HomeMy WebLinkAbout11-28-16 CC Mtg - A2. Amendment 1 with Allied for FEMA Appeal
Commission Memorandum
REPORT TO: Honorable Mayor and City Commission
FROM: Brian Heaston, Project Engineer
Craig Woolard, Director of Public Works
SUBJECT: Amendment No. 1 to Professional Services Agreement with Allied Engineering for
a Floodplain Map Appeal.
MEETING DATE: November 28, 2016
AGENDA ITEM TYPE: Action
RECOMMENDED MOTION: I move to adopt Amendment No. 1 to the Professional Services
Agreement with Allied Engineering Services, Inc. to prepare a floodplain map appeal at a cost of
$86,674 and authorize the City Manager to execute the PSA amendment on behalf of the City.
BACKGROUND: The Commission approved a Professional Services Agreement on May 9, 2016 which placed Allied Engineering under contract to perform an evaluation of the draft
FEMA Flood Insurance Study (FIS) and floodplain maps for Bozeman Creek and Tributaries. A
report was delivered by Allied on July 29, 2016 and is attached to this memo (hereafter the
Allied Report, or Report). Based on the findings of the Allied Report, we believe that the draft
FIS and floodplain maps prepared by FEMA can be improved upon to more accurately simulate flood behavior and risk, particularly in the downtown area, by utilizing a more sophisticated 2D
flood modeling approach.
The Report was presented to FEMA along with a request that the city be granted an opportunity
to work with the agency to revise the draft FIS in order to incorporate 2D modeling prior to the release of preliminary flood maps and the start of the formal 90-day map appeal process. The
request was denied by the agency, thus placing the city in the position to bring these 2D revisions
forward in a formal map appeal, an inherently adversarial process, as opposed to the cooperative
one we had advocated for initially. To FEMA’s credit, however, they have provided draft
guidance to the city outlining data and supporting materials needed with the appeal package.
The purpose of the 2D map appeal is to produce regulatory floodplain maps that depict flood risk
as accurately as possible given available data and modeling technology. Accurate risk mapping
is essential to the proper and equitable administration of the federal flood insurance mandate
since mortgaged buildings in the regulatory floodplain must carry a flood insurance policy. Annual flood insurance premiums are a significant cost burden that will only continue to escalate
over time. Furthermore, accurate risk mapping focuses the city’s local floodplain development
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regulations discriminately and appropriately on those areas determined to be at the greatest risk
to flooding.
Amendment No. 1 to the PSA is attached and provides for preparation of the 2D map appeal package. Allied has performed scope diligence to familiarize itself with FEMA appeal
requirements. It should be noted that the 2D floodplain appeals are a relatively new concept and
FEMA has yet to publish formal technical guidance for 2D model development. That said,
Allied has included with their team a firm from Oregon that has extensive experience working
with FEMA and 2D models. This firm will provide modeling oversight and quality assurance reviews which should elevate the chances of the appeal review being met favorably by the
agency.
Amendment No. 1 also includes tasks to continue evaluating the flood hazard mitigation
potential of Mill Ditch (which would serve to reduce flood hazards along Bozeman Creek in the historic core of the city). These tasks will determine improvements to Mill Ditch necessary to
convey a sufficient quantity of flood water down it such that flows in Bozeman Creek are
generally kept within its banks in the historic core. Upon completion of this work, the city will
be armed with sufficient information to determine whether a future flood hazard mitigation
project should be pursued or not. Federal flood mitigation grant dollars may be available for a project of this sort. It must be noted that the flood hazard mitigation project is distinct and
separate from the afore-described map appeal.
The final task of Amendment No. 1 provides for updating the draft FIS and flood maps to
incorporate the new Bond Street bridge crossing Bozeman Creek. This bridge was constructed after the new FIS was begun and unfortunately was not included in the study or maps. A data
package will be provided to FEMA during the appeal period to revise the FIS and mapping to
incorporate this bridge such that flood risk is accurately depicted in vicinity of the bridge.
Because the anticipated costs for the tasks in Amendment No. 1 exceed $20,000, an RFP was released to procure services based on qualifications pursuant to state law. Two RFPs were
received. Upon their respective review Allied Engineering was determined to be most qualified
to perform services for the project. Since an existing PSA is already in place with Allied,
Amendment No. 1 is hereby brought forward as the appropriate contracting vehicle.
FISCAL EFFECTS: Hearing for adoption of Resolution No. 4756 precedes this PSA
amendment action and if approved by the Commission will amend the Downtown TIF budget to
make $41,674 available to fund this PSA amendment. The Downtown Business Improvement
District has pledged $20,000 from its cash reserve account towards the project. Respective
letters from the downtown TIF and BID committing support for these contributions are attached. The adopted FY17 budget for the City Engineering Department will provide the remaining
$25,000 for the project.
ALTERNATIVES: As suggested by the Commission
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ATTACHMENTS: Allied Report from original PSA
Amendment No. 1 to Allied PSA
Funding commitment letters from Downtown BID and Downtown TIF
Report compiled on: November 18, 2016
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.
Report
Floodplain Evaluation for Bozeman
Creek and Tributaries
Bozeman, MT
July 29th, 2016
Prepared for:
City of Bozeman
Brian Heaston, PE bheaston@bozeman.net
Prepared by:
Allied Engineering Services, Inc.
Jennifer Johnson, PE, CFM – Project Engineer
Paul Sanford, PE, CFM – Project Manager
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TABLE OF CONTENTS
1.0 INTRODUCTION ........................................................................................................................... 1
1.1. Project Overview .................................................................................................................. 1
1.2. Site Description .................................................................................................................... 1
2.0 DATA COLLECTION .................................................................................................................... 2
2.1. Site Reconnaissance ............................................................................................................. 2
2.2. Topographic Survey ............................................................................................................. 2
3.0 FLOODPLAIN MODEL EVALUATION (1D) .............................................................................. 3 3.1. General Model Review (Bozeman Creek) ........................................................................... 3
Background .............................................................................................................................. 3
Model Setup Review ................................................................................................................ 3 3.2. Mill Ditch Diversion Evaluation .......................................................................................... 6
Site Description ....................................................................................................................... 6
Model Setup ............................................................................................................................. 7
Model Results .......................................................................................................................... 8 3.3. Creekside Park (Bozeman Creek) Evaluation ...................................................................... 8
Site Description ....................................................................................................................... 8
Model Investigation ................................................................................................................. 9
Creekside Park Mitigation Investigation ............................................................................... 13 Model Results ........................................................................................................................ 13
3.4. Bond Street Bridge Evaluation (Bozeman Creek) ............................................................. 15
Site Description ..................................................................................................................... 15 Model Setup ........................................................................................................................... 16
Model Results ........................................................................................................................ 17
4.0 FLOODPLAIN MODEL EVALUATION (2D) ............................................................................ 19
Site Description ..................................................................................................................... 20 Model Setup ........................................................................................................................... 20
Model Results ........................................................................................................................ 20
5.0 REFERENCES .............................................................................................................................. 22
LIST OF FIGURES
Figure 1. The extent of the Bozeman Creek and Tributaries Floodplain Mapping Project. ........................ 2
Figure 2. Plan view of the bridge bounded by cross-sections 9905 and 9721. ............................................ 4
Figure 3. Profile output from HEC-RAS of the 100-year event for the bridge bounded by cross-sections 9905 and 9721 (Michael Baker International, 2016). ................................................................................... 4
Figure 4. Mill Ditch Diversion ..................................................................................................................... 6
Figure 5. Mill Ditch Diversion location map. .............................................................................................. 7
Figure 6. Creekside Park location map. ....................................................................................................... 9
Figure 7. Flooding during the 2011 runoff event at Creekside Park (photos by Gary Weiner). ................ 10
Figure 8. Mapped inundation extents within Creekside Park with interpolated BFEs. ............................. 11
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Figure 9. A comparison between the original regulatory model flooding extents and the flooding extents produced by the regulatory model with added cross-sections through Creekside Park. ............................. 12
Figure 10. 100-year inundation extents from the existing geometry with added cross-sections and from
the cross-sections modified to include an inset floodplain on the right bank. ............................................ 14
Figure 11. Bond Street bridge (looking upstream). ................................................................................... 16
Figure 12. Model setup for the Bond Street bridge. ................................................................................... 17
Figure 13. Inundation extent for the 100-yr event. .................................................................................... 19
Figure 14. A comparison between the results of a 1D/2D model setup and a 1D model setup. ................ 21
LIST OF TABLES
Table 1. Water surface elevations for select cross-sections. ........................................................................ 5
Table 2. Water surface elevations for the regulatory model and the regulatory model with the added cross-sections. ............................................................................................................................................. 13
Table 3. Model results for Creekside Park for the 100-year event. ........................................................... 14
Table 4. Comparison between the original 2016 draft FIS model, the 2016 draft FIS model with the
added cross-sections, and the 2016 draft FIS model with the added cross-sections and bridge. ................ 18
ATTACHMENTS
Attachment A – Bozeman Creek Annotated Profile Plot
Attachment B – Proposed and Existing Cross-Sections for Creekside Park
Attachment C– Mill Ditch Diversion and Bozeman Creek Flow Adjustment Results
Attachment D – Model Files
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1.0 INTRODUCTION
1.1. PROJECT OVERVIEW
The Bozeman Creek and Tributaries Floodplain Mapping Project was completed by Michael
Baker International for the Federal Emergency Management Agency (FEMA) and is currently undergoing review and evaluation by the City of Bozeman prior to implementation. The
Bozeman Creek and Tributaries project aims to update floodplain mapping for the area using the
Army Corps of Engineer’s HEC-RAS, a hydraulic modeling program, and updated elevation data.
Large scale floodplain mapping was last completed for the Bozeman area in 1988 with a digital conversion of the data occurring in 2011.
Allied Engineering Services, Inc. (AESI) was hired by the City of Bozeman to assist with select
review and evaluation of the Bozeman Creek and Tributaries Floodplain Mapping Project as described below. In addition to general model review, manipulations to the model were also
completed to determine possible mitigation procedures to lower base flood elevations in areas
susceptible to flooding. Specifically, AESI analyzed Creekside Park and the Mill Ditch
Diversion.
A bridge on Bozeman Creek at Bond Street was constructed after the survey for the project was
completed, and AESI added the bridge to the model in anticipation of a future Letter of Map
Revision. Allied Engineering also completed a field survey of the new bridge. The effects of the
bridge on floodplain boundaries are included herein.
The Bozeman Creek and Tributaries project was completed using HEC-RAS V4.1.0. Since
modeling completion, HEC-RAS V5.0 and V5.0.1 has been introduced. Both new versions
include 2D modeling capabilities which could offer improved hydraulic simulations for split flow areas, especially in downtown Bozeman. Allied modified the model to include a 2D area from
Olive Street to Lamme Street, and the 2D model results were compared to the 1D modeling
results. The exercise is intended to be used by the City as a tool for determining modeling
methods moving forward.
1.2. SITE DESCRIPTION
The extent of the Bozeman Creek and Tributaries Floodplain Mapping Project is shown in Figure 1. The project area extends from Nash Road south of town and past the interstate to the north.
Bozeman Creek passes through downtown Bozeman, and several flow splits exist throughout the
area.
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Figure 1. The extent of the Bozeman Creek and Tributaries Floodplain Mapping Project.
2.0 DATA COLLECTION
2.1. SITE RECONNAISSANCE
Paul Sanford, PE and Jennifer Johnson, PE of AESI conducted a site visit to the downtown reach
and the Bond Street Bridge on June 23rd, 2016. Several photographs and hand measurements were taken of the bridge to assist with modeling and verify the topographic bridge survey.
2.2. TOPOGRAPHIC SURVEY
A 2013 LiDAR set commissioned specifically for the Bozeman Creek and Tributary Re-study
and used by Michael Baker for the regulatory model was used for 2D modeling and cross-section
data in addition to surveyed topographic points. Additionally, AESI was subcontracted by Atkins
in 2012 to complete field surveying for the Bozeman Creek and Tributaries Floodplain Restudy.
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Kyle Thompson, LS of AESI obtained survey data for structures, bridges, and bathymetric cross-sections for the project area during the fall/winter of 2012. He obtained survey data for the Bond
Street Bridge on June 27th, 2016.
3.0 FLOODPLAIN MODEL EVALUATION (1D)
3.1. GENERAL MODEL REVIEW (BOZEMAN CREEK)
Background
The preliminary FIS completed by Michael Baker International has already undergone several
rounds of QC review with the DNRC, Compass, and the City of Bozeman. AESI was asked by the City of Bozeman to complete a more general, outside review.
