HomeMy Public PortalAbout2013 Flood Protection Study - Section 5
Section 5
Flood Protection Plan and Cost Estimate for English
Landing Park
Flood protection consisting of a low levee/embankment (berm) system to protect the Park was reviewed. The study area is from the east bank of White Aloe Branch extending downstream along the Missouri River to the point where the Riverfront Trail has its first loop back toward the Railroad embankment and the Park’s interior, as shown on Figure 5-1. An alignment further downstream past where the Riverfront Trails merge, as shown in Figure 5-1, was also initially considered.
5.1 Park Flood Protection Planning Considerations Items considered for the Park flood protection included the previous Missouri River flood elevation estimates, ground elevations in the Park and along the trail, opportunities for flood protection tie-in based on natural and manmade high ground (such as the railroad embankment), constraints due to mature tree location along the proposed levee alignment, and the City’s goals for flood protection. The City’s goals for flood protection of the Park include:
Building a berm to achieve a level of protection that protects the Park from frequent floods that damage the Park, generally within the 5- to 25-year event range
Retaining existing large mature trees
Retaining trail alignment
Retaining the trail width of 12 feet
Retaining the Park’s connection with the Missouri River (aesthetic views) Building on the City’s goals, CDM Smith evaluated the project area from a regulatory and constructability perspective. This included the following parameters:
All proposed fill would be outside of the FEMA floodway. A levee designed and certifiable to FEMA or USACE design standards was not required. Another consideration and constraint for this plan is the FEMA floodplain impacts upstream, downstream and across the river.
Keeping the flood protection level between 5- to 25-year level should cause no significant impacts on the base (100-year) flood; however, the Missouri River was not hydraulically modeled as part of this study.
Since the proposed berm is intended to protect a low risk area, under seepage protection was not evaluated nor was a permanent pump stations considered to dewater the dry side of the berm.
Overtopping of the proposed berm for events beyond the level of protection was considered acceptable.
Physical constraints of berm caused by the trail height and width, trees, and tie-in points.
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Section 5 Flood Protection Plan & Cost Estimate for English Landing Park.docx
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Extended Park Flood Protection Alignment
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Feet(c) 2010 Microsoft Corporation and its data suppliers
Figure 5-1 Preferred Park Flood Protection Alignment and Extended Alignment Option
Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park
5.2 Park Flood Protection Evaluation The Park flood protection evaluation was based on regulatory considerations, desired level of protection, berm structure analysis, and pre-and post- flood protection activity related cost analysis.
5.2.1 Regulatory Considerations According to the effective FEMA Flood Study 290294V000 (FEMA Study) and FIRM 2902940001B both dated May 15, 1978, the entire English Landing Park is located within the regulated floodway as shown on Figure 5-2. This conclusion was reached as the 100-year floodplain boundary is located north of the entire Park and the FIRM for this area does not delineate the floodway. Per the FEMA Study, Pages 7 through 10, whenever the floodway edge and the 100-year floodplain boundary coincide only the floodway boundary is shown. The preliminary D-FIRM and profile does not remove the Park from the floodway (refer to Figure 3-2).
Figure 5-2 English Landing Park Study Area and FEMA Floodway Per 44 CFR 60.3 (d) (3) communities should prohibit encroachment (including fill) in floodways unless a hydrologic and hydraulic analysis, performed in accordance with standard engineering practice, demonstrates that the proposed encroachment will not result in any increase in the flood levels within the community during the occurrence of the base flood discharge.
5.2.2 Level of Protection Flood protection for the 10-Percent Annual Chance Flood (commonly referred to as the 10-year) event was chosen in order to meet the goal of a providing between a 5-year to 25-year level of flood protection for the Park. The reason for utilizing this flood event is that this is the only event within the 5-year to 25-year event range in the effective and preliminary FEMA model and profile. Per the preliminary profiles for the Missouri River as shown on Figure 3-2 in Section 3, the 10-Percent Annual
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Section 5 Flood Protection Plan & Cost Estimate for English Landing Park.docx
Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park Chance Flood event WSE (dashed blue line) for the Missouri River at the Park is 752 feet. Per the City provided 2-foot contours and the survey performed in November 2012, the average ground surface elevation of the Park along the Missouri River is 746 feet. It should be noted that the HDR 1999 report stated the elevation of the toe of the berm as 750 feet versus the average of 746 feet along the trail demonstrated by the November 2012 survey. The berm height needed to achieve a 10-Percent Annual Flood Chance protection was determined to be 6 feet. This was calculated based on the difference between the average ground elevation of 746 feet and the 10-Percent Annual Chance Flood WSE of 752 feet.
