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Dec 12 2011 mitigation plans.pdfCLAY/KERR MITIGATION PLAN FOR TREE CUTTING ACTIVITY & } F AT 7316 164th Street SW DEC 16 2'61 Prepared by Burrus Design Group OEVi LOH' ' ,1T EFIVICF March 18, 2011 COUNUR Revised December 12, 2011 SITE CONDITIONS: Subject site is an engineered slope constructed in 2000. Site currently is covered with rip rap type stone with native plants erupting through the stone periodically. TRIGGER EVENT: The owners of the property at 7316 164"' Street SW cut down nineteen (19) existing trees as part of their maintenance of the site. This activity was reported to the City of Edmonds and it was established that permits were required for this work that had not been obtained. As a result of this the City has required a replanting plan and mitigation plan be created. GOALS AND OBJECTIVES: The goal of these documents is to establish criteria whereby the vegetation that was cut down is removed, trees cut down are replaced and methods proposed to keep this slope and the wildlife habitat on and around it maintained. Included in the report are a Tree Replacement Plan prepared by Burrus Design Group which specifies the type of trees to be installed and their size and locations. The Mitigation Plan addresses the various factors used to determine how best to plant and maintain the slope including timing, special considerations for planting, a schedule for maintenance of vegetation on the slope and a monitoring program. Impacts: 1. The nineteen trees cut were left in place on the slope. This additional weight is a potential problem for the stability of the slope. 2. Wildlife habitat has been minimally effected by the removal of these nineteen trees. Clay/Kerr Mitigation Plan March 18, 2011 Revised December 12, 2011 Page 2 Erosion possibilities are minimal where trees were removed since it has exposed no bare earth. Mitigating Actions: 1. Removal of Felled Trees: Because the upper part of the slope is the most highly stabilized, the cleaned trunks of the nineteen felled trees shall be cut into lengths no longer than I Wand removed from the site by pulling them and branches over 2" diameter to the top of the slope. If the material were to be removed downslope as suggested by the City there is a stronger possibility of compromising the slope, especially the toe of the slope where it is in a native state. If materials were taken off site in this direction gouges could be made to the slope that would concentrate water flow in the future and thus encourage erosion. Repair of such soil disruption would further impact existing native vegetation. The upper slope area is largely covered in Himalayan Blackberry (Rubus discolor), an undesirable non-native species, so any damage caused to this species by removal activity would not be an impact to significant vegetation. 2. Pipe Protection/Pre-construction Meeting: The upper half of the southwest portion of the slope has existing HDPE pipes which cannot be disturbed. Therefore, a preconstruction meeting shall be held before trunk removal begins to determine the best route for removal of the cleaned trunks. It is agreed that the six southernmost trunks shall be removed using a choker set up at the end of the drive as approved by Robinson Noble, the Geotechnical Engineers who designed the slope. The meeting shall confirm this as well. Prior to the meeting the existing pipes and trunks to be removed shall have been flagged in such a way that they can be seen from the upper bank. Those attending the pre -construction meeting shall be representatives of the City of Edmonds, homeowners or their representatives and representatives from the firm contracted to complete the removal of the trunks and branches. The existing pipes shall be inspected before and after tree trunk removal occurs to verify they have not been impacted by the removal work. Clay/Keir Mitigation Plan March 18, 2011 Revised December 12, 2011 Page 3 If any damage occurs it shall be the responsibility of the homeowners to restore the pipes to good working condition. Should any pipe restoration be required, the scope of area and type of work to be performed shall be evaluated with regard to any need for erosion control during this activity. City of Edmonds, homeowners and their engineers and landscape architect shall be present at the on-site meeting where these decisions are discussed. A formal plan of action shall be presented to the City for their approval prior to commencement of said work if it is needed. 