Model Setup Review
Bridge Modeling
Some bridges, particularly in the downtown area are not ideal for standard bridge modeling given the long underground lengths the creek is conveyed (sometimes several hundred feet). The
governing equations for bridges, including weir flow over the bridge, are not applicable in these
situations. More likely, flow that cannot be contained within the bridge opening will split off and be conveyed down various streets and alleys in the downtown area.
An example of this occurrence can be seen at the bridge between cross-sections 9905 and 9721.
At this location, a structure blocks the upstream end, and flow will spill out to the side of the
structure and travel down alleys and streets before re-entering Bozeman Creek further downstream. Figure 2 and Figure 3 show the situation.
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Figure 2. Plan view of the bridge bounded by cross-sections 9905 and 9721.
2800 2900 3000 3100
4805
4810
4815
4820
Bozeman Plan: Bozeman Regulatory 6/27/2016
Main Channel Distance (ft)Elevation (ft)Legend
WS 100yr
Crit 100yr
Ground
972197559965BozemanCreek 3
Figure 3. Profile output from HEC-RAS of the 100-year event for the bridge bounded by cross-sections 9905 and 9721 (Michael Baker International, 2016).
The suspect bridge modeling results indicate that a 2D model setup may improve flood
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simulations for the downtown area.
1D/2D Setup
It appears that given the numerous split flows and highly urbanized nature of the downtown area,
a 2D model would better describe the hydraulics for downtown Bozeman. 1D models are highly dependent on cross-section placement and can be prone to error. Given the complex nature of downtown Bozeman, a 1D model has the potential to over-simplify the hydraulics of the area and
miss or underestimate split flow quantities.
1D conceptualization requires the modeler to manually apply lateral weirs at locations where flow is likely to split from the main channel. Given the large number of split flows, it is possible that
some splits have not been appropriately accounted for. Unaccounted splits could greatly
influence mapped flood depths and extents. Conversely, 2D model environments do not rely on
the modeler manually placing split flow locations and may better depict where flow is leaving the channel.
2D modeling is still not widespread for floodplain studies, and there are concerns that regulation
would be difficult based on 2D models. A combined 1D/2D model setup may give many of the advantages of a 2D model while still providing regulatory BFEs. A preliminary1D/2D model was constructed by AESI for the downtown area to illustrate possible discrepancies and errors
between 1D and combined 1D/2D setups. The results are presented in Section 4.0 and show
significant differences in split flow quantities from the main Bozeman Creek channel. Further research may be necessary regarding the ability to perform an encroachment analysis given a
combined 1D/2D setup. However, a 1D/2D model may be more applicable in simulating
flooding in downtown Bozeman.
Digital File Errors
While performing the tasks described below, an error was discovered in the S_XS Shapefiles.
Cross-sections 8709, 8691, and 8660 on Bozeman Creek report the wrong regulatory water surface elevation. The HEC-RAS model and the FIS profile (Attachment A) show the correct water surface elevations. Table 1 compares the water surface elevations reported by the S_XS
Shapefiles with the digital HEC-RAS model and the FIS profile.
Table 1. Water surface elevations for select cross-sections.
XS S_XS Water Surface
Elevation (ft)
Digital Model and FIS
Profile Water Surface
Elevation (ft)
8709 4800.4 4800.79
8691 4800.4 4800.88
8660 4800.5 4800.72
New Structure
While performing review and evaluation of the model, it was noted that a new bridge crossing the
Mill Ditch Diversion and providing access to Burke Park has recently been installed. The bridge
replaces a culvert crossing and was not included in the 2016 draft FIS model. The bridge was conditionally approved and will be subject to a post-project LOMR being completed.
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3.2. MILL DITCH DIVERSION EVALUATION
The Mill Ditch Diversion splits from Bozeman Creek upstream of the downtown area and flows
northeast. The 1988 FIS used a flow of 340 cfs for the Mill Ditch flow just north of Church
Street whereas the draft FIS uses 122.86 cfs at this same location. Currently, the City of Bozeman is considering using Mill Ditch for flood relief of Bozeman Creek during large runoff
events. The flow split at the Mill Ditch Diversion and Bozeman Creek was manipulated within
the HEC-RAS model to determine the possible extent of flood relief produced by increasing flow in the Mill Ditch from its current condition during flood level events. AESI’s scope of work did not include determining how the desired flow split would be achieved.
Site Description
The Mill Ditch Diversion is located near Story and Church Streets. The diversion is a concrete
culvert on the right side of Bozeman Creek (Figure 4). Approximately 200 ft south of the diversion, an additional flood split flow, named the Gallagator Split, diverts flow to Mill Ditch.
Figure 5 below shows the general layout of the area.
Figure 4. Mill Ditch Diversion
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Figure 5. Mill Ditch Diversion location map.
Model Setup
The effect of diverting flow to Mill Ditch for the 100-year event was determined by running several model simulations where flow was added to the Mill Ditch split in 50 cfs increments. The
amount added to the Mill Ditch was subtracted from Bozeman Creek. A total of four simulations
were run resulting in a max excess diversion of 200 cfs down Mill Ditch. The Gallagator split was not changed during the simulations.
The draft regulatory model either uses flow from the split with Bozeman Creek or from
RESPEC’s hydrologic analysis of Mill Ditch (RESPEC Consulting and Services, 2014),
whichever one is greater. The peaks from Bozeman Creek and Mill Ditch Diversion are assumed to not be coincident, but the larger flow should control floodplain mapping. Therefore, when
adding additional flow to Mill Ditch at the flow change locations within the model, a comparison
between the split flow value and the flows from hydrologic modeling were compared, and the larger one was applied.
Split flows exist on Bozeman Creek downstream of the Mill Ditch Diversion at Church and
Wallace Streets. Split flow quantities based on the new Bozeman Creek flow allocation were
determined using Michael Baker’s split flow model. Michael Baker created a separate model of Bozeman Creek and its tributaries using lateral weirs to determine split flow quantities. The
regulatory model does not include these lateral weirs and models each creek separately.
Manually entered flow change locations within the regulatory model are used to assign flow split
quantities determined by the split flow model.
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Mill Ditch had several flow splits north of Bozeman near the interstate. These splits were not analyzed with the new flow allocations, and results downstream of Mill Ditch cross-section 3576
are not valid.
Model Results
The simulation results after adding flow to Mill Ditch were compared to the original results obtained by Michael Baker for the FIS. Since a large amount of editing occurs from the raw output to the finished flood hazard areas, only the raw output from the model was used for
comparison purposes. The results show minimal changes in inundation extents for an increase of
50 cfs in the Mill Ditch, but noticeable results occur for an increase of 200 cfs. An added 200 cfs in Mill Ditch means that the watercourse is conveying ~323 cfs total (200 cfs + 123 cfs). The
100-year inundation extents for Mill Ditch increase but mostly remain within undeveloped areas.
Possible areas of concern may exist near Mill Ditch’s split with Bozeman Creek. Attachment C
gives the results of all four simulations. The figures do not show areas below cross-section 3576 of Mill Ditch at Mill Ditch’s far downstream end since split flows in that vicinity were not
analyzed. The digital model containing the simulations is provided in Attachment D.
3.3. CREEKSIDE PARK (BOZEMAN CREEK) EVALUATION
Site Description
Creekside Park is a small park located at the intersection of Lamme St. and Rouse Ave. and
contains Bozeman Creek (Figure 6). The creek takes a notable bend within the park and has been the location of past flooding issues.
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Figure 6. Creekside Park location map.
Model Investigation
In 2011, a runoff event estimated to be less than the 100 year event caused the creek to overtop its banks and encroach upon an adjacent property (Figure 7). The City of Bozeman is concerned that
the 2016 flood study does not accurately portray the flood risk and extents based on previous
observations. As shown in Figure 6, the 2016 mapped 100 year inundation extents estimate that
flooding would not go past Bozeman Creek’s left bank through much of Creekside Park. The City expressed their concern during the review process of the model. Michael Baker responded
as follows (Michael Baker International, 2015):
Our hydraulic model indicates that this area would not generally be inundated during the
100 year flood event. We have reviewed the modeled elevations, and the surveyed
elevations on the left overbank, and have determined that the elevation of the left
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overbank stays above the BFE for this entire reach. (We also note that the manning’s ‘n’
values in this reach of the model are higher than at any other point along Bozeman Creek,
to account for the sudden turns of the stream centerlines – yet the BFE still remains below
the left bank elevation.)
The photographs provided do not justify further adjustments to the model or map,
particularly considering ‘n’ values are already elevated to account for the bend. Flooding
elevations in this localized area in 2011 could have been higher than in the hydraulic
model due to unexpected blockage or debris in the floodpath, which is not accounted for
in our model – FEMA guidelines specify that blockage and debris are generally not to be
included in standard hydraulic models.
Figure 7. Flooding during the 2011 runoff event at
Creekside Park (photos by Gary Weiner).
AESI investigated the model and found no general issues with parameters used. However, the
sharp change in geometry may have warranted an extra cross-section to improve water surface
interpolations. It appears that results were mapped by creating a water surface elevation TIN that directly interpolates between Bozeman Creek cross-sections 8533 and 8385.
Before addressing changes to the HEC-RAS model, AESI completed a geometric exercise to
better determine flooding extents in the area based on the existing model setup. Three
interpolated cross-sections were added between cross-sections 8533 and 8385 to better describe Bozeman Creek’s geometry. A linearly interpolated water surface elevation was assigned based
on the cross-section’s river station, and a water surface elevation TIN was created from the
FEMA and interpolated cross-sections. When the results were mapped onto the existing elevation, inundation extents were shown beyond the left bank (Figure 8).
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Figure 8. Mapped inundation extents within Creekside Park with interpolated BFEs.
The area is shown to be sensitive to cross-section positioning because of the sharp bend. Additionally, while adding cross-sections to better map the area better align with observations, it
is difficult to determine its accuracy in relation to the 2011 event since the 2011 recurrence
interval is not known. However, in a hydraulic model created to support stream enhancement
efforts the 2011 event was roughly estimated to be a 20 percent chance annual peak discharge (Allied, 2012).
The cross-sections added by Allied for interpolating flood elevations and improving the mapped
flood extents were also modeled within HEC-RAS. The added cross-sections had a noticeable effect on the water surface elevations. The additional cross-sections caused a rise throughout
Creekside Park indicating that XS 8533 and XS 8385 are too far apart to adequately account for
losses in the reach. The Manning’s n values for the added cross-sections were kept consistent
with the upstream and downstream bounding cross-sections. While Michael Baker increased the Manning’s n value for cross-sections in the park to account for increased losses around the bend,
the results indicate that if cross-sections are added to the model, raising the Manning’s n value
may not be necessary. Figure 9 shows the flooding inundation changes. Table 2 gives the tabular output of water surface elevations for the two models. The results indicate that one or two additional cross-sections would better describe hydraulics throughout the bend and better align
model results with observations.
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Figure 9. A comparison between the original regulatory model flooding extents and the flooding
extents produced by the regulatory model with added cross-sections through Creekside Park.
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Table 2. Water surface elevations for the regulatory model and the regulatory model with the added
cross-sections.
XS River
Station
(*denotes added cross-section)
Water Surface
Elevation (ft)
Regulatory Model
Water Surface
Elevation (ft)
Existing Conditions with Additional Cross-Sections
Δ Increase in
Elevation Between Regulatory Model and Regulatory
Model with
Added XSs
8566 4799.41 4799.70 0.29
8533 4799.11 4799.57 0.46
8507.5* 4799.45
8487.6* 4799.38
8415.5* 4798.32
8385 4797.89 4797.89 0.00
Creekside Park Mitigation Investigation
AESI modified the added cross-sections to include an approximate 30-ft wide floodplain on the
right side through Creekside Park to determine potential flood mitigation benefits of a constructed
inset floodplain. Attachment B provides proposed and existing topography for the cross-sections. Bank full depth was maintained between ~2.5 and ~3.0 feet. Bank full depth is approximate and
was based on a discussion of stable configurations for Bozeman Creek in the report Bozeman
Creek Enhancement Project at Bogert Park (Confluence Inc., 2012).
Model Results
The model was run for the 100-year event using the existing geometry and the modified geometry
with the added floodplain. Results displayed in Figure 10 show the benefit of the added
floodplain. Table 3 gives water surface elevations at the modeled cross-sections.
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Figure 10. 100-year inundation extents from the existing geometry with added cross-sections and
from the cross-sections modified to include an inset floodplain on the right bank. The results were mapped onto the existing terrain.