5.2.3 Berm Structure Analysis The 2012 American Association of State Highway and Transportation Officials’ (AASHTO) Guide for the Development of Bicycle Facilities provides design criteria for a shared use path, such as the Riverfront Trail. Should the Riverfront Trail be reconstructed as part of the flood protection, it is recommended to follow these design criteria. The design criteria are defined in Table 5-1.
Table 5-1 Shared Use Path Design Criteria per AASHTO
Description Design Criteria
Two-directional shared path 10-foot minimum
11-foot minimum to allow for passing with steep side slopes
Berm Slope 1V:3H
Shoulder width 2-foot minimum
5-foot recommended when path is adjacent to bodies of water or downward
slopes of 1V:3H or steeper*
Obstacle clearance 2-foot minimum from edge of path to edge of obstacle
* If the width is less than 5-foot AASHTO recommends that a physical barrier be placed if slopes of 1V:3H or greater are
used next to a parallel body of water. The physical barrier can consist of dense shrubbery, railing, or fencing. The current trail is approximately 6 feet lower than the 10-Percent Annual Chance Flood event WSE. Since the scope of work for this project states that overtopping of the flood protection system is considered acceptable, no freeboard was included in this estimation (44 CFR recommends no less than 2 feet of freeboard). Taking into consideration the proximity and multi-purpose function of the trail to the river in conjunction with the steepness of the slope of the sides of the berm it is recommended that the top of the berm be no narrower than 21 feet using AASHTO design criteria. The dimensions of the berm to provide flood protection for a 10-Percent Annual Chance Flood event are shown on Figure 5-3 and listed in Table 5-2.
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Section 5 Flood Protection Plan & Cost Estimate for English Landing Park.docx
Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park
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Section 5 Flood Protection Plan & Cost Estimate for English Landing Park.docx
Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park
Table 5-2 Park Berm Dimensions
Description Dimension
Berm Height 6 feet
Berm Top Width 21 feet
Shoulder width 4 feet on land side (to allow for benches and lights along trail)
5 feet adjacent to the Missouri River
Trail Width 12 feet
Total Berm Width 57 feet (accounts for both sides maintaining a 1V:3H slope)
Berm Length 2,700 feet This Park is renowned for its many festivals (Arts, Blues, Jazz, and RiverJam, Parkville Days, Turkey Trot, and Christmas on the River) and is frequented by many people who currently enjoy its “scenic walking trails” which provide a unique connectivity to the Missouri River (City of Parkville English Landing Webpage, 2012). The height of the berm at 6 feet obstructs the view of the Missouri River from within the Park as shown on Figure 5-4. An additional negative impact would be the loss of over 50 mature trees, as shown on Figure 5-5, which currently run along the length of the Riverfront Trail.
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Section 5 Flood Protection Plan & Cost Estimate for English Landing Park.docx
Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park
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Section 5 Flood Protection Plan & Cost Estimate for English Landing Park.docx
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Preferred Park Flood Protection Alignment
!-D Tree Removal associated with 6-foot Berm
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Feet(c) 2010 Microsoft Corporation and its data suppliers
Figure 5-5 Tree Removal along Preferred Park Flood Protection Alignment
Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park
5.2.4 Cost Analysis of Flood Protection Options The cost analysis of the flood protection options for the Park was performed utilizing a historical flood analysis of the Park, conceptual costs of building and maintaining a berm, and the historical flood repair costs from the City.
