
402,233 |
87,079 |
515,597 |
92,161 |
|
|
|
|
|
|
|
|
|
Public |
188,740 |
15,315 |
259,743 |
17,431 |
472,297 |
49,372 |
708,060 |
60,569 |
|
|
|
|
|
|
|
|
|
Pub.
Content |
27,782 |
3,942 |
54,307 |
7,255 |
116,587 |
20,518 |
299,406 |
72,124 |
Streets |
87 |
|
123 |
|
198 |
|
479 |
|
|
|
|
|
|
|
|
|
|
Utilities |
0 |
|
575 |
|
763 |
|
1,086 |
|
|
|
|
|
|
|
|
|
|
Vehicles |
52 |
|
91 |
|
153 |
|
330 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Total |
8,722,867 |
11,968,180 |
18,876,098 |
28,475,151 |
||||
|
|
|
|
|
|
|
|
|
The elements of risk that were modeled are:
·
Hydrologic (15 years
of record using the LIMIT program)
·
Hydraulic (stage
elevation, standard deviation of 0.2 at the 1 percent-chance event)
·
Structure Elevation
(standard deviation of 0.2)
·
Structure and Content
Value (Standard deviation of 15 percent)
·
Depth Damage Curves
(Varies based on type and depth; based on latest guidance from IWR)
It is estimated that there is
approximately a 5 percent probability that average annual damages are greater than $2
million. The following table displays the
statistical risk. Note that several minor
categories were excluded since they were not performed using risk analysis.
|
AVERAGE
ANNUAL DAMAGES
|
|||||
|
BY
LAND USE CATEGORY |
|||||
|
(x
$1,000 September, 2001 price level) |
|||||
|
|
|||||
LAND
USE CATEGORY |
Average
Annual Damages |
|||||
(x
$1,000 September, 2001 price level) |
||||||
|
|
|||||
|
Probability
Avg. Ann. Damages |
|||||
|
Exceed
Indicated Amount |
|||||
Computed Average Annual Damages |
|
|
|
|
|
|
|
|
0.95 |
0.75 |
0.5 |
0.25 |
0.05 |
DAMAGES |
|
|
|
|
|
|
Residential |
1133.94 |
949.32 |
1057.84 |
1128.84 |
1193.86 |
1281.91 |
|
|
|
|
|
|
|
Res.
Contents |
658.15 |
552.09 |
615.12 |
655.95 |
693.23 |
744.61 |
|
|
|
|
|
|
|
Commercial |
40.22 |
34.85 |
37.99 |
40.20 |
42.08 |
44.62 |
|
|
|
|
|
|
|
Commercial
Contents |
38.55 |
32.01 |
36.09 |
38.64 |
40.76 |
44.35 |
|
|
|
|
|
|
|
Public |
17.63 |
14.21 |
16.19 |
17.68 |
18.83 |
20.88 |
|
|
|
|
|
|
|
Pub.
Contents |
8.64 |
6.71 |
7.84 |
8.67 |
9.36 |
10.50 |
|
|
|
|
|
|
|
Streets,
roads1 |
16.66 |
|
|
|
|
|
|
|
|
|
|
|
|
Utilities1 |
94.05 |
|
|
|
|
|
|
|
|
|
|
|
|
Vehicles1 |
10.81 |
|
|
|
|
|
|
|
|
|
` |
|
|
Irrigation
Fac. 1 |
N/A |
|
|
|
|
|
|
|
|
|
|
|
|
Agriculture1 |
N/A |
|||||
|
|
|
|
|
|
|
Railroad1 |
N/A |
|||||
|
|
|
|
|
|
|
Emergency
Costs1 |
30.28 |
|||||
|
|
1,582.48 |
1,771.07 |
1,889.98 |
1,998.12 |
2,146.87 |
TOTAL |
2,048.93 |
|||||
1
Excludes
categories which were not developed using risk analysis.
Discussion:
The concern is resolved.
Action required:
The information contained in the district response will be included in the draft
report.
Comment: c. Derivation
of Flood Flows. The discussion of
hydrologic analyses on pages 2-5 and 2-6, indicates that precipitation data were developed
for the 1-percent chance event. Precipitation
amounts for more frequent events were estimated using “return period factors.” Damages associated with the more frequent events
generally drive plan formulation and economic justification of alternatives. Given this, the report should document that use of
return period factors in-lieu of direct estimation of precipitation and runoff for
frequent events is appropriate.