Table 3. Model results for Creekside Park for the 100-year event.
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XS River
Station
(*denotes
added cross-
section)
Water Surface
Elevation (ft)
Regulatory
Model
Water Surface
Elevation (ft)
Existing
Conditions with
Additional Cross-
Sections
Water Surface Elevation (ft)
Proposed
Conditions
(Added Inset
Floodplain)
Δ In
Elevation
Between
Existing
Conditions
and Proposed
Conditions
8566 4799.41 4799.70 4799.46 0.34
8533 4799.11 4799.57 4799.28 0.29
8507.5 4799.45 4799.20 0.25
8487.6 4799.38 4799.14 0.24
8415.5 4798.32 4798.13 0.19
8385 4797.89 4797.89 4797.89 0.00
The results indicate that an added floodplain has minimal effects on flooding extents throughout
Creekside Park. The confined nature of the creek downstream of the park may also be causing
some backwater effects in the area.
3.4. BOND STREET BRIDGE EVALUATION (BOZEMAN CREEK)
A bridge crossing Bozeman Creek at Bond Street on the north side of Bozeman was recently permitted based on the 2011 effective FIS. The timing of the bridge construction excluded the structure from the 2012/2013 survey, and the bridge was not included in the draft 2016 FIS. AESI
surveyed the bridge and added the bridge to the 2016 HEC-RAS model to determine its effects on
flood inundation extents.
Site Description
The bridge spans 56-ft across Bozeman Creek aligned parallel to Bond Street. The bridge is
noticeably skewed, ~44°, across Bozeman Creek. At flood flows a hydraulic opening width of
40-ft is provided since the bridge is skewed. The bridge has ~2-ft tall guardrails. Figure 11 shows the bridge.
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Figure 11. Bond Street bridge (looking upstream).
Model Setup
Three cross-sections were added to the existing HEC-RAS model to simulate the bridge. Four
cross-sections are required to adequately model structures in the program, but an existing cross-section downstream of Bond Street was appropriately located to model expanded flow
downstream of the bridge. Cross-sections were added directly upstream and downstream of the
bridge, and one was placed ~100-ft upstream to model contraction losses. Field survey was completed to obtain bathymetric data for the cross-sections while LiDAR was used for the overbank areas. Figure 12 shows the cross-section layout.
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Figure 12. Model setup for the Bond Street bridge.
Manning’s n values were kept consistent with the bounding upstream and downstream cross-sections, and an n value of 0.045 was assigned to the channel while 0.06 described both right and
left overbanks. A 44° skew was assigned to the bridge and bridge bounding cross-sections.
Model Results
Table 4 and Figure 13 compare changes to water surface elevations and flooding extents caused by the inclusion of the Bond Street Bridge. Attachment D provides a digital copy of the updated
model.
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Table 4. Comparison between the original 2016 draft FIS model, the 2016 draft FIS model with the
added cross-sections, and the 2016 draft FIS model with the added cross-sections and bridge.
1. XS River
Station
2. 100-Yr WSE
from the
Original 2016 Draft FIS Model (FT)
3. 100-Yr WSE
from the
Original 2016 Draft FIS Model with the
Added Bond
Street Cross-
sections (FT)
4. 100-Yr WSE
from the
Original 2016 Draft FIS Model with the
Added Bond
Street Cross-
sections and
Bridge (FT)
5. ΔWSE
(Column 4 – Column 3) (FT)
3357 4744.91 4745.09 4745.09 0.00
3163 4743.17 4742.82 4742.82 0.00
2707 4739.17 4739.51 4739.51 0.00
2593 (Added) 4738.66 4738.66 0.00
2493 (Added) 4737.61 4737.87 0.26
2424 (Added) 4737.01 4737.01 0.00
2347 4736.66 4736.66 4736.66 0.00
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Allied Engineering Services, Inc. July 29th, 2016 19
Figure 13. Inundation extent for the 100-yr event.
The results demonstrate a minimal effect on overall water surface elevations and inundation
extents from the inclusion of the bridge. There is a slight rise directly upstream of the bridge.
4.0 FLOODPLAIN MODEL EVALUATION (2D)
With the release of HEC-RAS 5.0.1 and its 2D modeling capabilities, the City of Bozeman asked
AESI to explore the effects of 2D modeling on flood mapping for Bozeman Creek. Specifically, the
section of creek from Olive Street to Lamme Street, the reach containing downtown Bozeman, was requested for 2D model evaluation. The 2D model created for the City of Bozeman is intended to
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Allied Engineering Services, Inc. July 29th, 2016 20
help guide future decisions regarding appeals to the 2016 FEMA mapping. However, the model is preliminary and is not intended to be directly used for the appeals process. A significant effort
(beyond the scope of this contract) would be required to build a robust model incorporating the 2D
functionality of HEC-RAS.
Site Description
Bozeman Creek between Olive Street and Lamme Street is a highly controlled section of creek through a heavily urbanized environment. The creek is conveyed underground in several
locations, and several bridges cross Bozeman Creek throughout the reach.
Model Setup
The large number of structures and significant lengths over which the creek is conveyed
underground created several difficulties regarding a pure 2D modeling environment. For this
reason, a combined 1D and 2D model was employed. The creek channel was modeled as 1D, while the overbanks were modeled as 2D. Lateral weirs along the banks connected the 1D area to
the 2D area. The setup allowed for the hydraulic structures to be modeled in the 1D environment.
In the absence of a survey or site visit identifying high ground between Bozeman Creek and the
overbanks, lateral weirs were assigned elevations based on the existing LiDAR topography directly adjacent to the stream. They were designated as a “zero height” weir and assigned a weir
coefficient of 0.5 to signify flow over existing ground.
2D modeling requires an unsteady flow analysis. Unsteady flow analyses can be finicky to stabilize and require special attention to model variables including cross-section spacing, mesh cell sizing, and the computational time step. A maximum cross-section spacing of 50 feet was
chosen for the downtown area with guidance from Samuel’s equation (Samuel, 1989). Cross-
sections were interpolated between the original cross-sections using HEC-RAS’s interpolation tool. Mesh cell sizing was assigned at 40 ft x 40 ft. A relatively small time step of 10 seconds
was originally applied. After a convergent solution was successfully reached, the time step was
reduced to 4 seconds and theta, the implicit weighting factor, was reduced to 0.6 to improve result
accuracy.
Model Results
The 1D/2D combined model setup shows shallower depths and more flow conveyed down streets than the 1D model. Additionally, while the 1D/2D model is preliminary, the setup does show flow leaving the main channel at Main Street while the 1D model created by Michael Baker does
not. The 1D/2D model also generally shows more flow leaving the main channel and traveling
down streets within the downtown area. Figure 14 gives a comparison between the 1D/2D and 1D models.
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Allied Engineering Services, Inc. July 29th, 2016 21
Figure 14. A comparison between the results of a 1D/2D model setup and a 1D model setup. Note
that the 1D/2D flood inundation results were mapped onto a terrain set that included buildings while
the 1D model flood mapping used a terrain set with the buildings removed. Both setups were modeled with buildings included.
The 1D/2D model does have issues at the bridges. The lateral weirs do not transfer flow to the
overbank areas at the bridges, only directly before and after. This can create some discontinuity between water depths over the bridges and the areas directly adjacent to the bridge in the
overbank areas. This may warrant further attention if there is a greater modeling effort using 2D
areas.
After the model’s completion, it was observed that the bridge between cross-sections 9905 and 9721 (Bozeman Creek Family Health building as shown in Figure 2) is shown to overtop for both
the 1D and the 1D/2D models. This is not realistic since a structure directly blocks the overflow
path at the upstream end. More realistically, flow will spill out to the side of the structure and travel down alleys and streets before re-entering Bozeman Creek. Obstructions or a different 1D/2D configuration may need to be determined to better model this location.
Another problem area is at Main Street. Main Street does not overtop as a bridge, but flow will
exit the channel at the upstream end of Main Street on both sides of the channel. Flow exiting to the west will flow north through a narrow walkway and then intercept Main Street and be
conveyed east. A connection between 2D areas was used to hydraulically connect the left (west)
and right (east) 2D flow areas, but the 2D model does not move flow from the left overbank to the
right overbank area in its current state. Ground survey could be useful at this area to improve the model.
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Allied Engineering Services, Inc. July 29th, 2016 22
There are also some continuity issues at some lateral weirs that would require more investigation during the completion of a more robust model. For example, the flow rate change between cross-
sections before and after the first lateral weirs downstream of Main Street does not match the
flow leaving the lateral weirs. Mesh modifications or calculation variable adjustments could
rectify continuity issues.
A more detailed model would also improve the transitions from the 1D/2D section of the model
to the 1D sections by using inline structures to connect the areas.
Ultimately, the preliminary 1D/2D model shows that utilizing 2D areas for the downtown Bozeman area could have significant implications for flood mapping. A 1D/2D model setup appears to better describe flow splits and conveyance paths. Attachment D provides a digital
copy of the model.
5.0 REFERENCES
Allied Engineering Services, Inc. (2012, March). Bozeman Creek Hydraulic Model from Story Street to
Mendenhall Street. Bozeman, Montana.
FEMA. (2016). Bozeman Creek and Tributaries Floodplain Study. FEMA.
Michael Baker International. (2015, December 10). Comment Response Letter to the City of Bozeman.
RESPEC Consulting and Services. (2014, April). Bozeman Creek Hydrologic Analysis - Bozeman Creek
and Tributaries Digital Flood Insurance Rate Map Restudy Project. Bozeman, Montana.
RESPEC Consulting and Services. (2014, April). Mill Ditch Diversion Hydrologic Analysis - Bozeman Creek and Tributaries Digital Flood Insurance Rate Map Restudy Project. Bozeman, Montana.
Samuel, P. (1989). Backwater lengths in rivers. Proceedings - Institution of Civil Engineers, Part 2,
Research and Theory, 87, 571-582.
United States Army Corps of Engineers. (2016). Hydrologic Engineering System - River Analysis System (HEC-RAS) V.5.0.1. Davis, California.
US Army Corps of Engineers. (2010). River Analysis System (HEC-RAS) V4.1.0. Davis, California.
139
1
Amendment No. 1 to Professional Services Agreement
for Bozeman Creek and Tributaries Floodplain Mapping
Project – Select Review and Evaluation
THIS AGREEMENT is made as of this ________ day of ____________________, 2016 ,
between THE CITY OF BOZEMAN, a Municipal Corporation, Bozeman, Montana, herein referred
to as OWNER and ALLIED ENGINEERING SERVICES, INC., an Engineering Consulting Firm of
Bozeman, Montana, herein referred to as ENGINEER. WHEREAS, the parties have entered into a Professional Services Agreement dated May 9,
2016, herein referred to as Original Agreement for professional engineering services; and
WHEREAS, the parties desire to further amend the provisions of this Agreement. NOW, THEREFORE, IN CONSIDERATION OF THE MUTUAL COVENANTS
CONTAINED HEREIN, the parties agree as follows:
The conditions and provisions set forth in the attached Amendment No. 1 to Scope of Services for Bozeman Creek and Tributaries Floodplain Mapping Project – Select Review and Evaluation (“Attachment A”) are hereby incorporated in and made part of this agreement.
140
141
October 27, 2016
Brian Heaston
Project Engineer
City of Bozeman Engineering Division
bheaston@bozeman.net
RE: Bozeman Creek and Tributaries Floodplain Mapping Project – Select Review and Evaluation – Attachment A of PSA Amendment for Appeal Submittal
Dear Brian:
Attached is our proposed scope of work and budget for an appeal submittal for the Bozeman
Creek and Tributaries Floodplain Mapping Project and to evaluate the use of Mill Ditch as a
flood bypass channel to relieve flooding along Bozeman Creek. The proposed appeal submittal
will incorporate a combined 1D/2D or 2D hydraulic modeling approach for the downtown area
as well as the incorporation of the Bond Street Bridge into the 1D portion of the model.
The attached Exhibit A is our proposed scope of work and fees to complete the work. A table
(Exhibit B) showing a breakdown of the labor and expenses is also attached. Draft scoping
guidance provided by FEMA is also attached. Please give me a call if you have any questions.
Sincerely, Allied Engineering Services, Inc.
Paul Sanford, PE
Principal Civil Engineer
enc: Exhibit A – Scope of Work Exhibit B – Itemized Budget Draft scoping guidance provided by FEMA
MT-2 (LOMR) Forms
P:\2016\16-062 COB Floodplain Evaluation\01 Project Management\Proposals\Appeal\CoverLetter.doc
142
Attachment A - Exhibit A. Allied Engineering Services, Inc.