3. Removal of branches from felled trees. Branches under 2" diameter may be left on the slope to decompose. Branches shall be removed from the site if they are too numerous. Geotechnical Engineer shall make this determination at time of removal. It is my opinion that carrying the debris off the slope by manpower would endanger both those doing the work (steep slope and large rock provide ample opportunity for injury) and the existing vegetation. The latter damage would occur if pieces of trunk were dropped in transport and went crashing through existing underbrush. Further intrusion into the vegetation would be needed to remove those pieces that had been dropped. Areas that have been disturbed by removal activities shall be seeded with a native grass seed mix and covered with clean straw as mulch. 4. Tree Selection for Revegetation: Slope shall be replanted at a ratio of 2:1 for trees felled. This is a total of 38 proposed trees. Trees cut down were Alder and Big Leaf Maple. These are both short lived trees with negative impact on steep slopes. Alders tend to grow vertically for many years but with time start to lean away from the slope. Eventually they topple over, undermining that portion of the slope where their rootball was. Big Leaf Maples on the other hand grow to maturity but in senescence lose large branches or whole trunks. The impact of either of these situations would have dire consequences to this slope. Robinson Noble has noted that cutting the trees down was a benefit to the slope rather than having them blow over in a wind storm as is their nature. Trees proposed for revegetation are native to the vicinity, have wildlife habitat value, need minimal maintenance (human intrusion and safety factors) and will help to stabilize the slope. Clay/Kerr Mitigation Plan March 18, 2011 Revised December 12, 2011 Page 4 Vine Maples (Acer circinatum) and Western Hazelnut (Corylus cornuta) are the trees of choice for this site. They are small, multi -stemmed trees. Their shrubby growth habit diversifies the predominant habitat provided by Alders and Himalayan Blackberries present on the site. Habitat on surrounding slopes is mainly composed of mature forests of Alder, Big Leaf Maple and Western Red Cedar. Size of trees specified for revegetation are set at 4-5' ht rather than 1" diameter because smaller trees establish better than larger ones and this size of tree should be able to be taken down this steep slope without harm to the tree or those handling it. Because of the steepness of much of this slope and the rock covering other parts of it, it is important to use a plant with a rootball small enough to fit in the holes that will be appropriate to the site, i.e. larger rootballs would require more soil and slope disruption. PERFORMANCE STANDARDS: 1. An as -constructed plan showing location of newly planted trees shall be prepared following planting and sent to the Owners, City of Edmonds and monitoring company. 2. Success of this planting shall be met if 85% of the trees installed survive. Survival shall be defined as active growth taking place on a minimum of 60% of the tree. 3. If any tree fails to meet this requirement in any of the monitoring years it shall be replaced the following October at the size originally specified. CONSTRUCTION STANDARDS: 1. A preconstruction meeting shall be held on site with the following persons present: City of Edmonds, Landscape Architect, Owners or their representative and persons who will be performing the removal, mulching and planting work. Location and Planting of Replacement Trees: a mix of Vine Maples and Western Hazelnuts, 38 total, 4-5' ht with a minimum of 2 stems shall be installed in any areas on site where there is exposed ground. Areas covered with stone shall not be disturbed in order to plant. First preference shall be to plant on those areas that have the least slope to promote successful establishment of new trees. In areas where degree of slope would expose the rootball, branches from the felled trees shall be used to create a dam on the downhill side of the planting area. (See attached Tree Replacement Plan and Slope Planting Detail) Clay/Kerr Mitigation Plan March 18, 2011 Revised December 12, 2011 Page 5 Vegetation within 4' of newly planted trees shall be cut to the ground. Mulch newly planted trees with 3" of clean straw in 4' radius circle from trunk. Keep straw 6" away from trunk. Tie a 12" length of biodegradable material such as sisal, hemp or other spray painted orange loosely around a branch of each tree at approximately waist height. 