SUSTAINABLE DESIGN FOR THE SOLDIER CREEK LEVEE REPAIR. John Ruhl 1 Seth Laliberty 2 ABSTRACT

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1 SUSTAINABLE DESIGN FOR THE SOLDIER CREEK LEVEE REPAIR John Ruhl 1 Seth Laliberty 2 ABSTRACT The Soldier Creek Diversion Unit Repair Project represents the latest USACE Kansas City District investment in sustainable water infrastructure. Soldier Creek crosses the north side of the City of Topeka, Kansas through a partially developed floodplain of the Kansas River. The diversion unit, constructed in the 1950s, consists of eighteen miles of earthen levee, nine miles of improved channel, and thirty-five drainage structures. The 1950 s channelization project significantly changed the planform of the channel and induced substantial changes in profile. The instabilities identified today may be derived from the steep banks that resulted from these drops in channel elevation. The existing slope of the channel bed continues to amplify the rate of degradation, being steeper than the equilibrium slope, given the existing channel bed materials. In October 2005, the levee was overtopped and the diversion unit seriously damaged. Black & Veatch prepared a conceptual design for the repair using the Soar & Thorne approach and HEC-RAS to evaluate any changes in water surface profiles, stream velocities, and energy gradelines. The design features included rock checks to maintain bed elevation, vegetation to augment stability, and a meandering low flow channel within the levee system. Construction has been on-going since November A variety of construction challenges have arisen including unexpected utilities, differing geotechnical conditions from those expected, plant establishment, and high water events. Construction completion is expected late this year or early in INTRODUCTION Soldier Creek extends through a predominantly rural watershed downstream across the north side of the city of Topeka, Kansas in a partially developed floodplain area of the Kansas River. The watershed drains 334 square miles made up of approximately 60% grassland, 40% crops, and less than 1% urban area. The soils are generally silt loam and silty clay loam. The Topeka, Kansas Flood Protection Project which includes the Soldier Creek Diversion Unit was originally authorized for Federal funding in Construction of the Diversion Unit began in 1957 and was completed in The Diversion Unit is comprised of 17.9 miles of earthen levee, 9.2 miles of improved channel, and 35 drainage structures. These features extend upstream from the confluence at the Kansas River. The construction altered the confluence location of not only Soldier 1 Black & Veatch, 6601 College Blvd., Overland Park, KS, ruhljk@bv.com 2 Corps of Engineers, Kansas City District, 601 East 12 th Street, Kansas City, MO, seth.j.laliberty@usace.army.mil. Soldier Creek Levee Repair 839

2 Creek, but also Indian Creek, the previous confluence of which had been further east from the Soldier Creek confluence (See Figure 1). The project straightened the alignment of Soldier Creek in conjunction with the levee construction. Figure 1. Alignment of Soldier Creek Not only did the channelization project significantly change the planform of the channel, but very significant changes in the profile followed the completion of construction. In 2001, the USGS documented a 5-foot decline in the channel bed very soon after the completion of construction and a degradation rate of approximately 0.03 ft 1 year between 1962 and This resulted from the steepened channel gradient that was produced during original construction from the elimination of much of the sinuosity of the natural channel. This degradation has continued at a lesser rate throughout the subsequent years because the channel slope is steeper than the equilibrium slope given the existing channel bed materials. The history of bank failures in the Soldier Creek channel is the result of this combination of steepened channel slope and soil conditions. In October 2005, heavy rainfall resulted in levee overtopping and significant damage to the Soldier Creek channel. Approximately 10 miles of levee was damaged from the overtopping with the crushed aggregate surface on the levee crest washed away and minor erosion of the embankment resulting. Two reaches of the channel were damaged as shown in Figure 2. The longer damaged reach was from the confluence at the Kansas River to Kansas Avenue. A much shorter reach was damaged immediately downstream of Menoken Road. 840 Innovative Dam and Levee Design and Construction

