British Columbia Mine Reclamation Symposium

Revegetation restoration for culvert replacement in a wetland Ashenhurst, Amber; Polzin, Mary Louise 2010

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REVEGETATION RESTORATION FOR CULVERT REPLACEMENT IN A WETLAND   1Amber Ashenhurst, MSc., RPBio. 2Mary Louise Polzin, PhD., RPBio.   1 Hatfield Consultants #200 - 850 Harbourside Drive North Vancouver, B.C. V7P 0A3 2 Interior Reforestation Co Ltd. Box 874 - 4500 Mennie Rd Cranbrook, B.C. V1C 7B6  ABSTRACT  Impacts from industrial activities in and near sensitive wetlands and streams receive considerable attention resulting in a wide variety of environmental protection techniques. This paper examines impact mitigation to a small stream (Palmer Bar Creek, East Kootenay) and surrounding wetlands during a train crossing culvert replacement and decommissioning. Prior to the placement of fill and construction of working platforms for heavy equipment, wetland soil was removed and temporarily stockpiled. Once work was complete, the temporary fill was removed and the native soil was replaced. Revegetation of the disturbed areas involved a combination of transplanting species from the immediate undisturbed wetland and planting nursery stock of native species identified in the area. Restoration of the temporary access road included placement of randomly spaced large boulders along the road and seeding with a mixture of agronomic grasses and legumes to reduce overland flow erosion during large rain events. Seeding also reduced the likelihood of noxious weed establishment from the undisturbed upland habitat. The replacement of the stockpiled wetland soil provided an excellent growth medium resulting in 99.5% survival and mean growth of 30 cm for woody species of nursery stock the following year.  Key Words: native, soil, wetland, transplant, seeding, mitigation.  INTRODUCTION  Dillon Consulting Limited (Dillon) retained Interior Reforestation Co Ltd (Interior) to complete the terrestrial component of an Environmental Assessment Overview (EA) as well as environmental monitoring and revegetation restoration for the Swansea culvert replacement and decommissioning. In April 2008, prior to any construction activities, background flora and fauna information was collected. Collection of additional environmental information occurred throughout the rest of the spring and summer (e.g., nesting bird surveys). Monitoring activities concerning construction of the new culvert and decommissioning and burying of the old culvert commenced early August and ended September 2008 and site reclamation ensued. The project was associated with the Swansea CPR Siding Expansion Project and was located between Miles 8.0 and 10.0 on the Moyie Subdivision along Canadian Pacific Railway (CPR). This project included the extension of the existing siding of the railroad, realignment of the tracks, and a culvert replacement. The siding is adjacent to a ballast pit on the west side of the mainland track and Palmer Bar Creek on the east side of the track.  Environmental Monitors (EM) from Interior were on site during all in-stream construction activities. Monitored construction activities included: draining and redirecting water flow from sensitive wetland areas to isolate the construction area, construction of work pads for heavy equipment, placement and construction of a new concrete culvert, removal of work pads, re-installation of stocked piled wetland soil, and decommissioning and burial of the old concrete culvert.  Restoration occurred in the disturbance areas which included the pads created for equipment and access roads down to them. Riparian and wetland species were planted in the appropriate habitat with seeding of the upland habitat.  PRE- AND POST-CONSTRUCTION  Heavy Equipment Pad Construction and Pond Containment  The area across the width of Palmer Bar Creek (herein referred to as either the creek or the wetland), containing the existing and proposed culverts, was isolated with the placement of large bulk bags filled with crushed rock and fines that were placed on the upstream side of the culvert. These bags created an isolated construction area downstream (Figure 1). Several smaller sand bags were added to the isolation dam to further reduce water seepage into the work area. Fish salvages occurred over several days (between August 11 and August 20) within the isolated section of the creek. Salvages captured a total of 204 fish of varying sizes and species. The most predominant species were Eastern Brook Trout (Salvelinus namaycush) and Longnose Sucker (Catostomus catostomus). Upstream of the work area, a series of pumps and hoses (four and six inch) were used to provide continuous creek water flow to the reaches and wetland areas located immediately below the construction area (Figure 2). Any additional water was pumped into nearby vegetation and allowed to filter through the vegetation and re-enter the creek free of sediment.  