HomeMy WebLinkAboutPACKET Town Board Study Session 2019-06-11Tuesday, June 11, 2019
5:00 p.m. – 6:40 p.m.
Town Board Room
4:45 p.m. - Dinner
5:00 p.m. Downtown Estes Loop Quarterly Update.
(Project Technical Advisory Committee)
5:20 p.m. Regulatory Peak Discharge Forecasts for Floodplain
Management. (Director Muhonen)
6:00 p.m. Workforce Housing and Childcare Task Force Report.
(Assistant Town Administrator Machalek)
6:30 p.m. Trustee & Administrator Comments & Questions.
6:35 p.m. Future Study Session Agenda Items.
(Board Discussion)
6:40 p.m. Adjourn for Town Board Meeting.
Informal discussion among Trustees concerning agenda items or other Town matters may occur before this
meeting at approximately 4:30 p.m.
AGENDA
TOWN BOARD
STUDY SESSION
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PUBLIC WORKS Report
To: Honorable Mayor Jirsa
Board of Trustees
Through: Town Administrator Lancaster
From: Greg Muhonen, PE, Public Works Director
Project Technical Advisory Committee (TAC)
Date: June 11, 2019
RE: Quarterly Update on Downtown Estes Loop Project (DEL)
Objective:
Update the Town Board on the progress and activities that have taken place on the
Downtown Estes Loop Project (DEL) since the March 2019 Town Board Study Session.
Present Situation:
Right of Way: Offers for all seven of the full acquisitions have been made to
property owners. Purchase of three parcels is complete. The Transportation
Commission approved CDOT’s request for authorization to condemn the four
remaining parcels. Negotiations to purchase continue.
Consultant relocation agents have been meeting with the tenants and owners
who will be relocated to discuss specifics and the process of each relocation.
Design: updated wayfinding signage details are provided.
Hydraulics: The Project team continues work with CFLHD, CDOT, Town of Estes
Park and other regulatory agencies to refine the hydraulic analysis in
coordination with the CWCB’s Colorado Hazards Mitigation Program.
Schedule: The project schedule anticipates completion of the construction
documents in 2019. Right of way acquisitions are expected to extend into 2020.
Construction is expected to begin in the summer of 2021.
Scope Expansion: As directed by the Town Board at the May 14 meeting, we
hired AECOM to prepare an application for a federal BUILD grant that would fund
increased project scope to include the Riverside and Rockwell Bridges and
channel widening downstream to US36. The grant applicant is due July 19.
Proposal:
The TAC proposes to continue the design and right-of-way acquisition efforts in
preparation of bidding the construction work in early 2021.
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Advantages:
The project benefits are numerous and include relief to the Town’s downtown traffic
congestion problems, improved downtown mobility for bicyclists, reduction in downtown
flood risk from the Big Thompson River, and closure to property owner uncertainty
surrounding the DEL.
Disadvantages:
Resistance can be anticipated from some community member who do not support the
DEL.
Action Recommended:
n/a
Finance/Resource Impact:
The Town remains obligated to pay a local match in the amount of $4.2 million for the
Phase 1 project, and has offered an additional $1.5 million as an incentive local cost
share of a requested $25 million BUILD grant. The revised total project cost is $44
million for both phases. To date, $2,388,934 has been spent by the Town on this
project. Additional project costs have been incurred by CDOT and Central Federal
Lands.
Level of Public Interest
The known level of public interest in this item is high.
Attachments:
Preliminary copy of consultant presentation slides for the Phase 1 project
Preliminary copy of consultant presentation slides for the BUILD grant application
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6/12/2019
1
Draft Presentation subject to change.
Downtown Estes Loop Project
Estes Park Town Board Study
Session
June 11th, 2019
Draft Presentation subject to change.
Today’s Agenda
• Right-of-Way Update (CDOT)
• Design Status
• Project Schedule
• Q&A on Phase 1 of Downtown
Estes Loop Project
•Separate presentation BUILD
grant application for Full Build
Proposed Action
6/12/2019
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Draft Presentation subject to change.
Project Phasing – Phase 1
• Funded Phase 1:
• Reconstruction and realignment ofRiverside Drive
• Reconstruction of the Ivy StreetBridge
• New and Coordinated traffic signalswith Riverwalk
• Associated transportationimprovements along Elkhorn andMoraine
• New on street bike lane on Moraineand Riverside
• Continuous sidewalks along entireLoop
• Channel Improvements between IvySt and Rockwell St
• Wayfinding signs, parklands
• Does not include:
• Rockwell and Riverside Bridges
• Relocation of Public Restroom
• Downstream Floodplain Improvements
Draft Presentation subject to change.
Right-of-Way Update
6/12/2019
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Draft Presentation subject to change.
Right-of-Way Acquisitions Process
• CDOT is the lead agency for Right of Way (ROW) Acquisition on
the Project
• Process follows Uniform Relocation Assistance and Real
Property Acquisition Policies Act of 1970 (Uniform Act).
• CDOT has closed on 3
of the 7 property
Acquisitions
• CDOT is assisting
property owners and
tenants who require
Relocation
– Consultation with all rental
tenants and property
owner’s has occurred.
Relocations in process
X X
XXX X
X
Draft Presentation subject to change.
Status of Right-of-Way
Acquisitions & Relocations
• CDOT has initiated 7 full property acquisitions and 20 relocations
(owners and tenants)
– All offers, based on Fair Market Value from appraisals, have been
submitted to property owners
• Three (3) property owners have Agreed to price, closing
complete.
• Four (4) properties in Condemnation process. Negotiations
continuing (Note: It is possible to settle during condemnation
process)
– Relocations in process (looking for replacement properties,
estimating move expenses)
• Approximately 11 tenant relocations complete (to new rentals
or new home purchases)
6/12/2019
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Draft Presentation subject to change.
Update on Properties in
Condemnation
• CDOT TC authorized CDOT to initiate condemnation
process for four (4) properties
– Two properties are now under possession and use agreements
–One property is in process of settlement
– One property is in process of filing
• Negotiations continue with all four properties
• Relocation for owner and tenants continue at these properties
• Actively looking for replacement properties with each property
owner in the condemnation process
Draft Presentation subject to change.