3 Figure 2. Locations of Channel and Levee Repair The purpose of the Soldier Creek project is to restore the original project function. The project has included a study phase, a design phase, and a construction phase. The study phase, performed in 2008, compared the merits and the costs of two design alternatives. The first (the Conventional Alternative) consisted of repairing the banks to be consistent with the original design. The second alternative was a stable stream design which accounted for geomorphologic changes which the channel has experienced. The study resulted in the recommendation of the latter, the Stream Stability Alternative. The design phase, also performed during , produced plans and specifications for the selected alternative. The construction which began in 2009 is expected to be completed either in late 2011 or early STUDY PHASE Activities during the study phase included collection of topographic data, a field geomorphologic analysis, hydraulic modeling, development of the Stream Stability Alternative, and alternative assessment including preparation of cost estimates for each alternative. Collection of Topographic Data The primary topographic data source for this project was Light Detection and Ranging (LIDAR) data for Shawnee County, Kansas which was collected in This data was supplemented with field survey in areas of erosion. Soldier Creek Levee Repair 841

4 Field Geomorphologic Analysis Field reconnaissance consisted of a two-person team walking the channel to record observations. This reconnaissance was performed from the mouth of Soldier Creek upstream to Menoken Road. The types of observations made were as follows: the ordinary high water mark, top of bank, locations of riffles and pools, exposed bed rock or bed materials, scour and depositional areas, sandbar characterization, natural or invasive vegetation in the buffer zone, bank full depth and width, loss of riprap, flow orientation, and areas of debris collection. Figure 3 below is descriptive of the conditions which were observed. Figure 3. Looking Downstream at Meriden Road The reconnaissance was performed using a proprietary GIS-based, geomorphologic data acquisition system. The Kansas City Metropolitan Chapter of the American Public Works Association Channel Condition scoring matrix within APWA 5600 was the basis for identifying reaches of concern. Using the topographic and geomorphologic data, Black & Veatch determined the bank-full channel forming conditions, stream thalweg, total meander, valley length, and sinuosity. A condition score is determined for each stream reach. The results of the geomorphologic analysis are important in developing stream stability recommendations. 842 Innovative Dam and Levee Design and Construction

5 Hydraulic Modeling A HEC-RAS model was developed for each of the Conventional and Stream Stability Alternative conditions for the 2-year, 20-year, 100-year, and 200-year flood events. The models were based on a 2005 Kansas City District model with updates as required for bridge information, Manning s n values, and ineffective flow areas. Additional stream cross sections were also added. The shear stress was the most important variable analyzed from the HEC-RAS model. Shear stresses downstream of Kansas Avenue exceed 0.5 lbs/ft 2 for flows greater than the 10-year event. For the 200-year event, the shear stress values exceed 1 lbs/ft 2. Shear stresses are evaluated for the channel bottom, banks, and bends. The erosion due to insufficient shear strength of the bank materials is closely correlated to soil material type. The erosion is occurring in the alluvial clay loams, loams, and sandy loams of the Kansas River valley. Little erosion has occurred on the hillside slopes comprised of silty clay loams and relatively shallow bedrock. The model results indicated that Soldier Creek is a moveable bed system. The predominantly agricultural watershed provides a large sediment supply. The channel bed degradation documented by the USGS as mentioned above and the shear stress results from the HEC-RAS model are both consistent with this conclusion. As a result, the most important design criterion is the establishment of an equilibrium slope to stabilize the channel bed and prevent future degradation. The equilibrium slope balances the size and quantity of particles which the stream moves. Rock check dam spacing and sizing is based on the equilibrium slope. The Stream Stability Alternative maintains the 200-year water surface elevation within the project levees. Development of the Stream Stability Alternative The analysis of the topographic data, geomorphologic assessment, and hydraulic modeling led to the following conclusions: The channel has experienced mass wasting of erodible soils Formation of sand bars and flood benches has occurred The riprap was improperly sized. The drainage structures have become unstable The pool-riffle structure is undefined The channel lacks sinuosity Monoculture, invasive vegetation exists at the expense of a native grass/riparian corridor The research done by Philip J. Soar and Colin R. Thorne provides guidelines for stable stream design. The underlying assumptions from this research are that the dimensions of stable natural channels are proportional to the discharge and that they are inter-related. They indicate that the 2-year flood is an approximate upper boundary to bank full Soldier Creek Levee Repair 843

