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HomeMy WebLinkAboutERC_Report_Madsen_Creek_Flood_Improvement_Project_210525DEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT Project Location Map ERC_Madsen Creek Flood Improvement Project_FINAL ENVIRONMENTAL REVIEW COMMITTEE REPORT ERC Meeting Date: May 24, 2021 Project File Number: PR21-000001 Project Name: Madsen Creek Flood Control Improvement Project Land Use File Number: LUA21-000147, ECF, CAE Project Manager: Jill Ding, Senior Planner Owner/Applicant/Contact: Amanda Pierce, City of Renton, 1055 S Grady Way, Renton, WA 98057 Project Location: 15711 152nd Ave SE, 14937 Maple Valley HWY (King County Parcel Nos. 2323059021, 2323059118, 2323059020, 2323059070, and 2323059028) Project Summary: The applicant is requesting Environmental (SEPA) Review and a Critical Areas Exemption for the Madsen Creek Flood Improvement Project. The proposed project consists of four (4) sites requiring improvements to restore and increase the lower Madsen Creek network flood protection and capacity, as well as provide routine maintenance measures. Site 1 work consists of raising the berm surrounding the sediment basin and adding an emergency spillway that discharges to the high flow bypass channel. Site 2 work consists of widening the high flow bypass channel and removing accumulated sediments, as well as raising the right (east) bank of the upper high flow bypass channel to eliminate the low spot acting as a weir diverting flows to the low flow channel. Site 3 work would raise the elevation of the left (south) bank from the private property (14937 Maple Valley Hwy) through Wonderland Estates to the low flow culvert under SR 169. The banks would be raised through a shallow floodwall and flood control berm. Site 4 work would remove the existing Eco Block wall along the right (north) bank of the low flow channel between the outlet of the SR 169 culvert to the 149th Ave SE culvert entrance and replace it with a flood control berm. In addition to these improvements, the high flow bypass capacity will be increased, and maintenance actions and agreements will be implemented. The project site is mapped with a Type F stream, flood hazard area, seismic hazard area, wetlands, wellhead protection area, zone 2, sensitive slopes, and protected slopes. Exist. Bldg. Area SF: N/A Proposed New Bldg. Area (footprint): Proposed New Bldg. Area (gross): N/A N/A Site Area: 40,680 sq. ft. Total Building Area GSF: N/A STAFF RECOMMENDATION: Staff Recommends that the Environmental Review Committee issue a Determination of Non-Significance. DocuSign Envelope ID: 2185E4C6-EB4A-445F-8113-20CA6BCAD274 City of Renton Department of Community & Economic Development Madsen Creek Flood Control Improvement Project Staff Report to the Environmental Review Committee LUA21-000147, ECF, CAE Report of May 24, 2021 Page 2 of 5 ERC_Madsen Creek Flood Improvement Project_FINAL ENVIRONMENTAL REVIEW In compliance with RCW 43.21C.240, the following environmental (SEPA) review addresses only those project impacts that are not adequately addressed under existing development standards and environmental regulations. A. Environmental Threshold Recommendation Based on analysis of probable impacts from the proposal, staff recommends that the Responsible Officials: Issue a DNS with a 14-day appeal period B. Exhibits Exhibit 1: Environmental Review Committee (ERC) Report Exhibit 2: Madsen Creek Plan Set Exhibit 3: Environmental Assessment Report, prepared by Herrera Environmental Consultants, Inc., dated September 14, 2018 Exhibit 4: Mitigation Plan, prepared by Herrera Environmental Consultants, dated March 10, 2021 Exhibit 5: Advisory Notes Exhibit 6: Lead Agency Status Notification C. Environmental Impacts The Proposal was circulated and reviewed by various City Departments and Divisions to determine whether the applicant has adequately identified and addressed environmental impacts anticipated to occur in conjunction with the proposed development. Staff reviewers have identified that the proposal is likely to have the following probable impacts: 1. Earth Impacts: Although there are sensitive and protected slopes within the vicinity of the project site, the flood control improvements project work would not occur on or near any sensitive or protected slopes; therefore a Geotechnical Report was not required with the project application. The topography of the study area is generally flat due to its location within the floodplain of the Cedar River. Three soil series are mapped within the project area: Alderwood and Kitsap soils, very steep; Newberg silt loam; and Puyallup fine sandy loam. The soil in most of the study area is composed of Newberg silt loam while a smaller portion near the Cedar River is mapped as Puyallup fine sandy loam. Proposed sediment removal from the high flow bypass channel at Site 2, as a stormwater facility maintenance measure, will not impact any agriculturally or commercially significant soil. Proposed grading activities include 348 cubic yards of cut material and 408 cubic yards of fill material, which would result in a net 60 cubic yards of fill on the project site. It is