5.2.4.1 Background to Recommendation Analysis Approach: Historical Flood Analysis at
Park Using historical U.S. Geological Survey (USGS) gauge data, the number of days that the WSE has exceeded the average ground elevation in the Park was estimated (Table 5-3). Two USGS gauges were used, one upstream of the Park (Gauge 06820475) and one downstream of the Park (Gauge 06893000), to interpolate the daily WSE at the Park. This WSE was then compared to the average ground elevation in the Park. Figure 5-6 provides a visual representation of this analysis.
Table 5-3 Gauge Analysis of Historical Record of Flooding at English Landing Park
Period of Record
Days of
Record/Year
Number of Days
WSE Greater than 746 feet
Percentage of
Year
Days in 1990 91 0 0.00%
Days in 1991 364 0 0.00%
Days in 1992 365 4 1.10%
Days in 1993 364 57 15.66%
Days in 1994 364 0 0.00%
Days in 1995 364 37 10.16%
Days in 1996 365 11 3.01%
Days in 1997 364 2 0.55%
Days in 1998 364 7 1.92%
Days in 1999 364 12 3.30%
Days in 2000 365 0 0.00%
Days in 2001 364 2 0.55%
Days in 2002 364 0 0.00%
Days in 2003 364 0 0.00%
Days in 2004 365 0 0.00%
Days in 2005 364 0 0.00%
Days in 2006 364 0 0.00%
Days in 2007 364 7 1.92%
Days in 2008 365 9 2.47%
Days in 2009 364 0 0.00%
Days in 2010 333 15 4.50%
Days in 2011 364 76 20.88%
Days in 2012 226 0 0.00%
Total Historical Gauge 7935 239 3.01%
Number of days where Missouri River WSE calculated to exceed 746 feet.
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Section 5 Flood Protection Plan & Cost Estimate for English Landing Park.docx
Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park
Figure 5-6 Visual Representation of Gauge Analysis of Historical Record of Flooding at English Landing Park For the historical gauge record, it is estimated that the Park experiences Missouri River flooding approximately 3-percent of the time. This flooding has happened during 12 years of the total 22 year record of data. An analysis was also completed comparing the historical gauge data to an approximate berm height of 6 feet for the Park. The goal of this analysis was to approximate the frequency at which the Park would still experience flooding from the Missouri River, even with the installation of a berm. With the installation of a berm, it is estimated that the number of days that the Park would have experienced flooding during the historical record would have been reduced by 198 days to 41 days of flooding. With the installation of a berm 6 feet in height, flooding would still occur in the Park approximately 1-percent of the time. At the time of this study, flood repair costs incurred specifically for the Park were not available for the entire historical record or gauge data. However, City staff verbally quoted an average flood repair expense of the Park from 2007 through 2012 at $416,667 per event. These expenses included general clean-up efforts, sediment removal, seeding, and landscaping.
Option #1 No Action: Budget for Park Clean Up With flooding occurring at the Park less than 3-percent of the time based on the historical gauge data, one approach to addressing flood repair costs incurred is for the City to proactively budget for these anticipated costs using a pay-as-you-go sinking fund approach. This type of fund accumulates revenues until sufficient money is available for an identified project, or, in this case, a known cost incurred by the City on a regularly occurring basis. This would assist the City in building a fund to specifically address the flood recovery efforts in the Park when they are incurred.
