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Peer Review Memorandum
To: Jill Ding, Senior Planner
City of Renton
From: Jeff Gray, PWS (Otak)
Kevin Corrigan (Otak)
Copies: File
Date: November 4, 2022
Subject: Unico Longacres Property (Seattle Sounders FC Performance Center)
- Critical Areas Report and Conceptual Mitigation Plan Peer Review
Project No.: Renton: PRE21-000410
Otak: 20796.000
Otak, Inc. (Otak) conducted a review of the Critical Areas Report and Conceptual Mitigation Plan
(Mitigation Plan) dated October 7, 2022, prepared by Talasaea Consultants, Inc. (TCI) for the proposed
Seattle Sounders FC Performance Center (Project) on the Longacres Office Park (LOP) property in the
City of Renton (City). The project proponents are proposing a new training facility for the Sounders FC
that will include five full-sized soccer training fields, a goalkeeper field, operations building, a maintenance
facility, restroom facilities, a deck addition to the existing structure, and realignment of existing trails. The
City requested Otak to review the proposed impacts and mitigation to wetlands and wetland buffers on
site described in the Mitigation Plan for consistency with Renton Municipal Code (RMC) Critical Area
Regulations (RMC 4-3-050).
The LOP is 108 acres in size and comprised of 18 property parcels. The Project will be located on seven
of the 18 parcels, including: 2423049022, 08867001100, 0886700120, 0886700130, 0886700140,
0886700220, and 0886700370. The LOP property previously hosted a horse racetrack until The Boeing
Company purchased the property and developed the Customer Services Training Center in the early
1990s and the LOP in the mid-1990s. Development also included the implementation of the wetland
mitigation project titled Surface Water Management Projec t and Conceptual Mitigation Plan (Shapiro
Associates 1999). Wetland boundaries, classifications/ratings, and buffer widths were previously
reviewed as documented in Otak’s Wetlands Peer Review Memo dated June 9, 2022.
The following materials were reviewed by Otak:
• Critical Areas Report and Conceptual Mitigation Plan (38 pages), prepared by TCI, dated October
7, 2022, including Executive Summary (2 pages), Figures 1-14 (16 pages) and Appendices A-D
(105 pages).
• Civil Engineering Narrative, prepared by CoughlinPorterLundeen (CPL), dated August 8, 2022.
• Field Design Narrative, prepared by DA Hogan, dated July 27, 2022.
• Sounders/Longacres Conditional Use Permit – August 2022 (Civil Plan Set), prepared by
Generator Studio, sealed August 8, 2022.
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• Lighting Plans, prepared by Generator Studio, dated April 27, 2022
• Project Narrative, no date
• Engineering Report, Technical Information Report, prepared by CPL, dated August 2022.
Proposed Critical Areas Impacts and Mitigation
The Mitigation Plan states that the Project will have no direct impacts to Wetland A , and 15,467 square
feet of indirect impacts from the proposed encroachment into the Wetland A buffer. Mitigation of these
impacts is proposed through a combination of mitigation credit purchase through the Springbrook Creek
Mitigation Bank at a 0.5:1 ratio, and 4,616 square feet of buffer enhancement in areas of the Wetland A
upland buffer dominated by invasive species. The proposed buffer enhancements would be subject to
maintenance and monitoring for a period of five years per RMC 4-3-050L(2) and RMC 4-3-050L(3).
Findings – Mitigation Plan Review
Comment 1 is form the June 9, 2022 peer review memo, and comments 2 through 18 are new in regards
to the Mitigation Plan.
1. (Comment from previous peer review memo dated June 9, 2022) Wetland boundaries were
flagged in the field and verified during the May 18, 2022 site investigation. However, the Letter
Report does not include a mapping accuracy statement indicating if the flags were professionally
surveyed, located with a GPS, or estimated using aerial photography and previously prepared
maps by others.
Action by the applicant: Provide an accuracy statement for the wetland boundaries shown on
Figures 3 and 4 in the Letter Report.
Outcome: Resolved. The Mitigation Plan includes an accuracy statement describing that wetland
flags were located in the field with a hand-held GPS device with sub-meter accuracy.
2. The wetland categories and buffer widths for Wetlands A, C, and F described in the Mitigation
Plan are consistent with the wetland boundaries, classifications, and buffer widths reviewed
previously, and are consistent with RMC 4-3-050.F and 4-3-050.G.
3. Clarify if a conservation easement or similar protective instrument for the Boeing mitigation
wetlands area encumbers the northwest corner of the project site where the buffer impacts are
proposed. Conservation easements are commonly required for compensatory wetland mitigation
projects. If a conservation easement does exist, then it should be amended to reflect the future
site condition and recorded for compliance with RMC 4-3-050(G)(3) – Native Growth Protection
Areas. If not, then the applicant should address project compliance with RMC 4-3-050(G)(3).
4. The potential buffer enhancement areas shown on sheets 9-9A are different than what is shown
on Figures 10, 11, and 12. Figure 9A should only show the 100-foot offset from the edge of the
soccer fields to determine indirect wetland impacts pursuant to Washington Depar tment of
Ecology’s (Ecology) Wetland Mitigation in Washington State, Part 1: Agency Policies and
Guidance (Version 2, dated April 2021, Publication 21-06-003). Clarify why potential buffer
enhancement areas are limited to only the west side of the paved pedestrian trail. Other potential
buffer enhancement opportunities appear to the north as proposed on Figures 10 and 11 in the
Mitigation Plan.
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5. Remove the red post-construction buffer line shown on Figures 10, 11, and 12 of the Mitigation
Plan. If further buffer reduction is proposed as shown, then additional mitigation will be required
after justification is provided for the additional buffer reduction. Maximize all buffer enhancement
opportunities between the edge of development and Wetland A, excluding the paved trail, to
minimize impacts to habitat functions in Wetland A. Consider other buffer areas along the east
side of Wetland A north of the project but within the Unico Longacres property that are grass for
additional buffer mitigation (if feasible).
6. The proposed 0.50 credit purchase from the Springbrook Wetland Mitigation Bank as mitigation
for indirect wetland impacts to Wetland A appears consistent with Section 3.4.5.1 (Determining
the area of indirect impact) of Ecology’s Wetland Mitigation in Washington State, Part 1: Agency
Policies and Guidance (Version 2, dated April 2021, Publication 21-06-003), and is allowed per 4-
3-050(J)(4)(b)(vi). