Loading...
Wetland Buffer Mitigation Plan.pdfAr1 ����www.hartcrowser. CRowsrw Delivering smarter solutions 2182192nd Avenue West Wetland Buffer Mitigation Plan Edmonds, Washington Prepared for RF %F.Iv Rick Wichers jo PERMIT COUNTER May 29, 2007 12555-02 Prepared by Hart Crowser, Inc.-Pentec Environmental 120 Third Avenue South, Suite 110 Edmonds, Mshington 98020-8411 Fax 425.778.9417 Tel 425.775,4682 INTRODUCTION General Site Conditions Wetland Conditions T SITE DEVELOPMENT IMPACTS 2 PROPOSED MITIGATION 3 Enhancement Plantings, Log Placement, and Invasive Species Removal 3 Fencing and Signs 4 Post -Mitigation Wetland Buffer Functions and Values 5 GOALS AND PERFORMANCE STANDARDS 6 Goal i; Enhance Wetland Buffer Areas through Installation of Native Vegetation 6 Goal 2: Remove Invasive Plant Species within the Existing Wetland Buffer 6 MAINTENANCE AND CONTINGENCY PROCEDURES 6 CONSTRUCTION MANAGEMENT 6 MONITORING 7 Vegetation 7 Photopoints H Monitoring Schedule 8 Performance Bond $ LIMITATIONS 9 REFERENCES 9 Hart Crowser, Inc.—Pentee Environmental Page 12655-02 May 29, 2007 CONTENTS (CONT.) TABLES 1 Proposed Buffer Enhancement Plantings 2 Cost Estimate for Performance Bond FIGURES 1 Vicinity Map 2 Wetland Delineation Plan Hart Crowser, Inc —Pentec Environmental Page it 12655-02 May 29, 2007 21821 92ND AVENUE WEST WETLAND BUFFER MITIGATION PLAN EDMONDS, WASHINGTON INTRODUCTION This report discusses impacts and mitigation for a proposed subdivision located at 21821 92nd Avenue West in Edmonds, Washington (Figure 1). The property is recorded as parcel number 27043000200400 and is approximately 0.45 acres in size. The property is located in S30, T27N, R4E. The objective of this report is to discuss impacts to the on-site wetland buffer and provide mitigation measures to compensate for those impacts. General Site Conditions Dominant vegetation within the upland portion of the site consists of mowed lawn with a fringe of forested vegetation located around the property boundary. Douglas fir (Pseudotsuga menziesir), Pacific willow (Salixlasiandra), Scouler's willow (S. scoulerana), Indian plum (Oemleria cerasiformis), and Himalayan blackberry (Rubus armeniacus) dominate the forested portion of the site. The topography of the property is generally flat. Near the eastern and southern property boundaries, the property slopes to the south and east toward the wetfand system. The site is dominated by the Alderwood soil unit: a moderatefy well -drained soil that forms on till plains. Wetland Conditions In May of 2007, we prepared a wetland delineation and categorization report to ( document and describe the location and boundaries of the identified wetlands € within the subject property (Hart Crowser 2007). Our investigation identified one wetland (Wetland A) located near the southeastern property boundary. Wetland A is a depressionai wetland with a forested plant community class.. We rated Wetland A as a Category 111 wetland in accordance with the Washington State Wetland Rating System for Western Washington - Revised (Hruby 2004) based on the accumulation of 48 points. The wetland received 24 points for water quality function, 12 points for hydrologic function, and 12 points for habitat function. _ Hart Crowser, Inc.—Pentec Environmental Page 1 12655-02 May 29, 2007 Our report documented a small patch of Himalayan (Rubus armeniacus) and cut -leaf blackberry (tubus lacinatus) near the southeastern property corner. The wetland buffer contains low vegetative density and diversity, and is dominated by fawn. Our investigation did not document threatened or endangered species as occurring on the subject property or within Wetland A. Based on the City of Edmonds (City) critical area regulations, Wetland A requires. a 50 -foot buffer (Edmonds Municipal Code (EMC) 23.50.040(F)(1)). In addition, a minimum building setback of 15 feet is required from the edge of the wetland buffer (EMC 23.40.280). SITE DEVELOPMENT IMPACTS In order to accommodate the proposed subdivision, buffer reduction with buffer enhancement is proposed. Development activities will result in permanent wetland buffer impacts of approximately 2,423 square feet. The proposed subdivision has been designed to avoid impacts to critical areas to the maximum extent practical, while still accomplishing the goals of the development activities. No direct or indirect impacts will occur to Wetland A. The proposed development has been placed as far away from Wetland A and its buffer as possible. EMC 23.50.040(F)(3) allows for a reduction of a standard buffer width of up to 50 percent for Category Iii and IV wetlands providing: ■ The plan provides evidence that wetland functions and values will be increased or retained through plan implementation; ■ The plan documents existing native plant densities and provides for increases in buffer native plant densities to no less than three feet on center for shrubs and eight feet on center for trees; ■ The plan requires monitoring and maintenance; and Hart Crowser, lnc.