The worksite isolation allowed two heavy equipment pads to be created. The upstream work pad was created by placing fill into the isolated area immediately adjacent to the tracks and the new culvert location. Construction of the downstream pad involved removing and stockpiling the wetland soil prior to placing the fill. Mitigation also consisted of installing a sediment fence, which was reinforced with a wall of sandbags (Figure 3). A silt curtain, with fill material placed on its upstream side, was also drawn across the creek downstream of the work area to minimize the movement of silt.  Installation of New Culvert  Installation of the new culvert began with the removal of the section of railroad tracks above the new culvert location. Excavation for the new culvert then ensued, and once the desired elevation for the culvert was acquired, the base of the culvert pad was laid and back filled with gravel and fines (Figure 4). The fill was compacted to support the new culvert. Sections of the new culvert were then set into place, with the culvert wing walls added last (Figure 5). The excavation and movement of equipment, machinery and man power caused sediment plumes to flow downstream of the construction area. The disturbed sediment settled out quickly and a silt plume did not extend as far as the 50 m mark downstream. Following construction, the sand bags above the culverts were removed and a silt curtain was placed in front of the entrance to the old culvert to allow for natural water flow.  Removal of the work pads began on September 2, 2008. The upstream bulk bag isolation dam was pulled and the upstream work pad was removed and the site reclaimed as part of the creek bed. Deconstruction of the downstream work pad involved removing fill material until native wetland substrate was encountered (Figure 6). The area was then backfilled with the stock piled wetland substrate. The new concrete culvert was filled with wetland substrate to a depth of approximately 25 cm and the downstream pad silt fence/sandbag barrier was removed and replaced with pond bedding.  Riprap was placed alongside the west wing walls, located adjacent to the culvert opening, to approximately 1.5 m, and gradually sloped away from the structure. Native substrate was placed over the riprap and a low flow channel was contoured from the culvert opening. The channel was at a 0.5% grade and about one meter wide. Riprap was then installed at the toe of the east wing wall on the downstream side of the culvert and the remaining downstream crane pad was removed. Riprap was also placed at the culvert inlet in the same manner as the downstream side. During any in or near water work, water was removed from the excavation work area by a pump and six inch hose into a vegetated area. There were no downstream sediment plumes during the removal of the work pads.  Decommissioning and Burial of Old Culvert  An extension of the in-stream work window was granted by the Ministry of Environment to allow for abandonment procedures of the old box culvert. For this procedure, the silt curtain installed approximately 30 m downstream of the culverts remained in place. The fish fence immediately downstream of the old culvert was removed. Clean water upstream of the old culvert’s isolation barrier was discharged to a vegetated area to allow filtration following removal of the upstream sandbag isolation. Both pumps were kept running throughout the decommissioning to continue water flow downstream.  Isolation of the old culvert was completed upstream and downstream with poly, sandbags and native gravel to help seal water seepage. The culvert was then sealed with plywood, silicone and plastic and concrete poured. Standing water within the culvert was diverted into the isolation areas where it was pumped into designated locations with no direct access to the creek. Some of the standing water was absorbed by the concrete. To complete the concrete pour, the pumper-truck hose was placed into the upstream end of the old culvert and concrete was backfilled into the culvert to the upstream end. The water pumps continued to be active on both ends of the culvert in the primary isolation areas and until the isolation was removed. The downstream silt curtain captured most of the sediment released by this process and approximately 30 to 40 m downstream of the silt curtain the water ran clear. Eight-inch riprap was placed at the upper end of the old culvert. A final site visit noted that the water flow had created a natural wetted channel cross-section. Multiple observations of the creek channel demonstrated that equilibrium had been reached between substrate composition and water velocity. Immediately exiting the culvert, the substrate was a combination of silt/organic and sand/gravel.  