2. Timing for mitigation work: Removal of felled trees and branches shall occur in mid to late Spring. This will allow native vegetation that was disturbed by the process to re-establish in the growing season. Installation of trees for revegetation shall occur in October. Exact time of installation shall be determined by onset of seasonal rains. Install trees after first good rain of the season so ground is moist but not saturated. Following the proposed schedule will maximize success of both recovery of any existing plants impacted by the work and establishment of new trees. Estimated duration for removal work is 7 days with 3 men. Estimated time of installation as described above is 2 days with 3 men. 3. No grading is proposed for this site. Any bare ground shall be mulched with clean straw 3" deep. 4. Maintenance of Site: New saplings and sprouts off existing stumps shall be cut to within 3" of the ground before they reach 3" in diameter. These trimmings may be left on site to decompose. Vegetation within 4' of newly installed trees shall be cut to the ground each year in early summer for the first 3 growing seasons. Monitoring report in the third year shall advise if this activity needs to continue and for how long. MONITORING PROGRAM: 1. A monitoring program shall begin upon completion of installation of new trees. Because there are only forty trees being installed all trees shall be evaluated at each monitoring session. Trees shall be numbered on prepared as -constructed drawing. This numbering shall be used throughout the monitoring period. Clay/Kerr Mitigation Plan March 18, 2011 Revised December 12, 2011 Page 6 2. Reports shall include an evaluation of each tree including approximate height and percent of active growth. Photos shall be taken of ten representative trees and shall be included in each report. Photos shall include the most and least healthy trees evaluated. 3. Schedule: Monitoring shall last for three years. First monitoring report will be prepared one month after installation Thereafter reports shall be generated at the beginning and end of the first and second growing seasons and at the end of the third growing season. 4. Copies of all reports shall be provided to City and to Owners. 5. Monitoring reports shall be prepared by the same person each year. That person shall demonstrate a thorough understanding of the goals and objectives of this monitoring plan. 6. In the event of catastrophic failure of mitigation plantings (death of more than 50% of trees) monitoring period will restart at installation of replacement trees. CONTINGENCY PLAN: 1. In the event that success standards for mitigation plantings are not met corrective measure will be taken. They shall include substitution of tree type, changes to installation techniques, maintenance measures or other actions as are warranted. 2. Landscape Architect shall determine corrective measures to be taken. In the event that success standards for mitigation plantings are not met corrective measure will be taken. They shall include substitution of another type of tree, changes to installation techniques, maintenance measures or other actions as are warranted. FINANCIAL GUARANTEES: 1. In the event bonds are needed for this project, the following is a breakdown of costs for implementation of the mitigation plan: Removal of branches from felled trees using chainsaw $350.00 Removal of cleaned trunks from site 2,500.00 Installation of straw mulch in disturbed areas 200.00 Clay/Kerr Mitigation Plan March 18, 2011 Revised December 12, 2011 Page 7 Clearing of brush for installation of replacement trees 400.00 Installation of 38 replacement trees 2,400.00 Monitoring for three years (six reports) 2,400.00 Total price: $8,250.00 Prices include labor, materials and equipment CLAY/KERR CRITICAL AREAS REPORT FOR EROSION HAZARD AT 7316164 1h Street SW Prepared by Burrus Design Group March 18, 2011 Amended December 12, 2011 Contact Information: Diana Clay, Clay Enterprises 425-776-1234 Proposed Action for Site: Request is made for a permit to install 38 4-5' ht multi -stemmed native trees to mitigate for the cutting down of 19 large alders on this site. The stumps and roots of the alders remain in place. Trunks and large branches resultant from the felling of the 19 trees are to be removed from the site per Mitigation Plan attached. Subject Property: Site includes a flat area on the east side with a residence and paved driveway. To the west of this lies a steep slope (40% or greater) falling away from the home and drive. This site lies within the North Edmonds Earth Subsidence and Landslide Hazard Area as defined by the City of Edmonds. Slope has been stabilized since 1999 when it was modified according to a plan by Robinson Noble Geotechnical Engineers. Slope continues to be successful. Critical Areas on and around Site: In addition to the steep slopes noted above this site located is located in a mapped fish