6 discharge. Studies in Kansas for urban streams have indicated that the 1-year event may be a better estimate. For Soldier Creek, a 1.5-year event was used. The channel width, pool-riffle (shallows) spacing, radius of curvature, and sinuosity were also determined. The appropriate spacing of pools and riffles can reduce shear stresses and decrease the need for resistive materials in between riffles. Figure 4 describes these stream characteristics. L Amp R c Alternative Assessment Figure 4. Soar and Thorn Stream Parameters As a final step in the study, the Conventional Alternative and the Stream Stability Alternative were compared. The alternatives can be summarized as follows: Conventional Alternative This alternative conformed to the Kansas City District Project Information Report developed following the 2005 flood. It consisted of reconstruction of the original 2 (H) to 1 (V) bank slope and a channel bottom width of 125 feet (25 feet wider than the original channel width). The channel near existing bridges would be restored to the original design to avoid impacting the bridge piers and foundation. Riprap would be placed on repaired channel slopes to restore the original condition. In areas where the levee has been overtopped, the crest would be graded to the original profile and resurfaced with 6 inches of crushed aggregate. The study level cost for this alternative was approximately $11,800,000. Stream Stability Alternative This alternative used the equilibrium slope and stable channel cross section as described above for the two project reaches shown in Figure 2. The low flow channel increases the channel length and results in a milder slope. Small rock check dams allow the channel to maintain an equilibrium slope and stable channel bed and preserve the channel toe. Enhanced vegetation was designed to provide stability and roughness to the flood bench which reduces the velocity and the associated erosive potential on the upper slopes. The treatment of the overtopped levee areas is identical to that for the Conventional Alternative. The study level cost for this alternative was approximately $8,500,000. Black & Veatch recommended the Stream Stability Alternative. This alternative provided the best choice for future stream stability and reduced maintenance costs, enhanced habitat, and could be constructed at the lowest capital cost. 844 Innovative Dam and Levee Design and Construction

7 DESIGN PHASE During the design phase, Black & Veatch prepared construction plans, specifications, a design analysis report, and updated cost estimate for the Stream Stability Alternative. The design included the stable stream features, bridge scour analysis, riprap, slope stability, hydraulic and structural analysis of the drainage structures, utilities, and ecosystem restoration features. Alignment and Stable Stream Design Features As determined in the study phase, two reaches as follows were identified for design: Project Site 1 This project reach extends from a location just upstream of the confluence at the Kansas River to Kansas Avenue. This reach is approximately 1.9 miles in length. Rock Checks #1 and #9 are located at the downstream and upstream ends of this project reach. The reach also includes bridges at the Union Pacific Railroad, US Highway 24, the ATT & SF Railroad, and Northeast Meriden Road; a total of eight rock check dams; eleven drainage structures, and the confluence of Indian Creek. Project Site 2 This project reach extends over approximately 1800 feet immediately downstream of NE Menoken Road. Rock Check #10 is near the downstream end of this reach. This reach does not include any bridges, other rock checks, drainage structures, or confluences. For Project Site 1, the existing survey documented centerline elevations of at the downstream end and at the upstream end for an average slope of approximately Eleven pools with alternating riffles were spaced according to the Soar and Thorne methodology. Bend scour calculations were used to determine a pool depth of 5 feet and the associated pool width. The Schoklitsh Method and Meyer-Peter, Muller Methods were used to determine the equilibrium channel slope based on a 1.5-year flood discharge and a mean sediment diameter of 2.4 mm for bed materials. The Newbury Rock riffle design method was applied to develop the rock check dimensions. A glide slope (upstream face) of 2(H) to 1 (V) and a run slope (downstream face) of 10 (H) to 1 (V) were developed. The rock checks are keyed into the bank slopes and are protected with riprap to resist the 200-year discharge. The rock check keys will be covered with topsoil to accelerate vegetation growth and blending into the adjacent banks. The construction plans included fourteen plan and profile sheets for Project Site 1 and three plan and profile sheets for Project Site 2. These sheets depict existing grade and finished grade contours in plan; existing grade, finished grade, and thalweg (deepest alignment through pools) in profile, finished grade lines in profile, locations of rock checks and drainage structures, and extent of riprap. Cross sections are also provided at intervals of 50 feet. The typical channel section reflects a lower channel side slope of 3 (H) to 1 (V), a bench of 10 (H) to 1 (V) side slope, and an upper slope of 3 (H) to 1 (V) to Soldier Creek Levee Repair 845