District Response:
A key decision was made early in the study to use the City of Albuquerque
Development Process Manual (DPM) as stated on page 2-5 of the report. The “return period factors” are used in
the DPM to determine precipitation for 2yr, 5yr, 10yr, 25yr, and 50yr frequency storms as
a fraction of the 100yr precipitation taken from the NOAA Atlas, Volume IV, New Mexico. These “return period factors” are based
on the relationship between precipitation values given in the NOAA Atlas, Volume IV, New
Mexico for the various frequency storms. The
precipitation values used in this report (as a result of using “return period
factors”) have been verified as being consistent with the values given in the NOAA
Atlas, Volume IV, New Mexico, just as if they had been taken directly from it. This will be clarified in the draft report.
Discussion: The district response resolves the concern.
Action
Required: The information in the
district response will be added to draft report.
Comment: d. Use
of MONTE Instead of HEC-FDA. The
AFB document notes that the MONTE program was used to assess damages and benefits of the
various flood damage reduction alternatives. The
MONTE computer program is a precursor to the HEC-FDA program and provides much less
sophisticated output information for evaluation of reasonableness. The report should document the rationale for use
of MONTE in lieu of HEC-FDA.
District Response:
We selected MONTE in lieu of FDA for its ease of use and speed, as well as our
estimation that MONTE was better equipped to analyze the study area’s problems and
opportunities than HEC-FDA. The outputs from
MONTE have provided the information requirements of ER-1105-2-101.
Discussion:
The District has determined that MONTE program is more applicable to evaluating
ponding situations. Concern is resolved.
Action Required: No action required.
5. FLOOD DAMAGE REDUCTION BENEFITS.
Comment: a. Benefits Associated With Separable
Features. Tables in the AFB
document indicate that incremental benefits and costs have been identified for each
alternative. Only values for total benefits
are shown in the various tables. The report
should document the components that contribute to total benefits for each alternative.
District Response:
Concur. Tables in the draft
feasibility report will include the components of the incremental costs and benefits. These will be presented by component and pond for
each separable feature.
Discussion:
Concern is resolved.
Action Required:
The draft report will document and summarize the components that contributed to
total benefits for each alternative.
Comment: b. Potential Flood Insurance Cost Savings. The text on page 2-37 cites indicates that New
Mexico has a participation rate of 12.1 percent in the National Flood Insurance Program. It is not clear that this is representative of the
communities in the study area. More
localized information should be used or information should be presented to document the
applicability of state data for the study area. Additionally,
text on page 2-37 states the following: “… the average annual savings in flood
insurance is $35,750 ($135 x .121 x 2,188).” Table
2-15 indicates that there are only 1,436 structures in the 100-year floodplain. The report indicates that the tentatively selected
plan would generally retain runoff from the 25-year and more frequent events. While this could diminish the areal extent of the
100-year floodplain, this is not supported by information presented in the AFB document. The draft report should verify that there are
potential savings in administration costs for Federal flood insurance associated with the
various alternatives. The report should
explicitly indicate the areas where such benefits would be expected to accrue.
District
Response: Concur. If available, we will obtain the Bernalillo County
participation rate for inclusion in the draft report.
No benefits of the administrative costs associated with flood insurance are being
claimed since the projects’ level of protection is below the 100-year.
Discussion: The response resolves the concern.
Action
Required: If available, the
district will obtain the Bernalillo County NFIP participation rate for inclusion in the
draft report.
Comment: c. Current
Versus Future Benefits. The
report text suggests that much of the project area in currently undeveloped. It appears that benefits are claimed for savings
of costs to elevate future structures above the 100-year flood plain level. An implemented plan would have to remove the
undeveloped areas from the future-with-project 100-year floodplain for such benefits to be
valid. Given that the tentatively selected
plan would generally only retain runoff from the 25-year and more frequent events, it is
not apparent that claiming such benefits is appropriate.
The draft report must clearly detail the assumptions associated with the derivation
of any benefits attributed to future development. The
report should present the benefit-cost ratio based on existing conditions for each
separable feature of the recommended plan.
District Response:
Concur. The draft report will
clearly state that the baseline condition in the study area is highly urbanized. Benefits for future fill will not be claimed since
the project protection level is below the 100-year. Therefore,
the benefit-cost analysis for each separable element is for the existing condition.