General Condemnation Process
6/12/2019
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Draft Presentation subject to change.
Ongoing Design Refinements
• Hydraulic analysis in coordination with CWCB
• Roundabout refinements
• Pavement markings and signing updates
• Utility coordination and design refinements to
incorporate utility relocations
• Anticipated 90% submittal of plans in early fall
Draft Presentation subject to change.
Ongoing Hydraulic Analysis
• Expand final hydraulic analysis model to
include the full EA Proposed Action
– Includes modeling bridge replacements at Ivy, Rockwell
and E. Riverside and Downstream Channel
improvements from E. Riverside to US 36
– Information will inform BUILD Grant Application
– Coordination with CWCB – CHAMP Project
• Use of full Proposed Action hydraulic
modeling to confirm best Ivy Bridge
configuration
– two span vs. single span
6/12/2019
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Draft Presentation subject to change.
Final Wayfinding Sign Concepts
Draft Presentation subject to change.
Final Wayfinding Sign Concepts
6/12/2019
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Draft Presentation subject to change.
Project Schedule
(Phase 1)
Draft Presentation subject to change.
Near-Term Next Steps
• Complete Final Design Refinements
• Continue Right of Way Acquisition
– Develop schedule for Building Removals (winter/spring 2020)
• Finalize Utility Relocation Plans and Schedule
– Initial relocations in late 2019, early 2020
• Final Design Plans (Fall 2019)
• Town Board Updates
• Incorporate BUILD Grant Scope (if successful)
6/12/2019
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Draft Presentation subject to change.
Questions and Answers
6/12/2019
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Draft Presentation subject to change.
Downtown Estes Loop BUILD
Grant Application
Estes Park Town Board Study
Session
June 11th, 2019
Draft Presentation subject to change.
BUILD Grant Application
• About BUILD Grant
• U.S. Department of
Transportation Grant Program
• Better Utilizing Investments to
Leverage Development (BUILD)
• $900 M program for 2019
• 2/3 of funds allocated for rural
projects
• 2018 program awarded to 91
projects (62 rural) with an
average BUILD award value of
$16.5 M
6/12/2019
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Draft Presentation subject to change.
Downtown Estes Loop
BUILD Grant Application Scope
The BUILD Grant Scope of
Work includes the remaining
elements from the Full
Proposed Action identified in
the Environmental Assessment
Draft Presentation subject to change.
BUILD Grant Application
• Initial Framework for Downtown Estes Loop BUILD
Grant
• Leverage current FLAP Project (Phase 1) with BUILD GrantScope of Work (Full Build Proposed Action ) Request
–$25 M in BUILD Funds Requested
– $1.5 M Additional Town of Estes Funding commitment
– $190 K Additional CDOT Funds (and ~$90k in ROW donation)
– $17.2 M FLAP Project (Phase 1)
» $4.2 M Local Funds
» $13 M Federal FLAP
–TOTAL Project = ~$44 M
• Analysis and preparation of BUILD grant application
is underway
6/12/2019
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Draft Presentation subject to change.
Benefits of BUILD Funding
for Estes Park
• Completes Full Build improvements identified in
Downtown Estes Loop Environmental Assessment
• Substantial floodplain benefits to downtown
properties.
– Critical resiliency and risk reduction to downtown
• Minimize future disruption and quality of life impacts
– Consolidates construction impacts to one larger project, no
future detour traffic conditions to replace bridges
• Improved bicycle and pedestrian connections through
downtown and along the Big Thompson River
– New multi-use path on south side of Big Thompson River
connects to on-street
– Connection to FTA funded multi-modal facility at Visitor
Center / Parking Garage
Draft Presentation subject to change.
Benefits of Downtown Estes Loop
Project for BUILD Grant
• BUILD elements are through environmental (NEPA)
process
• ROW is underway and additional ROW is minor
(Town and CDOT properties)
• Can easily be added to current project without delay
(shovel ready)
• Overall Project hits all selection criteria
– Safety
– State of good repair
– Economic competitiveness
– Environmental sustainability
– Quality of life
– Partnership
6/12/2019
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Draft Presentation subject to change.
BUILD Benefit Cost Analysis
• BUILD Grant requires a benefit cost analysis (BCA)
• Leveraging current FLAP Project into BUILD request allowsfor more benefits in BCA analysis
• Specific Benefit generators in BCA include:
• Travel Time
– Approximately 7 minutes per vehicle of travel time saving betweenexisting and Loop roadway configuration
– Reduced emissions through reduced delay
• Safety
– 147 documented crashes in last 5-years; Loop enhancements will reduceconflict points and improve safety
• Floodplain reduction property benefits
– Removing properties from floodplain reduces property damage risk andflood insurance premiums
• Multi-modal improvements
– Improved transit time through downtown to the Visitor center in Loopconfiguration
– Continuous bike and pedestrian facilities from Visitor Center throughproject limit
Draft Presentation subject to change.
Questions and Answers
PUBLIC WORKS Report
To: Honorable Mayor Jirsa
Board of Trustees
Through: Town Administrator Lancaster
From: Greg Muhonen, PE, Estes Park Public Works Director
Date: June 11, 2019
RE: Regulatory Peak Discharge Forecasts for Floodplain Management
Objective:
Discuss the history and content of the 2017 Wright Water Engineering hydrology study
and the option of appealing the preliminary Flood Insurance Maps (FIRMs) under
development by the Colorado Water Conservation Board (CWCB) for the Fall River
and/or Big Thompson River in the Estes Valley.
Present Situation:
In September 2013 the Town experienced extensive flooding which prompted CDOT to
reevaluate regulatory base flood flows for the Big Thompson and Fall River basins that
impact their highway facilities in Estes Park. Concern regarding the accuracy of their
proposed flood flow values prompted the Town to pursue state grant funding in the
amount of $105,000 to hire a qualified hydrology consulting firm to use current
technological tools and stream gauge records to update the regulatory peak discharges,
understanding they would be used by FEMA for future flood insurance mapping purposes.