October 27, 2016 Page 1
APPEAL TO FEMA FOR BOZEMAN CREEK AND
TRIBUTARIES FLOODPLAIN MAPPING PROJECT
WORK SCOPE, BUDGET AND SCHEDULE
BACKGROUND
The Bozeman Creek and Tributaries Floodplain Mapping Project is being completed by Michael Baker
International for the Federal Emergency Management Agency (FEMA) and is currently undergoing review and evaluation by the City of Bozeman prior to implementation. The Bozeman Creek and
Tributaries project aims to update floodplain mapping for the area using one-dimensional hydraulic
modeling with the Army Corps of Engineer’s HEC-RAS computer program and updated elevation data. Large scale floodplain mapping was last completed for the Bozeman area in 1988 with a digital conversion of the data occurring in 2011.
In July 2016 Allied Engineering Services, Inc. (AESI) completed a Floodplain Evaluation report for the
City of Bozeman which provided select review and evaluation of the Bozeman Creek and Tributaries Floodplain Mapping Project. The work included the following major tasks:
1. General Model Review for Bozeman Creek;
2. Mill Ditch Diversion Evaluation. Evaluate effect of increasing flow to Mill Ditch;
3. Creekside Park Evaluation. Evaluate accuracy of model at Creekside Park and evaluate floodplain impacts for potential stream enhancement at the site;
4. Bond Street Bridge Evaluation. Complete a survey of Bond Street Bridge, revise the hydraulic
model to incorporate the bridge, and evaluate the bridge’s effect on floodplain elevations and inundation extents; and
5. Evaluate incorporating the two-dimensional modeling capabilities of HEC-RAS into the section
of Bozeman Creek from Olive Street to Lamme Street.
The scope of work described herein further expands the floodplain evaluation and modeling for items #2, #4, and #5 listed above. Specifically, the scope of work includes development of an appeal to incorporate
1D/2D or 2D modeling in the downtown area and to update the preliminary 1D model to include the
Bond Street Bridge. The scope of work also includes evaluation of the Mill Ditch as a flood bypass channel.
The objectives of this project include:
1. Develop a 1D/2D or 2D hydraulic model of the downtown area and incorporate into the
preliminary FIS model and mapping;
2. Incorporate the Bond Street Bridge into the preliminary FIS model and mapping;
3. Develop an appeal package to submit to FEMA; and
4. Evaluate the Mill Ditch as a flood bypass channel such that the flow remaining in Bozeman Creek downstream of the Mill Ditch split flow results in bankfull flow or less in Bozeman Creek.
The project goals are to include the 1D/2D (or 2D) model of the downtown area and the Bond Street
Bridge in the final Flood Insurance Study for the Bozeman Creek and Tributaries Floodplain Mapping
Project and to evaluate the use of the Mill Ditch as a flood bypass channel to relieve flooding along Bozeman Creek in the downtown area.
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Attachment A - Exhibit A. Allied Engineering Services, Inc.
October 27, 2016 Page 2
WORK SCOPE
1 Project Management
Internal Project Management
Manage the project, AESI staff, and sub-consultant.
Administration
Prepare invoices. Provide project setup. Assist with preparation of deliverables.
Communication with Stakeholders
Communicate with client, FEMA, DNRC, and other stakeholders.
Conference Calls
Project Manager and Hydraulic Engineer attend up to two conference calls with stakeholders.
2 Data Collection
Site Visit
Project team performs a site visit to evaluate the existing conditions in the downtown model reach. Document the observed field conditions with notes and ground photographs.
Survey to Refine Lateral Weirs and Flow Splits
Perform survey to establish detailed location and profile of proposed lateral weir flow splits.
Obtain Record Drawings & Incorporate New Town Pump Culvert into Mill Ditch Diversion Model
Obtain record drawings (and any relevant floodplain development permit application information) from
City for the recently installed culvert that conveys Mill Ditch under the Town Pump site. Incorporate culvert into Mill Ditch Diversion hydraulic model.
3 Floodplain Modeling
3.1 Incorporate 1D / 2D or 2D Model in Downtown Area into Preliminary FIS
Develop Layout for Revised Hydraulic Analysis
Work with stakeholders to develop a proposed schematic layout for the 1D/2D or 2D hydraulic model.
Summarize proposed layout and methodologies in a memorandum and provide to FEMA for
review/approval. The memorandum will discuss proposed methodologies including but not limited to:
selection of a 1D/2D or 2D model; split flows; lateral weirs; Manning’s n; floodway determination; hydraulic structures; and annotation of FIRM, Flood Profiles, and FIS Report Tables.
Develop Hydraulic Model
Revise the preliminary FIS hydraulic model to incorporate a 1D/2D or 2D hydraulic model in the downtown area. Preliminary analysis by AESI used a 1D/2D model setup, but a methodology recently
uncovered for modeling long culverts (like those that exist downtown) in a purely 2D environment will be
evaluated. Discussions with FEMA will need to take place regarding the acceptance of any methodologies employed. If a 1D/2D model is pursued, the preliminary model will need to be refined
and updated. Levee stations will need to be better defined and some overtopping culvert/bridge areas
need revision to better mimic existing conditions. Additionally, general model parameters will need to be
refined based on sensitivity simulation trials.
Provide the hydraulic model to stakeholders for review prior to developing the floodway model (below).
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Attachment A - Exhibit A. Allied Engineering Services, Inc.
October 27, 2016 Page 3
Develop Floodway Model
Develop floodway boundaries within the 1D/2D hydraulic model or 2D model. A first cut evaluation will
utilize the encroachment stations in the preliminary FIS 1D model into the 2D model to verify that the
maximum allowable surcharge is not exceeded.
Limited guidance is offered by FEMA for floodway analysis in 2D models, but there are several options
available. One likely method is to check conveyance reductions and surcharges at established 1D cross-
sections extended into the 2D area. The model would still be run in a 1D/2D or 2D environment and
require an iterative approach with manually adjusted encroachments. An average water depth rise may be employed to prevent problems caused by one or two individual cells showing larger than allowed
surcharges. Any option pursued will need prior acceptance by FEMA. It is anticipated that inundation
results from the floodplain extents model will influence how to proceed with the floodway analysis. Split flows down streets may require separate floodways.
Close communication with Client and FEMA and several iterations are expected throughout the
development of the 1D/2D or 2D floodway model.
Develop Explanation for Superiority of Alternative Methodology
Develop text to demonstrate that the 1D/2D or 2D modeling approach results in more correct estimates of
flood hazard determinations in the downtown area.
Meeting with Stakeholders to Review Preliminary Model Results
Meet with stakeholders to review the preliminary model results (1D/2D (or 2D) and Bond Street Bridge).
Evaluate the benefits and risks with moving forward with an appeal. Develop a brief memorandum to summarize the meeting and any follow up correspondence.
Complete Revisions to Model
Based on the outcome of the stakeholder meeting, complete revisions to the hydraulic model.
3.2 Mill Ditch Diversion Flood Capacity Analysis (Bozeman Creek and Mill Ditch)
Develop 1D Hydraulic Model with Existing Geometry (Bozeman Creek at Bankfull; Mill Ditch
Takes Remainder)
Determine the 100-year flow split required at the Mill Ditch Diversion that results in approximately
bankfull flow along Bozeman Creek in the downtown area downstream of the split. Revise the
preliminary FIS hydraulic model to reflect the flow split.
Develop Inundation Exhibits for Existing Geometry Scenario
Develop inundation exhibits to show the effect of the increased flow split on the flooding extents along
Bozeman Creek and Mill Ditch for the existing geometry scenario.
Develop Rough Proposed Geometry to Increase Conveyance Capacity in the Mill Ditch
After evaluating the inundation exhibits for the increased flow slit and the existing geometry, evaluate
improvements necessary along Mill Ditch to handle the increased flow. Develop proposed geometry for the improvements.
Develop 1D Hydraulic Model with Proposed Mill Ditch Geometry
Create a proposed geometry hydraulic model to reflect improvements to the Mill Ditch corridor.
Develop Inundation Exhibits for Proposed Mill Ditch Geometry Scenario
Develop inundation exhibits to show the effect of the increased flow split on the flooding extents along
Bozeman Creek and Mill Ditch for the proposed geometry scenario.
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Attachment A - Exhibit A. Allied Engineering Services, Inc.
October 27, 2016 Page 4
Develop Draft Technical Memorandum
Develop a brief draft technical memorandum to document and summarize the Mill Ditch Flood Capacity
Analysis. The memorandum will include a copy of the hydraulic model and the inundation exhibits.
Develop Final Technical Memorandum
Following review by the Client, develop a final technical memorandum.
3.3 Incorporate Bond Street Bridge into Preliminary FIS
Refine 1D Hydraulic Model
Review and refine the portion of the preliminary AESI 1D hydraulic model containing the Bond Street
Bridge.
Develop Floodway Model
Develop a floodway model to incorporate the Bond Street Bridge.
4 Floodplain Mapping (1D/2D or 2D Downtown Area and Bond Street Bridge)
Revise Flood Zone Boundary and Regulatory Floodway Boundary Delineations
Develop revised flood zone boundaries to reflect the 1D/2D or 2D model addition and the addition of the
Bond Street Bridge.
Develop Annotated Copies of FIRM, Flood Profiles, and FIS Report Tables
Develop annotated copies of FIRM, flood profiles, and FIS report tables to reflect the addition of the
1D/2D or 2D model and the Bond Street Bridge. The approach to developing the annotated copies of the
FIRM, Flood Profiles, and FIS Report Tables for the 1D/2D or 2D section of the model will require
acceptance from FEMA. For a 2D model, a set of cross sections will need to be employed at BFE contour lines and extended into the floodway fringe on both sides of the floodway. Cross-sections will also be
placed at changes in floodway width and at a spacing to represent stream characteristics. For a 2D model,
the profile will show the profile baseline and modeled hydraulic structures. For a 1D/2D model, the production of the annotated products will utilize the 1-D cross-sections applied to the stream channel.
Existing cross-sections developed for the main channel will be used to establish BFEs while new cross-
sections will be developed on an as-needed basis for split flows that require separate floodways.
Produce a Certified Topographic Work Map.
5 Develop Appeal Submittal Package
Develop Draft Summary Report
Develop a draft summary report to document and summarize the hydraulic model and mapping developed
for the appeal.
Develop Draft Appeal Submittal Package
Develop a draft cover letter and materials for submittal to FEMA. The materials will include the
hydraulic model and floodplain mapping.
Develop Final Summary Report
Following review by the Client (and ideally FEMA/DNRC), develop a final summary report.
Develop Final Appeal Submittal Package
Following review by the Client (and ideally FEMA/DNRC); develop a final appeal submittal package.
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Attachment A - Exhibit A. Allied Engineering Services, Inc.
October 27, 2016 Page 5
6 Address FEMA Review Comments
This task provides an estimated scope and budget to address FEMA Review Comments. The task will be
completed on a time and materials basis for a not-to-exceed cost of $10,447. The not-to-exceed budget was estimated based on the assumed hours shown on Exhibit B. Work associated with this task may
include the following: communication with FEMA Reviewers; revisions to hydraulic model; revisions to
floodplain mapping; and development of a revised appeal submittal package.
Assumptions
1. Methodologies will require prior approval from FEMA;
2. The appeal will not modify hydrology;
3. The format of the model, maps, and report will follow the requirements laid out by FEMA for a
LOMR submittal (refer to attached MT-2 Forms 1, 2, and 3);
4. FEMA will update cHECk-RAS to run with HEC-RAS 5.0 or FEMA will grant a waiver from the
requirement to run cHECk-RAS; and
5. Regulatory floodway revision notification as shown in Section D.3 of the LOMR application MT-
2 form 2 will not be required.
Client Responsibilities
1. Provide plans (certified by a registered professional engineer) for the Bond Street Bridge;
2. Provide review fees if required; and
3. Facilitate communication and coordination with review agencies.
DELIVERABLES
The following deliverables will be submitted to the Client in completion of this scope of work.
Deliverables will be submitted in an electronic format except where hard copies are required by reviewing agencies.
