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HomeMy WebLinkAboutSR_HEX_Memo_4th_Dimension_Building_251120_FINAL DATE: November 20, 2025 TO: Phil Olbrechts, City of Renton Hearing Examiner FROM: Jill Ding, Senior Planner SUBJECT: 4th Dimension Building (LUA25-000193, ECF, SA-H, RUV-H) As requested, this memorandum is intended to update and elaborate on staff’s recommended Variance Analysis for the proposed 4th Dimension Building as well as the justification provided to the variance criteria found in FOF 21 of the Staff Report to the Hearing Examiner (Exhibit 17). 21. Variance Analysis: The applicant is requesting a Reasonable Use Critical Areas Variance to allow the piped stream to be redirected to a new surface channel that would be constructed in the central portion of the site (Exhibit 15). The stream is classified as a Type Ns Stream, and when relocated to a surface channel, would have a standard buffer of fifty feet (50’) and a fifteen-foot (15’) building setback from the edge of the buffer. Building structures over a natural stream that is located in a surface channel, underground pipe or culvert, and within the stream buffer, except as may be granted by a variance under RMC 4- 9-250, is prohibited. The proposal to remove the stream from the existing pipe and redirect the stream to a new concrete surface channel that would be constructed in the central portion of the site (Exhibit 3). The new building is proposed to be constructed with an open space under the building to accommodate the new stream channel and to provide additional flood storage during storm events. The applicant is requesting a variance from the adopted Critical Areas Regulations (RMC 4-3-050) and is compliant with the following Reasonable Use Variance criteria, pursuant to RMC 4-9-250B.7. Therefore, staff recommends approval of the requested variance. Compliance Variance Criteria and Analysis ✓ a. That the granting of the variance will not be materially detrimental to the public welfare or injurious to the property or improvements in the vicinity and zone in which subject property is situated; Staff Comment: The project proposes to replace the existing 24-inch (24”) storm drainage pipe bisecting the site with a proposed concrete trapezoidal surface channel that would be constructed beneath the proposed building. The proposed building would be constructed with an open space under the building footprint to accommodate the new stream Hearing Examiner Olbrechts Page 2 of 4 November 20, 2025 channel and provide additional storage during storm events. The applicant contends that granting the Reasonable Use Variance would not impact the public or any properties in the vicinity because the drainage system currently utilizing the site would not be diminished (Exhibit 15). According to the project’s wetland scientist with Raedeke Associates, Inc., the overall project is anticipated to improve the flow of drainage across the site and reduce potential impacts from flooding on neighboring properties. Staff concurs with the applicant that granting of the variance to daylight the piped stream, by replacing the existing 24-inch (24”) storm drainage pipe that bisects the site with a proposed concrete trapezoidal channel, would not be materially detrimental to the public welfare, nor injurious to the property itself or to improvements in the vicinity and zone in which the subject property is situated. The daylighting and creation of compensatory storage under the building would improve existing drainage conditions on the site and reduce localized flooding. ✓ b. There is no reasonable use of the property left if the requested variance is not granted; Staff Comment: The applicant contends that the property is encumbered by an existing drainage pipe and that during severe storm activity, overflow storage of stormwater occurs on the site. The applicant maintains that the stormwater stored is from upstream and neighbor ing properties, and because the property has a depressed area on the north end, water would naturally collect at this location should the drainage pipe become filled to capacity. The applicant further contends that any changes to the topography of the site would impact the quantity of stormwater in which the site would hold. Moreover, City regulations generally do not allow stormwater pipes or storage outright under new structures because of potential difficulties in maintaining the structures. According to the Technical Memorandum for Stream and Wetland Reconnaissance, prepared by Raedeke Associates, Inc. (Raedeke), dated June 25, 2019 (Exhibit 6), the existing 24-inch (24”) diameter culvert and pipe servicing the property are not adequate to accommodate water from the stream during heavy storm events. This results in water overtopping the culvert and ponding in the central portion of the site. For this reason, the stream channel is proposed to be removed from the existing pipe and redirected into a concrete surface channel located within an open space beneath the proposed building. The channel would be accessible by maintenance crews. A surface channel would be subject to a fifty -foot (50’) buffer and fifteen-foot (15’) building setback. The application of the critical area buffer and building setback to the surface channel would encumber the majority of the project site. Staff concurs with the applicant that, without allowing the relocation of the piped stream system, into the proposed concrete channel beneath the Hearing Examiner Olbrechts Page 3 of 4 November 20, 2025 building, only a small portion of the site would be developable due to the topography and the hydrology of the existing piped stream as well as the applicable buffers and building setbacks that would apply to a surface channel. Under strict application of the code, no reasonable use of the property is feasible. Provided all mitigation measures and conditions of approval are complied with, the concrete trapezoidal stream channel construction solution proposed under the center of the building would allow reasonable use of the property. ✓ c. The variance granted is the minimum amount necessary to accommodate the proposal objectives; Staff Comment: The applicant contends that the requested variance is the minimum needed in order to accommodate development of the site and simultaneously maintaining the drainage system. All other options, including upsizing the entire system so the storage would not be needed, or constructing additional drainage structures on-site or off-site, would all be more costly and destructive to the site and its surroundings. According to the applicant, constructing over the storage area is the simplest solution with the smallest impact on all parties involved (Exhibits 5 and 6). Staff concurs with the applicant that granting the Reasonable Use Variance is the minimum amount necessary to accommodate development of the site while simultaneously maintaining the drainage system, as contemplated in the CA zone. Based on the stormwater analysis and geotechnical engineering, construction of the building over the stormwater compensatory storage area is the simplest solution with the least drainage impacts while still allowing development of the site. ✓ d. The need for the variance is not the result of actions of the applicant or property owner; and Staff Comment: Approval of this variance would not be the result of actions of the applicant or property owner. The property owner recently acquired the property with the existing 24-inch (24”) storm drainage pipe bisecting the site. According to the applicant, the situation is unusual given the use of private property is not usually required to accommodate the stormwater of neighboring and upstream properties under the current size and volumes experienced. The applicant contends that allowing the variance would enable the developer to maintain and even improve the storm drainage system without deeming their property unusable. Staff concurs that the need for the variance is not the result of actions of the applicant or the current property owner. Allowing the Reasonable Use Variance would enable the owner to improve the storm drainage system and critical areas on and off-site. ✓ e. The proposed variance is based on consideration of the best available science as described in WAC 365-195-905; or where there is an Hearing Examiner Olbrechts Page 4 of 4 November 20, 2025 absence of valid scientific information, the steps in subsection F of this Section are followed. Staff Comment: As described in the project submittal documents and staff reports, the proposed variance is based on consideration of the best available science including the geotechnical, stormwater, civil construction, and critical areas reports prepared for the project site (Exhibits 1, 3, 5, 6, and 7).