and wildlife habitat conservation area. There is evidence of year round seeps but no stream was observed. Impact of Proposal on Site: There is no increased erosion hazard on this site caused by the felling of the trees, the removal of the resultant debris (see Mitigation Plan for techniques of removal and protection procedures), or the installation of the trees proposed as mitigation for those felled. Clay/Kerr Critical Areas Report Erosion Hazards March 18, 2011 Amended December 12, 2011 Page 2 Because the trees were simply felled and their stumps and roots remain in place no soil was exposed by this action. Additionally, no increase in erosion due to raindrop impact is likely because the slope is heavily armored with rip rap along its entire face. Water will not be affected by any proposed operations since there will not be exposed soil. Dewatering of the site will continue through existing pipes across the engineered slope. Existing pipes shall be inspected before and after tree trunk removal occurs to verify they have not been impacted by the work. If any damage occurs it shall be the responsibility of the homeowners to restore the pipes to good working condition. Should any pipe restoration be required, the scope of area and type of work to be performed shall be evaluated regarding any need for erosion control during this activity. City of Edmonds, homeowners and their engineers and landscape architect shall be present at the on-site meeting where these decisions are discussed. A formal plan of action shall be presented to the City for their approval prior to commencement of said work if it is needed. Trees are to be installed in areas that have as little slope as possible with the downhill side of the planting areas reinforced with tree branches from felling operation. All installed plant material shall be mulched with 3" of clean straw covering any soil exposed by planting operation. Proposed trees shall eventually replace canopy lost due to felling operation. These new trees are of smaller stature than those removed and will diversify habitat by adding another layer of vegetation and establishing a canopy of leaves that offer not only protection to wildlife but reduction to raindrop velocity prior to their hitting the slope. Sequencing: As spelled out in the Mitigation Report attached, debris removal work is proposed to occur in late spring or early summer to allow for any vegetation damaged by the removal process to recover during the growing season. Installation of the proposed trees shall be done in mid to late October, after the seasonal rains begin. This will allow the trees to get established with the minimum amount of stress and demand on their roots as would be present during active growth. Report was written and research done by Ruth Burrus of Burrus Design Group, Registered Landscape Architect. CLAY/KERR CRITICAL AREAS REPORT FOR LANDSLIDE HAZARD AT 7316164 th Street SW Prepared by Burrus Design Group March 18, 2011 Amended December 12, 2011 Contact Information: Diana Clay, Clay Enterprises 425-776-1234 Proposed Action for Site: Request is made for a permit to install 38 4-5' ht multi -stemmed native trees to mitigate for the cutting down of 19 alders on this site. The stumps and roots of the alders remain in place. Trunks and large branches resultant from the felling of the 19 trees are to be removed from the site per Mitigation Plan attached. Subject Property: Site includes a flat area on the east side with a residence and paved driveway. To the west of this lies a steep slope (40% or greater) falling away from the home and drive. This site lies within the North Edmonds Earth Subsidence and Landslide Hazard Area as defined by the City of Edmonds. Slope has been stabilized since 1999 when it was modified according to a plan by Robinson Noble Geotechnical Engineers. Slope continues to be successful. Critical Areas on and around Site: In addition to the steep slopes noted above this site located is located in a mapped fish and wildlife habitat conservation area. There is evidence of year round seeps but no stream was observed. Impact of Proposal on Site: There is no increased landslide hazard on this site caused by the felling of the trees, the removal of the resultant debris (see Mitigation Plan for techniques of removal and protection procedures), or the installation of the trees proposed as mitigation for those felled. Clay/Kerr Critical Areas Report Landslide Hazards March 18, 2011 Amended December 12, 2011 Page 2 Because the trees were simply felled and their stumps and roots remain in place no soil was exposed by this action. No increase in landslide hazard due to raindrop impact is