=Pentec Environmental Page 2 12655-02 May 29, 2007 Fit ■ The plan documents methodology and provides performance standards for assessing increase in wetland buffer functioning as related to: 0 Water quality protection; • Provision of wildlife habitat; • Maintenance of wetland hydrology; and • Restricting wetland intrusion and disturbance. The project applicant proposes a 40 percent Duffer reduction accompanied by buffer enhancement to improve the functions and values of the existing buffer area. The proposed 40 percent reduction would reduce the existing 50 -foot buffer to 30 feet. The remaining buffer area will be enhanced with native vegetation to improve wildlife habitat, restrict intrusion and disturbance in the wetland, and increase the functions and values provided by the current buffer area. The project proposes 2,423 square feet of permanent buffer impacts, and 1,295 square feet of buffer enhancement. PROPOSED MITIGATION The project applicant proposes improvement of the functions and values provided by the buffer of Wetland A through buffer enhancement. The proposed enhancement will include removal of invasive vegetation, specifically Himalayan and cut -leaf blackberry, followed by the installation of native trees, shrubs, groundcovers, and a habitat log. The proposed mitigation will maintain and improve the wetland buffer functions and values over time. Enhancement Plantings, Log Placement, and Invasive Species Removal Buffer Enhancement Plantings A variety of native trees, shrubs and groundcover species have been selected to improve water quality, provide wildlife habitat, maintain wetland hydrology, and restrict access to the wetland. We identified one planting area for the project site (Figure 2). The planting area is located within the southeastern portion of the property adjacent to Wetland A. This area its currently dominated by lawn. The existing forested fringe on the subject property will remain undisturbed. The overall transplant densities for the planting area has been selected to eventually provide a moderately dense, structurally diverse plant community in Hart Crowser, Inc —Pentec Environmental Page 3 12655-02 May 29, 2007 the buffer area. Natural volunteer vegetation of the species listed for planting shall be counted towards the desired densities of enhancement plants. Volunteer vegetation not fisted below may substitute for the specified plants. with approval ofCity staff, provided the plants are not invasive species. Il Buffer enhancement planting densities are as follows: ■ Trees - S feet on center ■ Shrubs - 5 feet on center ■ Groundcover - 3 to 5 feet on center Native plant species, sizes and quantities for the proposed planting areas are listed in Table 1. Native groundcover enhancement is not required; however, we provide groundcover plant species for optional planting. We recommend that plant installation occur during the early spring or late fall, and plant material be obtained from a reputable nursery. Plant species can be placed randomly throughout the identified buffer enhancement area at the densities previously discussed. Log Placement We recommend placement of a minimum of one log within the wetland buffer to provide additional habitat for birds and small mammals. No logs will be placed directly in Wetland A. Logs should be a minimum of 12 inches in diameter and a minimum of 6 feet in length. We recommend interspersing native vegetation with the log to further improve habitat. Invasive Species Removal Prior to plant installation, we recommend removal of a small patch of Himalayan and evergreen blackberry within the existing buffer area. Manual removal is recommended to reduce impacts to adjacent existing native and. desirable vegetation. Care shall be taken not to impact existing vegetation adjacent to the blackberry. Fencing and Signs if determined necessary by the director, a split -rail fence will be constructed along the edge of the wetland buffer and permanent signs will be installed along the fence per EMC 23.50.040(G) (see Figure 2). Hart Crowser, Inc.—Pentee Environmental Page 4 12655-02 May 29, 2007 -._. _..