Discussion: District response resolves the concern.
Action
Required: The draft report will include
the information contained in the district response.
Comment: d. Structure Values. Page 2-41 states that estimated structure value
were derived from property tax information and sales information. ER 1105-2-100, paragraph E-19.k.(4) Use
of Assessed Value Real Estate Appraisal and Market Value Data in Flood Damage Reduction
Studies states the following: “Flooding
causes physical damages to structures. In the
past the Corps frequently estimated damages and cost of repair directly. The Corps now uses a risk-based procedure as
defined by ER 1105-2-101. This procedure
requires the use of depth-damage curves, which
express an average relationship between depth of flooding and damages. Damages are expressed as a percentage of structure
value. When depth-damage curves are used, the
correct measure of structure value, consistent with cost-benefit concepts, is replacement
cost less depreciation to the existing (pre-flood) structure. The draft report should explain how sales
information was used in the derivation of depreciated replacement costs.
District Response: Concur. Pages
2-34 and 2-41 will be revised to convey the following:
Bernalillo County assessor records were consulted to determine the assessed value
for land in the study area and improvements to that land.
Those assessments were then compared to recent sales figures by District Real
Estate personnel to establish a factor to be applied to those assessed structure values in
order to get the depreciated replacement cost of those structures. That computation was then verified in the field
through interviews with local real estate agents, and inspection/assessment of selected
structures using the Marshall Valuation Service. A
windshield survey of selected structures was also conducted to establish an average first
floor elevation of structures in each damage reach.
Discussion: District response resolves the concern.
Action
Required: The draft report will be
revised to include information in the district response.
6. FORMULATION OF ECOSYSTEM
RESTORATION ALTERNATIVES. The text presentation on the formulation and
evaluation of ecosystem restoration alternatives does not adequately support the plan
selection. If ecosystem restoration plans or
multipurpose flood control / ecosystem restoration plans are to be pursued, the following
review concerns must be addressed.
Comment: a. Significance
and Value of Ecosystem Restoration Alternative Outputs. Paragraph E-30.c. of ER 1105-2-100 indicates that
the significance of outputs is particularly important in the formulation of ecosystem
restoration alternatives. ER 1165-2-501
provides clear policy by stating “The purpose of Civil Works ecosystem restoration
activities is to restore significant ecosystem function, structure, and dynamic processes
that have been degraded.” The AFB
document does not demonstrate that the proposed work would meet the requirements cited in
the guidance. The document does not indicate
that the area historically contained wetland functions.
The text presents little information regarding the need for wetlands in the project
area or their relative value and scarcity as a resource.
Information should be presented in the report to demonstrate that wetland losses
have occurred historically and the habitat restoration is significant and warranted. The proposed sites appear to be small isolated
areas within an urban setting where the environmental value and potential for use by
wildlife may be very limited. The report
should provide information on the potential ecological viability of the small wetland
parcels that could be created. The AFB
materials indicate that there will be 24.5 acres of wetland realized; however, this is a
cumulative total of acres that would not be contiguous.
The significance of small separable wetland acres needs to be demonstrated from a
biological/ecological perspective, especially within an urban setting, which does not
provide supporting habitat. Finally, many of
the restoration elements (e.g., sloping of the banks, planting of native species) could be
viewed as environmentally sensitive design and not ecosystem restoration.
District
Response: Wetland ecosystems have been
reduced significantly from the southwest valley region.
In Bernalillo County, emergent wetlands have decreased 58.7% and scrub-shrub
wetlands have decreased 84.4% from 1935 to 1989. Topographic
maps from 1922 (produced by the Bureau of Reclamation Service) show numerous wetlands in
the region of the proposed project that are no longer existent.
Wetlands are a
significant part of the Central Flyway, in which New Mexico is directly in the path. The Central Flyway is second only to the Texas
Gulf Coast and the most important wintering area for hundreds of thousands of waterfowl. Wetlands are important for some of these birds for
overwintering in New Mexico.
An ecosystem
restoration plan can optimize the use of water directed to flood retention areas to
restore wetlands. The recommended plan
proposes small wetlands, i.e. 0.5 acres for the Mayflower wetland, as well as larger
wetlands, i.e. 8.4 acres for Isleta Drain 1 wetland.
Small wetlands are proposed as a result of the land availability constraint,
however, these wetlands are important for waterfowl habitat due to the location of the
project area in the Central Flyway. The
sloping of the banks and planting of native species are all integral to native wetland
habitat, and without those features, a successful wetland restoration project could not be
accomplished.