8 tie into the levee or natural grade. Grading design was performed with Intergraph InRoads. The computation of earthwork quantities indicated an excess of excavated material. Identification of an off-site disposal area for this material was identified. Geotechnical Analyses/Riprap Two soil borings were taken in order to determine the grain size of the embankment materials and to collect strength data for slope stability analysis. Subsurface information from the original Soldier Creek Diversion Unit plans were also used. The original construction drawings show that the channel embankments were sloped at 2 (H) to 1 (V) The proposed channel embankments for Project Site 1 are to have slopes at 3 (H) to 1 (V) with a maximum height of the embankment including the levee of 46 feet. Most of this reach includes a bench near the middle of the slope. A conservative assumption to not include the bench in the slope stability analysis was made. Riprap was included at each of the Union Pacific Railroad, US Highway 24, ATT & SF Railroad (at and downstream for approximately 500 feet), and NE Meriden Road. Riprap was also included on the toe of slope between the Union Pacific Railroad and US Highway 24 bridges, on the outside of the bend upstream of US Highway 24 for approximately 1000 feet, and at the Indian Creek confluence. For the Project Site 2, the south embankment will be sloped at 2.5 (H) to 1 (V). The maximum height of the south embankment will be 30 feet. The slope will have riprap placed to a depth of 2 feet along the lower 12 feet of vertical height of the embankment. The slope stability analyses were performed using the SLOPE/W program for undrained, drained, and rapid drawdown conditions. The soil strengths were based on data from the subsurface exploration and engineering judgement. The results of the stability analyses confirmed that the proposed slopes meet the required factors of safety. An analysis of bridge scour was performed in order to design the riprap at each bridge. Contraction scour and local scour at piers were analyzed using the FHWA NHI , HEC18, Evaluating Scour at Bridges manual. This analysis resulted in riprap size and depth at each bridge. Drainage Structure Design The eleven drainage structures within the Project Site 1 are in various conditions of disrepair. In some cases, the pipe outlet structure and/or the channel that conveys flow to Soldier Creek are also in poor condition. In additional instances, the proposed channel slope is being flattened to a 3 (H)to 1 (V) to and requires modification to the structure. The proposed modifications included repairing, extending, or shortening the existing culverts without making any changes to their size. Modifications to the energy dissipators were also made on an as required basis. These modifications included either concrete structures with downstream riprap or riprap alone. 846 Innovative Dam and Levee Design and Construction

9 Other Design Considerations Project Sites 1 and 2 include a minimum of utilities impacted by the design. The only crossing is a force main approximately 800 feet downstream from the upstream end of Project Site 1. Because no vertical profile information for the force main was available, it required locating and possibly deepening a portion of the pipe in order to maintain the required cover depths. Vegetation was incorporated in the design in order to stabilize and reduce erosion on the stream banks. The following three planting zones were included: Zone A: Streamside Seeding Blend This blend will be provided for the portion of the cross section nearest to the water level. The blend will include plant communities that are adapted to periods of inundation, storm flows, and moist to saturated soil conditions. A salix species is also included in the Zone A area. Zone B Streambank and Lower Flood Bench Seeding Blend This zone is located immediately upslope from Zone A. Deep rooted prairie species will be included tolerant of either inundation of periods of drought. Zone C - Levee Seeding Blend This blend applies to levee areas which are required to be periodically inspected and maintained. Four native grasses will be used in these areas. The project specifications include information on ecological maintenance requirements. Levee reaches which were either overtopped during the 2005 flood or for which the crests are degraded shall be restored to a profile not lower than the higher of the original construction profile and the profile at the beginning of construction. Construction Summary CONSTRUCTION PHASE The construction contract for the Soldier Creek Diversion Unit repairs was awarded in November of 2009 to LaForge and Budd from Parsons, KS for $9.069M. The original contract duration was 360 days. To date (October, 2011), $1.2 million in modifications have been awarded and the period of performance has been extended over 400 days, primarily due to weather delays. The Corps of Engineers has a field office established in a construction trailer on site and co-located with the North Topeka Drainage District s maintenance shed and the construction contractor s field office. Project engineer services are provided through a contract with HNTB, while construction quality assurance is performed by the Kansas City District s resident office in Kansas City. Additionally, Black and Veatch is contracted to provide Engineering During Construction services. Soldier Creek Levee Repair 847