This hydrologic analysis was completed by Wright Water Engineers (WWE) over a five-
month period in 2016. This was followed by five more months of extensive public
involvement and peer review processes at an additional cost of $52,000 to the state
(CWCB) and over $12,000 spent by FEMA. Professional peer review comments were
received from 16 individuals and consulting firms, including local engineers and
hydraulics specialists from FEMA, CWCB, CDOT, UC Denver, and USGS. WWE
modified their forecast flow rates and modeling methodology as a result of this peer
review. The process culminated in the receipt of a final hydrology report from WWE in
January, 2017 and a public report and educational meeting on February 27, 2017.
In January 2017, FEMA hired an independent hydrology consultant to review the WWE
hydrology report. Based on their favorable review, FEMA adopted the WWE
recommended flow rates for use in the mapping of the new FIRMs.
At its March 22, 2017 Board meeting, the CWCB adopted the WWE hydrology for use in
the Colorado Hazard Mapping Program (CHAMP) updates to the floodplains and
floodways in the Estes Valley. No members of the public attended or commented at this
meeting. These maps are expected to be the basis of new FIRMs to be adopted by
FEMA in 2021.
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At its May 9, 2017 meeting, the Town Board adopted Ordinance 13-17 which accepts
the WWE hydrology study as the best available data for the purposes of floodplain
administration in Estes Park. A copy is attached.
On May 30, 2018, the CHAMP team presented the draft floodplain maps to the Estes
Park community at a public meeting for review and comment. No challenge to the
proposed regulatory base flood flows was received.
On May 14, 2019 the CHAMP team delivered the draft floodway maps to the Estes Park
Public Works Department. These were shared with the Town Board and the Board of
County Commissioners at the May 15, 2019 joint public meeting regarding a proposed
stormwater utility for the Estes Valley. PW staff has provided some minor mapping
correction comments to the CHAMP team regarding these maps. Considering the
extensive technical reviews of the CHAMP modeling and mapping provided by the
hydrologists from CDOT, AECOM, and FHWA for the Downtown Estes Loop team, and
knowing that the City of Loveland has hired Ayres & Associates to perform detailed
technical reviews of their 2D models and maps, the PW staff determined there is limited
value or justification in the Town hiring another consultant to perform additional map
review for the Town.
The estimated timeline for completing the Flood Insurance Rate Map adoption by FEMA
includes the following milestones:
June 2019 – CHAMP team submits the draft floodway maps to FEMA for review
July 2019 – FEMA responds
August 2019 – AECOM responds
September 2019 – CHAMP team finalizes the floodplain maps and flood insurance
study (FIS)
November 2019 – CHAMP team delivers preliminary FIRMs and FIS for local agency
review
January 2020 – CCO (consultation coordination officer) meeting. CWCB and AECOM
meet with local agencies to present FIRMs, FIS, and confirm remaining steps. Receive
local agency mapping comments on FIRMs and FIS.
Date TBD--CWCB presents prelim FIRMS and FIS at a community outreach meeting.
March 2020 – Appeal period starts
June 2020 – Appeal period ends
August 2020 – Appeal finalization
October 2020 – FEMA issues a Letter of Final Determination
April 2021 – New FIRMs are effective for the Estes Valley. Town required to regulate
activities in the floodplain in accordance with the new maps in order to maintain
eligibility for ongoing participation in the National Flood Insurance Program.
Proposal:
PW Staff has identified two options for discussion and consideration. The advantages
and disadvantages listed below are representative for discussion purposes, and are not
intended to be all-inclusive.
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OPTION 1. Take no new action. Accept the results of the hydrology report prepared by
WWE and approved by the Town Board, CDOT, CWCB and FEMA.
Advantages
The WWE base flood flows have been rigorously vetted and are approved and
adopted by CWCB, FEMA, and the Town. CWCB and FEMA have incurred
considerable expense developing models and maps using these flows.
Completion of the new flood plain maps identifies areas of future flood risk and
establishes a certified basis from which the Town Board can implement the adopted
strategic plan goal of pursuing funding for flood mitigation projects.
The WWE hydrology study was critically reviewed by a regional team of the highest
qualified and experienced hydrology professionals in the industry. The accuracy and
reliability of the revised final report were improved as a result of this effort.
It is in the best interest of the public health, safety, and welfare to have realistic
projections of major flood flows to guide individual and community planning and
spending decisions.
This report advances updates to the FIRMs which elevate public awareness and
preparedness for flood risk. This decreases the Town’s liability.
Disadvantages
The new floodplains resulting from the WWE hydrology are estimated to impact 156
parcels in downtown Estes Park that have an estimated value of $92 million (Larimer
County assessor data).
The cost of flood insurance will increase for many of these properties which were not
previously in the flood fringe or floodway.
OPTION 2. Hire a qualified hydrology consultant to prepare an alternative FIRM
package (new hydrology, new modeling, new FIS, and new FIRMs) for submittal to
FEMA for one or more drainage basins in Estes Park.
Advantages
Completion of another hydrology study might bring closure to the allegations of flaws
in the WWE report, and demonstrate Town responsiveness to the expressed
concerns.
A new study might improve confidence for some individuals regarding the regulatory
flows used to establish updated FIRMs.
Disadvantages
It is not procedurally possible to simply submit a new hydrology report to CWCB or
FEMA for consideration in the current mapping process. The window in time for
submitting a technical comment on the hydrology study (such as incorrect peak flood
flow rates) closed in 2017 when the WWE hydrology report was approved by CWCB,
FEMA, and the Town Board.
Town submittal of a formal Appeal of the preliminary FIRM is required to change the
regulatory peak discharge. The required submittal documents are comprehensive
and include a complete FIRM package prepared by a qualified consultant (new
hydrology, new modeling, new FIS, and new FIRMs). This will be an expensive,
long-duration, and rigorous process. Differing opinions in the exercise of
engineering judgement are not a recognized basis for an appeal. FEMA’s Appeal &
Comment Processing Guidance Document 26 states:
“The sole basis of appeal is the possession of knowledge or information
indicating that the flood hazard determinations proposed by FEMA are
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scientifically or technically incorrect. 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). Due to
this, 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.”
The estimated deadline for submitting an appeal is approximately 12 months away.