Figure 1. Silt fence, bulk bags and pump upstream of old culvert and the start of the 2nd pad.  Figure 2. Galvanized aluminum culverts placed though old concrete culvert, with four inch hose running though for continuous water flow. August 14, 2008.  Figure 3. Pad construction (and sandbags/silt fence) on downstream side of culvert and stock- piled soil. August 11, 2008.  Figure 4. Placement of base of culvert pad after excavation for the culvert was completed.  Figure 5. Crane placement of new culver sections. August 22, 2008.   Figure 6. The downstream construction pad and removal of fill material down to the native soil. REVEGETATION AND RESTORATION  Restoration of Wetland Area  The approximate emergent area restored was 450 m2. Figure 7 shows the area when initial transplanting occurred downstream of the new culvert (note: lower left corner of the picture). Clumps of wetland plants were hand dug from adjacent undisturbed areas and transplanted into the wetland restoration site. An estimated 150 clumps of plants were spaced over the newly created emergent wetland (Figure 8). Transplanting of sedges, grasses, and wetland plants from the surrounding area resulted in a diverse species list as indicated in Table 1. Sedges, rushes and grasses made up approximately 80 % (~120 clumps) of the transplanted species.   Figure 7. Emergent area with transplanting initiated in the lower left hand corner.  Figure 8. Emergent and riparian zone after transplanting and planting completion.  Table 1. A list of the plants transplanted from the adjacent wetland into the downstream work pad site. Vegetation group are either obligate (OBL), or facultative wetland species (FACW) or facultative species (FAC). Common Name* Scientific Name Vegetation Group Beaked sedge Carex utricutata OBL Green sedge Carex viridula OBL Creeping spike-rush Eleocharis palustris OBL Taper-tipped rush Juncus acuminatus OBL Jointed rush Juncus articulatus FACW Simple-stem bur-reed Sparganium emersum OBL Nodding bur-marigold Bidens cernua OBL Douglas’s water-hemlock Circuta douglasii OBL Cut-leaf water-horehound Lycopus americanus OBL Field mint Mentha arvensis FACW Narrow-leaved collomia Collomia linearis FAC Water parsley Oenanthe sarmentosa OBL Smooth alumroot Heuchera glabra FACW Smartweed Polygonum hydropiperoides OBL Stiff clubmoss Lycopodium annotinum OBL Hair bentgrass Agrostis scabra FAC *A variety of grasses were present but not identified. The 150 plant clumps were obtained from an undisturbed adjacent wetland, approximately 0.2 ha in size, where there was a high density of the given plant species. The collection did not deplete the undisturbed area nor was the removal of the plants noticeable. All of the plants transplanted were either obligate wetland species (OBL) that almost always occur under natural conditions in wetlands or facultative wetland species (FACW) that usually occur in wetlands but are occasionally found in non-wetlands. Some of the species planted on the upper zone (dryer edge) of the wetland were facultative species (FAC) that are equally likely to occur in wetlands or non-wetlands. Some riparian nursery plugs were planted at the upper, dryer edge of the wetland zone. These nursery species were FAC and FACW species such as alder (Alnus sinuata), red-osier dogwood (Cornus sericea), Saskatoon (Amelanchier alnifolia), and willow (Salix spp.).  Four vegetation survey plots were completed after transplanting, in the wetland emergent zone. Average density of plantings (transplants were recorded as clumps as opposed to the number of individual plants in each clump) was 3.3 stems and clumps per square meter (Table 2).  Table 2. Plot survey results for the wetland area; plot radius was 1.78 m (10 m2 area). Plot 1 Count Plot 2 Count Plot 3 Count Plot 4 Count Clumps 14 Clumps 22 Clumps 28 Clumps 27 Willow 9 Willow 12 Willow 9 Willow 7 Alder 1 Smartweed 1 Bur-marigold 1 Total  34 Saskatoon 1 Saskatoon 1 Total 38 Total  25 Total  36  Restoration of the Riparian Area  The riparian area that had been compacted was ripped and covered with the stock piled native topsoil. The area which was approximately 200 m2 was planted with 510 plugs of shrub species (Table 3). The five surveyed plot results showed that the riparian zone planting averaged a density of 1.94 stems/m2 and an average species diversity of 4 (Table 4). Figure 9A shows the riparian zone once planting was completed. Planted stock averaged 7.5 cm tall so it is difficult to see the small seedlings in the photo. The riparian zone was also lightly seeded with the moist/dry seed mix (about ½ lb of seed mix from Table 5).  