likely because the slope is heavily armored with rip rap along its entire face. This is a slope that has been stable for over ten years (see letter from Geotechnical Engineers Robinson Noble dated March 21, 2011). Debris removal shall be done by hand and at the top of the slope where it is most secure. No work is proposed at the toe of the slope where it is weakest. Because all work will occur in areas that are heavily armored no changes will be made to the existing water flow patterns. This slope is dewatered by many pipes lying beneath it. These pipes will not be impacted by this work. Pipes shall be inspected before and after tree trunk removal occurs to verify they have not been impacted by the work. If any damage occurs it shall be the responsibility of the homeowners to restore the pipes to good working condition. Water quality in the area will not be affected by any proposed operations since there will not be exposed soil. Should any pipe restoration be required, the scope of area and type of work to be performed shall be evaluated regarding any need for erosion control during this activity. City of Edmonds, homeowners and their engineers and landscape architect shall be present at the on-site meeting where these decisions are discussed. A formal plan of action shall be presented to the City for their approval prior to commencement of said work if it is needed. Trees shall be installed in areas with as little slope as possible and shall have the downhill side of the planting areas reinforced with tree branches from felling operation. All installed plant material shall be mulched with 3" of clean straw covering any soil exposed by planting operation. Proposed trees shall be of smaller stature than the alders that were removed. The natural life cycle of an alder (Alnus rubra) is to grow vertically to a height of 40-60' and then begin to lean over the slope. Eventually the weight of the tree pulls the rootball out of the slope, thus exposing it to danger of erosion and landslide. The proposed trees do not follow that pattern. They are small trees (Vine Maple/Acer circinatum and Western Hazelnut/Corylus cornuta) that regenerate by means of sprouting new trunks from the base rather than growing taller. Their eventual height is between 20 and 30'. Their roots will provide shallow stabilization of the slope. Clay/Kerr Critical Areas Report Landslide Hazards March 18, 2011 Amended December 12, 2011 Page 3 Sequencing: As spelled out in the Mitigation Report attached, debris removal work is proposed to occur in late spring or early summer to allow for any vegetation damaged by the removal process to recover during the growing season. Installation of the proposed trees shall be done in mid to late October, after the seasonal rains begin. This will allow the trees to get established with the minimum amount of stress and demand on their roots as would be present during active growth. Report was written and research done by Ruth Burrus of Burrus Design Group, Registered Landscape Architect. See attached field notes and photos. CLAY/KERR CRITICAL AREAS REPORT FOR STREAM AT 7316164 th Street SW Prepared by Burrus Design Group March 18, 2011 Amended December 12, 2011 Contact Information: Diana Clay, Clay Enterprises 425-776-1234 Proposed Action for Site: Request is made for a permit to install 38 4-5' ht multi -stemmed native trees to mitigate for the cutting down of 19 alders on this site. The stumps and roots of the alders remain in place. Trunks and large branches resultant from the felling of the 19 trees are to be removed from the site per Mitigation Plan attached. Subject Property: Site includes a flat area on the east side with a residence and paved driveway. To the west of this lies a steep slope (40% or greater) falling away from the home and drive. This site lies within the North Edmonds Earth Subsidence and Landslide Hazard Area as defined by the City of Edmonds. Slope has been stabilized since 1999 when it was modified according to a plan by Robinson Noble Geotechnical Engineers. Slope continues to be successful. Critical Areas on and around Site: In addition to the steep slopes noted above this site located is located in a mapped fish and wildlife habitat conservation area. There is evidence of year round seeps but no stream was observed nor was one found on the Edmonds Critical Areas Inventory Map. Impact of Proposal on Site: Because no stream was found no impact to a stream is predicted by this action. Report was written and research done by Ruth Burrus of Burrus Design Group, Registered Landscape Architect. See attached field notes and photos. CLAY/KERB CRITICAL AREAS REPORT FOR WILDLIFE HABITAT AT 7316164 