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HomeMy WebLinkAboutSR_ERC_Mt._Olivet_Power_Generation_Facilities_060821STAFF REPORT A. BACKGROUND ERC MEETING DATE Project Name: Applicant/Contact: File Number: Project Manager: Project Description: Project Location: Exist. Bldg. Area gsf: Site Area: RECOMMENDATION: Project Location Map City of Renton Department of Planning I Building I Public Works ENVIRONMENTAL REVIEW COMMITTEE REPORT August 21, 2006 Mt. Olivet Power Generation Tom Malphrus, City of Renton 1055 S Grady Way, Renton, WA 98055 LUA-06-083, SA-H, V-H, ECF Jill K. Ding, Senior Planner The applicant is requesting Site Plan approval, Variance approval, and Environmental (SEPA) Review for the construction of a 1,216 square foot power generator building to house one stationary and one mobile diesel powered generator on a Residential Multi- Family (RM-F) zoned property. The subject property totals 165,092 square feet in area. An existing 3 million gallon water reservoir and a booster pump station are located on the subject property. The proposed generators would provide emergency power to the existing booster pump station and wells 1, 2, and 3 when commercial power to these facilities is interrupted. The proposed power generator building would require a 5-foot deep cut into a protected slope area. A critical areas variance has been requested to alter a protected slope. (Project description continued on page 2). 250 Bronson Way NE 10,648 square feet 165,092 square feet Proposed New Bldg. Area: 1,216 square feet Total Building Area gsf: 11,864 square feet Staff recommends that the Environmental Review Committee issue a Determination of Non-Significance -Mitigated (DNS-M). LUA06-083ercrpt PROJECT DESCRIPTION CONTINUED: The reservoir and booster pump station sit on a level area of the site that appears to have been terraced into a previously existing slope. The east side of the site slopes upward with slopes in the 25 percent to 40 percent slope range. The west and south edges of the site slope downward with slopes in the 25 percent to 40 percent range The layout of the proposed building will require a maximum 5-foot deep cut into the slope on the east side of the site. A retaining wall will be constructed to support this cut. A security fence will be constructed to enclose the reservoir. booster pump station and proposed building. The generators will be exercised once a month for approximately 30 minutes each, otherwise the generators will sit idle and will only operate during a power outage. Two conduits in parallel, will serve the Wells 1, 2, and 3 building from the Mt. Olivet site. These conduits will carry power and communications conductors between the two sites. These conduits are currently installed but recent inspection found that several sections need replacement, including the section under Maple Valley Highway, the section in the northwest corner of Cedar River Park, a section of the power conduit in the southwest corner of Cedar River Park, and a section of the communications conduit in the southeast corner of Liberty Park. In order to avoid open cutting Maple Valley Highway, the section under Maple Valley Highway will be replaced by pipe bursting the existing conduits and pulling the new conduits under the highway. This section is approximately 140 feet in length. The section in the northwest corner of Cedar River Park will be replaced by open cutting the park. This section is approximately 220 feet in length. The section in the southwest corner of Cedar River Park will be replaced by open cutting between the two existing utility vaults. This section is approximately 40 feet in length. The section in the southeast corner of Liberty Park will be replaced by open cutting along an existing pathway. This section is approximately 100 feet in length. B. RECOMMENDATION Based on analysis of probable impacts from the proposal, staff recommends that the Responsible Officials make the following Environmental Determination: DETERMINATION OF XX NON-SIGNIFICANCE XX Issue DNS with 14 da A eal Period. Issue DNS with 15 day Comment Period with Concurrent 14 day Appeal Period. C. ENVIRONMENTAL IMPACTS DETERMINATION OF NON -SIGNIFICANCE -MITIGATED. Issue DNS-M with 14 da A eal Period. Issue DNS-M with 15 day Comment Period with Concurrent 14 day Appeal Period. In compliance with RCW 43.21 C. 240, the following project environmental review addresses only those project impacts that are not adequately addressed under existing development standards and environmental regulations. 1. Earth Impacts: The subject site is designated on the City's Critical Areas Maps as containing steeply sloped areas that qualify as either sensitive or protected slopes. The topography of the subject site is generally flat with steep slopes ranging from 25 to 40 percent on the southern and eastern portions of the property. Slopes that range from 25 to 39.9 percent qualify as sensitive slopes and slopes that exceed 40 percent qualify as protected slopes. No development is permitted on protected slope areas without the approval of a variance. The applicant has requested a critical area variance for a maximum 5-foot deep cut into the protected slope located on the eastern portion of the subject site. An Engineering Geology Report prepared by RH2, dated November 2005 was submitted with the project application. The report included a summary of the site reconnaissance that had been performed. The report concludes that origin of the steep slopes along the south side of the property is likely from excavation for the construction of NE 3'd Street. This slope has experienced several small slope failures and is presently undergoing creep. The report also concludes that the steep slope on the east side of the property is likely due to excavation and grading that was apart of quarrying operations or preparation of the site for the existing reservoir. This steep slope does not appear to be subject to a deep mast wasting, but is experiencing creep. The report recommends that precautions should be taken to ensure the construction of the new generator building will not increase the risk of slope instability. In addition to the site reconnaissance, a subsurface investigation of the site was conducted consisting of three test pits. Test pits TP1 and TP2 were located south of the existing reservoir adjacent to the southern steep slope. Test pit TP3 was located near the eastern steep slope. Test pits TP1 and TP2 generally exposed approximately 2.5 feet of fill underlain by very fine silty sand with minor gravel. In TP1 there was a buried soil horizon. Test pit TP3 generally Project Location Map LUA06-083ercrpt.doc City of Renton P/8/PW