Average Ground Elevation of Park = 746 feet
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Section 5 Flood Protection Plan & Cost Estimate for English Landing Park.docx
Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park To estimate the needed annual contribution to this type of fund in order to build an adequate safety-net, the average annual flood repair expense at the Park was extrapolated over the number of years in the historical record that the Park has experienced flooding based on the USGS gauge interpolation (Table 5-3). (𝑇𝑜𝑡𝑎𝑙 𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝐸𝑠𝑡𝑖𝑚𝑎𝑡𝑒𝑑 𝐶𝑜𝑠𝑡 𝑓𝑜𝑟 𝐹𝑙𝑜𝑜𝑑 𝑅𝑒𝑝𝑎𝑖𝑟𝑠 𝑡𝑜 𝑃𝑎𝑟𝑘)=(𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐴𝑛𝑛𝑢𝑎𝑙 𝐹𝑙𝑜𝑜𝑑 𝑅𝑒𝑝𝑎𝑖𝑟 𝐸𝑥𝑝𝑒𝑛𝑠𝑒,2007 −2012) 𝑚𝑢𝑙𝑖𝑡𝑝𝑙𝑖𝑒𝑑 𝑏𝑦 (𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑌𝑒𝑎𝑟𝑠 𝑜𝑓 𝑃𝑎𝑟𝑘 𝐹𝑙𝑜𝑜𝑑𝑖𝑛𝑔) $5,000,004 =$416,667 𝑥 12 𝑦𝑒𝑎𝑟𝑠 This total estimated historical cost incurred for flood repairs at the Park was then divided by the total number of years in the historical record to obtain an annual cost incurred for flood repairs. (𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝐴𝑛𝑛𝑢𝑎𝑙 𝐶𝑜𝑠𝑡 𝑜𝑓 𝐹𝑙𝑜𝑜𝑑 𝑅𝑒𝑝𝑎𝑖𝑟𝑠 𝑡𝑜 𝑃𝑎𝑟𝑘) =(𝑇𝑜𝑡𝑎𝑙 𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝐸𝑠𝑡𝑖𝑚𝑎𝑡𝑒𝑑 𝐶𝑜𝑠𝑡 𝑓𝑜𝑟 𝐹𝑙𝑜𝑜𝑑 𝑅𝑒𝑝𝑎𝑖𝑟𝑠 𝑡𝑜 𝑃𝑎𝑟𝑘)(𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑌𝑒𝑎𝑟𝑠 𝑖𝑛 𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝑅𝑒𝑐𝑜𝑟𝑑) $228,000 =$5,000,004 ÷ 22 Therefore, it is estimated that the City could contribute approximately $230,000 annually to a sinking fund dedicated to Park flood repairs in order to anticipate the costs incurred from a flood event. Table 5-4 summarizes the estimated cost for this option.
Table 5-4 Option #1 No Action, Budget for Park Clean Up, Estimated Annual Cost
Total Annual Flood Repair Estimate Based on Historical Gauge Record
Average Flood Repair Cost $416,667
Total Historical Estimated Flood Repair Cost $5,000,004
Average Annual Flood Repair Cost $228,000
Recommended Annual Sinking Fund Budget, Park $230,000
Total City Annual Costs $230,000
Option #2 Six-Foot Berm Construction: Raise Trail Elevation to 752 feet The City has expressed a desire to construct a berm to provide flood protection of the Park as described previously. Table 5-5 provides a conceptual level estimated one-time construction cost of a berm 6 feet in height and Figure 5-1 shows an approximate alignment of this berm. This berm is estimated to provide the Park protection from a 10-year flood event.
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Section 5 Flood Protection Plan & Cost Estimate for English Landing Park.docx
Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park
Table 5-5 Option #2 Six-Foot Berm Construction, Estimated Conceptual Construction Cost to Raise the
Trail Elevation to 752 feet
Estimated Conceptual Construction Cost of Berm
Initial Construction Cost Description Cost Assumptions
Berm (6 feet) Estimated Construction Cost $1,184,349 Initial Cost, (27,543 Cubic Yards * $431/CY)
Utility Coordination/Relocation
(8% of Construction Cost) $94,748 Benches and Electrical Relocation; Tree
Removal
Local/State/Federal Permitting
(5% of Construction Cost) $59,217 CLOMR/LOMR/MDNR Permitting
Engineering Design Fee
(15% of Construction Cost) $177,652 Geotechnical Design Required
Contingency (25% of Construction Cost) $296,087
Total Conceptual Construction Costs $1,812,054
1 Cost per cubic yard based on the HDR 1999 report converted to 2013 dollars using Engineering News Record