Table 3. Native woody species from Tipi Native Plants nursery descriptions. Species Size of Plug Amount Mean Heights Vegetation Group Sitka alder 415C 150 10 cm FAC Choke cherry 415B 150 5 cm FAC Rose 415B 86 4 cm FAC Saskatoon 415B 70 5 cm FAC Red-osier dogwood 415B 70 6 cm FACW Willow 415B 20 15 cm FACW  Total 546 Mean 7.5 cm   Table 4. Diversity and density plots in the riparian zone (2008). Plot 1 Count  Plot 2 Count Plot 3 Count Plot 4 Count  Plot 5 Count Rose 4 Rose 5 Rose 6 Rose 7 Alder 6 Alder 4 Alder 8 Alder 4 Alder 4 Cherry 7 Cherry 6 Cherry 8 Cherry 8 Cherry 5 Saskatoon 5 Saskatoon 1 Saskatoon 4 Willow 1 Saskatoon 3 Total 18 Total 15 Willow 1 Total 19 Total 19   Total 26  Restoration of the Temporary Road Down to Wetland Area  The temporary road down to the riparian zone restoration had a layer of fine gravel and sand mix spread over the area and large boulders randomly spaced (Figure 10A). The area (~ 200 m2) was seeded with 4.5 pounds of moist/dry seed mix after a few shrubs (16 plugs) were planted (Table 5). Grass and forb planting of the area should help to reduce soil erosion during rain events and reduce the bare ground area which could be colonized by invasive species from the surrounding uplands.  Table 5. The moist/dry seed mix percentages by species and by weight. Weight (%) Species Species % 22 Smooth brome 09 20 Crested wheatgrass 10 15 Perennial rye 11 14 Creeping red fescue 26 07 Orchard grass 13 03 Timothy 11 15 Alfalfa 10 04 White clover 10 100 Totals 100%  Survival and Growth of Planted Vegetation  The vegetation survival and growth was tracked in 2009 and 2010. The first site visit on June 5, 2009 surveyed survival since the September 2008 planting. The five random plots within the riparian zone had 100% survival and new growth had not started yet. The wetland zone could not be surveyed because it was inundated. A walk through the riparian zone by three people found two shrubs that did not survive (99.5% survival for the riparian zone). The seeded temporary road down to the riparian zone had good coverage (Figure 10B).  An August 5, 2009 site visit tracked survival and growth of the planted shrubs. Survival was 100% within plots and the average growth rate was 30 cm with a range of 3 to 48 cm of growth during the two-month time interval (Figure 9B). The average plant density was 1.96 stems/m2, similar to 2008, with no new natural recruitment. Species diversity averaged five per plot. The wetland area closest to the creek was still partially inundated in August so no plots were completed to reduce disturbance from walking on the water-saturated ground (Figure 11B). Most of the plants on the creek side of the sediment fence were gone, probably as a result of scour and/or prolonged flooding. The wetland area was observed to have reduced density and the surviving planted clumps were reduced in size. This reduction was attributed to the elevation of the wetland area, as the initial soil replacement should have been higher to match the adjacent wetland level which was not inundated during the site visit. Additionally, the prolonged inundation may have removed the top layer of soil increasing the loss in elevation in subsequent years. A wattle fence installed on the downstream side of the new culvert along the creek edge would have held the new bank in place and protected the ground and vegetation behind the fence from erosion. A lesson learned from this would be to survey the site before soil removal and during soil replacement to ensure a correct elevation is achieved, as restored banks of a creek even with very low velocity require protection from erosion.  The results from a vegetation survey on June 5, 2010 showed survival at 100% and average height of 38 cm, with a range of heights from 15 to 84 cm. However, the majority of plants sampled were browsed and the red-osier dogwood was heavily browsed with many plants browsed back to 10 to 20 cm from August 2009 height. Because of the browse, growth rates could not be measured so just the total height of plants was recorded. The overall growth has been excellent when comparing the initial planted riparian zone with the June 5, 2010 vegetation heights (Figure 9C). Again, the wetland zone was inundated during the June 2010 site visit, so it was not surveyed (Figure 11C). The adjacent wetland vegetation was also inundated; however, the depth of the inundation in the restored section was greater in the area closest to the railway tracks.  Plant densities had increased from 1.9 stems/m2 to 2.3 stems/m2 (Table 6). This increase was the result of natural recruitment of rose, Saskatoon, choke cherry, and raspberry (Rubus idaeus). Raspberry was not a planted species. The average species diversity was 6 species per plot. The initial diversity sampling in 2008 showed that the planted stock was distributed across the site with no dense patches of only one or two species. As time progresses and more natural recruitment occur, diversity of species not planted should increase. However, initial planted species selection was from the naturally occurring species on site.  