The draft report will include additional
information on historical wetlands in the area and status and trends of wetlands in the
Problems and Opportunities section. Also,
existing wetland information will be added in the existing condition section of the
report. The report will demonstrate that
wetland losses have occurred historically and the habitat restoration is significant and
warranted.
Discussion:
The district should also provide additional discussion in the draft report
concerning the significance of the Rio Grande flyway to specific species of migratory
wildfowl. The report should also discuss
existing habitat in the study area.
Action
Required: The draft report will
incorporate information contained in the district response and expand commentary to
include additional discussion of the significance of the Rio Grande flyway and existing
migratory wildfowl habitat.
Comment: b. Scope of Ecosystem Restoration
Alternatives. It is appropriate
to consider ecosystem restoration as part of multipurpose projects in accordance with
Section E-30 of ER 1105-2-100. However, there
is no evidence that broader ecosystem restoration alternatives were considered beyond the
creation of wetlands at the bottom of floodwater retention sites. If
restoration is to be pursued as a project purpose, a broader array of alternatives should
be presented in the report, including alternatives not necessarily tied to the current
array of floodwater retention basins.
District Response:
The project area is located in an area of high urban use; therefore, there is
little vacant and agricultural land available in the Southwest Valley. The availability of land was a constraint to the
development of broader ecosystem restoration alternatives.
Because
wetlands are dependent on a source of hydrology for their existence, plan formulation for
wetland/ecosystem restoration and flood damage reduction project purposes were
piggybacked. Since storm water will be the
major source of water for the proposed wetlands, the retention ponds were necessary to
provide the water needed to sustain the wetlands.
Discussion: The selected plan was formulated from a
broad array of alternatives. Several of the
alternatives were not tied to the flood control basins.
The district should provide additional back-up data and expand its discussion of
restoration alternatives considered.
Action
Required: The district will include
additional back-up data and expand discussion of restoration alternatives considered in
the draft report.
Comment: c. Incremental
Analysis. Guidance on Cost
Effectiveness and Incremental Cost Analyses is given in Section E-36, starting on page
E-153 of ER 1105-2-100. The incremental cost
per unit of output, not the average cost per unit of output, is used to conduct the
incremental analysis, as shown in Figure E-8 on page E-157 of the regulation. The AFB document includes a presentation on cost
effectiveness and incremental cost analysis that uses the cumulative cost per acre rather
than the incremental cost per acre for successive increments of investment in wetland
creation. The text presents the rationale for
plan selection based on the cumulative or average cost per acre as the level of outputs is
increased. Costs increase dramatically beyond
the initial investments up to 15.2 acres. This
includes the investments in the Bonito, Isleta 2, Muniz, Barcelona, and DeVita sites, with
incremental costs ranging from $9,777 per acre for Bonito to $18,182 per acre at DeVita. The incremental cost per acre for Mayflower Road
is $62,600, which is over three times higher than the previous increment for DeVita Road
and the successive investments at Isleta 30 is $72,048 per acre and Isleta 1 at $95,179
per acre. It is not clear why the investments
at the Mayflower Road, Isleta 30, and Isleta 1 retention basins are considered economical. The text does not adequately support their
inclusion in the selected plan. A revised
incremental cost analysis should be completed and presented in the report to support the
plan formulation and selection.
District Response:
The incremental cost analysis will be presented in the draft report using the
incremental cost per unit of output, not the average cost per unit of output as presented
in the AFB Documentation. The incremental
cost analysis will be used as a tool for the decision makers, the sponsors and Corps, to
determine what level of output are we willing to pay in order to meet the ecosystem
restoration objectives. The incremental cost
per acre for Mayflower, Isleta 30 and Isleta 1 are high, but the restoration benefits are
significant enough for the sponsors to be willing to pay the higher cost. The draft report will demonstrate that there is a
real demand and willingness to pay the higher incremental cost to meet the stated
ecosystem objectives.
Discussion: The district response resolves the concern.
Action
Required: The draft report will
include the information identified in the district response.
