Post Date: 11/4/2019
Contributed by Corey Engen, Parker Scherman, and Curt Bender, FlyWater, Inc.
THE STREAMCREST IMPLEMENTATION STORY
I want to start off with a thank you to the Colorado Riparian Association (CRA) for including FlyWater, inc. and the Streamcrest construction team in the CRA’s 2013 Flood Recovery Blog Series. Like previous blog authors, my intention is to inform the reader about specific aspects of the contributions of our team to the overall success of the Streamcrest project and hopefully illustrate how a river construction project works from the constructor’s point of view. In particular, I will show how the design elements described in Julie’s Post 5 moved from design drawings, through the construction process, and into actual floodplain and in-stream structures functioning in a living, breathing stream channel.
The Design-Build Team
This project was a massive undertaking that required the knowledge, skills, and input of a variety of team members. Lefthand Watershed Oversight Group (LWOG), as the client, provided an environment focused on collaboration, coordination, and communication; Otak developed the engineering designs; and the construction team of Iron Woman Construction, Wildlands Restoration Volunteers (WRV), and FlyWater, inc completed installation of the design elements. We learned one thing for certain: you cannot expect exceptional results without an exceptional team working together. The working relationships and collaborations that developed within the Streamcrest team are a prime example of this lesson.
Riverine Construction
Now, let’s look at how we get from a riverine design plan set to a completed construction project that is satisfactory to stakeholders. Construction in a riverine environment has many variables regarding how the work will be implemented in order to produce the design improvements depicted in the plans. Chief among these variables are the actual conditions discovered in the field. Often, plans are based on satellite imagery and limited site walks, but when construction commences, unanticipated conditions are found that affect the ability of constructors to build according to plans. This is where the term “field fit” comes into play. Designers and builders must be in constant communication in order to identify and address these situations. Effective communication results in successfully reducing the need to rework already constructed features and stream bed/bank modifications. Reworking can be costly both in terms of time lost and potentially difficult working conditions. When an operator understands the designer’s vision, the operator can more effectively build necessary functional elements with less direct oversight, which is another important aspect of effective communication.
Another important variable to consider is the often-evolving expectations of stakeholders like property owners within the project area. LWOG did an admirable job of maintaining communication between the stakeholders and ensuring that both design and construction teams were alerted to any potential changes/additions to the original plans. Managing and communicating expectations is an important role when transitioning from the design process to construction.
The actual construction begins with a discussion of the Process or order of construction that will best allow for a timely, efficient, and cost-effective completion.
Process – Sequence of activities matter greatly in a river improvement project. Projects are layered with activities that need to be performed to realize maximum benefit from the effort. Just as a house cannot be built to completion from one corner, a river and its adjacent riparian floodplain cannot be built in its entirety at a given location as well. In recognizing and planning for this, steps taken at each layer can add value to the next action.
The Streamcrest project had many components associated with it to bring the project to life from a set of paper plans. Pre-construction communication between the prime contractor and sub-contractors is a must to increase understanding and efficiencies to this construction process. This is where a detailed outline and schedule to how the construction process for the project will flow which starts to bring life to the project. The following will walk us through the process of the construction of the Streamcrest project from start to finish.
First there needs to be a physical representation of the plans laid out on the site via staking and flagging. This allows stakeholders to envision actual element locations and any potential “field fit” adjustments.
Alignment – Field staking proposed channel alignments and structures identify intertwined environments such that field variables can be assessed, and designers and constructors can “field fit” accordingly.
The field staking for the Streamcrest project took place before equipment hit the project site. During this project staking field variables are sometimes encountered that have changed during the design process or there may be new findings in the field that may result in the construction contractors and the design team to employ “field fit”. Examples of this on the Streamcrest project were in locations where existing healthy vegetation and/or trees were located within an overflow channels alignment or floodplain benching. The solution to these areas where healthy and important established vegetation is located was a change or a “field fit” of the alignment to exclude these areas from the grading cut or excavation. This flexibility between the construction crew and the designs is just one example of how communication and understanding of overall stream function and design intent by all parties involved can be instrumental in a project’s success.
The materials required to build structures and complete construction will need to be clearly identified, acquired, and staged for ease of access by constructors.