Swift decision-making and funding are required to meet this deadline.
Preparing a new FIRM package disrespects the input from highly trained and
experienced professionals who invested their knowledge, experience, and
professional credibility in the WWE study.
This effort will be time-consuming and expensive for the Town. No funds are
budgeted in 2019 for this work.
Submittal of an appeals package requires approval from the same professionals who
have already reviewed and ruled on the acceptable methodology and accuracy of
the WWE hydrology. The likelihood of identifying and proving errors is extremely
remote.
Action Recommended:
Staff requests guidance on the preferred next-step. Does the Town Board want PW staff
to bring back a 2019 budget amendment for approval, and then proceed with sole-
source negotiations with a specific consultant (or issue a competitive Request for
Proposals) to prepare and submit a new FIRM package to FEMA to appeal the validity
of the proposed FIRMs prepared by CWCB for any drainage basin the Estes Valley?
Finance/Resource Impact:
A new hydrology study meeting the technical requirements of CWCB and FEMA is
estimated to cost over $150,000. The modeling, FIS preparation, and mapping are
expected to cost an additional $200,000 to $400,000. Funds for this work have not
been included in the adopted 2019 budget. We are not aware of any grant funding to
support this effort.
Level of Public Interest
The level of public interest is moderate for this program. A small number of residents
continue to question the validity of the WWE study completed and adopted in 2017.
Attachments:
Link to Draft Floodway maps for Estes Park
Conclusions of the WWE study
Email comments from Dave Bangs
Letter from Todd Plummer
Email from Andrew Earles
Ordinance 13-17
Hydrology Study Methodology FAQs
Hydrology Study Peer Review Outcomes
Link to Preliminary presentation slides
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Hydrologic Analysis of Fall River, Upper Big Thompson River, Black Canyon Creek & Dry Gulch, Estes Park, CO
161-013.000 Wright Water Engineers, Inc. Page 64
January 2017
Mud and debris flows can be triggered by as little as 0.25 inches of rain in 30 minutes on steep,
burned slopes. Mud and debris flows are most common in smaller tributaries, but some “bulking”
would be expected even on the main stems due to ash, sediment, and debris. In addition, debris
damming and subsequent breaching (which are not accounted for in the modeling) can
significantly increase the peak discharges in post-wildfire floods. WWE did not account for
sediment bulking in this hydrologic analysis, and additional analysis would be needed to determine
appropriate bulking factors for different reaches. Debris damming and breaching also was not
evaluated as a part of this study. If there are high risk locations that could be affected by this
phenomenon in Town, additional analysis using dam break routines could be used to estimate
potential peak discharges.
These post-wildfire flooding analyses are just representative scenarios. Additional studies could
be performed to evaluate different burn area scenarios based on factors including locations of key
infrastructure in the watershed, applying USGS debris flow regression equations to specific sub-
basins, varying burn area size and severity, and other considerations discussed above.
9.0 CONCLUSIONS
This effort to develop updated hydrology for the Upper Big Thompson River, Fall River, Black
Canyon Creek, Dry Gulch, and direct flow areas to Lake Estes has been based on sound science
and engineering. Multiple methods have been used to determine the peak discharges in Table 17,
including statistical analysis of stream gauge data, HEC-HMS modeling of the September 2013
storm and design storms, evaluation of high water mark peak discharge data, and comparison with
past and recent studies.
The recommended peak discharge results for the Upper Big Thompson River, Fall River, Black
Canyon Creek, and Dry Gulch presented in Table 17 differ greatly than the existing regulatory
hydrology defined within the February 6, 2013 FIS which date back to the hydrologic analysis that
was originally conducted in 1977. The discharges presented in the FIS for Fall River and the Upper
Big Thompson River were computed using the Bulletin 17B analysis using stream gauge data.
These discharges were weighted with those obtained using regression equations. Since there are
no stream gauges located along Black Canyon Creek and Dry Gulch, the regulatory discharges
were based on regression equations.
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Hydrologic Analysis of Fall River, Upper Big Thompson River, Black Canyon Creek & Dry Gulch, Estes Park, CO
161-013.000 Wright Water Engineers, Inc. Page 65
January 2017
Currently there are over 15 years of additional stream gauge data for Fall River and nearly 40 years
of additional stream gauge data for the Upper Big Thompson River. Therefore, this hydrology
study has the benefit of running statistical analysis on a much longer period of record for the stream
gauge. However, there is a lack of large storm events in the stream gauge records aside from the
September 2013 event (which is not available at all stream gauges), therefore, providing a
hydrologic analysis using rainfall-runoff modeling calibrated to the well-documented September
2013 storm in combination with the results of the statistical analysis of the stream gauge data
provides a much more detailed hydrologic analysis than those utilized in 1977 when calculating
the regulatory peak flows in the FIS. Although this hydrology study does not utilize consistent
methods between the various storm events, the driving hydrologic conditions are different for more
frequent return periods (heavy snowmelt influence) and large rainstorms with infrequent periods.
Therefore, the methodology presented in this hydrology report are justified and necessary despite
the large differences with the existing regulatory hydrology.
Results of this study provide reasonable estimates of peak discharges to support floodplain
management in the Town. WWE recommends that the Town work with CWCB to update peak
discharge in the FIS. While some of the changes in regulatory peak discharges will affect properties
in the Town, it is in the best interest of public health, safety, and welfare to have realistic
projections of major flood flows. These peak discharge estimates can be used to more realistically
assess flood hazards and to plan for and design appropriate mitigation.
This study and report have benefitted from extensive peer review and/or input from entities
including the following:
• Town of Estes Park – Tina Kurtz, CFM and Kevin Ash, P.E.
• CWCB – Kevin Houck, P.E., CFM
• FEMA – Stephanie Bany Porter, CFM
• University of Colorado Denver - Dr. James Guo, Ph.D., P.E.
• AECOM – Isaac Allen, EIT
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Hydrologic Analysis of Fall River, Upper Big Thompson River, Black Canyon Creek & Dry Gulch, Estes Park, CO
161-013.000 Wright Water Engineers, Inc. Page 66
January 2017
• Dr. Bob Jarrett, Ph.D., Retired USGS
• Van Horn Engineering – William Van Horn, P.E., John A. Spooner, Ph.D., P.E., Lonnie
Sheldon, P.E., and David Bangs, P.E.