— The split -rail fence shall be constructed of cedar or a similar type of wood. The fence will allow for wildlife movement between the wetland, buffer and surrounding upland areas, but will discourage human access within the enhanced buffer. _ A sign designating the presence of an environmentally sensitive area shall be Posted along the edge of the wetland buffer. A minimum of one sign will be posted for the subject property. The sign shall be worded as follows: PROTECTED WETLAND AREA DO NOT DISTURB CONTACT THE CITY OF EDMONDS REGARDING USES AND RESTRICTIONS Post -Mitigation Wetland Buffer Functions and Values Post -construction functions and values will be increased and improved through proposed wetland buffer enhancement. The addition of native trees, shrubs and. groundcovers will improve water quality, flood/stormwater control, habitat functions, and cultural/socioeconomic functions. Enhancement plantings within lawn areas will slow surface water flows during storm events and filter the surface water before it enters Wetland A. These plantings will also increase plant and wildlife species diversity and habitat. Specifically, amphibian; mammal and bird habitat will increase from a low level of function to a moderate level of function. Finally, the plantings will provide an increased aesthetic and educational value. We used the Semi -Quantitative Assessment Method (SAM) 2000 (Cooke, 2000) to evaluate the pre -and post -construction functions and values for the wetland buffer within the project area. Flood/Storm Water Control Low Base Flow/Ground Water Support NA Erosion/Shoreline Protection NA Water Quality Improvement Moderate Natural Biological Support Low – Moderate Overall Habitat Functions Low – Moderate Specific Habitat Functions Low Cultural/Socioeconomic Low– Moderate Overall Functions and Values- Low – Moderate Hart Crowser, Inc.—Pentec Environmental 12655-02 May 29, 2007 Low – Moderate �y 41 GOALS AND PERFORMANCE STANDARDS EMC 23.50.040(3)(c) requires wetland monitoring be performed fora period of 3 or more years. We identify goals and performance standards for the proposed l mitigation and monitoring of the site below. Goal is Enhance Wetland Buffer Areas through installation of Native Vegetation Performance Standards: a) Survival of planted native trees, shrubs, and groundcover will be a minimum of 80 percent after 3 years. • Year 1: 100 percent survival of installed plants • Year 2: 80 percent survival of installed plants • Year 3: 80 percent survival of installed plants b) Areal coverage of native trees, shrubs, and groundcover will be a minimum of 80 percent after 3 years. • Year 1: 20 percent cover • Year 2: 60 percent cover • Year 3: 80 percent cover Goal 2: Remove Invasive Plant Species within the Existing Wetland Buffer a) Invasive plant areal coverage will be less than 10 percent after 3 years. • Years 1 through 3: 10 percent or less coverage of invasive plants MAINTENANCE AND CONTINGENCY PROCEDURES Maintenance and contingency actions shall consist of irrigation, pruning, replacement of dead/dying or undesirable transplants with the appropriate vegetation, substitution of plant species, and weeding and removal of noxious and invasive weeds. No post -planting applications of fertilizer are anticipated. We recommend occasional deep irrigation of.the mitigation plantings during the summer months of the first year. CONSTRUCTION MANAGEMENT The Contractor shall be responsible for protection of the required wetland buffer area, maintaining appropriate protective barriers, and field staking the Hart Crowser, inc.—Pentec Environmental 12655-02 May 29, 2007 Page 6 MONITORING Vegetation construction areas. A contractor who is familiar with landscape and plant installation shall perform buffer enhancement installation and invasive species removal. A qualified biologist may be present on site to oversee buffer enhancement activities. The City of Edmonds requires a minimum 3 -year monitoring period for mitigation activities (EMC 23.40.130). Buffer enhancement monitoring will include quantitative and qualitative data collection to measure the success of the proposed mitigation. A project biologist or mitigation specialist will implement all monitoring methods. " The project biologist or mitigation specialist conducting monitoring activities will make a number of qualitative observations on vegetation and wildlife during quantitative data collection. Qualitative data on plant cover, density, survival and naturally colonizing plants will be collected. in addition, observations of wildlife use, including birds, amphibians, reptiles, and small.mammals, will be recorded during