1. Schematic layout for revised hydraulic analysis and methodologies memorandum;
2. Preliminary Hydraulic Model (which incorporates 1D/2D or 2D and Bond Street Bridge) for review by stakeholders;
3. Memorandum to Document Stakeholder Meeting Regarding the Preliminary Hydraulic Model
(1D/2D or 2D and Bond Street Bridge);
4. Draft Mill Ditch Diversion Flood Capacity Analysis Technical Memorandum;
5. Final Mill Ditch Diversion Flood Capacity Analysis Technical Memorandum;
6. Draft Summary Report and Appeal Submittal Package;
7. Final Summary Report and Appeal Submittal Package; and
8. Revised Appeal Submittal Package.
BUDGET
The estimated budget to undertake the scope of work is $86,674. A table (Exhibit B) showing a breakdown of the labor and expenses is attached.
Invoicing will be based on percent complete and will utilize the following two tasks: 1. Appeal; and 2.
147
Attachment A - Exhibit A. Allied Engineering Services, Inc.
October 27, 2016 Page 6
Mill Ditch Diversion Flood Capacity Analysis.
SCHEDULE
Assuming authorization to proceed is granted by November 9, 2016, the following preliminary schedule is estimated for completion of major project milestones:
1. Preliminary estimate of flow that would need to be diverted from Bozeman Creek to Mill Ditch to
result in bankfull flow along Bozeman Creek in the downtown area – November 9, 2016;
2. Layout for revised hydraulic analysis and proposed methods memorandum – December 2, 2016;
3. Preliminary hydraulic model for review by stakeholders – January 11, 2017;
4. Preliminary floodway model for review by stakeholders – February 10, 2017;
5. Memorandum to Document Stakeholder Meeting Regarding the Preliminary Hydraulic Model – March 3, 2017;
6. Draft Summary Report and Appeal Submittal Package – March 31, 2017;
7. Final Summary Report and Appeal Submittal Package – April 28, 2017;
8. Draft Mill Ditch Diversion Flood Capacity Analysis Technical Memorandum – May 19, 2017;
9. Revised Appeal Submittal Package – May 24, 2017; and
10. Final Mill Ditch Diversion Flood Capacity Analysis Technical Memorandum – June 16, 2017.
148
TASK NO.Principal Engineer/Project Manager, PE, CFMHydraulics Engineer - QC, PEHydraulics Senior Engineer - QC, PEHydraulic Engineer, PE, CFMLand Surveyor, LSAdministrationTOTAL HOURSTOTAL FEESTOTAL COSTTravel Other
1 PROJECT MANAGEMENT
Internal Project Management 10 10 $1,350 $1,350
Administration (Invoicing, Project Setup, Copies, etc.)4 4 $220 $50 $270
Communication with Stakeholders 8 8 16 $1,880 $1,880
Conference Calls 6 6 12 $1,410 $1,410
Subtotal Hours 24 0 0 14 0 4 42
Subtotal Costs $4,860 $0 $50 $4,910
2 DATA COLLECTION
Site Visit 2 2 4 $470 $10 $480
Survey to Refine Lateral Weirs and Flow Splits 4 2 6 $600 $10 $100 $710
Obtain Record Drawings & Incorporate New Town Pump Culvert Into Mill Ditch Diversion Model 4 4 $400 $400
Subtotal Hours 2001020 14
Subtotal Costs $1,470 $20 $100 $1,590
3 FLOODPLAIN MODELING
Task 3.1 - Incorporate 1D / 2D Model in Downtown Area to Preliminary FIS
Develop Layout for Revised Hydraulic Analysis 4 4 1 12 21 $2,533 $2,533
Develop Hydraulic Model 16 20 1 80 117 $13,097 $13,097
Develop Floodway Model 2 8 1 120 131 $13,599 $13,599
Develop Explanation for Superiority of Alternative Methodology 2 4 6 $668 $668
Meeting with Stakeholders to Review Preliminary Model Results 3 3 6 $705 $705
Complete Revisions to Model 2 2 40 44 $4,538 $4,538
Task 3.2 - Mill Ditch Diversion Flood Capacity Analysis (Bozeman Creek and Mill Ditch)
Develop 1D Hydraulic Model with Existing Geometry (Bozeman Cr. At Bankfull; Mill Ditch Takes Remainde 2 20 22 $2,270 $2,270
Develop Inundation Exhibits for Existing Geometry Scenario 6 6 $600 $600
Develop Rough Proposed Geometry to Increase Conveyance Capacity in the Mill Ditch 8 24 32 $3,480 $3,480
Develop 1D Hydraulic Model with Proposed Mill Ditch Geometry 4 24 28 $2,940 $2,940
Develop Inundation Exhibits for Proposed Mill Ditch Geometry Scenario 8 8 $800 $800
Develop Draft Technical Memorandum 4 8 12 $1,340 $1,340
Develop Final Technical Memorandum 4 8 12 $1,340 $1,340
Task 3.3 - Incorporate Bond Street Bridge to Preliminary FIS
Refine 1D Hydraulic Model 4 4 $400 $400
Develop Floodway Model 2 4 32 38 $4,006 $4,006
Subtotal Hours 51 40 3 393 0 0 487
Subtotal Costs $52,316 $0 $0 $52,316
4 FLOODPLAIN MAPPING (1D / 2D Downtown Area and Bond Street Bridge)
Revise Flood Zone Boundary and Regulatory Floodway Boundary Delineations 4 4 40 48 $5,076 $5,076
Develop Annotated Copies of FIRM, Flood Profiles, and FIS Report Tables 4 32 36 $3,736 $3,736
Subtotal Hours 4807200 84
Subtotal Costs $8,812 $0 $0 $8,812
5 DEVELOP APPEAL SUBMITTAL PACKAGE
Develop Draft Summary Report 4 2 1 32 39 $4,265 $4,265
Develop Draft Appeal Submittal Package 2 2 4 8 $938 $25 $963
Develop Final Summary Report 4 2 16 22 $2,408 $2,408
Develop Final Appeal Submittal Package 2 2 4 8 $938 $25 $963
Subtotal Hours 12 8 1 56 0 0 77
Subtotal Costs $8,549 $0 $50 $8,599
6 ADDRESS FEMA REVIEW COMMENTS
Communicate with FEMA Reviewers 2 4 6 $670 $670
Revisions to Hydraulic Modeling (Tasks 3.1 and 3.3) 4 4 40 48 $5,076 $5,076
Revisions to Floodplain Mapping 2 2 20 24 $2,538 $2,538
Develop Revised Appeal Submittal Package 2 2 16 20 $2,138 $25 $2,163
Subtotal Hours 10 8 0 80 0 0 98
Subtotal Costs $10,422 $0 $25 $10,447
TOTAL HOURS 802
TOTAL COSTS $86,429 $20 $225 $86,674
$39,300 $0
ATTACHMENT A - EXHIBIT B - ITEMIZED BUDGET
October 27, 2016
$257 $100$134$135
$200 $0
APPEAL TO FEMA for BOZEMAN CREEK and TRIBUTARIES FLOODPLAIN MAPPING PROJECT
2
$0
$0
4
$0
HOURS AND FEES
$0
TASK DESCRIPTION INDIRECT COSTS$0
$100
$220
$55
$3,240 $0 $1,400
$6,885 $5,360 $771
$1,072 $0 $7,200
$5,600$257$1,620 $1,072
103 64 4
$540
$62,500 $220$13,905 $8,576 $1,028 $200
$270 $0 $0 $1,000
625
$0
$0
$1,350 $1,072 $0 $8,000 $0 $0
149
Compass PTS JV
a JV led by AECOM and CDM Smith
3101 Wilson Boulevard, Suite 900
Alexandria, VA 22201
Memorandum
To:
From:
Date:
Subject: City of Bozeman 1D/2D Appeal
1. Introduction
At the request of FEMA Region VIII, Compass has provided recommendations in preparation for
responding to a potential appeal from the City of Bozeman, Gallatin County, Montana. The City
will be conducting a high-level analysis of the 2D modeling using the latest version of HEC-RAS that
includes a combined 1D/2D modeling approach. The City has indicated that a combined 1D/2D
modeling method is superior to the more simplistic 1D approach in the complex urban
environment and that it is in the best interest of the floodplain program. Downtown Bozeman is a
good example of where a combined 1D/2D modeling approach may better reflect flood behavior
and risk.
2. Project site
The project site is located in the City of Bozeman, Gallatin County, Montana: 45°41'7.11"N + 111°
4'10.39"W (click hyperlink to view in Google Maps). The study area is shown in Figure 1.
Figure 1 – Bozeman HEC-RAS 1D model geometry
150
3. Submission of Appeals and Comments on Preliminary FIRMs
When the Federal Emergency Management Agency (FEMA) releases the preliminary Flood
Insurance Rate Maps (FIRMs) and Flood Insurance Study (FIS) report for Gallatin County showing
updated flood hazard data for the communities, local officials and residents have the opportunity
to identify concerns before the FIRMs and FIS report are adopted by the community and become
the basis of floodplain management, development, and flood insurance requirements. Feedback
can be provided any time after the release of the preliminary FIRMs until the end of a statutory
90-day appeal period. Each submittal received is categorized as an appeal or comment based on
the nature of the concern, the type of information provided to support the concern, and when it
was received. If warranted, the preliminary FIRM and/or FIS report will be updated before it is
finalized based on the feedback provided.
WHAT IS THE APPEALS PROCESS AND HOW DOES IT WORK?
The appeals process is part of the regulatory mapping process outlined in Title 44, Chapter I, Part
67 of the Code of Federal Regulations. (Click hyperlink to view FEMA Website) Whenever FEMA
issues preliminary FIRMs that involve changes to flood hazard information, a statutory 90-day
appeal period is required. FEMA starts the appeals process by:
• Publishing a notice in the Federal Register (Click hyperlink to view FEMA Website);
• Notifying the affected communities by letter of the start of the appeal period; and
• Publishing a news release twice in a prominent local newspaper.
During the appeal period, anyone can submit information (first reviewed by their local
officials) that shows the proposed flood hazards or other information on the preliminary FIRM or
in the FIS report are not correct. Local officials then provide this information to FEMA for review.
If needed, the preliminary FIRM will be updated before it is finalized.
WHAT IS CONSIDERED AN APPEAL?
To be considered an appeal, a submittal must:
• Include data that shows the proposed flood hazard information (e.g. new or modified
Special Flood Hazard Area zones or boundaries, Base Flood Elevations, base flood
depths, and/or floodway boundaries) is scientifically or technically incorrect;
• Include the revised data for the FIRM and/or FIS report (e.g. boundaries of revised
floodplains); and
• Be received during the statutory 90-day appeal period.
The designation of a submittal as an appeal provides certain appellant rights, including the
opportunity for the affected community to have data reviewed by a Scientific Resolution Panel
(SRP).
HOW WILL THE APPEAL BE EVALUATED, AGAINST WHAT CRITERIA, AND HOW WILL A
DETERMINATION BE MADE IF THE APPEAL IS VALID?
The process to evaluate Appeals and Comments is outlined in “Guidance for Flood Risk Analysis
and Mapping” Appeal and Comment Processing (May 2016) (click hyperlink to view FEMA
Website). Specifically, this document provides guidance on appeal and comment processing
procedures that occur during the Post-Preliminary Processing (PPP) phase of a Flood Risk Project
or Physical Map Revision (PMR), or following a Letter of Map Revision (LOMR) issuance, as related
151
to Title 44, Chapter 1, Code of Federal Regulations Part 67 and 42 U.S Code § 4104(a)-(g) for flood
hazard determinations.
The appeal will be valid if all the applicable requirements for Part 67 are met. Additional detail on
the criteria for appealing proposed changes in flood hazard information on FIRMs may be found in
FEMA’s “Criteria for Appeals of Flood Insurance Rate Maps (November 30, 2011)” (Click hyperlink
to view FEMA Website).
“The sole basis of appeal is the possession of knowledge or information indicating that the flood
hazard determinations proposed by FEMA are scientifically or technically incorrect. Since scientific
and technical correctness is often a matter of degree rather than absolute (except where
mathematical or measurement error or changed physical conditions can be demonstrated),
appellants are required to demonstrate that alternative methods or applications result in more
correct estimates of flood hazard determinations, thus demonstrating that FEMA's estimates are
incorrect.”
If the appeal is valid FEMA will proceed with the revision to the appeal area as described on the
workflow in Figure 2.
Figure 2 – Appeal and Comment Resolution Overview
WHAT DATA WOULD BE NEEDED FOR A VALID APPEAL?
The understanding is that the City’s contractor will be using HEC-RAS 5.0 that includes the 1D/2D
combined modeling and it is an accepted model by FEMA. Below are some of the applicable
FEMA Standards and Guidance that apply for data submittal to support an appeal.
• General Hydrologic Considerations for 2D models can be found in FEMA’s “General
Hydrologic Considerations (May 2016)” Section 4.4.3 Two-Dimensional Models (Click
hyperlink to view FEMA Website).