multiplier. Along the trail alignment, berm construction elevation should adhere to the “Shared Use Path Design Criteria” per AASHTO for trail design (Figure 5-3). For the purposes of this analysis, a 10- to 12-foot trail width was assumed. For the portions of the berm east of the Park road cul-de-sac, a 2-foot wide shoulder on the dry side of the berm and a 5-foot wide shoulder on the river side of the berm were assumed for fill calculations. While the berm may initially seem a more permanent solution with less recurring costs, annual costs are still incurred with routine inspection and maintenance of a berm. Because a berm would only be constructed to provide a 10-year level of protection for the Park, flooding would still occur and, therefore, the City would still incur flood repair and clean-up costs to the Park. These costs are typically not reimbursable by Federal flood recovery assistance programs, and therefore should be addressed through budgeting endeavors. The estimation of Option #2 annual costs used the same approach for estimating costs as presented in Option #1. The average cost incurred for flood repair expenses at the Park between 2007 and 2012 was extrapolated over the number of years in the historical record that the Park has experienced flooding greater than the estimated 6-foot height of the berm (752 feet) based on the USGS gauge interpolation (Table 5-3). (𝑇𝑜𝑡𝑎𝑙 𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝐸𝑠𝑡𝑖𝑚𝑎𝑡𝑒𝑑 𝐶𝑜𝑠𝑡 𝑓𝑜𝑟 𝐹𝑙𝑜𝑜𝑑 𝑅𝑒𝑝𝑎𝑖𝑟𝑠 𝑡𝑜 𝑃𝑎𝑟𝑘)= (𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐴𝑛𝑛𝑢𝑎𝑙 𝐹𝑙𝑜𝑜𝑑 𝑅𝑒𝑝𝑎𝑖𝑟 𝐸𝑥𝑝𝑒𝑛𝑠𝑒,2007 −2012) 𝑚𝑢𝑙𝑡𝑖𝑝𝑙𝑖𝑒𝑑 𝑏𝑦 (𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑌𝑒𝑎𝑟𝑠 𝑜𝑓 𝑃𝑎𝑟𝑘 𝐹𝑙𝑜𝑜𝑑𝑖𝑛𝑔 𝑊𝑖𝑡ℎ 𝐵𝑒𝑟𝑚) $1,666,668 =$416,667 𝑥 4 𝑦𝑒𝑎𝑟𝑠 This total estimated historical cost incurred for flood repairs at the Park was then divided by the total number of years in the historical record to obtain a conceptual annual cost that the City would still incur for flood repairs. (𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝐴𝑛𝑛𝑢𝑎𝑙 𝐶𝑜𝑠𝑡 𝑜𝑓 𝐹𝑙𝑜𝑜𝑑 𝑅𝑒𝑝𝑎𝑖𝑟𝑠 𝑡𝑜 𝑃𝑎𝑟𝑘) =(𝑇𝑜𝑡𝑎𝑙 𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝐸𝑠𝑡𝑖𝑚𝑎𝑡𝑒𝑑 𝐶𝑜𝑠𝑡 𝑓𝑜𝑟 𝐹𝑙𝑜𝑜𝑑 𝑅𝑒𝑝𝑎𝑖𝑟𝑠 𝑡𝑜 𝑃𝑎𝑟𝑘)(𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑌𝑒𝑎𝑟𝑠 𝑖𝑛 𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝑅𝑒𝑐𝑜𝑟𝑑) $75,758 =$1,666,668 ÷ 22
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Section 5 Flood Protection Plan & Cost Estimate for English Landing Park.docx
Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park Therefore, it is estimated that the City could contribute approximately $76,000 annually to a sinking fund dedicated to Park flood repairs in order to anticipate the costs incurred from a flood event, with the berm installation. It should be noted that with the construction of a berm in a defined floodway, significant damage could be incurred to a berm subjected to a prolonged flooding event that could entail complete reconstruction of the berm. Therefore, an annual sinking fund should also be considered to address these significant repairs. In the available historical record of 22 years, WSE exceeding the estimated berm height of 752 feet for a prolonged period of time has occurred once: 1993 (35 days). The estimated total construction cost of the berm (Table 5-5) was extrapolated over the historical record to estimate an additional annual sinking fund budget specifically for reconstruction of a berm. As part of this estimate, it was assumed that 50-percent of the original construction would be salvageable following a flood event. (𝐸𝑠𝑡𝑖𝑚𝑎𝑡𝑒𝑑 𝐴𝑛𝑛𝑢𝑎𝑙 𝐶𝑜𝑠𝑡 𝑜𝑓 𝐵𝑒𝑟𝑚 𝐶𝑜𝑛𝑠𝑡𝑟𝑢𝑐𝑡𝑖𝑜𝑛)
=�𝑇𝑜𝑡𝑎𝑙 𝐸𝑠𝑡𝑖𝑚𝑎𝑡𝑒𝑑 𝐶𝑜𝑠𝑡 𝑓𝑜𝑟 𝐵𝑒𝑟𝑚 𝐶𝑜𝑛𝑠𝑡𝑟𝑢𝑐𝑡𝑖𝑜𝑛 𝑚𝑢𝑙𝑡𝑖𝑝𝑙𝑖𝑒𝑑 𝑏𝑦 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝑊𝑆𝐸 𝐸𝑥𝑐𝑒𝑒𝑑𝑎𝑛𝑐𝑒 𝐸𝑣𝑒𝑛𝑡𝑠�× 50%(𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑌𝑒𝑎𝑟𝑠 𝑖𝑛 𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝑅𝑒𝑐𝑜𝑟𝑑) $164,732 = $(1,812,054 × 4 × 0.5 ) ÷ 22 In addition, an estimated annual maintenance cost of the berm was included at 3-percent of the estimated construction cost. Table 5-6 summarizes the estimated annual costs for this option.