anticipated that the City’s adopted erosion control measures would adequately mitigate any grading impacts as a result of project construction; therefore no further mitigation is recommended. Mitigation Measures: None recommended. Nexus: N/A 2. Water a. Wetland, Streams, Floodplain Impacts: An Environmental Assessment Report, prepared by Herrera Environmental Consultants, Inc., dated September 14, 2018 (Exhibit 3) and a Mitigation Plan, prepared by Herrera Environmental Consultants, dated March 10, 2021 (Exhibit 4) were submitted with the project application materials. This report included classifications of the onsite wetlands and streams. Nine DocuSign Envelope ID: 2185E4C6-EB4A-445F-8113-20CA6BCAD274 City of Renton Department of Community & Economic Development Madsen Creek Flood Control Improvement Project Staff Report to the Environmental Review Committee LUA21-000147, ECF, CAE Report of May 24, 2021 Page 3 of 5 ERC_Madsen Creek Flood Improvement Project_FINAL wetlands were identified in the study area. Wetland A is a large, complex depressional and riverine wetland associated with the Cedar River and Madsen Creek. Wetlands B and C are depressional wetlands, and Wetlands D, E, F G, H, and I are riverine wetlands associated with Madsen Creek. Three of these wetlands are located within the vicinity of the project site (Wetlands C, E, and F). Wetlands C and E are classified as Category II wetlands with a standard buffer width of 100 feet and Wetland F is classified as a Category III wetland with a standard buffer width of 75 feet. Madsen Creek and the Madsen Creek High Flow Bypass Channel are identified as Type F streams with associated buffers of 115 feet. The proposed project will result in alterations to the 100-year floodplain, the Madsen Creek high flow bypass channel, and regulated stream and wetland buffers. No direct wetland impacts are associated with the project. In-stream work is limited to removal of accumulated sediment, as a stormwater facility maintenance practice, at Site 2 to assure sufficient freeboard above the peak 100-year flood level, and local widening and deepening of the high flow bypass channel at Site 2 to increase flood storage capacity. The majority of the proposed spillway construction at Site 1 would overlay an existing gravel- surfaced maintenance access road. Site 1 is not within a mapped 100-year floodplain. Proposed buffer impacts at Site 1 are limited to only that portion of the work that extends beyond the existing roadway. In-water work is restricted to approximately 10 cubic yards of rock placement within an area of 100 square feet where the downstream end of the spillway will extend to the bottom of the high flow bypass channel at Site 1. The new spillway and surrounding fill would extend 1,160 square feet beyond the existing maintenance access road footprint, resulting in the conversion of existing low-functioning herbaceous buffer vegetation that is associated with the high flow bypass channel to rock surfacing. Mitigation to compensate for the spillway’s buffer encroachment includes the removal of invasive vegetation and the proposed installation of native plants within 1,160 square feet of buffer area along the east bank of the high flow bypass channel downstream of Site 1. The specified trees and shrubs proposed for installation will improve habitat conditions by increasing the diversity of representative native species and vegetation strata within the buffer. Water quality functions within the buffer will also be increased. The proposed buffer mitigation ratio is 1:1, as required for compliance with the City’s Critical Areas regulations. Site 2 work proposes removing sediment accumulation below the OHWM in the high flow bypass channel of Madsen Creek, along with minor widening of the channel beyond its originally constructed dimensions to increase flood storage. The volume of sediment and soil to be excavated from 4,276 square feet of the channel below the OHWM is an estimated 110 cubic yards. Channel excavation will only be conducted during the dry season when there are no active flows in the channel. The in-stream work at Site 2 is considered to be a temporary alteration because the channel will require periodic maintenance in the future when the extent of sediment accumulation reaches a level that affects 100-year flood conveyance capacity. It is anticipated that new sediment and vegetation within the channel will regenerate naturally with time. Mitigation to compensate for project-associated alterations to the floodplain and stream buffers would be provided to achieve no net loss of habitat area and functions per the requirements of the Critical Areas Regulations. Reduction of public flood hazard areas is considered an exempt activity within the 100 year floodplain and stream, if buffer restoration and enhancement is provided at a 1:1 ratio, and modifications to existing regional stormwater facilities (Madsen Creek High Bypass Channel) are and exempt activity within wetland areas (RMC 4-3-050.C.3). Site 2 project work will alter approximately 16,850 square feet of existing regulated buffer area, which is primarily composed of nonnative herbaceous