152
• FEMA Standards for Flood Risk Analysis and Mapping can be found in FEMA’s “FEMA
POLICY Standards for Flood Risk Analysis and Mapping FEMA Policy #FP 204-078-1
(Rev 5)” (Click hyperlink to view FEMA Website). Related Existing Standards for
Engineering, PMRs, H&H Analyses, 2D Models, Floodway, Flood Profiles, and tie-in are
shown in Appendix A.
• In the case of a two-dimensional model, floodway boundaries are generally developed
through trial and error; applying engineering judgment to delineate the boundary
needs to be defined.
• There are no guidance or quality assurance protocols for the review of floodway
boundaries derived from two-dimensional model results. At this point per Standard
73, pre-approval is required if they want to use anything other than 1D steady-state.
• A general recommendation when using unsteady HEC-RAS 5.0 is to do the multi-
profile model in unsteady, then get the peak flows from that and plug them into a
steady state run for the floodway.
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FEMA Form 086-0-27, (2/2011) Previously FEMA Form 81-89 MT-2 Form 1 Page 1 of 3
U.S. DEPARTMENT OF HOMELAND SECURITY FEDERAL EMERGENCY MANAGEMENT AGENCY OVERVIEW & CONCURRENCE FORM
O.M.B No. 1660-0016 Expires February 28, 2014
PAPERWORK BURDEN DISCLOSURE NOTICE
Public reporting burden for this form is estimated to average 1 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing, reviewing, and submitting the form. You are not required to respond to this collection of information unless it displays a valid OMB control number. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Department of Homeland Security, Federal Emergency Management Agency, 1800 South Bell Street, Arlington, VA 20958-3005, Paperwork Reduction Project (1660-0016). Submission of the form is required to obtain or retain benefits under the National Flood Insurance Program. Please do not send your completed survey to the above address.
PRIVACY ACT STATEMENT
AUTHORITY: The National Flood Insurance Act of 1968, Public Law 90-448, as amended by the Flood Disaster Protection Act of 1973, Public Law 93-234.
PRINCIPAL PURPOSE(S): This information is being collected for the purpose of determining an applicant's eligibility to request changes to National Flood Insurance Program (NFIP) Flood Insurance Rate Maps (FIRM).
ROUTINE USE(S): The information on this form may be disclosed as generally permitted under 5 U.S.C § 552a(b) of the Privacy Act of 1974, as amended. This includes using this information as necessary and authorized by the routine uses published in DHS/FEMA/NFIP/LOMA-1 National Flood Insurance Program (NFIP); Letter of Map Amendment (LOMA) February 15, 2006, 71 FR 7990.
DISCLOSURE: The disclosure of information on this form is voluntary; however, failure to provide the information requested may delay or prevent FEMA from processing a determination regarding a requested change to a (NFIP) Flood Insurance Rate Maps (FIRM).
A. REQUESTED RESPONSE FROM DHS-FEMA
This request is for a (check one):
CLOMR: A letter from DHS-FEMA commenting on whether a proposed project, if built as proposed, would justify a map revision, or proposed hydrology changes (See 44 CFR Ch. 1, Parts 60, 65 & 72). LOMR: A letter from DHS-FEMA officially revising the current NFIP map to show the changes to floodplains, regulatory floodway or flood
elevations. (See 44 CFR Ch. 1, Parts 60, 65 & 72)
B. OVERVIEW
1. The NFIP map panel(s) affected for all impacted communities is (are):
Community No. Community Name State Map No. Panel No. Effective Date
Example: 480301 480287 City of Katy Harris County TX TX 48473C 48201C 0005D 0220G 02/08/83 09/28/90
2. a. Flooding Source: b. Types of Flooding: Riverine Coastal Shallow Flooding (e.g., Zones AO and AH) Alluvial fan Lakes Other (Attach Description)
3. Project Name/Identifier: 4. FEMA zone designations affected: (choices: A, AH, AO, A1-A30, A99, AE, AR, V, V1-V30, VE, B, C, D, X) 5. Basis for Request and Type of Revision: a. The basis for this revision request is (check all that apply) Physical Change Improved Methodology/Data Regulatory Floodway Revision Base Map Changes
Coastal Analysis Hydraulic Analysis Hydrologic Analysis Corrections Weir-Dam Changes Levee Certification Alluvial Fan Analysis Natural Changes New Topographic Data Other (Attach Description) Note: A photograph and narrative description of the area of concern is not required, but is very helpful during review.
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FEMA Form 086-0-27, (2/2011) Previously FEMA Form 81-89 MT-2 Form 1 Page 2 of 3
b. The area of revision encompasses the following structures (check all that apply) Structures: Channelization Levee/Floodwall Bridge/Culvert Dam Fill Other (Attach Description)
6. Documentation of ESA compliance is submitted (required to initiate CLOMR review). Please refer to the instructions for more information.
C. REVIEW FEE
Has the review fee for the appropriate request category been included? Yes Fee amount: $ No, Attach Explanation Please see the DHS-FEMA Web site at http://www.fema.gov/plan/prevent/fhm/frm_fees.shtm for Fee Amounts and Exemptions.
D. SIGNATURE
All documents submitted in support of this request are correct to the best of my knowledge. I understand that any false statement may be punishable by
fine or imprisonment under Title 18 of the United States Code, Section 1001.
Name: Company:
Mailing Address:
Daytime Telephone No.: Fax No.:
E-Mail Address:
Signature of Requester (required): Date:
As the community official responsible for floodplain management, I hereby acknowledge that we have received and reviewed this Letter of Map Revision (LOMR) or conditional LOMR request. Based upon the community's review, we find the completed or proposed project meets or is designed to meet all of the community floodplain management requirements, including the requirements for when fill is placed in the regulatory floodway, and that all necessary Federal, State, and local permits have been, or in the case of a conditional LOMR, will be obtained. For Conditional LOMR requests, the applicant has documented Endangered Species Act (ESA) compliance to FEMA prior to FEMA’s review of the Conditional LOMR application. For LOMR requests, I acknowledge that compliance with Sections 9 and 10 of the ESA has been achieved independently of FEMA’s process. For actions authorized, funded, or being carried out by Federal or State agencies, documentation from the agency showing its compliance with Section 7(a)(2) of the ESA will be submitted. In addition, we have determined that the land and any existing or proposed structures to be removed from the SFHA are or will be reasonably safe from flooding as defined in 44CFR 65.2(c), and that we have available upon request by FEMA, all analyses and documentation used to make this determination.
Community Official’s Name and Title: Community Name:
Mailing Address:
Daytime Telephone No.: Fax No.:
E-Mail Address:
Community Official’s Signature (required): Date:
CERTIFICATION BY REGISTERED PROFESSIONAL ENGINEER AND/OR LAND SURVEYOR
This certification is to be signed and sealed by a licensed land surveyor, registered professional engineer, or architect authorized by law to certify elevation information data, hydrologic and hydraulic analysis, and any other supporting information as per NFIP regulations paragraph 65.2(b) and as described in the MT-2 Forms Instructions. All documents submitted in support of this request are correct to the best of my knowledge. I understand that
any false statement may be punishable by fine or imprisonment under Title 18 of the United States Code, Section 1001.
Certifier’s Name: License No.: Expiration Date:
Company Name: Telephone No.: Fax No.:
Signature: Date: E-Mail Address:
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FEMA Form 086-0-27, (2/2011) Previously FEMA Form 81-89 MT-2 Form 1 Page 3 of 3
Ensure the forms that are appropriate to your revision request are included in your submittal. Form Name and (Number) Required if …
Riverine Hydrology and Hydraulics Form (Form 2) New or revised discharges or water-surface elevations
Riverine Structures Form (Form 3) Channel is modified, addition/revision of bridge/culverts, addition/revision of levee/floodwall, addition/revision of dam Coastal Analysis Form (Form 4) New or revised coastal elevations
Coastal Structures Form (Form 5) Addition/revision of coastal structure Alluvial Fan Flooding Form (Form 6) Flood control measures on alluvial fans
Seal (Optional)
156
FEMA Form 086-0-27A, (2/2011) Previously FEMA Form 81-89 MT-2 Form 2 Page 1 of 3
U.S. DEPARTMENT OF HOMELAND SECURITY FEDERAL EMERGENCY MANAGEMENT AGENCY RIVERINE HYDROLOGY & HYDRAULICS FORM
O.M.B No. 1660-0016 Expires February 28, 2014
PAPERWORK BURDEN DISCLOSURE NOTICE
Public reporting burden for this form is estimated to average 3.5 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing, reviewing, and submitting the form. You are not required to respond to this collection of information unless a valid OMB control number appears in the upper right corner of this form. Send comments
regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Department of Homeland Security, Federal Emergency Management Agency, 1800 South Bell Street, Arlington VA 20958-3005, Paperwork Reduction Project (1660-0016). Submission of the form is required to obtain or retain benefits under the National Flood Insurance Program. Please do not send your completed survey to the above address.
PRIVACY ACT STATEMENT
AUTHORITY: The National Flood Insurance Act of 1968, Public Law 90-448, as amended by the Flood Disaster Protection Act of 1973, Public Law 93-234.
PRINCIPAL PURPOSE(S): This information is being collected for the purpose of determining an applicant's eligibility to request changes to National Flood Insurance Program (NFIP) Flood Insurance Rate Maps (FIRM).
ROUTINE USE(S): The information on this form may be disclosed as generally permitted under 5 U.S.C § 552a(b) of the Privacy Act of 1974, as amended. This includes using this information as necessary and authorized by the routine uses published in DHS/FEMA/NFIP/LOMA-1 National Flood Insurance Program (NFIP); Letter of Map Amendment (LOMA) February 15, 2006, 71 FR 7990.
DISCLOSURE: The disclosure of information on this form is voluntary; however, failure to provide the information requested may delay or prevent FEMA from processing a determination regarding a requested change to a NFIP Flood Insurance Rate Maps (FIRM).
Flooding Source:
Note: Fill out one form for each flooding source studied
A. HYDROLOGY
1. Reason for New Hydrologic Analysis (check all that apply)
Not revised (skip to section B) No existing analysis Improved data
Alternative methodology Proposed Conditions (CLOMR) Changed physical condition of watershed
2. Comparison of Representative 1%-Annual-Chance Discharges
Location Drainage Area (Sq. Mi.) Effective/FIS (cfs) Revised (cfs)
3. Methodology for New Hydrologic Analysis (check all that apply) Statistical Analysis of Gage Records Precipitation/Runoff Model Specify Model:
Regional Regression Equations Other (please attach description) Please enclose all relevant models in digital format, maps, computations (including computation of parameters), and documentation to support the new analysis. 4. Review/Approval of Analysis If your community requires a regional, state, or federal agency to review the hydrologic analysis, please attach evidence of approval/review. 5. Impacts of Sediment Transport on Hydrology Is the hydrology for the revised flooding source(s) affected by sediment transport? Yes No If yes, then fill out Section F (Sediment Transport) of Form 3. If No, then attach your explanation..
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FEMA Form 086-0-27A, (2/2011) Previously FEMA Form 81-89 MT-2 Form 2 Page 2 of 3
B. HYDRAULICS
1. Reach to be Revised
Description Cross Section Water-Surface Elevations (ft.)
Effective Proposed/Revised
Downstream Limit*
Upstream Limit*
*Proposed/Revised elevations must tie-into the Effective elevations within 0.5 foot at the downstream and upstream limits of revision.
2. Hydraulic Method/Model Used:
3. Pre-Submittal Review of Hydraulic Models*
DHS-FEMA has developed two review programs, CHECK-2 and CHECK-RAS, to aid in the review of HEC-2 and HEC-RAS hydraulic models, respectively. We recommend that you review your HEC-2 and HEC-RAS models with CHECK-2 and CHECK-RAS. 4.