1h Street SW Prepared by Burrus Design Group March 18, 2011 Amended December 12, 2011 Contact Information: Diana Clay, Clay Enterprises 425-776-1234 Proposed Action for Site: Request is made for a permit to install 38 4-5' ht multi -stemmed native trees to mitigate for the cutting down of 19 alders on this site. The stumps and roots of the alders remain in place. Trunks and large branches resultant from the felling of the 19 trees are to be removed from the site per Mitigation Plan attached. Subject Property: Site includes a flat area on the east side with a residence and paved driveway. To the west of this lies a steep slope (40% or greater) falling away from the home and drive. This site lies within the North Edmonds Earth Subsidence and Landslide Hazard Area as defined by the City of Edmonds. Slope has been stabilized since 1999 when it was modified according to a plan by Robinson Noble Geotechnical Engineers. Slope continues to be successful. Critical Areas on and around Site: In addition to the steep slopes noted above this site located is located in a mapped fish and wildlife habitat conservation area. There are no specific high value animals or fish noted on the Edmonds Critical Areas Inventory Map. There is evidence of year round seeps but no stream was observed. Impact of Proposal on Site: The area surrounding this site is largely covered with mature forests of native vegetation. Predominant to the south is Red Alder (Alnus rubra). To the north Big Leaf Maple (Acer macrophyllum) and Western Red Cedar (Thuja plicata) are also present. Clay/Kerr Critical Areas Report Wildlife Habitat March 18, 2011 Amended December 12, 2011 Page 2 Because this site was largely disturbed in 1999 when the dewatering work was done the habitat on adjacent sites is much more diverse than on subject site.. The predominant plant material on site at this time is Himalayan Blackberry (Rubus discolor) and Red Alder (Amus rubra). The trees that were cut down were Red Alder. These plants tend to grow as monocultures, providing habitat of limited importance or diversity on the site. The proposed trees trees (Vine Maple/Acer circinatum and Western Hazelnut/Corylus cornuta), though not native to the specific site are indigenous to the Pacific Northwest and will diversify the habitat provided in this area, especially for small birds and herbivores. Proposed trees are smaller in stature than the alders that were removed. The natural life cycle of an alder (Alnus rubra) is to grow vertically to a height of 40-60' and then begin to lean over the slope. Eventually the weight of the tree pulls the rootball out of the slope, thus exposing it to danger of erosion and landslide. The proposed trees do not follow that pattern. They are small trees that regenerate by means of sprouting new trunks from the base rather than growing taller. Their eventual height is between 20 and 30'. In addition to habitat, their roots will provide shallow stabilization of the slope. A further advantage of planting these smaller trees is that they will not need any maintenance once they are established. The steepness of the slopes in this area keeps human intrusion to a minimum (other than when needed for maintenance). Further, the slopes are of significant width on this site (over 100') that any animals resident to the area or traversing through it would not be effected by the cutting of these trees or by the installation of new trees. Trees shall be installed in areas with as little slope as possible and shall have the downhill side of the planting areas reinforced with tree branches from felling operation. All installed plant material shall be mulched with 3" of clean straw covering any soil exposed by planting operation. Wire cages will also be installed around the trunks of newly planted trees to minimize damage to cambium from rodents. Sequencing: As spelled out in the Mitigation Report attached, debris removal work is proposed to occur in late spring or early summer to allow for any vegetation damaged by the removal process to recover during the growing season. Clay/Kerr Critical Areas Report Wildlife Habitat March 18, 2011 Amended December 12, 2011 Page 3 Installation of the proposed trees shall be done in mid to late October, after the seasonal rains begin. This will allow the trees to get established with the minimum amount of stress and demand on their roots as would be present during active growth. Report was written and research done by Ruth Burrus of Buirus Design Group, Registered Landscape Architect. See attached field notes and photos. --- - ------- (0(0 • co CO ® 0 0 O V 0 /0 0 00 ez 0 06 I. 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