vegetation. The project work will require the removal of six of a total of seven existing multi-stemmed deciduous trees present at the site on the east side of the high flow bypass channel. The six trees proposed for removal include one native red alder (Alnus rubra), two nonnative Norway maples (Acer platanoides), one common hawthorn (Crataegus monogyna), one cherry DocuSign Envelope ID: 2185E4C6-EB4A-445F-8113-20CA6BCAD274 City of Renton Department of Community & Economic Development Madsen Creek Flood Control Improvement Project Staff Report to the Environmental Review Committee LUA21-000147, ECF, CAE Report of May 24, 2021 Page 4 of 5 ERC_Madsen Creek Flood Improvement Project_FINAL (Prunus sp.), and one Oregon ash (Fraxinus latifolia). Trees to be removed at Site 2 will be replaced at a ratio greater than 2:1 within a native vegetation planting area adjacent to and south of the constructed berm. Invasive plants are to be removed and native shrubs and ground cover plants will be installed within 16,850 square feet of the Site 2 project area, adjacent to the high flow bypass channel. The proposed mitigation planting area is equal to the disturbed buffer area at a mitigating ratio of one-to-one, as required by the City for regulatory compliance. Site 3 work is within SR 169’s southern right-of-way and the landscaped frontage of Wonderland Estates. Site 3 work will construct a new berm along the left (south) bank of the Madsen Creek low flow channel on the Wonderland Estates property and a low floodwall made of concrete masonry units in the SR 169 right of way in front of (north of) the single-family residential property to the east, with the floodwall connecting to the berm for continuous flood containment. The wall and berm will extend at a relatively constant top elevation, east to west, from high ground near the culvert that conveys the Madsen Creek low channel beneath the high flow bypass channel at the east end to the Madsen Creek low flow channel culvert entrance in the SR 169 right-of-way at the west end. This combination berm and small concrete masonry unit wall will reduce the risk of creek overflows entering the low-lying Wonderland Estates residential development during the 100-year flood event. The wall and berm will extend approximately 210 linear feet in total along the left bank, representing 1,180 square feet in total footprint area. Excavation for Site 3 work will be minor, only requiring tying the base of the berm into native soil and smoothing the ground surface at the base of the concrete masonry unit wall. The proposed berm will consist of compacted low-permeability soil and a top layer of soil for planting vegetation. Estimated fill volumes within, and outside of, the 100-year floodplain represent 30.5 cubic yards and 21 cubic yards, respectively. The berm has been designed to avoid direct impacts to the wetland paralleling the opposite (right) bank of the creek. The small concrete wall will be built adjacent to vegetation (an arborvitae hedge) lining the southern (left) bank of the creek. The existing vegetation that will have to be cleared within the project area’s creek buffer on the Wonderland Estates property is composed primarily of nonnative weedy herbaceous species that provide low habitat functions. Native groundcover and shrub species proposed for installation on the flood control berm have been specified to provide enhanced buffer functions when compared to existing conditions. No new vegetation will be planted adjacent to the floodwall because there is no space to plant in that area. The project will require approximately 640 square feet of vegetation clearing on the Wonderland Estates property to create two temporary 12- foot-wide equipment access corridors that will extend from an existing paved parking area. The vegetation to be removed consists of a mix of native and nonnative landscaped shrubs. This existing vegetation provides low habitat functions and the proposed installation of native plants to restore these disturbed areas will enhance buffer conditions. Site 4 work is located on the north side of SR 169 between the Cedar River Trail and the southwest corner of the private residence at 15214 149th Avenue Southeast. Site 4 work is partially within the City of Renton city limits with the remainder being located within Unincorporated King County. Site 4 work will raise the right (north) bank of the low flow channel to provide increased protection against the Madsen Creek 100-year flood flow in the low flow channel from overtopping that bank and flooding residential properties to the north. The new earthen berm will be approximately 115 feet long and will replace approximately 60 linear feet of existing ecology blocks that were installed by WSDOT in the 1990s. The berm construction will require approximately 38 cubic yards of net fill above existing grade, all of which will be within the 100-year floodplain of the Cedar River. The total area of fill represented by the project at this location is 1,135 square feet within the 100-year floodplain. The existing riparian vegetation at this site is in poor condition on both banks of the stream, particularly