10 Major Construction Features Construction effort can be divided into three main areas: bank repairs, in-channel work (including rock check dam construction and thalweg construction), and levee top repairs. Each main effort is discussed further below. Bank Repairs. The bank repairs consisted of demolition, cut/fill, riprap placement, drainage structure outlet repair or replacement, and plantings. This was the first significant construction effort and repaired several vertical eroded banks that threatened levee integrity. Demolition included removal of flood debris, deteriorated and cracked drainage structures, and eroded riprap that had shifted out of place. The construction contractor used a digital model provided by the designer to create a surface that could be read by a GPS system mounted on their equipment. The GPS allowed accurate cut or fill operations at every location in the construction area. Riprap was placed on channel banks in select places to resist shear forces where the hydraulic model predicted high shear forces. The design didn t create a riprap surface, so plan and cross-section views were used to manually calculate riprap quantities. Several drainage structure outlets were either repaired or replaced due to erosion of their foundations. And finally, temporary seeding, native grasses seeding, and willow plantings were performed to stabilize the bank. The native grasses require three years to fully establish while the willows will establish in one year. In-Channel Construction. With few exceptions, in-channel construction was done at low flows (less than 15 cfs, or an elevation of one foot). The stable stream design relies on a series of pools and riffles created by rock check dams and thalweg pools. The rock check dams also act as grade control structures to control bed degradation. The thalwegs were excavated to create pools and sinuosity in the channel while the rock check dams hold the water back and fill the pools. The exception to construction during low flows was rock check construction, which was done in the dry. Construction of the first few check dams was done using a temporary inflatable dam upstream of the rock check and a temporary berm downstream of the rock check. The remaining water, and seepage, between the temporary dam and berm was pumped downstream to reveal the bottom of the channel. At low flows, this system provided 8-10 hours to construct the rock check. At the end of the day, the temporary dam was deflated enough to pass water overnight, then re-inflated the following day to resume work. Installation and removal of the temporary inflatable dam took between 2-5 hours, and it could not be left in place for extended periods. This process was labor-intensive and required constant monitoring. As water levels rose behind the dam, the risk of the dam rolling increased. Also, if flows increased, the work time decreased rapidly. An alternate method to construct the rock checks was developed by installing temporary sheet piles across the channel upstream of the rock check dam (or series of rock check dams). This created a more reliable and controllable temporary dam that could be quickly removed if higher flows arrived. Water was pumped around the dry reach. The pumps weren t sized to handle the entire flow, but they increased work time significantly. 848 Innovative Dam and Levee Design and Construction

