Loading...
HomeMy WebLinkAboutRS_Critical_Areas_Assessment_190426_v1Environmental Overview Technical Memo 1 Critical Areas Overview Technical Memorandum Renton Shop CONTRACT NO. E00491E17 November 2018 Department of Natural Resources and Parks Parks and Recreation Division King Street Center, KSC-NR-0700 201 S Jackson Street, Suite 700 Seattle, WA 98104 King County Parks – Renton Shop Critical Areas Overview Technical Memo 2 Technical Memorandum To: Brenda Bradford (King County) From: Karissa Kawamoto and Tobin Story (HDR) Date: October 31, 2018 Subject: Critical Areas Overview for Renton Shop Project 1.0 Introduction The King County Department of Natural Resources and Parks, Parks and Recreation Division is replacing the existing Central Maintenance Facility in the City of Renton (City), WA. The purpose of this technical memo is to document environmental critical areas located on or adjacent to the proposed project site, as regulated by the City of Renton under Renton Municipal Code (RMC) 4-3- 050, otherwise known as the City’s Critical Areas Ordinance. 2.0 Project Setting and Description The proposed project is located within the City of Renton, Washington, in Section 16, Township 23 North, Range 5 East (Figure 1). The proposed project would occur on King County Parcel 1434000012. The project parcel is owned by King County Parks. Currently, the parcel is occupied by the existing King County Parks Central Maintenance Facility. The site is zoned light industrial. Adjacent land uses include: • North: former King County Public Health office building recently purchased for redevelopment by Renton Technical College • South: owned by King County Roads Division, vehicle and equipment storage • East: beyond the access road is a vacant private parcel that was historically mined for sand and gravel and is now being used to accept fill dirt • West: Self-storage business Existing topography on the site is mostly flat, with a gentle slope downward from east to west. A short section of relatively steep slopes is located on the western property boundary. The project site was subdivided into an approximately 5.7 acre (248,672 square foot) parcel from a larger County-owned property in 2016 (REC #20160303900006), and is zoned light industrial. The new facility would consist of 3 new buildings, staff and visitor parking, fleet and equipment parking, and covered and uncovered storage. The Crew/Administration Building A (2-story, approximately 27,000 sq. ft.) is oriented to take advantage of the southern exposure and southerly winds to act as natural ventilation and cooling. The Shop Building B (2-story, approximately 20,900 sq. ft.) is more centrally located on the site. Along the north and west boundaries, a variety of storage areas will include ecology block material storage bins, utility trailers and other equipment parking, and enclosed storage in Building C (single-story, approximately 4,500 sq. ft.). King County Parks – Renton Shop Critical Areas Overview Technical Memo 3 The site utilities would be upgraded to include constructing approximately 2,000 LF of 12-inch diameter water main extension for fire and domestic water use to serve the site. The water system will be installed from the intersection of Jefferson Avenue NE and NE 2nd Street going north on Jefferson Avenue toward NE 4th Street where it will be capped and terminated for future expansion/connection. A sewer main will be constructed partially within City of Renton right-of-way, new utility easement from NE 3rd Street south between the self-storage development and the Renton Technical College property, and on-site. The sewer improvement is comprised of approximately 600 feet of 12-inch diameter sewer main and 300 feet of 8-inch diameter sewer main. The project will include other dry utility construction to underground approximately 600 feet of electrical power lines and extend fiber optic and communication systems into the site. Applicable Regulations The City regulates activities in critical areas and their applicable buffers under RMC 4-3-050. Environmental critical areas regulated by the city include flood hazard areas, geologically hazardous areas, habitat conservation areas, streams and lakes, wellhead protection areas, and wetlands. The critical areas identified in the vicinity of the proposed project include steep slopes and wellhead protection areas. Steep Slopes The City defines steep slopes in two distinct categories. Sensitive slopes are “a hillside, or portion thereof, characterized by: an average slope of 25 percent to less than 40 percent as identified in the City of Renton Steep Slope Atlas (Renton 2018) or in a method approved by the City; or an average slope of 40 percent or greater with a vertical rise of less than 15 feet, or abutting an average slope of 25 to 40 percent”. Protected slopes are “a hillside, or portion thereof, characterized by an average slope of 40 percent or greater grade and having a minimum vertical rise of fifteen feet as identified in the City of Renton Steep Slope Atlas or in a method approved by the City” (RMC 4-3-050 G.5.a). Protected slopes require a building setback of 15 feet from the top or toe of the slope (RMC 4-3-050 G.2). Wellhead Protection Areas The City defines wellhead protection areas as the portion of an aquifer within the zone of capture and recharge area for a well or well field owned or operated by the City (RMC 4-3-050 G.8.a.i). Wellhead protection