on the north bank. Invasive plants, such as Himalayan blackberry, are prevalent in the understory. Native trees and shrubs will be protected and retained on the south bank as part of the mitigation planting plan. Site 4 work is within a private residential property’s southwest corner (15214 149th Avenue Southeast) and borders the Cedar River Trail, SR 169, and 149th DocuSign Envelope ID: 2185E4C6-EB4A-445F-8113-20CA6BCAD274 City of Renton Department of Community & Economic Development Madsen Creek Flood Control Improvement Project Staff Report to the Environmental Review Committee LUA21-000147, ECF, CAE Report of May 24, 2021 Page 5 of 5 ERC_Madsen Creek Flood Improvement Project_FINAL Avenue Southeast. These boundaries cause buffer encroachments; and along with the prevalence of nonnative vegetation, the habitat is low to moderately functioning at this site. Site 4 construction work will remove forest vegetation that is primarily composed of native Pacific and Sitka willow (Salix lucida ssp. lasiandra, S. stichensis). red-osier dogwood, salmonberry, spiraea (Spiraea douglasii), nonnative Himalayan blackberry and English Ivy (Hedera helix) vines and other invasive herbaceous plants, including reed canarygrass. Existing cottonwood and alder trees adjacent to the Cedar River Trail will be retained and protected from construction activities. No direct impacts to Wetland E that parallels the creek and SR 169 are proposed. Native plants are proposed for installation on and adjacent to the constructed flood-control berm. Residential lawn and nonnative Himalayan blackberry are present on the private residential property to the north of the channel where additional buffer mitigation plantings are proposed beyond the required berm revegetation. Site 4 extends beyond the city of Renton limits into unincorporated King County over an approximate area of 755 square feet (separate plans and permits are required for work outside of the Renton City Limits). King County requires a 3:1 mitigation ratio for impacts to Type F aquatic area buffers. The proposed native vegetation planting area associated with the Site 4 buffer alterations within King County is 2,270 square feet. The total planting area for Site 4, including King County and City of Renton mitigation areas, is 2,650 square feet. The proposed floodplain improvement project would result in a net excavation of 54 cubic yards within the 100 year floodplain, which would meet the compensatory storage requirements as adopted within the City’s Critical Areas Regulations. It is anticipated that critical area impacts would be mitigated through the implementation of the City’s Critical Areas Regulations, therefore no further mitigation is recommended. Mitigation Measures: None recommended Nexus: N/A D. Comments of Reviewing Departments The proposal has been circulated to City Department and Division Reviewers. Where applicable, their comments have been incorporated into the text of this report and/or “Advisory Notes to Applicant.” ✓ Copies of all Review Comments are contained in the Official File and may be attached to this report. The Environmental Determination decision will become final if the decision is not appealed within the 14-day appeal period (RCW 43.21.C.075(3); WAC 197-11-680). Environmental Determination Appeal Process: Appeals of the environmental determination must be filed in writing on or before 5:00 p.m. on June 8, 2021. Due to Governor Jay Inslee’s Proclamation 20-25 (“Stay Home, Stay Healthy”), the City Clerk’s Office is working remotely. For that reason, appeals must be submitted electronically to the City Clerk at cityclerk@rentonwa.gov. The appeal fee, normally due at the time an appeal is submitted, will be collected at a future date. Appeals to the Hearing Examiner are governed by RMC 4-8-110 and additional information regarding the appeal process may be obtained from the City Clerk’s Office, cityclerk@rentonwa.gov. If the situation changes such that the City Clerk’s Office is open when you file your appeal, you have the option of filing the appeal in person. DocuSign Envelope ID: 2185E4C6-EB4A-445F-8113-20CA6BCAD274 CITY OF RENTON DEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT STAFF REPORT TO THE ENVIRONMENTAL REVIEW COMMITTEE EXHIBITS Project Name: Madsen Creek Flood Control Improvement Project Land Use File Number: LUA21-000147, ECF, CAE Date of Meeting May 24, 2021 Staff Contact Jill Ding Senior Planner Project Contact/Applicant Amanda Pierce City of Renton 1055 S Grady Way, Renton, WA 98057 Project Location 15711 152nd Ave SE, 14937 Maple Valley HWY (King County Parcel Nos. 2323059021, 2323059118, 2323059020, 2323059070, and 2323059028) The following exhibits are included with the ERC Report: Exhibit 1: Environmental Review Committee (ERC) Report Exhibit 2: Madsen Creek Plan Set Exhibit 3: Environmental Assessment Report, prepared by Herrera Environmental Consultants, Inc., dated September 14, 2018 Exhibit 4: Mitigation Plan, prepared by Herrera Environmental Consultants, dated March 10, 2021 Exhibit 5: Advisory Notes Exhibit 6: Lead Agency Status Notification DocuSign Envelope ID: 2185E4C6-EB4A-445F-8113-20CA6BCAD274