each monitoring visit. Wetland buffer enhancement plant communities will be sampled along a permanent vegetation transect using a circular quadrant (1 -meter radius). A minimum of two transects will be established in the enhanced buffer. Transect lengths will range between 25 and 50 feet. A minimum of 3 permanent quadrants will be established along each transect. In order to ensure the same locations are monitored each year, permanent markers will be established at the ends of each transect and at each quadrant sampling point (either PVC, wood lathe, or a combination of PVC and rebar). A map of the vegetation zones, sample plots, and property boundaries will be created for use during monitoring events. Buffer enhancement plantings will be visually evaluated along.each transect to determine the rate of survival, health, and vigor. Plants will be recorded as live, stressed, or dead/dying. Plant survival will be calculated by dividing the number of installed living plants by the number of initially installed plants. The percent cover of individual plant species present within each quadrant will be visually estimated. Data collection will consist of species composition and percent cover, total percent plant cover, percent cover of volunteer plants, and percent cover of invasive species such as Himalayan blackberry, reed _ Hart Crowser, Inc.—Pentec Environmental Page 7 12655-02 May 29, 2007 canarygrass, Scot's broom; English ivy, etc. Species coverage values will be summed to determine the total areal coverage in each quadrant. Photopoints To supplement the qualitative data, permanent photopoints will be established within the buffer enhancement area. Photopoints will be established at topographic vantage points that provide complete views of the enhancement area, if possible. Photos will document relative changes in plant cover, density, and height. Permanent markers will be established at each photo point (either PVC, wood lathe, or a combination of PVC and rebar). Monitoring Schedule The following project monitoring reports will be provided to the City: ■ At time of construction; ■ Year 1; ■ Year 2; and ■ Year 3 (Final). The project applicant shall submit an "At time of construction" or "As -built report" to the City within 30 days after completion of plant installation. The report will document mitigation site conditions at completion of plant installation and invasive species removal, and will be used as a baseline for future monitoring events. We recommend that monitoring occur during the fall and prior to leaf drop of Years 1 through 3. Years 1, 2, and 3 (Final) detailed monitoring reports will be submitted to the City by December 1 of each year. Performance Bond The City requires a maintenance, monitoring, and performance bond equal to 120 percent of the cost of the mitigation fora period of 3 years to ensure applicant compliance with approved mitigation (EMC 23.40.290). The bond shall be released after a 3 -year period providing that the mitigation performance standards have been met. If the performance standards have not been met after the 3 -year monitoring period outlined above, a contingency plan shall be implemented. A cost estimate for the performance bond is provided in Table 2. Hart Crowser, Inc.—Pentec Environmental Page 8 12655-02 May 29, 2007 REFERENCES Work for this project was performed, and this report prepared, in accordance with generally accepted professional practices for the nature and conditions of the work completed in the same or similar localities, at the time the work was performed. It is intended for the exclusive use of Rick Wichers for specific application to the referenced site. This report is not meant to represent a legal opinion. No other warranty, express or implied, is made. Subsurface conditions interpreted from observations of soil materials and seepage encountered in our explorations and/or investigations, in conjunction with soil properties inferred from field tests, formed the basis for developing our recommendations in this report. The nature and extent of conditions between the explorations and/or investigations may change over time and may not become evident until site work begins. If significant variations then appear evident, we should be consulted to re-evaluate the conclusions and recommendations in this report. It should be noted that fluctuations in the level of the groundwater may occur and are dependent on variations in rainfall, temperature, and other climatic factors. Cooke, Sarah S. ed., 1997. A Field Guide to the Common Wetland Plants of Western Washington and Northern Oregon. Seattle Audubon Society, Seattle, Washington. Cooke, Sarah S., 2000. Wetland and Buffer Functions, a Semi -quantitative Assessment Methodology. Cooke Scientific Services, Inc., Seattle, Washington. Debose, A. and M.W. Klungland, 1983. Soil Survey of Snohomish County Area, Washington. U.S. Department of Agriculture; Soil Conservation Service. July 1983. Hart Crowser, Inc., 2007. Critical Areas Report -. Wetlands, Wichers Property at 21821 952nd Avenue West, Edmonds, Washington. May 3, 2007. Project number 12655-01. Hruby, T., 2004. Washington State Wetland Rating System for Western Washington - Revised. Washington State Department of Ecology Publication #04-06-025. Hart Crowser, Inc.—Pentec Environmental Page 9 12655-02 May 29, 2007 Pojar, Jim and Andy MacKinnon et al., 1994. Plants of the Pacific Northwest Coast: Washington, Oregon, British Columbia, and Alaska. B.C. Forest Service, Research Program. Lone Pine Publishing. Vancouver, British Columbia. Reed, P.B. Jr., 1988. National List of Plant Species that Occur in Wetlands; 1988 Northwest (Region 9). U.S. Fish and Wildlife Service, Inland Freshwater Ecology Section, Biological Report 88 (26.9), St. Petersburg, Florida. Reed, P.B. et al., 1993. Supplement to List of Plant Species that Occur in Wetlands; Northwest (Region 9). U.S. Fish and Wildlife Service, Inland Freshwater Ecology Section, Supplement to Biological Report 88 (26.9), St. Petersburg, Florida. TopoZone. U.S.G.S. Edmonds East quadrangle, Snohomish County, Washington. http://Www.topozone.com. Accessed on September 8, 2006. Scale 1:50,000. Washington State Department of Ecology, U.S. Army Corps of Engineers Seattle District, and U.S. Environmental Protection Agency Region 10, March 2006. Wetland Mitigation in Washington State - Part 1: Agency Policies and Guidance (Version 1). Washington State Department of Ecology Publication #06-06-011 a. Olympia, Washington. Washington State Department of Ecology, U.S. Army Corps of Engineers Seattle District, and U.S. Environmental Protection Agency Region 10, March 2006. Wetland Mitigation in Washington State - Part 11: Developing Mitigation Plans (Version 1). Washington State Department of Ecology Publication #06-06-071 a. Olympia, Washington. 00655\002\Wichers Wetland Delineation 05-29-2007\Wichers Wetland Buffer Mitigation Report.doc Hart Crowser, Inc.—Pentec Environmental 12655-02 May 29, 2007 Page 10 00655\002\Wichets Wetland Delineation 05-232007\Tables T and 2.doc Table 2 - Cost Estimate for Performance Bond 00655\002\Wichem Wetland Delineafion 05-212007\Table T and 2.doc rrL, i 7 i i 3 J EnQiSy`•• ` Park. ,` { ,.+'3 ' Oi 5k s Lynnwood 1° rlr. r kfr fP r}�._.......-Y ti, j`._ �t ��ryry >$�....,�`++ p iA"�� 7.. _ 1 ' f, „i"" JI9 .w. -.—F•__' �� T kis -rY »✓ 2 R rflrrffff rel rr r' u is ^.�$��•-•�7E �� yf III Ir rr / jf+rsfl i S YJ' } is — 1 dell ljrrffirr r,lf ✓{f �;,.� ��t ��.t 9 �:E�' a� f.. r�rilll/Il�l;�r�f+lrlJrl �� lr.....f l grI�rI�5Z4f r r T �. t '01 �l/I fy�irr��Tljff"p /y +, j f u_ k• •� i A i til k s isr']r1L1 09 � �i1rlj1 r} }ff1f! ll4� µ� T �qrr EW Vvv /@ =W 611__ �-� _::.sus574v=" �, ea ijL'—[tea' t& i*L' I LJ L -. 1.:....:.' i--. r a i .ii ri7r A it .f i 1'S' �G..- f '. I e� 49 L�YE7�I _"� �3 _ It t H�. : L E-_... Js[J p� L= Ei rt� f Eirr�- r Li € J BtF� S qq LD. LIZ .: �, ��. _ J� �}� "� {�, 1�'..�! iii - � ✓��, ��.1`L�' �kk � ;„�S�I�i._....,53�� UO ILI 71 1. r i .-- - I I Subject PropertyIF boa Mauwrtlatee Ln 77 L 71L ,, -N { '{L'•'._�'"."._—....J ___.L-1,(,✓ ...� �i -.. tyio` »,..I ! tnY '" rs5i' "� Frl yr s �} t J, L {'" zC' r .Y-,'`; ]1 r�i LJ 61r jr`rrr Iir< ia+ rd 0 A I'll II j-, �f ,✓� ! fr :. I r r fj, d! f rl' l"r rf t jry 1( r� y rfr}7n9w ! xd ��'l { ! � SITE i F!'f�%ANk �k �T 'i'lfrh'If� rrfr t'ya a _ i4, If rlfl �r {'rr/r r! 1rr , f jrsll h1''ifl s„Ir�Ih� Y. t- IIhr1 iiiFFF��,ar! r1 rrI I( r eNxr�� 1 + r r' �i ti v I r y :���;r�;r>•!,r/{�+r.i� }f 4..r+f�,l '�Ai.I `h i al :rk t ��,n„� N 0 2000 4000 Scale in Feet Wichers Property Wetland Rating Edmonds, Washington Vicinity Map 12655-02 5/07 Figure Y 1 o Bgg : a` c I wl m a yI4 3 �I W R d 4 4 ., a i i T' b m rn sQ I b � I— C% p qOq al O p j j j I N J -- ----------------- L C O N \y ^\ \ % I i A 3nN3AV PUZ6 f" W d LL ! 4 m 4 4 —��-- 4 4 �I ' I I I illii. 4 i ..�d..............\ \ \,y p I \ ....\— ` 3 :tel ...... \\ 4 N 4 Q o �mca,� N, n ����'\ > 4 11 R', I I\ i �I 4 4I CO � 1 [ X • \ 3.LO.gc00 ,00'18 zt. La i 1 .:. l ..• I I \\\ 2 I I Bgg : I wl ., 0.- � i T' b m rn r b -- ----------------- L C O N \y ^\ \ % I i A 3nN3AV PUZ6 f" W d LL I.. I tial sroz m 'o —��-- 4 _ y@fie-- ®--------- c