areas are defined into two zones: Zone 1 is the land area situated between a well owned by the City and the 365-day groundwater travel time contour; Zone 2 is the land area situated between the 365-day groundwater travel time contour and the boundary of the zone of potential capture for a well or well field owned or operated by the City (RMC 4-3-050 G.8.a.ii). Development standards for wellhead protection zones are detailed in RMC 4-3-050 G.8.b. Wetlands The City defines wetlands as “Areas that are inundated or saturated by surface water or groundwater at a frequency to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions” (RMC 4-11-230 Definitions W). The City also regulates those areas within 200 feet of regulated wetlands (RMC 4-3- 50 B.1.f). The City requires that wetlands be delineated by a wetland specialist through the performance of a field investigation in accordance with the approved federal wetland delineation manual and applicable regional supplements, and that wetlands be categorized using the 2014 King County Parks – Renton Shop Critical Areas Overview Technical Memo 4 Washington State Wetland Rating System for Western Washington (Hruby 2014). The City regulates wetland buffers according to a standard buffer width, assigned according to wetland rating category. 3.0 Methods Critical areas were identified through a two-step process. HDR biologists first reviewed existing documents including public-domain information such as on-line maps and public databases, as well as documentation prepared specifically for the project. In addition to this review, HDR biologists completed a field investigation of the study area. The study area for the purposes of this memo is defined as the project parcel and the surrounding 200 feet. 3.1 Review of Existing Information Existing documents reviewed for this critical areas memo include the following: • City of Renton Critical Areas Map Viewer (2018) • Preliminary Geotechnical Investigation – Renton Shop – Prepared by Aspect Consulting (2018) • Upper Balch Pit Wetland Reconnaissance – Prepared by Raedeke Associates, Inc. (2010) • U.S. Department of Agriculture’s Natural Resources Conservation Service (USDA NRCS) Web Soil Survey (2018) • U.S. Fish and Wildlife (USFWS) National Wetland Inventory (NWI) maps (2018) • Washington Department of Fish and Wildlife (WDFW) Priority Habitats and Species (PHS) on the web (2018) These documents provide background information on the soils, hydrology, land use, wildlife use, and documented wetlands, streams, and other critical areas in the study area. Review of existing information indicated one potential wetland located outside the proposed project area but within the study area on an adjacent parcel to the east, and steep slopes located on the western boundary of the site. 3.2 Field Investigation HDR biologists conducted a site visit to the project location on September 27, 2018. The site visit focused primarily on the project area. Potential critical areas located outside the project area were assessed based on characteristics visible from the Jefferson Avenue NE (a private road owned by King County) or from available information in existing documents and studies, maps, and aerial photographs. 4.0 Results Critical areas identified in the vicinity of the proposed project include steep slopes and wellhead protection areas. In addition, a potential wetland on an adjacent parcel to the east was identified based on online map resources. Each of these critical areas in the study area are described in the sections below. The project has no potential impacts to flood hazard areas, habitat conservation areas, or streams and lakes, so these types of critical areas will not be discussed in this memo. King County Parks – Renton Shop Critical Areas Overview Technical Memo 5 4.1 Steep Slopes Soils in the area are mapped primarily as Arents (Everett material) by the USDA NRCS web soil survey (USDA 2018). Arents are soils with no discernible horizons due to past human activities including plowing, grading, or other soil moving activities. Soils observed during the site visit are consistent with this mapped soil type, and the project site appears to be located primarily on historic fill material. This observation was corroborated in the preliminary geotechnical evaluation performed for the project by Aspect Consulting, where geotechnical borings noted 1.5 to 5 feet of fill throughout the project site (Aspect 2018). Steep slopes are present in the vicinity of the proposed project according to the City’s GIS data (Renton 2018). The steep slope areas within the study areas include slopes located along the west side of the project, these slopes do not appear to be natural features, but are likely formed by historic fill and grading. These slopes are included in the City of Renton’s Steep Slope atlas, and range from approximately 15 to 40 percent slope, becoming generally steeper toward the south end of the project site. The majority of slopes are shown to be between 15 and 25 percent slope. A narrow band of 25 to 40 percent slope (sensitive slopes) is located near the toe of slope (further from the project area). A small area of slopes on the extreme southern end of the site is mapped by the City as between 40 and 90 percent slope. Visual observation indicates this is likely a mapping anomaly, as slopes appear consistent in approximately the 30 percent range. The slopes feature a rise of approximately 15 feet in height, and are approximately 50 feet in length. Vegetation in the area is primarily invasive shrub species, including Scotch broom (Cytisus scoparius) and Himalayan blackberry (Rubus armeniacus), with a few scattered trees, primarily introduced cherry species (Prunus spp.). 