Table 5-6 Option #2 Six-Foot Berm Construction, Estimated Conceptual Annual Costs Incurred to Raise
the Trail Elevation to 752 feet
Total Annual Maintenance and Flood Repair Estimate for Berm Construction
Average Flood Repair Cost $416,667
Total Historical Estimated Flood Repair Cost for Park $1,666,668
Average Annual Flood Repair Cost $75,758
Total Historical Estimated Berm Reconstruction Cost $3,624,108
Average Annual Budget for Berm Reconstruction $164,732
Recommended Annual Sinking Fund Budget, Berm Reconstruction $165,000
Recommended Annual Sinking Fund Budget, Park Repairs $76,000
Estimated Annual Maintenance of a Berm (3% of Construction Cost) $35,500
Total City Annual Costs $276,500 The total annual costs associated with berm construction are estimated to be similar in cost of proactively planning for flood repairs (Option #1).
Option #3 Temporary Flood Protection: Water-Filled Tubes In lieu of a permanent berm, the City could pursue a temporary flood protection option for the Park. Section 3 discussed advantages and disadvantages of three temporary flood protection options: fabric membrane, water-inflated tubes, and baffled bladders. Of these, water-filled tubes would allow the City the flexibility of choosing the best alignment to protect resources within the Park, while also allowing the City to purchase additional material as funds are available. This would allow the City to adjust flood
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Section 5 Flood Protection Plan & Cost Estimate for English Landing Park.docx
Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park protection of the Park to a desired level for future flood events. However, this method of flood protection is dependent on a readily available source of water to fill the tubes at the point of installation. Table 5-7 provides an estimated cost for temporary flood protection using water-filled tubes for a wall 3 feet in elevation and a wall 6 feet in height for the alignment shown in Figure 5-1.
Table 5-7 Option #3 Temporary Flood Protection, Estimated Material Cost for Water-Filled Tubes
Estimated Material Cost of Temporary Flood Protection, Water-Filled Tubes
Estimated Material Cost
Height of Temporary Flood Protection
3-foot 6-foot
Estimated Material Cost per linear foot, (Dollars) $100 $190
Alignment Length, (linear foot) 2700 2700
Total Estimated Material Costs $270,000 $513,000 Similar to the permanent berm, annual costs are still incurred with temporary flood protection technologies (storage, etc.). Because the temporary flood protection would only provide flood protection to a defined level for the Park, flooding would still occur. Therefore, the City would still incur flood repair and clean-up costs to the Park. The estimated cost methodology to define this annual cost is the same as presented for Option #2. In addition, labor and inspection costs associated with installation can be estimated. An estimated labor cost per installation was extrapolated over the number of years in the historical record that the Park has experienced flooding greater than the average ground elevation of the Park (746 feet). Similarly, an estimated inspection cost per installation was extrapolated over the number of days in the historical record that the Park has experienced flooding greater than the average ground elevation of the Park (746 feet). All of these estimated costs could be anticipated through annual contributions to a sinking fund. Table 5-8 summarizes the estimated annual costs for this option.