• David Bauer, P.E.
All peer review comments and WWE’s responses to these peer review comments are provided in
Appendix H.
In reviewing any flood study, it is important to keep two important things in mind: (1) probability
and (2) uncertainty. Probability tells us that major floods can occur in any given year and even in
consecutive years. It also means that there are floods larger than the 500-year flood. Uncertainty
is demonstrated by the confidence limits of annual peak discharges from the gauge analysis and in
the confidence limits of the point precipitation values from NOAA Atlas 14 that were used to
develop design storms. Uncertainty is even greater when considered relative to fluctuations in
precipitation related to climate (UDFCD and WWE, 2015). This study addresses some of this
uncertainty through calibration to the September 2013 event and evaluation of design storm results
relative to statistical confidence limits. However, given inherent uncertainty, the recommended
peak discharges should be considered estimates that are based on detailed engineering analysis.
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Hydrologic Analysis of Fall River, Upper Big Thompson River, Black Canyon Creek & Dry Gulch, Estes Park, CO
161-013.000 Wright Water Engineers, Inc. Page 67
January 2017
Table 17. Peak Discharge Results for Upper Big Thompson River, Fall River, Black Canyon Creek, and Dry Gulch
in the Vicinity of Estes Park1
1 See Appendix G for correlation of model junction to design point location and mapping.
.
Model
Junction Description Q2 (cfs)
Q5 (cfs)
Q10 (cfs)
Q25 (cfs)
Q50 (cfs)
Q100 (cfs)
Q500 (cfs)
Upper Big Thompson River
N/A At Visitors Center (downstream of Black Canyon Creek) 995 1,390 1,660 2,000 2,600 3,010 3,870
N/A Downstream of Confluence with Fall River 995 1,390 1,660 2,000 2,600 3,010 3,870
1_2 Upstream of Confluence with Fall River 735 925 995 1,200 1,400 2,170 3,700
3_4 Moccasin Street 735 925 995 1,200 1,400 2,170 3,690
5_6 Near Fun City 735 925 995 1,200 1,400 2,160 3,690
7_8 Pine River Lane 730 920 990 1,200 1,390 2,160 3,690
11_12 Riverside Drive & Turquoise Trail 730 920 985 1,190 1,390 2,150 3,670
15_16 At WorldMark Estes Park 725 915 985 1,190 1,380 2,150 3,660
22_26 Mary’s Lake Road 715 895 965 1,160 1,360 2,100 3,590
Fall River
1 Confluence with Upper Big Thompson River 260 465 665 1,020 1,370 1,860 3,370
2 Between W Elkhorn Avenue and Filbey Court 260 465 665 1,020 1,370 1,860 3,360
3 Approx. 200 feet Downstream of Old Ranger Dr 260 460 660 1,010 1,360 1,850 3,350
4 Approx. 260 feet Upstream of Fall River Lane bridge 255 460 660 1,010 1,360 1,840 3,330
20_21_23 At Fish Hatchery Road 225 405 580 890 1,200 1,650 2,950
24 Approx. 900 feet Downstream of Cascade Cottages 205 370 530 815 1,090 1,490 2,690
Black Canyon Creek
1 Confluence with Upper Big Thompson River 65 120 170 265 285 310 910
2 Approximately 800 feet Upstream of W. Wonderview Avenue 65 115 170 255 280 305 890
3 Near MacGregor Avenue & Evergreen Lane 65 115 165 255 275 300 875
3NE Upstream of Devils Gulch Road 60 110 160 240 265 285 835
Dry Gulch
1 Confluence with Big Thompson River downstream of Lake Estes 40 70 100 150 415 715 1,580
2 Approx. 500 feet upstream of Dry Gulch Road & N Lake Avenue 35 65 95 145 400 685 1,510
3 Approx. 400 feet downstream of Dry Gulch Road & Wildfire Road 35 65 90 140 380 655 1,450
8_10 Dry Gulch Road Crossing just upstream of Stone Gate Drive 30 50 70 110 305 525 1,160
16 Dry Gulch Road & Little Beaver Drive 30 50 70 110 305 525 550
17 Dry Gulch Road & Eagle Rock Drive 10 20 25 40 110 190 420
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Greg Muhonen <gmuhonen@estes.org>
Comments on Hydrology Study
David Bangs <dbangs@trailridgece.com>Thu, Jun 6, 2019 at 2:54 PM
To: Greg Muhonen <gmuhonen@estes.org>
Hi Greg-
Thanks for taking the time recently to sit down with me and discuss the 2017 WWE Hydrology Study. I am writing this email to you to provide some additional
written comments regarding the 2017 WWE Hydrology Study. Feel free to pass this along to whomever would benefit from reading my thoughts. I also want to
preface that these comments are generally related to my initial comments made regarding the draft report and the follow up revisions made to address them.
These comments reflect my own personal opinions and do not reflect any design or engineering work that Trail Ridge Consulting Engineers has done.
In September of 2016 I wrote a letter regarding my technical review comments for the initial draft of the Hydrology Study. I submitted my comments to Town Staff
who was working with Wright Water Engineers. My letter and the WWE response was included with the Final Draft of the Hydrology Report. I understand that in
response to peer review of the draft report, additional estimates were completed to provide more data points for peak flow estimates from the 2013 event to use in
rainfall/runoff models and statistical analyses. My personal opinion of the original peak flow estimates from the flood is that they were high. I had concern about
those estimates being used to complete statistical analyses and model calibration. My comments regarding the peak flow estimates from the flood being high were
specifically related to the Fall River Basin. I had completed some hydraulic analysis of a bridge on Fall River that did not overtop during the flood which helped me
form this opinion. I had not completed any such analyses in other basins. I was suspicious that peak flow estimates for other drainage basins may also be
overestimated. I don't have any personal knowledge of other bridges in the surrounding basins that may provide additional useful data. Another point of contention
regarding the statistical analysis completed was whether the 2013 flood should be considered an outlier. I personally don't find the guidance in Bulletin 17 to be
very specific one way or the other. It seems the approach to include 2013 within the record as part of the statistical analysis is completed is within the guidelines of
that document. My only remaining concern about using the peak flow estimates as that they are just that. Estimates. They are not peak flow gage measurements
and some of the estimates have been proven to be high. So if those estimates are plus or minus 30%, it could sway the resultant flows pretty drastically across the
varying recurrence intervals. However, it does not seem to be against the procedures laid out in Technical Bulletin 17 to include them in the analysis. It just seems
like the conservative way to approach the problem.