11 Levee Top Repairs. Levee crest repairs restored nine miles on both sides of the channel to the originally constructed 1958 elevations. Over time, two factors primarily contributed to decreased levee height. The first is levee consolidation and settling of the soil. The second is minor erosion caused by overtopping during flood events. In addition to restoring the 1958 elevations, six inches of aggregate was placed on the levee crests to prevent wheel ruts when the soil is moist. Construction Challenges and Considerations Construction Sequence. A construction sequence was not specified in the design. The contractor chose to start work at the upstream end of the project and progress downstream, saving the majority of rock check dams and the entire lower reach until the majority of bank repairs are complete. This was not what the designer envisioned and resulted in increased risk exposure to high water or floods. The features critical to controlling degradation and erosion were not in place for the majority of the construction period. Also, the keystone rock check, the one closest to the mouth of the diversion unit, was not constructed until the end of the construction period. Significant weather delays and high water extended the construction period and further increased the risk of erosion. The construction sequence that most reduces risk may not be the most cost effective, so prior to bidding it is important to communicate the relative benefits of alternative construction sequences to potential construction contractors in order to allow them to factor them their bids. Plant Establishment Time. The willows require a one year establishment period while native grasses require a three year period. High water that inundates the willows or grasses for more than a week will kill the plants and require replanting. If the high water erodes the toe of the bank before the vegetation is established, reconstruction of the bank may be required if the erosion is severe or if it is in a critical location. Reconstruction of eroded areas is challenging due to the requirement to move equipment to the bottom of the channel while minimizing disturbance of repaired areas higher up the bank. High water isn t normally a frequent occurrence, but two or three sustained high water events in a three year period would not be unusual. These events could result in costly repairs of eroded areas. Customer Satisfaction. Customer satisfaction is very important. The customer was not involved in the technical design phases or the construction, but the customer is the end user and will ultimately judge the design performance and quality of construction. The completed work must allow the end user to operate and maintain the project at minimum expense and effort. Currently, the customer has expressed concerns with the design and construction related to sustainability and safety. Sustainability. The sustainability concern arose after two successive high water events (2- year and 5-year flows) during construction that eroded the toe of the channel in several locations. To a small degree, minor erosion is expected in the channel, especially below the willows. However, the erosion experienced during the two high water events was more severe than expected and the water stayed high for about 14 days. This severely Soldier Creek Levee Repair 849

12 impacted some of the willows by either washing them away completely or inundating them and killing them. However the area of most concern was just downstream of the confluence of Soldier Creek and Indian Creek. Erosion reached the toe of the levee in that location. Due to the relative watershed sizes of the two creeks, water from Indian Creek entered the Solider Creek channel at approximately a 45 degree angle and eroded the opposite bank until the water surface in Solider Creek increased sufficiently to dissipate the energy from the tributary. 3 Rock check #7, just downstream of the tributary confluence, also affects normal flow patterns that might otherwise center the flow. Riprap will be added in the areas where erosion was more severe. The potential for erosion should be significantly reduced once the willows are established. Occasional replacement of willows may be required if water levels stay high for extended periods. Safety. The safety concern is related to the removal of ramps and turnaround areas. Occasionally the customer hauls truckloads of rock or soil for minor repairs on the levees. These trucks need turnarounds and ramps to reach lower areas of the channel. These weren t reproduced in the new design. Levee Integrity & Sustainability. Soldier Creek is a flood damage reduction project and helps protect the City of Topeka from flooding. It is critical that the focus of design and construction be on proven methods for sustainability, reliability, operation, and maintenance. Levees that protect lives and property should keep sustainable construction methods in balance. While a uniform riprapped channel may be expensive to construct and less aesthetic, it is a proven and reliable flood damage reduction tool. A better balance between conventional and sustainable design should be sought. While the riprap provides immediate erosion protection, the willows contribute to a more visually appealing channel. Thalwegs. Construction of the thalweg pools was difficult due to the sandy soils prevalent in the channel. As soon as a bucket of soil was excavated, the side would cave in and nearly fill in the excavated area. Additionally, it only took a minor flow to transport enough sediment to fill in the thalwegs. In a channel with a sandy bed, it is nearly impossible to maintain anything but a flat channel bottom without constant and steady turbulence. Eventually the sand will self-level to remove any constructed slopes. Seven of the eleven thalweg pools were constructed and each filled in completely with the first high water event. Three of the four remaining pools were not constructed. The final pool, around the long bend near the mouth, was constructed. The long radius of this pool is more likely to develop a rolling current that will self-scour to maintain the pool structure as designed. Channel Bed Material. The channel bed material upstream of the approximate location of rock check #3 consists of coarse sand and pebbles. Downstream of rock check #3, the bed materials transition to a fine silt and sandy loam where the Kansas River frequently backs 3 Observations of Alan Schlindwein, P.E., river hydraulic engineer, with the Kansas City District of the US Army Corps of Engineers. 850 Innovative Dam and Levee Design and Construction