4.2 Wellhead Protection Areas The site is mapped by the City as being located within a Zone 2 wellhead protection zone, the Maplewood Ten Year Capture Zone. Zone 2 is defined as the land area situated between the 365- day groundwater travel time contour and the boundary of the zone of potential capture for a well or well field owned or operated by the City. No groundwater was observed during previous geotechnical borings on the site (conducted in February 2018). 4.3 Wetlands Review of existing information, including NWI maps and the City of Renton critical area maps, indicated the potential presence of a wetland on the parcel located to the east of the project area (Parcel 1623059059), known as the Upper Balch Pit. The Upper Balch Pit is a reclaimed gravel mine, the lowest portions of which are currently used to dispose of fill material from other sites in accordance with a City of Renton fill permit. An area of ponding has been known to exist at certain times of the year on the adjacent property. It is unknown if the area meets the criteria for a regulated wetland because property access to survey the area was denied. However, even if it does meet the criteria for a regulated wetland, the City of Renton requires projects proposed within 300 feet to conduct an analysis if alterations of the subject property are likely to impact the wetland or wetland buffer. HDR reviewed a wetland reconnaissance memo for the parcel prepared by Raedeke Associates in 2010, which concluded that the site lacked the presence of hydric soils and hydrophytic vegetation, and that the occasional presence of surface water on the site was a result of surface water runoff from a pipe along the eastern slope. Raedeke concluded that ponding on the King County Parks – Renton Shop Critical Areas Overview Technical Memo 6 surface was due to varying degrees of permeability in the fill soils (Raedeke 2010). Raedeke Associates determined that no wetlands were present on the site as of 2010. HDR biologists were unable to access the site due to lack of landowner’s permission, but did observe the site from the private access road. No obvious wetland characteristics were observed, including either surface ponding or obvious hydrophytic vegetation. No other wetlands were observed within the project area or in the adjacent 200 feet. 5.0 Potential Critical Area Impacts The project seeks to avoid critical area and buffer impacts to the extent possible. A brief discussion of potential impacts to critical areas is below. Steep slopes The proposed project is located adjacent to a narrow section of sensitive slopes; however, no building construction is proposed on or adjacent to steep slopes, and no building setback is required for sensitive slopes. As such, no impacts are proposed to sensitive or protected slopes. A final geotechnical report will be submitted to the City during the building permit process discusses potential impacts from construction on the steep slopes with a list of engineering recommendations if there are any impacts. Wellhead Protection Areas The proposed future use of the site will include storage of hazardous materials including vehicle fuel, fertilizers, pesticides, and equipment maintenance fluids. The City regulates the storage of hazardous materials within wellhead protection zones, including requiring secondary containment, periodic monitoring, and emergency collection devices (RMC 4-3-050 G.8.b). King County will comply with applicable development standards for the Zone 2 wellhead protection area described in RMC 4-3-050 G.8.b, during construction and operation of the facility. Wetland and Wetland Buffer Impacts The proposed project will not result in impacts to wetlands or wetland buffers. No wetlands are located within the project area, and no wetlands were observed on adjacent properties. No wetlands are located within 200 feet of the proposed site. 6.0 References Aspect Consulting. 2018. King County Parks and Recreation Division – Renton Shop. Preliminary Geotechnical Evaluation. Prepared for HDR Architecture. March 20, 2018. City of Renton (Renton). 2018. City of Renton Map Viewer. Available online at http://rp.rentonwa.gov/Html5Public/Index.html?viewer=CORMaps. Accessed October 2018. Hruby, T. 2014. Washington State wetland rating system for Western Washington: 2014 Update. Washington State Department of Ecology Publication #14-06-029. Olympia, Washington. Washington Department of Ecology. Raedeke Associates, Inc. 2010. Upper Balch Pit Wetland Reconnaissance Technical Memo. July 30, 2010. USDA Natural Resources Conservation Service (NRCS). 2018. Web Soil Survey. Available online at https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx. Accessed October 2018. King County Parks – Renton Shop Critical Areas Overview Technical Memo 7 U.S. Fish and Wildlife Service (USFWS). 2018. National Wetland Inventory (NWI) Mapper. Available online at https://www.fws.gov/wetlands/data/mapper.html. Accessed October 2018. Washington Department of Fish and Wildlife (WDFW). 2018. Priority Habitats and Species Mapper. Available online at https://wdfw.wa.gov/mapping/phs/. Accessed October 2018.