Table 5-8 Option #3 Temporary Flood Protection, Estimated Annual Costs Incurred with Water-Filled Tubes
Total Annual Estimated Costs for Temporary Flood Protection
Cost Description Height of Temporary Flood Protection
3-foot 6-foot
Average Flood Repair Cost $416,667 $416,667
Total Historical Estimated Flood Repair Cost for Park $5,000,004 $5,000,004
Average Annual Flood Repair Cost $227,273 $227,273
Total Labor Incurred over the Historical Record 1 $162,000 $307,800
Total Annual Labor Budget $7,364 $13,991
Total Inspection Incurred over the Historical Record 2 $143,400 $143,400
Total Annual Inspection Budget $6,519 $6,519
Estimated Annual Maintenance of Temporary Flood Protection
(1% of Material Cost) $3,000 $6,000
8Recommended Annual Sinking Fund Budget, Park Repairs $228,000 $228,000
Recommended Annual Sinking Fund Budget, Temporary Flood Protection
(labor/inspection) $14,000 $21,000
Total City Annual Costs $245,000 $255,000
1 Five-percent of material cost times 12 times in historical record.
2 239 days x 4 hours/day x 2-people x $75/hour
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Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park
Option #4 Three-Foot Berm Construction: Raise Trail Elevation to 749 feet An additional alternative could include the City pursuing incremental flood protection of the Park by elevating the trail approximately 1 to 3 feet to an elevation of 749 feet. Appendix C includes conceptual plan and profile views of what this trail elevation could look like. Table 5-9 summarizes the estimated construction cost for this option.
Table 5-9 Option #4 Three-Foot Berm Construction, Estimated Construction Cost Incurred to Raise the
Trail Elevation to 749 feet
Estimated Conceptual Construction Cost of Trail Elevation
Initial Construction Cost Description Cost Assumptions
Trail Elevation Estimated Construction Cost $434,816 Initial Cost, (10,112 Cubic Yards * $431/CY)
Utility Coordination/Relocation
(8% of Construction Cost) $34,785
Benches and Electrical Relocation; Tree
Removal
Local/State/Federal Permitting
(5% of Construction Cost) $21,741
CLOMR/LOMR/MDNR Permitting
Engineering Design Fee
(15% of Construction Cost) $65,222
Geotechnical Design Required
Contingency (25% of Construction Cost) $108,704
Total Conceptual Construction Costs $665,268
1 Cost per cubic yard based on the HDR 1999 report converted to 2013 dollars using Engineering News Record
multiplier. The City could potentially incur an estimated cost savings of up to 25-percent by using City resources or volunteer labor for trail elevation construction. Along the trail alignment, trail elevation construction should adhere to the “Shared Use Path Design Criteria” per AASHTO for trail design (Figure 5-3). For the purposes of this analysis, a 10- to 12-foot trail width was assumed. For the portions of the trail east of the Park road cul-de-sac, a 2-feet wide shoulder on the dry side of the trail and a 5-feet wide shoulder on the river side of the trail was assumed for fill calculations. Annual costs would still be incurred with routine inspection and maintenance of elevating the trail. Flooding of the Park would still occur at elevations greater than 749-feet, and therefore, the City would still incur flood repair and clean-up costs to the Park. These costs are typically not reimbursable by Federal flood recovery assistance programs, and therefore should be addressed through budgeting endeavors. The estimated annual costs for this option was derived similarly to Option #2, with the main difference being in the number of times in the historical record that the WSE has exceeded 749-feet (7 times). Table 5-10 summarizes the estimated annual costs for this option.