The wetland transplanted clumps have expanded since the August 2009 field visit but not as quickly as anticipated. This is attributed to the low elevation of the replaced wetland soil and loss of topsoil during spring inundation. A second visit on August 10, 2010 will record survival and growth and will be presented at the 34th B.C. Mine Reclamation and 35th Canadian Land Reclamation Association Conference. Based on the June 5, 2010 survey, it is expected that growth rates for 2010 will be similar to the August 2009, but possibly affected by the level of browse and weather conditions during the growing season of 2010. No browsing was noted during the August 2009 survey; therefore, it appears that heavy browsing pressure may occur during the fall and winter months.  The 2010 spring survey recorded frost damage to buds on most species. Damage occurred predominantly on the alder, with none on the rose. This consisted of buds that did not open along the top portion of some branches. The first frost occurred during the first week of October 2009 and was very hard occurring before some plants had hardened off with the low reaching -100C. This damaged some of the buds set in 2009, resulting in poor to no viability the following spring. Not all plants suffered and there were no apparent patterns to the effect. For example, two plants very close together would have one damaged and the other not. No dead plants were found but some were substantially reduced in height with a size reduction ranging from 10 to 25 cm in height.  Table 6. Diversity and density for plots in the riparian zone in 2010. Plot 1 Count  Plot 2 Count  Plot 3 Count Plot 4 Count  Plot 5 Count Rose 5 Rose 5 Rose 8 Rose 6 Rose 10 Alder 4 Alder 6 Alder 2 Alder 4 Alder 4 Cherry 3 Cherry 2 Cherry 4 Cherry 1 Cherry 6 Saskatoon 1 Saskatoon 4 Saskatoon 6 Saskatoon 1 Saskatoon 4 Dogwood 2 Dogwood 4 Dogwood 2 Dogwood 6 Dogwood 1 Total 15 Total 21 Total 22 Willow 1 Raspberry 2      Sedge 5 Sedge 5      Total 24 Total 32  CONCLUSION  Working within the natural environment means that there are many factors that can not be controlled. Weather is one of the factors that can affect a restoration project dealing with planting and transplanting of vegetation. The weather for the transplanting and planting of the restoration area was cool with light precipitation, which was perfect for planting conditions. Excellent planting weather and subsequent cool wet fall and cool wet spring contributed to the substantial survival and growth rates of the planted areas. The summer of 2009 did not experience extended periods of drought, further contributing to the excellent survival and growth results. Spring of 2010 survey results showed outstanding survival and new recruitment establishment. Some reduction of growth from ungulate browse and weather was recorded.  The transplanted clumps of plants in the wetland zone did not expand as well as anticipated. This was attributed to a slight decrease in elevation of the replacement material and soil erosion during spring inundation. The seeded temporary road continued to have good vegetation cover with no noxious weed establishment. Some noxious weeds such as spotted knapweed and Dalmatian toadflax have started to spread from the undisturbed upland site into the riparian zone. The continued growth of the shrubs and grasses should help to control the spread and limit weed colonization.  For future projects of this nature, it is recommended that a survey of the area be completed prior to soil removal, so that soil can be stockpiled and replaced to the original level. A second consideration is the installation of a wattle fence. A wattle fence is live bank protection which provides a means of stabilizing stream sides after bank disturbance. This structure stabilizes the stream bank by reducing the surface area of contact between the flowing water and the bank material. Flowing water applies force to the cuttings that make up the wattle fence, as opposed to recently disturbed soil. This allows the newly transplanted and planted material time to establish roots that will eventually hold the soil in place. Wattle fence installation along a newly formed channel edge should be implemented regardless of stream velocity to assist in the prevention of soil erosion and establishment of plants.   Figure 9. Planted riparian zone September, 2008 (A), August, 2009 (B) and June 2010 (C).   Figure 10. Reclaimed temporary road seeded September 2008 (A), August 2009 (B), and June 2010 (C).   Figure 11. Wetland after transplanting September, 2008 (A), August, 2009 (B), and June 2010 (C). A B C A B C A B C


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