Comment:
d. Justification and Cost Allocation. The AFB document does not indicate that
single purpose ecosystem restoration alternatives were formulated. Restoration measures are add-on features to
alternatives specifically formulated to address flood damage reduction. Yet the AFB document presents cost allocation
tables for multipurpose project alternatives. However,
since the plan formulation process followed does not conform to multipurpose planning, it
is not appropriate to refer to the recommended plan as multipurpose. The costs shown are neither true separable or
joint costs; hence, the SC-RB analysis as presented in the report is not appropriate.
The
report must demonstrate that there is a real demand and willingness to pay for the
ecosystem restoration outputs. This can be done through establishing
significance, performing cost effectiveness and incremental analysis (ER 1105-2-100,
Section 2-3 f(3), page 2-7), and addressing whether incremental outputs justify
incremental costs. Both single purpose ecosystem restoration
plans and single purpose flood control plans must be formulated. Given the proper formulation of both single
purpose flood damage reduction and ecosystem restoration plans, the SC-RB cost-allocation can be employed.
District
Response: Concur. A revised SC-RB analysis will be presented in the
draft feasibility report.
Discussion: The district response resolves the concern.
Action
required: The district will include
the revised SC-RB analysis in the draft feasibility report.
Comment: e. Retention
Basin Sizing Uncertainty. The
descriptions of wetland alternatives all note that the retention basins need to be
excavated to within one foot of the groundwater table in order to provide a sustainable
wetlands. However, each site is sized to
accommodate the desired volume of runoff with an excavated depth of about 6 feet. Therefore, there is uncertainty as to the acres of
output and incremental costs until the depth of groundwater is determined. Information should be presented regarding the
approximate depth of groundwater at the alternative sites to minimize uncertainty
regarding the outputs of the alternatives and the costs per acre used in the incremental
analysis. Further, the report should address
the impact of this uncertainty on the estimate of alternative costs (excavation, real
estate, etc).
District Response:
Concur. The following will be added to
the final report. “The depth used for
the excavation of the detention and/or retention basins is derived from historic ground
water data collected by Bernalillo County and AMAFCA.
The six-foot depth incorporates seasonal fluctuations. Preliminary geotechnical investigations verify
this depth to groundwater. Design
refinements for specific sites will be incorporated at final design, but such changes will
have negligible effects on real estate takings.”
Uncertainties in project costs are
typically contained within M-CACES as “contingencies” which are added to the
cost of the alternative for purposes of the B/C analysis, consistent with current
regulations.
Discussion: The district should provide additional
information concerning the side-slopes in the retention basins. (2.5/1 vs 10/1). The district should also discuss the hydrologic
cycle and seasonal fluctuations to justify depths within one foot of water table.
Action
Required: The district will provide
additional information concerning the side-slopes in the retention basins and include
discussion related to the hydrologic cycle and seasonal fluctuations to justify depths
within one foot of water table.
Comment: f. Costs. There are no discussions regarding adaptive
management or the costs for replanting, maintenance, or monitoring of the wetland areas. If restoration benefits are to be claimed as
project outputs, sufficient costs should be included to assure that the wetlands will
successfully be developed and sustained as projected.
Costs associated with potential adaptive management, operations, maintenance, and
monitoring should be addressed in the draft report. The
retention basins would be constructed in residential areas.
Consequently, providing safety fencing at these locations should be considered.
District Response:
Concur. The draft report will
include adaptive management and O&M cost in the latest cost estimates for analysis and
exposition.
Discussion: The
draft report will need to clearly identify the monitoring and adaptive management
activities to be accomplished as part of construction, i.e. included in total project
costs and cost shared accordingly, and those activities to be accomplished at full
non-Federal expense as part of OMRR&R.
Action Required:
The draft feasibility report will clearly identify the nature, extent and cost of
monitoring and adaptive management actives to be accomplished and cost shared as part of
construction, and extent and cost of required OMRR&R activities to be accomplished at
full non-Federal expense.
7. REAL ESTATE.
The District presented
no real estate related policy issues for discussion at the upcoming AFB. ER 405-1-12 requires that a comprehensive real
estate plan be prepared and included in the District’s feasibility study report. Based on the limited information contained in the
AFB document the following real estate related issues might need to be discussed at the
AFB.
Comment: a. The cost of LER should be analyzed closely including the cost of pipeline easements indicated on some of the project maps. BCR looks close on some of these retention ponds.
District Response: The cost of pipeline easements has already been included.
Discussion: Concern is resolved.
Action Required:
None
Comment: b. Will additional real estate interests be needed on property adjacent to the retention ponds; i.e. will the holding ponds increase the risk of collateral flooding on property next to the flood control structure?