Models Submitted Natural Run Floodway Run Datum
Duplicate Effective Model* File Name: ______________ Plan Name: ______________ File Name: ______________ Plan Name: ______________ __________
Corrected Effective Model* File Name: ______________ Plan Name: ______________ File Name: ______________ Plan Name: ______________ __________
Existing or Pre-Project Conditions Model File Name: ______________ Plan Name: ______________ File Name: ______________ Plan Name: ______________ __________
Revised or Post-Project Conditions Model File Name: ______________ Plan Name: ______________ File Name: ______________ Plan Name: ______________ __________
Other - (attach description) File Name: ______________ Plan Name: ______________ File Name: ______________ Plan Name: ______________ __________
* For details, refer to the corresponding section of the instructions. Digital Models Submitted? (Required)
C. MAPPING REQUIREMENTS
A certified topographic work map must be submitted showing the following information (where applicable): the boundaries of the effective, existing, and proposed conditions 1%-annual-chance floodplain (for approximate Zone A revisions) or the boundaries of the 1%- and 0.2%-annual-chance floodplains and regulatory floodway (for detailed Zone AE, AO, and AH revisions); location and alignment of all cross sections with stationing control
indicated; stream, road, and other alignments (e.g., dams, levees, etc.); current community easements and boundaries; boundaries of the requester's property; certification of a registered professional engineer registered in the subject State; location and description of reference marks; and the referenced vertical datum (NGVD, NAVD, etc.). Digital Mapping (GIS/CADD) Data Submitted (preferred) Topographic Information:
Source: Date:
Accuracy:
Note that the boundaries of the existing or proposed conditions floodplains and regulatory floodway to be shown on the revised FIRM and/or FBFM must tie-in with the effective floodplain and regulatory floodway boundaries. Please attach a copy of the effective FIRM and/or FBFM, at the same scale as the original, annotated to show the boundaries of the revised 1%-and 0.2%-annual-chance floodplains and regulatory floodway that tie-in with the boundaries of the effective 1%-and 0.2%-annual-chance floodplain and regulatory floodway at the upstream and downstream limits of the area on revision.
Annotated FIRM and/or FBFM (Required)
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FEMA Form 086-0-27A, (2/2011) Previously FEMA Form 81-89 MT-2 Form 2 Page 3 of 3
D. COMMON REGULATORY REQUIREMENTS*
1. For LOMR/CLOMR requests, do Base Flood Elevations (BFEs) increase? Yes No a. For CLOMR requests, if either of the following is true, please submit evidence of compliance with Section 65.12 of the NFIP regulations:
• The proposed project encroaches upon a regulatory floodway and would result in increases above 0.00 foot compared to pre-project conditions.
• The proposed project encroaches upon a SFHA with or without BFEs established and would result in increases above 1.00 foot compared to pre-project conditions.
b. Does this LOMR request cause increase in the BFE and/or SFHA compared with the effective BFEs and/or SFHA? Yes No
If Yes, please attach proof of property owner notification and acceptance (if available). Elements of and examples of property owner notifications can be found in the MT-2 Form 2 Instructions. 2. Does the request involve the placement or proposed placement of fill? Yes No
If Yes, the community must be able to certify that the area to be removed from the special flood hazard area, to include any structures or proposed structures, meets all of the standards of the local floodplain ordinances, and is reasonably safe from flooding in accordance with the NFIP regulations set forth at 44 CFR 60.3(A)(3), 65.5(a)(4), and 65.6(a)(14). Please see the MT-2 instructions for more information. 3. For LOMR requests, is the regulatory floodway being revised? Yes No
If Yes, attach evidence of regulatory floodway revision notification. As per Paragraph 65.7(b)(1) of the NFIP Regulations, notification is required for requests involving revisions to the regulatory floodway. (Not required for revisions to approximate 1%-annual-chance floodplains [studied Zone A designation] unless a regulatory floodway is being established. Elements and examples of regulatory floodway revision notification can be found in the MT-2 Form 2 Instructions.)
4. For CLOMR requests, please submit documentation to FEMA and the community to show that you have complied with Sections 9 and 10 of the Endangered Species Act (ESA).
For actions authorized, funded, or being carried out by Federal or State agencies, please submit documentation from the agency showing its compliance with Section 7(a)(2) of the ESA. Please see the MT-2 instructions for more detail.
* Not inclusive of all applicable regulatory requirements. For details, see 44 CFR parts 60 and 65.
159
FEMA Form 086-0-27B, (2/2011) Previously FEMA Form 81-89B MT-2 Form 3 Page 1 of 11
DEPARTMENT OF HOMELAND SECURITY FEDERAL EMERGENCY MANAGEMENT AGENCY RIVERINE STRUCTURES FORM
O.M.B. NO. 1660-0016 Expires February 28, 2014
PAPERWORK BURDEN DISCLOSURE NOTICE
Public reporting burden for this form is estimated to average 7 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing, reviewing, and submitting the form. You are not required to respond to this collection of information unless a valid OMB control number appears in the upper right corner of this form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Department of Homeland Security, Federal Emergency Management Agency, 1800 South Bell Street, Arlington, VA 20598-3005,
Paperwork Reduction Project (1660-0016). Submission of the form is required to obtain or retain benefits under the National Flood Insurance Program. Please do not send your completed survey to the above address.
PRIVACY ACT STATEMENT
AUTHORITY: The National Flood Insurance Act of 1968, Public Law 90-448, as amended by the Flood Disaster Protection Act of 1973, Public Law
93-234.
PRINCIPAL PURPOSE(S): This information is being collected for the purpose of determining an applicant's eligibility to request changes to National Flood Insurance Program (NFIP) Flood Insurance Rate Maps (FIRM).
ROUTINE USE(S): The information on this form may be disclosed as generally permitted under 5 U.S.C § 552a(b) of the Privacy Act of 1974, as amended. This includes using this information as necessary and authorized by the routine uses published in DHS/FEMA/NFIP/LOMA-1 National Flood Insurance Program; Letter of Map Amendment (LOMA) February 15, 2006, 71 FR 7990.
DISCLOSURE: The disclosure of information on this form is voluntary; however, failure to provide the information requested may delay or prevent FEMA from processing a determination regarding a requested change to a NFIP Flood Insurance Rate Maps (FIRM).
Flooding Source: Note: Fill out one form for each flooding source studied.
A. GENERAL
Complete the appropriate section(s) for each Structure listed below: Channelization...............complete Section B Bridge/Culvert................complete Section C
Dam...............................complete Section D Levee/Floodwall.............complete Section E Sediment Transport........complete Section F (if required) Description Of Modeled Structure
1. Name of Structure: Type (check one): Channelization Bridge/Culvert Levee/Floodwall Dam
Location of Structure: Downstream Limit/Cross Section: Upstream Limit/Cross Section:
2. Name of Structure: Type (check one): Channelization Bridge/Culvert Levee/Floodwall Dam
Location of Structure: Downstream Limit/Cross Section: Upstream Limit/Cross Section:
3. Name of Structure: Type (check one) Channelization Bridge/Culvert Levee/Floodwall Dam
Location of Structure: Downstream Limit/Cross Section:
Upstream Limit/Cross Section:
NOTE: FOR MORE STRUCTURES, ATTACH ADDITIONAL PAGES AS NEEDED.
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FEMA Form 086-0-27B, (2/2011) Previously FEMA Form 81-89B MT-2 Form 3 Page 2 of 11
B. CHANNELIZATION
Flooding Source: Name of Structure:
1. Hydraulic Considerations The channel was designed to carry (cfs) and/or the -year flood.
The design elevation in the channel is based on (check one):
Subcritical flow Critical flow Supercritical flow Energy grade line
If there is the potential for a hydraulic jump at the following locations, check all that apply and attach an explanation of how the hydraulic jump is controlled without affecting the stability of the channel.
Inlet to channel Outlet of channel At Drop Structures At Transitions
Other locations (specify):
2. Channel Design Plans Attach the plans of the channelization certified by a registered professional engineer, as described in the instructions.
3. Accessory Structures The channelization includes (check one):
Levees [Attach Section E (Levee/Floodwall)] Drop structures Superelevated sections
Transitions in cross sectional geometry Debris basin/detention basin [Attach Section D (Dam/Basin)] Energy dissipator Weir Other (Describe): 4. Sediment Transport Considerations Are the hydraulics of the channel affected by sediment transport? Yes No
If yes, then fill out Section F (Sediment Transport) of Form 3. If No, then attach your explanation for why sediment transport was not considered.
C. BRIDGE/CULVERT Flooding Source: Name of Structure: 1. This revision reflects (check one):
Bridge/culvert not modeled in the FIS
Modified bridge/culvert previously modeled in the FIS
Revised analysis of bridge/culvert previously modeled in the FIS
2. Hydraulic model used to analyze the structure (e.g., HEC-2 with special bridge routine, WSPRO, HY8): If different than hydraulic analysis for the flooding source, justify why the hydraulic analysis used for the flooding source could not analyze
the structures. Attach justification. 3. Attach plans of the structures certified by a registered professional engineer. The plan detail and information should include the following (check the information that has been provided):
Dimensions (height, width, span, radius, length) Distances Between Cross Sections
Shape (culverts only) Erosion Protection
Material Low Chord Elevations – Upstream and Downstream
Beveling or Rounding Top of Road Elevations – Upstream and Downstream
Wing Wall Angle Structure Invert Elevations – Upstream and Downstream
Skew Angle Stream Invert Elevations – Upstream and Downstream
Cross-Section Locations
4. Sediment Transport Considerations Are the hydraulics of the structure affected by sediment transport? Yes No If Yes, then fill out Section F (Sediment Transport) of Form 3. If no, then attach an explanation.
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FEMA Form 086-0-27B, (2/2011) Previously FEMA Form 81-89B MT-2 Form 3 Page 3 of 11
D. DAM/BASIN
Flooding Source: Name of Structure: 1. This request is for (check one): Existing dam/basin New dam/basin Modification of existing dam/basin 2. The dam/basin was designed by (check one): Federal agency State agency Private organization Local government agency
Name of the agency or organization: 3. The Dam was permitted as (check one): Federal Dam State Dam
Provide the permit or identification number (ID) for the dam and the appropriate permitting agency or organization Permit or ID number __________________ Permitting Agency or Organization _____________________________ a. Local Government Dam Private Dam
Provided related drawings, specification and supporting design information. 4. Does the project involve revised hydrology? Yes No
If Yes, complete the Riverine Hydrology & Hydraulics Form (Form 2). Was the dam/basin designed using critical duration storm? (must account for the maximum volume of runoff)
Yes, provide supporting documentation with your completed Form 2. No, provide a written explanation and justification for not using the critical duration storm. 5. Does the submittal include debris/sediment yield analysis? Yes No
If Yes, then fill out Section F (Sediment Transport). If No, then attach your explanation for why debris/sediment analysis was not considered? 6. Does the Base Flood Elevation behind the dam/basin or downstream of the dam/basin change? Yes No
If Yes, complete the Riverine Hydrology & Hydraulics Form (Form 2) and complete the table below. Stillwater Elevation Behind the Dam/Basin FREQUENCY (% annual chance) FIS REVISED
10-year (10%)
50-year (2%)
100-year (1%)
500-year (0.2%)
Normal Pool Elevation
7. Please attach a copy of the formal Operation and Maintenance Plan
E. LEVEE/FLOODWALL
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FEMA Form 086-0-27B, (2/2011) Previously FEMA Form 81-89B MT-2 Form 3 Page 4 of 11
1. System Elements
a. This Levee/Floodwall analysis is based on (check one):
b. Levee elements and locations are (check one): earthen embankment, dike, berm, etc. Station to
structural floodwall Station to
Other (describe): Station to
c. Structural Type (check one): monolithic cast-in place reinforced concrete reinforced concrete masonry block sheet piling
Other (describe):
d. Has this levee/floodwall system been certified by a Federal agency to provide protection from the base flood?
Yes No If Yes, by which agency?
upgrading of an existing
levee/floodwall system
a newly constructed
levee/floodwall system
reanalysis of an existing
levee/floodwall system
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FEMA Form 086-0-27B, (2/2011) Previously FEMA Form 81-89B MT-2 Form 3 Page 5 of 11
e. Attach certified drawings containing the following information (indicate drawing sheet numbers): 1. Plan of the levee embankment and floodwall structures. Sheet Numbers:
2. A profile of the levee/floodwall system showing the Base Flood Elevation (BFE),
levee and/or wall crest and foundation, and closure locations for the total levee system. Sheet Numbers:
3. A profile of the BFE, closure opening outlet and inlet invert elevations, type and size
of opening, and kind of closure. Sheet Numbers:
4. A layout detail for the embankment protection measures. Sheet Numbers:
5. Location, layout, and size and shape of the levee embankment features, foundation treatment,
Floodwall structure, closure structures, and pump stations. Sheet Numbers:
2. Freeboard
a. The minimum freeboard provided above the BFE is:
Riverine 3.0 feet or more at the downstream end and throughout Yes No
3.5 feet or more at the upstream end Yes No
4.0 feet within 100 feet upstream of all structures and/or constrictions Yes No
Coastal
1.0 foot above the height of the one percent wave associated with the 1%-annual-chance stillwater surge elevation or maximum wave runup (whichever is greater). Yes No 2.0 feet above the 1%-annual-chance stillwater surge elevation Yes No
Please note, occasionally exceptions are made to the minimum freeboard requirement. If an exception is requested, attach documentation addressing Paragraph 65.10(b)(1)(ii) of the NFIP Regulations. If No is answered to any of the above, please attach an explanation. b. Is there an indication from historical records that ice-jamming can affect the BFE? Yes No
If Yes, provide ice-jam analysis profile and evidence that the minimum freeboard discussed above still exists. 3. Closures
a. Openings through the levee system (check one): exists does not exist If opening exists, list all closures:
Channel Station Left or Right Bank Opening Type Highest Elevation for Opening Invert Type of Closure Device
(Extend table on an added sheet as needed and reference) Note: Geotechnical and geologic data
In addition to the required detailed analysis reports, data obtained during field and laboratory investigations and used in the design analysis for the following system features should be submitted in a tabulated summary form. (Reference U.S. Army Corps of Engineers [USACE] EM-1110-2-1906 Form 2086.)