From reading the responses to my comments in the WWE final report and the subsequent revisions to the report itself, I feel that the adjustments made to the
report generally address most of my technical review comments. My personal opinion is that the report may still overestimate some peak flow numbers from the
flood which would obviously impact model calibration, statistical analyses and the peak flows for the various return periods. I am still somewhat concerned with how
those peak flow estimates, which I believe to be high, can impact the report if it is found that they are indeed high through further analysis. Having said that, my
personal opinion is also that there would likely be little change to the peak flows by providing further analyses of the other basins. Mapping rivers and completing
hydrologic evaluations of mountainous watersheds is not an exact science. In my view, the tools we have to try and explain and define this phenomena are
relatively crude for the actual physical processes taking place. In other words, no two floods are ever the same. The methods of analyses allow the user to make
some engineering judgement calls with regard to their approach to the analysis. I generally feel the WWE study tended to land on the more conservative side of
the range of judgement that could've been used. This is evident from comparing the modeled peak flows to the actual gage readings that we have. I am
suspicious that the new hydraulic models of the river corridors would show that the estimated peak flow from the '13 flood produces higher base flood elevations
than actually were observed during the flood. I have not reviewed those maps and models myself but understand they are in draft form. Could the report have
come up with lower numbers and still been completed within the rules and regulations that define the study procedures? Yes I firmly believe that. I do believe that
with the revisions made to the final report, I am fairly satisfied that the results are within reason or that there would not be a significant impact to the final results
caused by completing more analyses of the surrounding watersheds without throwing out all the work completed and starting from scratch with a different
consultant. I believe the Town hired an experienced consultant in the field who employed many experts with decades of experience studying and evaluating
floods. I tend to believe that other consultants with the same qualifications would likely come up with similar results.25
Thanks again for reaching out to me to discuss these topics. I appreciate the chance to comment on these types of engineering debates. If you or anybody else
would like to discuss my opinions further, I am happy to do so.
Regards,
David Bangs, P.E.
Principal Engineer
Trail Ridge Consulting Engineers, LLC
970-308-8221
dbangs@trailridgece.com
www.trailridgece.com
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Revisiting the Hydrologic Analysis Prepared by
Wright Water Engineers, January 2017
Background
After the devastating 2013 floods, there was a state funded effort to quantify the observed flood flows of 2013 and
utilize those new flood flow estimates to redo the Hydrologic Analysis of calculated flood flows in effected drainage
basins. The Town of Estes Park contracted with Wright Water Engineers to do the hydrologic analysis for Fall River,
Upper Big Thompson, Black Canyon Creek and Dry Gulch. As a part of this analysis, a draft version of the report was
submitted to local engineers for review and comment.
Van Horn Engineering and Surveying personnel in particular, took issue with the draft report and were able to prove that
some of the Wright Water Engineers analysis and foundational data was flawed for the Fall River Basin. In response
Wright Water Engineers utilized flow calculations for only one bridge across Fall River to revise their flow estimates and
revised their draft report and submitted a final report for review and comment. The revised report corrected a number
of obvious errors, but still contained a number of debatable assumptions and questionable data points affecting Fall
River flow calculations.
During the review period for the final version of the report, when conversations with Dr. Earles reached an impasse, I
asked if there was a possibility of future revisions. The answer was, “Yes, if new data indicated problems with their
findings.” Specifically, I was concerned that observed 2013 flood high water marks would indicate problems with the
floodway boundaries that would be generated using the 2017 Hydrologic Analysis for Fall River.
Application of the “Hydrologic Analysis” Findings
The purpose of the Wright Water Engineers Hydrologic Analysis was to establish estimated stream flow probabilities and
specifically to establish a calculated “100 yr” flood flows for the impacted basins. These “100 yr” flood flows are then
used by FEMA to calculate flood elevations along the river corridors and map floodway boundaries along the rivers and
streams. Any property within the mapped floodway is then subject to Flood Insurance requirements and will have
limited future development potential.
By a happy coincidence, the 2013 estimated flood flow on Fall River was nearly identical to the “100 yr” stream flow
predicted by the Wright Water Engineers Hydrologic Analysis. I say “happy coincidence” because this means that the
observed 2013 flood limits should coincide with the now calculated “100 yr” floodway.
I believe that my fears have proven true. The FEMA mapping of the Fall River Floodway which was generated based on
the 2017 Hydrologic Analysis of Fall River, by Wright Water Engineers includes numerous properties that were NOT
affected by the 2013 flood. This is an indication of additional problems with the 2017 Analysis.
Analysis of the New Data
The first inescapable conclusion of this new data is that 2,000 cfs was NOT flowing down Fall River in the 2013 flood.
Engineers at Van Horn Engineering had disputed the 2,000 cfs flow estimate for Fall River in the 2013 flood and this new
information seems to confirm VHE’s concerns. A reduction in the estimate of the 2013 stream flow for Fall River will
reduce the calculated “100 yr” flow for Fall River and thereby reduce the impacted area in the floodway.
At the minimum, further work should be done to provide a better estimate of the 2013 flood flows along Fall River in
Estes Park.
I also believe that the 67 years of gauge data at the Visitor’s Center stream gauge demonstrates that the 2013 event was
an “historic event” and deserves to be treated as historic in the HEC statistical analysis of the stream flow data. This
would have significant effect on the calculated “100 yr” stream flow calculation, further reducing the impacted floodway
area.