Materials – Those items that are to be harvested from the field need to be confirmed and if materials are limited, alternatives must be identified and planned for early on. Furthermore, there may be materials not specified in the plans that are critically important to the successful completion of a river project (such as appropriate substrate to us in the river construction). These need to be recognized, set aside, and used in the best fit location.
To achieve the materials needed to produce and install the Streamcrest project to design specifications, the team recognized that many of the materials needed for construction could become available during the action of opening up the floodplain, such as the grubbing or removal of trees in overflow channel locations, and the excavated cut of the overflow channels. However, the need for import of rock from offsite to build the cross channel structures was also discovered during this time. The excavated material was cut and hauled to a neighboring property where the construction team worked with the landowner to set up what is called a batch plant or a material processing location. In this location, a large screen was used to sort the excavated material from the floodplains of Streamcrest into usable materials, such as soil, cobble, gravel etc. This material can then be reincorporated into the project on an as-needed basis. This forward thinking allows for a project to reuse materials to benefit the project as a whole. One other way that the project reused materials is that non-invasive trees which had to be cleared to expand the floodplain were carefully harvested by an excavator so that the rootwad would stay intact. These trees were then used in the bank stabilization log structures which help with erosive forces on the stream banks but also add greatly increased habitat for aquatic and terrestrial species.
When the field staking and initial materials are in place, the excavation of the project can begin. We generally break this process into macro-grading (i.e., overbank, floodplain and major channel grading) and micro-grading (i.e., fine channel grading) Working with designers the construction team transforms design contours to replicate the natural contours of the project reach that fall in line with the valley floor, anticipated water surface elevations, and groundwater. This is done by maintaining real-time quality control over critical features such as channel profile, bank heights, and hydraulic grade lines.
Macro-grading – These are the activities associated with reconfiguring the riparian floodplain and associated infrastructure. This will often include large scale mass excavation including storage or off-site disposal of excess material.
Micro-grading – Once the river and floodplain has been macro-graded, final grading, installation of hydraulic and erosion control structures, and riparian plantings layered in rock work will take place. Micro-grading will take place in a top (upstream) to bottom (downstream) fashion when possible, as this creates the best water conditions to allow the constructors to install structures to the proper specification of the designer.
The construction team for the Streamcrest project specializes in addressing the design plan and extracting the exact location, type, and level of difficulty of the excavation and grading that must take place to produce a final product that the design portrays while maintaining a natural feel. Our construction team divided the overall excavation into the two subsets discussed above. The large scale macro-grading took place first which was achieved by using large heavy equipment that can move large quantities of material. Once the macro-grading was completed, micro-grading took place with smaller excavators to achieve the natural feel to the project. This is another situation where the construction team worked directly with the design team and stakeholders to determine how to “field fit” specific treatments to give the Streamcrest project a little “frosting on top”. We enjoy producing a project that is not only fully geomorphically, ecologically, and hydrologically sustainable and resilient, but also anthropogenically sustainable and resilient.
Habitat – Care must be taken to leave physical habitat in the best possible configuration allowable, in areas with design elements as well as the areas outside of the design that are impacted by the process of construction (i.e. staging areas and access routes). Our team understands that excellent river work goes beyond the design plans with a team that makes every effort to construct a resilient system that all stakeholders will be proud of and support. Habitat elements are often overlooked in the design process to no fault of the design team as, especially in the flood recovery effort, time was of the essence in producing a plan to move forward with the project while maintaining support from all agencies. However, we truly believe the difference between a good project and a great project is adding these habitat elements.
Habitat on the Streamcrest project was a collaborative effort between all stakeholders. Generally, the in-stream habitat was focused on the fish species, specifically trout. We increased the capacity of this reach by adding small wood and habitat boulders. Over bank habitat was increased by the addition of woody debris and rock to the floodplain. Over time, both of these habitat treatments will naturalize and allow for greater biodiversity in the Streamcrest reach.
Once the revegetation is complete and the heavy equipment has been demobilized off site, the construction phase is complete. It is now time for the river valley to work with what has been created and the stakeholders to monitor this work to determine how the project performs.