District Response: The basins were sized to preclude collateral flooding in the areas adjacent to the basin. No additional real estate interest will be required.
Discussion: Concern is resolved.
Action
Required: None
Comment: c. How does New Mexico water rights effect project
costs? If the environmental features of the
project extracts ground water to maintain water coverage (all ponds are to be excavated to
within one foot of ground water elevation) in the wetland environment who pays for the
water? Are water rights in New Mexico real
property interests? Is it LER, O&M or
neither?
District Response.
Water rights are treated like real estate (LER) in New Mexico and if any of the
project sites have water rights attached, we will compensate the owner of the water rights
only if we determine that there would be a detrimental impact on the owner’s interest
in the water rights. We will research the
files at the Office of the State Engineer to determine if any water rights are owned at
the project sites and determine if the Federal project would have an impact, however, none
is foresee at this time.
Discussion: The district noted it is coordinating with the New
Mexico State Engineer’s Office to acquire a waiver to the 96-hour flood water
retention rule. The district indicated that
based on recent coordination they expect to receive a waiver for the project. The district and non-Federal sponsor noted that
without the waiver water rights would be required if the water is retained for periods
longer than 96 hours.
Action
Required: The district will document the
results of its coordination with the State Engineer’s Office regarding the waiver to
the 96-hour flood water retention rule. If a
waiver is not obtained the non-Federal sponsor will be required to obtain any necessary
water rights.
8. MISCELLANEOUS
Comment: a. Statement of Compliance with
Applicable Statutes. During the
review, it was noted that neither the Farmland Protection Policy Act nor E.O. 11988 on
Floodplain Protection was identified. ER
1105-2-100, Section 2-3 c.(1), page 2-4 requires compliance with all existing laws and
regulations. In addition to the other laws,
regulations, statues, and executive orders identified the two previously mentioned need to
be addressed in the draft feasibility report.
District Response:
The project is in compliance with both the Farmland Protection Policy Act and E.O.
11988 on Floodplain Protection. The draft
report will describe compliance in more detail.
Discussion: Concern is resolved.
Action Required: The draft report and EIS will describe how the project is in compliance with both the Farmland Protection Policy Act and E.O. 11988 on Floodplain Protection.
Comment: b. Capture, Retention, and Concentration of Contaminants. It was noted (e.g., page 4-10) that there are contaminants in the area that may be captured in the wetlands. During the feasibility phase, it must be shown that the contaminants will not be a problem. If the retention basins provided habitat and wildlife is drawn to the area, it must be assured that the wetland habitat is of a quality that will not cause harm to the wildlife that it is intended to benefit.
District Response: The infiltration system incorporated into the plan will receive the first flush from streets, which has the highest level of pollutants. This stormwater will be handled consistent with Best Management Practices as required by the EPA.
Discussion: The district will clarify the difference
between pollutants and contaminants and state that the non-Federal sponsor will use Best
Management Practices to contain pollutants.
Action Required:
The draft report will be revised to reflect the discussion items.
Comment: c. Incorrect Text. Please note that the statement on page 5-18 is
incorrect with regard to the black-footed ferret. The
black-footed ferret is not “likely extinct” with the remaining individual
collected for captive breeding. Black-footed
ferrets have been found in the wild and the captive-breeding program has proved so
successful that individuals are being released in their historic range. The text should be corrected.
District Response:
The text in the draft report will be revised to state that the black-footed ferret
is extirpated in New Mexico.
Discussion: The district will coordinate with the U.S.
Fish and Wildlife Service (USFWS) to determine if any special status plants or animals are
scheduled to be introduced into the project area. If
so, will the proposed project have any effect on these species.
Action Required:
The district response and results of coordination with the USFWS regarding
special status plants or animals will be added to the draft report.
Comment: d. Funding History. The funding history shown on page 1-2 does not
conform to standard 50 percent Federal / 50 percent non-Federal cost sharing for
feasibility studies. The report should
document that the study is being cost shared consistent with WRDA 86 requirements, as
amended and section 2-8.c. of ER 1105-2-100.
District
Response: Concur. The text has been changed as follows:
Funds for the feasibility study were
allocated from fiscal years 1999 through 2001. Total
Federal allocations are $555,000 $900,000. An additional $300,000 $500,000 has been requested for
fiscal year 2002.