Todd M. Plummer
303-810-4258
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Greg Muhonen <gmuhonen@estes.org>
Re: Good morning
1 message
Andrew Earles <aearles@wrightwater.com>Wed, Jun 5, 2019 at 12:08 PM
To: Greg Muhonen <gmuhonen@estes.org>
Cc: David Hook <dhook@estes.org>, Greg Gladov <ggladov@estes.org>
Hi Greg: Basically treating the 2013 flood like a historic event instead of a documented event in the systematic record creates a wider band of uncertainty on the
results and “dilutes” the effect of the event on the predicted flood frequency relationship from statistical analysis. In fact, we have a high level of confidence in the
flow estimates from Dr. Jarrett, who is one of the most experienced people in the business for making these estimates. In addition, the peak flow rate that we
developed produces flooding extents in AECOM’s model that are very close to what was actually observed. If you look at NRCS’s evaluation of the flood, they used
an even higher flow rate upstream (on the order of 3,000 cfs if I recall). We did not rely on that data point because we thought it was likely a surge from a debris
dam breaking, but the point is that even higher flows were noted during the event. Another flaw in the logic of Mr. Plummer in looking at more flows through town is
that bridges restricted flows in some locations. It is irresponsible engineering practice to consider restriction effects of bridges that are not designed for flood control
because they could be upsized in the future to convey more flow or they could blow out.
I hope these thoughts are helpful. I strongly disagree with the notion that 2013 should be treated as a historic flow when it occurred in 2013 and we have good
documentation supported by multiple lines of evidence as to the magnitude of the flow. The flows we used were vetted through an extensive peer review process.
I hope these thoughts are helpful. Andrew
Andrew Earles, Ph.D., P.E., D.WRE
Vice President
Wright Water Engineers, Inc.
Over 50 Years of Service
2490 W. 26th Avenue Suite 100A
Denver, CO 80211
(303) 480-1700
(303) 480-1020 FAX
HTTP://www.wrightwater.com
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HYDROLOGY STUDY METHODOLOGY
ESTES PARK, CO — FAQs
How major floods like Estes Park’s 2013 event provide critical data to assess future flood risk.
IS A FLOOD EVENT EVER TOO LARGE TO EXCLUDE
FROM HYDROLOGY STUDIES OR RECORDS?
A flood event is never too large to be excluded from the hydrologic (frequency) study. Bulletin 17B, issued by the
Interagency Advisory Committee on Water Data in March 1982, advises that, “Flood peaks considered high outliers
should be compared with historic flood data and flood information at nearby sites. If information is available which
indicates a high outlier(s) is the maximum in an extended period of time, the outlier(s) is treated as historic flood data
as described in Section V.B.10. If useful historic information is not available to adjust for high outliers, then they should
be retained as part of the systematic record.”
Bulletin 17C, which will soon replace Bulletin 17B, advises that “Extraordinary floods are those floods that are the
largest magnitude at a gaging station or miscellaneous site and that substantially exceed the other flood observations.”
Colorado’s Big Thompson River flood of 1976 is an example of an extraordinary flood event. The flood event in Estes in
2013 was of lesser magnitude. As stated in Bulletin 17C, these extraordinary floods are of critical importance because the
estimates have a direct and large influence on the flood frequency distribution and are the events of interest to estimate
flood magnitude and frequency.
WHY IS IT A BEST PRACTICE TO INCLUDE DATA FROM MAJOR EVENTS
IN A SAMPLE SET INSTEAD OF OMITTING THEM AS OUTLIERS?
The largest floods in the record provide the most information about the flood potential for a watershed. The most
accurate estimate of design floods, such as the 100-year flood, is obtained when the large floods are included in
the analysis. By omitting the large floods from the analysis, one is implying these floods cannot occur in the future;
that is a flawed approach. If a large event occurred in the past, then it can occur in the future. As mentioned above,
Bulletins 17B and 17C speak to this issue.
IS IT SAFE TO ASSESS RISK WITHOUT CONSIDERING MAJOR EVENTS?
No, it is not. The major events represent the historically known potential for flooding and excluding these major
events would underestimate design floods, such as the 100-year flood.
IS THERE A WIDELY ACCEPTED STANDARD PRACTICE FOR INCLUDING
OR OMITTING DATA FROM MAJOR EVENTS BECAUSE OF THEIR EFFECT
ON AN ANALYSIS?
The widely accepted or appropriate practice is to include all major events as described in Bulletin 17B and Bulletin 17C.
All extraordinary flood observations are to be retained and used in frequency analysis.
– Bulletin 17C
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SOURCES
Bulletin 17B: Guidelines For Determining Flood Flow Frequency developed by the Federal Interagency Advisory
Committee on Water Data in March of 1982 (http://water.usgs.gov/osw/bulletin17b/bulletin_17B.html).
Bulletin 17B contains the current national guidelines for performing flood frequency analyses at gaging stations
where annual peak flow data are available. All Federal agencies are requested to use these guidelines in all planning
activities involving water and related land resources. The Federal Emergency Management Agency’s Guidelines
and Specifications for Flood Hazard Mapping Partners, “Appendix C: Guidance for Riverine Flooding Analyses and
Mapping,” states “The Mapping Partner must analyze peak flow data in accordance with those standards as presented
in Bulletin 17B and subsequent modifications.”
State, local, and private organizations are also encouraged to use these guidelines to ensure more uniformity,
compatibility, and comparability in flood frequency estimates, which all concerned agencies and citizens must use
for many vital decisions.
Bulletin 17C: Guidelines For Determining Flood Flow Frequency will be published by the USGS (http://acwi.gov/
hydrology/Frequency/b17c/index.html).
This document is the update to Bulletin 17B that was developed by the Hydrologic Frequency Analysis Work Group
of the Subcommittee on Hydrology under the Interagency Advisory Committee on Water Information. Bulletin 17C
is currently under review and it will be adopted as the updated regulatory standard in the near future. As with
Bulletin 17B, all Federal agencies and State, local, and private organizations are requested to use these guidelines.
Reviewed by: Wilbert (Will) Thomas
Qualifications of reviewer: Will Thomas has 51 years of specialized experience in conducting water resources projects
and analyzing water resources data. He represents the Association of State Floodplain Managers (ASFPM) on the
Interagency Advisory Committee on Water Information, Subcommittee on Hydrology (SOH), and currently chairs
the Hydrologic Frequency Analysis Work Group of the SOH that updated the national flood frequency guidelines
(Bulletin 17C). He is a Member Emeritus of the Transportation Research Board (TRB) Hydrology, Hydraulics, and Water
Quality Committee (AFB60) and chaired a TRB National Cooperative Highway Research Program (NCHRP) Panel on
“Estimating Joint Probabilities of Design Coincident Flows at Stream Confluences.” He is the author of more than
75 papers and abstracts on a variety of surface water topics with an emphasis on flood frequency analysis. He was a
member of the Federal Interagency Hydrology Subcommittee that developed Bulletin 17B: Guidelines for Determining
Flood Flow Frequency in March 1982 and was the Chair of the Hydrologic Frequency Analysis Work Group that has
drafted the Bulletin 17C update. Thomas spent 30 years as a hydrologist with the U.S. Geological Survey (USGS),
and he is a nationally well-known and respected hydrologist. He has given courses on statistical hydrology to USGS,
the U.S. Army Corps of Engineers, ASFPM, and other groups.
NOVEMBER 2016 Learn more by visiting
www.estes.org/floodmitigation
Town of Estes Park
170 MacGregor Ave. | P.O. Box 1200
Estes Park, CO 80517 | 970-586-5331
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TOP OUTCOMES OF THE HYDROLOGY PEER REVIEW PROCESS
The Town of Estes Park and its partners have taken great care to ensure the analytical methods in the hydrology study of the Estes
Valley are scientifically and technically correct and the results of the study are accurate. Peer review of the original study was an
essential step in reaching those outcomes. These are the most significant actions and outcomes of the peer review process.
The original report used estimates of rainfall events based on a data set for the region. Brian Cahill suggested
using new information provided by the National Oceanic and Atmospheric Administration (NOAA) that includes
more recent data that is more localized with higher quality control standards. The NOAA data set contributed
better quality information, resulting in lower estimated flood flows for specified flood events in the Big
Thompson and Fall Rivers.
A three-day rainfall event was used in the original study. Kevin Houck pointed out that using a 24-hour rainfall
event in estimating chances of flooding would be more consistent with best practices established throughout the
state, including other mountain communities. Adjusting the three-day rainfall event to 24 hours resulted in lower
estimated flood flows for specified flood events in the Estes Valley.
ADDING DATA FROM THE 2013 FLOODS OF THE BIG THOMPSON AND FALL RIVERS
The original report relied on one published data source from the Natural Resources Conservation Service (NRCS)
to analyze 2013 flood impacts on the Fall River. Dr. Robert Jarrett surveyed the Big Thompson and Fall Rivers to
provide additional data for model calibration during the peer review period. Dr. Jarrett’s advanced study
increased the amount of data and accuracy of conclusions drawn from that data in the final report.
OPPORTUNITIES TO PROTECT OUR COMMUNITY
The community has more options to mitigate flood risk now, thanks to the greater certainty of our risk
assessment following the peer review process. This means more opportunities for state and federal grant
funding for projects and more options for our businesses and residents to protect what is important: our
properties, assets and way of life.
Kevin Houck, P.E., CFM
Colorado Water Board Coalition (CWCB)
Kevin Houck is the Chief of Watershed and Flood Protection for
the CWCB. He is a registered Professional Engineer, Certified
Floodplain Manager, past Chair of the Colorado Association of
Stormwater and Floodplain Managers and has been with the
CWCB for 13 years following 8 years of private consulting work.
Brian Cahill, P.E., CFM
Compass Professional and Technical Services
Brian Cahill is a Civil Engineer specializing in Hydrologic and
Hydraulic Modeling with 15 years of experience performing
watershed studies of various sizes. He is a registered Professional
Engineer, a Certified Floodplain Manager and reviewed the Estes
Valley hydrology study on behalf of the Federal Emergency
Management Agency.
Robert D. Jarrett, Ph.D.
U.S. Geological Survey (retired)
Dr. Jarrett is an internationally renowned expert with nearly
50 years of experience in flood hydrology and hydraulics.
Much of his career focused on integrating paleoflood
hydrology into floodplain management, flood hazard
mitigation, dam safety, and related water resources issues.
Most recently, as a consulting hydrologist, he applied new
methods to document 144 peak discharges for stream sites
aected by the record September 2013 flood in Colorado.
The data were used to help calibrate and validate
rainfall-runo models, and improve flood frequency analyses
for post-flood recovery and engineering design studies.
James Guo, Ph.D., P.E.
University of Colorado — Denver
Dr. Guo is a teaching and research professor and director of
the Hydrology and Hydraulics Graduate Program at
University of Colorado Denver and a registered Professional
Engineer. He is an expert with 40 years of experience in flood
flow predictions, stormwater and watershed modeling. He
has been recognized with both international and national
awards presented by the American Society of Civil Engineers
to honor his achievements in technical publications and the
development of new hydrologic methods.
ADOPTING HIGHER QUALITY DATA ON RAINFALL ESTIMATES FOR BIG THOMPSON AND FALL RIVERS
ADJUSTING THE DURATION OF A POTENTIAL RAINFALL EVENT FROM THREE DAYS TO 24 HOURS
The contributions of the independent hydrology
experts listed below have helped us ensure the
most accurate, scientifically sound results for the
hydrology study of the Estes Valley watershed.
Town of Estes Park
170 MacGregor Ave.
P.O. Box 1200
Estes Park, CO 80517
970-586-5331
Learn more by visiting
www.estes.org/floodmitigation
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June 25, 2019
Flood Plain Management to
Maintain Compliance in the National
Flood Insurance Program and
Community Rating System
Fund Balance Policy
Process for Board Review of
Compliance with Governance
Policies
September 10, 2019
Downtown Estes Loop Quarterly
Update
Items Approved – Unscheduled:
Estes Park Housing Authority
Project on Highway 7 – Part II
Discussion with Town Prosecutor
and Municipal Judge
Future of Human Resources
Management – HR Strategic Plan
Distributed Energy Discussion
ADUs and Sue Ballou
Items for Town Board Consideration:
None
Future Town Board Study Session Agenda Items
June 11, 2019
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