 Concrete Arch Installation, Down East Lakes Land Trust. Headwater streams are often small and perceived as inconsequential. However, first and second order streams make up 80% of the linear distance of a watershed network. They also represent a large percentage of roadstream crossings in a giving watershed. This morning we are getting ready to do a roadstream crossing restoration on a small tributary of Grand Lake Stream called Billy Brown Brook. The project here is essentially to replace an old undersized culvert with a bottomless arch culvert to create a natural stream channel that will allow a natural movement of especially brook trout but also other aquatic wildlife. This is a fairly typical forest road stream crossing and it is too small culvert side by side. They're both too small to allow movement of fish through the site. When flows are high, the velocities through the culverts would be too high. They've also gradually become deteriorated, partly crushed and have been contributing to flooding upstream of the road. A site like this, there's a risk that at high flow you'll wash your road out completely and dump a lot of sediment into the stream. Generally speaking, smaller streams present fewer challenges during construction. However, the perception of an increased cost associated with stream smart installations present a social challenge. The concrete arch culvert presented in this video provides a cost effective alternative for small headwater streams. The traditional round galvanized culverts have somewhere 17 to 20 year lifespan. I haven't specifically talked with regard to this concrete arch but my guess is going to have a 70 to 100 year lifespan. There is no bottom to disintegrate in this particular structure. Assessment and design. Field assessment for design of an open bottom arch culvert installation includes longitudinal profile, cross section of a reference reach and evaluation of the substrate. In the case of the Down East Lakes Land Trust site, an undisturbed reference reach could not be determined given the presence of additional sites both upstream and downstream in close proximity. Therefore, in order to determine bankfull width, we relied on a local regression relationship between bankfull width and watershed area upstream of the road crossing, establishing 8 feet as appropriate width for the replacement structure. The longitudinal profile establishes the elevation of the stream channel through the road crossing and channel gradient. Scour potential is evaluated by observing the pool depths in the stream. The Deargo Timberlands 8 foot cement arch is constructed in sections. Footers are 24 inches wide and 12 inches in height. The arch has an inside width dimension of 95 and a half inches and height of 38 and a half inches. For this installation, the bottom of the footer was set one foot lower than the stream channel elevation. Final top of road was reestablished providing two feet of road material above the culvert. The placement and alignment of the replacement culvert conformed to that of the existing culvert. Project SHARE staff was on site to assist the contractor with setting elevations and culvert placement. Water control. During the entire construction phase, cofferdams were in place upstream and downstream outside of the working area. Pumps were used to divert clean water around the construction site back into the stream below the downstream cofferdam. A second pump was used to divert muddy water offsite into the riparian buffer where the fine sediment was filtered out minimizing impacts to the stream below the construction site. The arch was installed in August of 2013 when flows were low. A high water rain event in the days prior to construction presented difficult conditions for water control at the site. The contractor set up water diversion pumps during the rain event to prevent washout of the road. This incident emphasizes the importance of working with the contractor with sufficient equipment and experience to handle high water events. What we want to make sure is during construction is we have clean water being pumped around the stream and because from the block net on down we still have brook trout and other kind of stream fishes in here so we want to maintain a flow through here. And the other thing you can look in right now we have the water nice and clean as if construction wasn't happening. So the dirty water we pump out into the woods, the clean water we pump around and maintain a stream with our construction site isolated. Construction. The pipe prior to the start of any excavation. Note the material between the footers was excavated down to the elevation of the stream bed leaving natural stream bed material in place and avoiding the need to build the center of the stream bed back up with foreign material. Placement of larger rocks along the inside edges of the footers. This material serves two purposes. One it provides for scour protection and two it creates an artificial stable stream bank creating a low flow channel through the culvert. Placement of the concrete arch. Once the footers are in place sections of the arch are set in the key channel in the top of the footers. Sections of the footers and arch are placed so that joints are offset providing for structural stability. The arch comes in four foot sections designed to be light enough so that a single excavator can be used to handle them. The completed arch culvert is draped with geotextile fabric to prevent loss of fine material through the joints between sections. Cables are used to hold the sections together to prevent shifting over time. Completed arch, channel shaping, and adjacent road backfill. At this stage the site is ready for backfill another critical stage in construction. The backfill behind the concrete arch is placed in 6 to 12 inch lifts that are mechanically compacted with a hand compactor. The backfill for the road beyond the abutment backfill is typically just compacted with larger equipment such as an excavator or bulldozer. Even though the road fill beyond the abutment backfill is not mechanically hand compacted it still should be placed in lifts no greater than 12 inches with adequate compaction between lift placements. This will help to minimize settling in the road surface especially closer to the arch. The amount of rip-wrap reinforcement against the abutments should be limited to only the amount needed to minimize encroaching on the stream channel bottom. If the opening for the arch is properly sized sediments will be deposited upstream, downstream, and under the arch to form a continuous natural low flow channel. With a properly sized opening the natural channel continues uninterrupted under the arch and can adjust according to storm intensities and sediment transport loads. Support for the production of this video comes from Poland Spring, the Sewol Foundation, and the USDA Natural Resources Conservation Service. StreamSmart is a collaboration of the following partners. Thank you to the following organizations and individuals who helped make this video possible.