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FEMA Form 086-0-27B, (2/2011) Previously FEMA Form 81-89B MT-2 Form 3 Page 6 of 11
4. Embankment Protection a. The maximum levee slope land side is: b. The maximum levee slope flood side is: c. The range of velocities along the levee during the base flood is: (min.) to (max.) d. Embankment material is protected by (describe what kind): e. Riprap Design Parameters (check one): Velocity Tractive stress Attach references
Reach Sideslope Flow Depth
Velocity Curve or Straight
Stone Riprap Depth of Toedown D100 D50 Thickness
Sta to
Sta to
Sta to
Sta to
Sta to
Sta to
(Extend table on an added sheet as needed and reference each entry) f. Is a bedding/filter analysis and design attached? Yes No
g. Describe the analysis used for other kinds of protection used (include copies of the design analysis):
Attach engineering analysis to support construction plans.
5. Embankment And Foundation Stability
a. Identify locations and describe the basis for selection of critical location for analysis: Overall height: Sta.: , height ft. Limiting foundation soil strength:
Strength φ = degrees, c = psf Slope: SS = (h) to (v)
(Repeat as needed on an added sheet for additional locations) b. Specify the embankment stability analysis methodology used (e.g., circular arc, sliding block, infinite slope, etc.):
c. Summary of stability analysis results:
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FEMA Form 086-0-27B, (2/2011) Previously FEMA Form 81-89B MT-2 Form 3 Page 7 of 11
E. LEVEE/FLOODWALL (CONTINUED)
5. Embankment And Foundation Stability (continued)
Case Loading Conditions Critical Safety Factor Criteria (Min.)
I End of construction 1.3
II Sudden drawdown 1.0
III Critical flood stage 1.4
IV Steady seepage at flood stage 1.4
VI Earthquake (Case I) 1.0
(Reference: USACE EM-1110-2-1913 Table 6-1)
d. Was a seepage analysis for the embankment performed? Yes No
If Yes, describe methodology used: e. Was a seepage analysis for the foundation performed? Yes No f. Were uplift pressures at the embankment landside toe checked? Yes No
g. Were seepage exit gradients checked for piping potential? Yes No h. The duration of the base flood hydrograph against the embankment is hours.
Attach engineering analysis to support construction plans.
6. Floodwall And Foundation Stability
a. Describe analysis submittal based on Code (check one): UBC (1988) Other (specify): b. Stability analysis submitted provides for: Overturning Sliding If not, explain:
c. Loading included in the analyses were: Lateral earth @ PA = psf; Pp = psf Surcharge-Slope @ , surface psf Wind @ Pw = psf
Seepage (Uplift); Earthquake @ Peq = %g 1%-annual-chance significant wave height: ft.
1%-annual-chance significant wave period: sec. d. Summary of Stability Analysis Results: Factors of Safety. Itemize for each range in site layout dimension and loading condition limitation for each respective reach.
Loading Condition
Criteria (Min) Sta To Sta To
Overturn Sliding Overturn Sliding Overturn Sliding
Dead & Wind 1.5 1.5
Dead & Soil 1.5 1.5
Dead, Soil, Flood, & Impact 1.5 1.5
Dead, Soil, & Seismic 1.3 1.3
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FEMA Form 086-0-27B, (2/2011) Previously FEMA Form 81-89B MT-2 Form 3 Page 8 of 11
(Ref: FEMA 114 Sept 1986; USACE EM 1110-2-2502) Note: (Extend table on an added sheet as needed and reference)
E. LEVEE/FLOODWALL (CONTINUED)
6. Floodwall And Foundation Stability (continued) e. Foundation bearing strength for each soil type:
Bearing Pressure Sustained Load (psf) Short Term Load (psf)
Computed design maximum
Maximum allowable
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FEMA Form 086-0-27B, (2/2011) Previously FEMA Form 81-89B MT-2 Form 3 Page 9 of 11
f. Foundation scour protection is, is not provided. If provided, attach explanation and supporting documentation: Attach engineering analysis to support construction plans.
7. Settlement a. Has anticipated potential settlement been determined and incorporated into the specified construction elevations to maintain the established freeboard margin? Yes No b. The computed range of settlement is ft. to ft. c. Settlement of the levee crest is determined to be primarily from : Foundation consolidation Embankment compression Other (Describe):
d. Differential settlement of floodwalls has has not been accommodated in the structural design and construction. Attach engineering analysis to support construction plans.
8. Interior Drainage a. Specify size of each interior watershed:
Draining to pressure conduit: acres
Draining to ponding area: acres
b. Relationships Established
Ponding elevation vs. storage Yes No
Ponding elevation vs. gravity flow Yes No
Differential head vs. gravity flow Yes No
c. The river flow duration curve is enclosed: Yes No d. Specify the discharge capacity of the head pressure conduit: cfs e. Which flooding conditions were analyzed?
• Gravity flow (Interior Watershed) Yes No
• Common storm (River Watershed) Yes No
• Historical ponding probability Yes No
• Coastal wave overtopping Yes No
If No for any of the above, attach explanation.
e. Interior drainage has been analyzed based on joint probability of interior and exterior flooding and the capacities of pumping and outlet facilities to provide the established level of flood protection. Yes No If No, attach explanation. g. The rate of seepage through the levee system for the base flood is cfs
h. The length of levee system used to drive this seepage rate in item g: ft.
E. LEVEE/FLOODWALL (CONTINUED)
8. Interior Drainage (continued)
i. Will pumping plants be used for interior drainage? Yes No If Yes, include the number of pumping plants: For each pumping plant, list:
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FEMA Form 086-0-27B, (2/2011) Previously FEMA Form 81-89B MT-2 Form 3 Page 10 of 11
The number of pumps
Plant #1 Plant #2
The ponding storage capacity
The maximum pumping rate
The maximum pumping head
The pumping starting elevation
The pumping stopping elevation
Is the discharge facility protected?
Is there a flood warning plan?
How much time is available between warning and flooding?
Will the operation be automatic? Yes No
If the pumps are electric, are there backup power sources? Yes No (Reference: USACE EM-1110-2-3101, 3102, 3103, 3104, and 3105) Include a copy of supporting documentation of data and analysis. Provide a map showing the flooded area and maximum ponding elevations for all interior watersheds that result in flooding.
9. Other Design Criteria
a. The following items have been addressed as stated: Liquefaction is is not a problem
Hydrocompaction is is not a problem
Heave differential movement due to soils of high shrink/swell is is not a problem
b. For each of these problems, state the basic facts and corrective action taken:
Attach supporting documentation c. If the levee/floodwall is new or enlarged, will the structure adversely impact flood levels and/or flow velocities floodside of the structure? Yes No Attach supporting documentation
d. Sediment Transport Considerations: Was sediment transport considered? Yes No If Yes, then fill out Section F (Sediment Transport). If No, then attach your explanation for why sediment transport was not considered.
10. Operational Plan And Criteria a. Are the planned/installed works in full compliance with Part 65.10 of the NFIP Regulations? Yes No
b. Does the operation plan incorporate all the provisions for closure devices as required in Paragraph 65.10(c)(1) of the NFIP regulations?
Yes No
c. Does the operation plan incorporate all the provisions for interior drainage as required in Paragraph 65.10(c)(2) of the NFIP regulations?
Yes No If the answer is No to any of the above, please attach supporting documentation.
E. LEVEE/FLOODWALL (CONTINUED)
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FEMA Form 086-0-27B, (2/2011) Previously FEMA Form 81-89B MT-2 Form 3 Page 11 of 11
11. Maintenance Plan Please attach a copy of the fomal maintenance plan for the levee/floodwall
12. Operations and Maintenance Plan
Please attach a copy of the formal Operations and Maintenance Plan for the levee/floodwall.
CERTIFICATION OF THE LEVEE DOCUMENTION
This certification is to be signed and sealed by a licensed registered professional engineer authorized by law to certify elevation information data, hydrologic and hydraulic analysis, and any other supporting information as per NFIP regulations paragraph 65.10(e) and as described in the MT-2 Forms Instructions. All documents submitted in support of this request are correct to the best of my knowledge. I understand that any false statement may be punishable by fine or imprisonment under Title 18 of the United States Code, Section 1001.
Certifier’s Name: License No.: Expiration Date:
Company Name: Telephone No.: Fax No.:
Signature: Date: E-Mail Address:
F. SEDIMENT TRANSPORT
Flooding Source:
Name of Structure: If there is any indication from historical records that sediment transport (including scour and deposition) can affect the Base Flood Elevation (BFE); and/or based on the stream morphology, vegetative cover, development of the watershed and bank conditions, there is a potential for debris and sediment transport (including scour and deposition) to affect the BFEs, then provide the following information along with the supporting documentation: Sediment load associated with the base flood discharge: Volume acre-feet
Debris load associated with the base flood discharge: Volume acre-feet Sediment transport rate (percent concentration by volume) Method used to estimate sediment transport:
Most sediment transport formulas are intended for a range of hydraulic conditions and sediment sizes; attach a detailed explanation for using the selected method. Method used to estimate scour and/or deposition: Method used to revise hydraulic or hydrologic analysis (model) to account for sediment transport: Please note that bulked flows are used to evaluate the performance of a structure during the base flood; however, FEMA does not map BFEs based on bulked flows.
If a sediment analysis has not been performed, an explanation as to why sediment transport (including scour and deposition) will not affect the BFEs or structures must be provided.
170
November 17, 2016 City of Bozeman
Engineering Department
PO Box 1230
Bozeman MT 59771
**Delivered to Brian Heaston, City of Bozeman Engineering Department**
RE: BID Funding for Formal Appeal of FEMA’s Proposed Bozeman Creek Floodplain Map
City of Bozeman:
I am writing on behalf of the Downtown Business Improvement District (BID) Board to inform
you they have allocated Twenty Thousand dollars ($20,000.00) for the formal appeal of the
proposed Bozeman Creek FEMA floodplain map.
The BID Board agreed to make a $10,000 payment upon the execution of the consultant’s
contract and the second $10,000 payment upon the completion of the consultant’s contract.
The BID Board recognizes that the regulations stipulated by the proposed FEMA floodplain map would significantly impact a portion of downtown including the eastern section of the Main Street
Historic District. Not only does the expanded floodplain impact current downtown property
owners, but also has serious implications for future development and therefore the very vitality
of the downtown district.
I will coordinate with the Public Works and Finance Departments to make the pledged
contributions.
Respectfully submitted,
Chris Naumann, Executive Director
171
November 17, 2016 City of Bozeman
Engineering Department
PO Box 1230
Bozeman MT 59771
**Delivered to Brian Heaston, City of Bozeman Engineering Department**
RE: TIF Funding for Formal Appeal of FEMA’s Proposed Bozeman Creek Floodplain Map
City of Bozeman:
I am writing on behalf of the Downtown Tax Increment Finance (TIF) Board to inform you they
have allocated Forty-One Thousand Six-Hundred and Seventy-Four dollars ($41,674.00) for the
formal appeal of the proposed Bozeman Creek FEMA floodplain map.
The TIF Board recognizes that the regulations stipulated by the proposed FEMA floodplain map
would significantly impact a portion of downtown including the eastern section of the Main Street
Historic District. Not only does the expanded floodplain impact current downtown property
owners, but also has serious implications for future development and therefore the very vitality of the downtown district.
I will coordinate with the Public Works and Finance Departments to make the necessary budget
amendment and fiscal transfer at a time mutually agreed upon by all parties.
Respectfully submitted,
Chris Naumann, Executive Director
172