13 up into Soldier Creek. Neither of these bed materials lend themselves to thalweg pool construction or anchoring rock check dams. In particular, the first rock check dam called for 3-ton riprap to be placed in the bed. The bedding of these rocks is critical to maintain their grade in a fine sand channel 4, however due to the difficulty in preparing such bedding, a more economical solution was sought. The final solution was to shift the first rock check upstream to connect with riprap under the Union Pacific Railroad Bridge. The size of the rock check riprap was reduced to 1-ton. Hydraulic models demonstrated that shear forces permit the smaller riprap size. Figure 6. High Water Event at Downstream Bridges Channel-to-pier Alignment. It was discovered during construction that a large bend near the mouth of the diversion unit did not align flows with a pair of bridges at the exit of the bend (see Fig. 6 5 ). The design was modified to align the flows parallel to the bridge piers and minimize turbulence. Earthwork and Riprap Quantities. The construction contract is a lump sum contract. This simplifies the contract structure and bidding process, but leads to difficulties when negotiating modifications, as the designer and construction contractor rarely agree on quantities. In a large earthwork project, the quantities of cut/fill and riprap are significant costs and accurate quantities are necessary for pricing. A future recommendation would be to structure the contract to include certain unit prices to simplify future negotiations. Construction Successes Equipment-mounted GPS. The construction contractor used excavation equipment with GPS mounted on the blade or bucket. This gives the ability to construct very accurate channel banks and beds. This feature saves time and results in construction that more accurately reflects the intended design. 4 Ibid. 6 Photo credit US Army Corps of Engineers. Soldier Creek Levee Repair 851

14 Digital model. The design surface was provided to the construction contractor for their use. While it required conversion to a format they could use, it was a valuable tool for them to transfer the drawings to the channel construction. Temporary dams. Rock checks were constructed using temporary dams. After difficulties were encountered with inflatable dams, the sheet pile temporary dams offered a much improved solution. Aesthetics. The sinuous channel is more visually appealing than a uniform riprap-lined channel. In urban areas, although aesthetics are important, the right balance between sustainable and conventional design should be sought. Flexibility. Although, constructing the lower reach of the channel last was not anticipated, it did allow observation of the constructed upper reaches of the channel in two high water events. Through these observations, significant changes were made to the lower reach design, which will result in a more stable channel. CONCLUSIONS The following are the three foremost conclusions which have been drawn over the course of the study, design, and construction phases of this project: Construction performed based on the design principles common during the 1950 s (primarily involving stream straightening), may subsequently produce degraded profiles and eroded stream banks. Stream stability design principles should produce streams with reduced long term maintenance costs. These design principles include optimizing channel geometry, sinuosity, pool-riffle spacing, rock check dams, and vegetation. It is important to have a thorough knowledge of the site geology in order to achieve this. Construction challenges should be expected even for a contractor experienced with water control issues associated with working in a stream. Careful planning needs to go into the construction sequence in order to maximize the opportunity for plant establishment relative to the seasonal timing of high water events. REFERENCES Bentley, Intergraph Inroads, Version 8, Exton, PA. FHWA NHI , HEC-18, Evaluating Scour at Bridges, 4 th Edition, May GEO-SLOPE International, Ltd., SLOPE/W 2007, Calgary, Alberta, Canada. Juracek, Kyle. Historical Change Along Soldier Creek, Northeast Kansas. USGS Water Resources Investigations Report Innovative Dam and Levee Design and Construction

15 Kansas City Metropolitan Chapter, American Public Works Association (KCAPWA), Construction and Material Specifications, Section 5600 Storm Drainage Systems and Facilities, Design Criteria. Pemberton E.L. & Lara, J.M. (1984). Computing Degradation and Local Scour. Technical guideline for Bureau of Reclamation, U.S. Department of Interior, Bureau of Reclamation, Denver, CO. Soar, Philip J. and Thorne, Colin R., Channel Restoration Design for Meandering Rivers. Engineer Research and Development Center, US Army Corps of Engineers. U.S. Army Corps of Engineers (USACE) Channel Stability Assessment for Flood Control Projects. Engineer Manual U. S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-RAS, Hydrologic Modeling System, Version 3.1.3, Davis, California, January U.S. Army Corps of Engineers, Project Information Report, Rehabilitation of Damaged Flood Control Works. Part II. Basic Report, May Soldier Creek Levee Repair 853

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