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Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park
Table 5-10 Option #4 Three-Foot Berm Construction, Estimated Annual Costs Incurred to Raise the Trail
Elevation to 749 feet
Total Annual Maintenance and Flood Repair Estimate for Trail Elevation
Average Flood Repair Cost $416,667
Total Historical Estimated Flood Repair Cost for Park $2,916,669
Average Annual Flood Repair Cost $132,576
Total Historical Estimated Trail Elevation Reconstruction Cost $2,328,440
Average Annual Budget for Trail Elevation Reconstruction $105,838
Recommended Annual Sinking Fund Budget, Trail Elevation Reconstruction $106,000
Recommended Annual Sinking Fund Budget, Park Repairs $133,000
Estimated Annual Maintenance of a Berm (3% of Construction Cost) $13,100
Total City Annual Costs $252,100
5.3 Considerations for Flood Protection of English Landing
Park Table 5-11 summarizes the estimated initial (construction and/or material acquisition) costs and estimated annual costs for the options presented in Section 5.2.
Table 5-11 Estimated Costs Summary for Flood Protection of English Landing Park
Option Description
Estimated Cost (2012) 1
Initial Cost Annual Cost 2
Option #1 No Action Budget for Park Clean Up $0 $230,000
Option #2 Six-Foot Berm
Construction Raise Trail Elevation to 752 feet $1,820,000 $280,000
Option #3 Temporary Flood
Protection 3 3-Foot High Water Filled Tubes $270,000 $250,000
6-Foot High Water Filled Tubes $520,000 $260,000
Option #4 Three-Foot Berm
Construction Raise Trail Elevation to 749 feet $670,000 $260,000
Raise Trail Elevation to 749 feet –
City Self Perform Construction $510,000 4 $230,000 5
1 Estimated costs have been rounded up to the nearest $10,000.
2 Annual costs do not include intangible costs that cannot be quantified (i.e. loss of use)
3 Use of water-filled tubes is considered infeasible and is not recommended for further consideration.
4 Assumes City cost to construct is 75% of contracted cost.
5 Assumes City would self-perform annual maintenance and flood repair. Under the “No Action” option, no initial cost would be incurred by the City. Instead, the City would proactively budget for anticipated future flood repairs in the Park. The annual costs for Options #2 and #4 include building the berm, repairing the berm after minimal flood events, and annual maintenance of the berm. These costs do not included loss of use during flood events, the impact of any berm construction adjacent to established trees, modification to existing light poles and benches, and a reduction of the river view from the Park (particularly from the River
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Section 5 • Flood Protection Plan and Cost Estimate for English Landing Park Stage Park Shelter). Raising the trail along the southern edge of the Park reduces accessibility to the trail and increased maintenance tasks. Currently the trail is accessible from any point in the Park for physically challenged people. Adding additional areas of accessibility to the trail would increase the financial costs associated with the berm. The additional maintenance tasks include inspecting for damage from burrowing animals, inspecting for scouring from high WSE events, and repairing noted damages. Any fill placed for a berm or trail elevation should be compacted to meet USACE standards. This fill should be placed in 6 to 10 inch lifts. With the significant number of trees adjacent to the existing trail alignment, an arborist should be consulted to determine fill allowable near trees or design requirements for tree protection. Existing stormwater conveyance paths through the Park to the river are critical to retain. In addition, tie-in of a trail elevation or berm could pose challenges at the railroad tracks. Additional requirements may be required from BNSF to place any fill adjoining the railroad embankment. It should be noted that the entirety of the Park is within the FEMA regulated floodway of the Missouri River and will require a City floodplain permit for any land modifications. Sandbag closures would be required at certain points where berm construction or trail elevation is not feasible. These locations include the Park road entrance, existing boat ramp, and Park road cul-de-sac, as well as potentially the connection adjacent to the railroad. A one to two day lead time would most likely be required to construct these measures prior to flooding. The Park would be closed leading up to and during any flood event. During the flood event, the berm and/or trail elevation area would require continuous monitoring to assess the structural integrity as well as the dewatering needs within the Park. Following any flood event, a full inspection of any berm and/or trail elevation should be completed with repairs completed as identified. Due to the current lack of available water at the Park, the use of water-filled tubes (Option #3) as a temporary means of flood protection is considered infeasible. It is also uncertain how well the tubes would hold up under prolonged flooding conditions of the Missouri River as their placement would be in an area of higher flow velocity.
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