Discussion: This section should be deleted from the report.
Action Required:
The district will delete discussion of the funding history from the draft report.
Comment: e. Delineation of Overflow Areas. The fourth paragraph on page 2-1 references blue
colored areas on Plates 3 through 13 representing areas subject to flooding from
overflowing agricultural drains. These areas
are not identified in the legends on the plates and are not readily identifiable. ER 1105-2-100 requires that the areas with
potential to be affected by flood damage under the without project conditions be clearly
defined. The presentation should be clarified
to identify the areas subject to flooding from agricultural drains.
District Response:
Concur. The plates for the draft
report will be revised to ensure that these areas are readily identifiable.
Discussion: Concern is resolved.
Action Required:
The district will include the revised plates in the draft report.
Comment: f. Isleta 30 Flood Retention Basin. The information presented on page 4-29 of the
text conflicts with information elsewhere in the text.
(1) Inflow Volumes.
The inflow volumes are shown for sub-basins 30, 210, 212, 212A, 217, and 219. Whereas, page 4-28 indicates only the first four
sub-basins were to be accommodated by the retention basin.
Only the inflows from those sub-basins that contribute flow to the project area
should be listed, consistent with the project description.
District
Response: Concur. The text in the report will be corrected to
reflect the correct inflow volume. Isleta 30
is the only sub-basin contributing flow to the retention basin.
Discussion: Concern is resolved.
Action Required:
The text will be corrected in the draft report.
(2) Excavation Quantities. The values shown for excavation quantities (in
cubic yards) correspond to the acre-feet of inflow volume from only sub-basin 30. Therefore, it is not clear that the benefits and
costs as presented are for the same scale plan, and accurately measure the cost
effectiveness of the plan, consistent with the guidance in Section 2-4.c. of ER
1105-2-100. The table should be modified to
reflect the appropriate size basins for the four sub-basins described.
District Response:
Concur. The excavation quantities are
correct since Isleta 30 is the only sub-basin contributing flow (see 7.f(1) above.
Discussion: Concern is resolved.
Action Required:
The text will be corrected in the draft report.
(3)
Wetland Acreage. The wetland acreage to
be created at the retention basin is shown as 8.35 acres for the 25-year event project on
page 4-29, however page 4-50 indicates that 24.05 acres (cumulative output from Table
4-10) are being created. This information
should be made consistent.
District
Response. Concur. Wetland acreage on page 4-50 will be changed to
8.35 acres.
Discussion: Concern is resolved.
Action Required: The draft report will be revised per the District response.
Comment: g. Report Presentation. The text in the Flood Routings and Without
Project Overflow Analysis sections has numerous references to dam and road locations that
are not identified on the plates. The
locations of all dams, roads, and flow conveyance features referenced in the text should
be shown on the plates in order to clarify the presentation of without project conditions.
District Response:
Concur. This will be clarified in the
draft report.
Discussion: Concern is resolved.
Action Required:
The district will include revised maps in the draft report.
Comment: h. Price Level and Discount Rate. The discount rate and price level shown in the
economic criteria section on page 3-4 is inconsistent with that shown on the subsequent
economic tables. Paragraph 2-4.i. of ER
1105-2-100 requires that formulation be accomplished using a consistent price level for
benefits and costs and a discount rate in accordance with the annual Economic Guidance
Manual published by HQUSACE. Paragraph 4 on
page 3-4 should show the interest rate as 6.125 percent and the price level as September
2001, consistent with the formulation text.
District Response.
Concur. This has been corrected as
follows: Annual costs and benefits for this study have been calculated at the current
interest rate of 6.375 6.125 and November 2000
September 2001 price levels.
Discussion: Concern is resolved.
Action Required:
As indicated in the district response.
Comment: i. Incorrect Citation. The AFB
document cites a House Document No. 4911. This
was an incorrect citation. Actually the quote
is from the Public Law and H.R. 4911 is the bill number (HR for House of Representatives
not House Document). This should be corrected
for the feasibility report.
District Response:
Concur. This has been corrected as
follows: The Southwest Valley feasibility
study was authorized by the Flood Control Act of 1941 (Public Law 228) as contained in
House Document of
Representatives No. 4911, 77th Congress, 1st Session, dated
18 August 1941.
Discussion: The district will need to verify the citation
noted in the response. It does not appear to be correct.
Action Required:
The district will verify the above citation and include the correct information in
the draft report.