Deparlment Mt. Olivet Power Generation Facilitie- REPORT AUGUST 21, 2006 En nental Review Committee Staff Reporl LUA-06-083, SA-H, ECF, V-H Page 3 of 4 exposed approximately 0.5 to 1 feet of fill overlying a soil horizon that was approximately 1-foot thick. Below the soil horizon was a medium to medium-dense, fine to medium sand with zones of silt and zones of gravel. The sand in TP3 had bedding planes that dipped to the northwest. Groundwater was not encountered in any of the excavations. The report provided conclusions and recommendations regarding geologic hazards, water & wet weather earthwork, excavation, subgrade preparation & bearing capacity, temporary shoring and permanent retaining wall alternatives, and backfill. A Technical Information Report (TIR) prepared by RH2, dated March 2006 was also submitted with the project application. The submitted TIR proposes to utilize the Volume II of the 2005 Department of Ecology Stormwater Management Manual for erosion and sedimentation control during construction of the proposed project. Mitigation Measures: The recommendations provided in the submitted Geotechnical Report and TIR are self mitigating, no further mitigation is recommended. Nexus: N/A 2. Water -Stormwater The submitted TIR was prepared in accordance with the 2005 King County Surface Water Design Manual. The report indicates that most of the precipitation reaching the site is infiltrated, however any runoff from the site would be collected in a catch basin/pipe network along the south edge of Bronson Way and the north edge of NE 3'' Street, which border the site. The proposed method of stormwater runoff control is the installation of 102 linear feet of infiltration trenches. The report indicates that the soils present onsite are conductive to infiltration. Mitigation Measures: The proposal to design control runoff from the project site in accordance with the 2005 King County Surface Water Design Manual would result in a higher level of runoff control than required by the adopted 1990 King County Surface Water Design Manual. The proposal to utilize a higher requirement for stormwater runoff control is self mitigating, therefore no further mitigation is recommended. Nexus: N/A 3. Plants The subject site is largely forested with a grassy are located in roughly the central portion of the subject site where the existing reservoir and pump station are located. The proposed construction of the generator building would result in the removal of 9 cottonwood trees, 2 big leaf maples, and 4 alder trees. Mitigation: No further mitigation is recommended Nexus: N/A E. COMMENTS OF REVIEWING DEPARTMENTS The proposal has been circulated to City Departmental I Divisional Reviewers for their review. Where applicable, these comments have been incorporated into the text of this report as Mitigation Measures and/or Notes to Applicant. ...K_ Copies of all Review Comments are contained in the Official File. Copies of all Review Comments are attached to this report. Environmental Determination Appeal Process Appeals of the environmental determination must be filed in writing on or before 5:00 PM September 11, 2006. Appeals must be filed in writing together with the required $75.00 application fee with: Hearing Examiner, City of Renton, 1055 South Grady Way, Renton, WA 98055. Appeals to the Examiner are governed by City of Renton Municipal Code Section 4-8-110.B. Additional information regarding the appeal process may be obtained from the Renton City Clerk's Office, (425) 430-6510. LUA06-083ercrpt.doc City of Renton P/8/PW Department Mt. Olivet Power Generation Faciliti•~ REPORT AUGUST 21, 2006 mental Review Committee Staff Report LUA-06-083, SA-H, ECF, V-H Page 4 of 4 Advisory Notes to Applicant: The following notes are supplemental information provided in conjunction with the environmental determination. Because these notes are provided as information only, they are not subject to the appeal process for environmental determinations. Planning 1. RMC section 4-4-030.C.2 limits haul hours between 8:30 am to 3:30 pm, Monday through Friday unless otherwise approved by the Development Services Division. 2. Commercial, multi-family, new single family and other nonresidential construction activities shall be restricted to , the hours between seven o'clock (7:00) a.m. and eight o'clock (8:00) p.m., Monday through Friday. Work on Saturdays shall be restricted to the hours between nine o'clock (9:00) a.m. and eight o'clock (8:00) p.m. No work shall be permitted on Sundays. 3. Within thirty (30) days of completion of grading work, the applicant shall hydroseed or plant an appropriate ground cover over any portion of the site that is graded or cleared of vegetation and where no further construction work will occur within ninety (90) days. Alternative measures such as mulch, sodding, or plastic covering as specified in the current King County Surface Water Management Design Manual as adopted by the City of Renton may be proposed between the dates of November 1st and March 31st of each year. The Development Services Division's approval of this work is required prior to final inspection and approval of the permit. Fire 1. The preliminary fire fiow is 1500 GPM. One hydrant is required within 150 feet of the structure and one additional hydrant is required within 300 feet of the structure. 2. Fire department access roadways are required to within 150 feet of all portions of the building exteriors. 3. A permit will be required for the diesel tanks. Plan Review Transportation 1. Per City of Renton code section 4-6-060; projects that are valued at greater than $50,000 are required to install street frontage improvements. These projects would therefore require installation of curb, gutter, sidewalks, and storm drainage along the frontage of the parcel. A waiver or payment of a fee in-lieu of the required frontage improvements may be requested. Plan Review -General 1. Retaining walls greater than 4 feet in height are reviewed under a separate building permit. A licensed engineer with geo-technical expertise must stamp the design plans for retaining walls or rockeries greater than four feet in height. The engineer must monitor the rockery construction and verify in writing that the rockery was constructed in accordance with ARC standards. Writing verification by the engineer must be provided to the City of Renton public works inspector prior to approval of an occupancy permit. Locations of water and sewer mains will be considered in relation to the retaining walls. It may require special protection or relocation of the lines under or near the retaining wall construction. 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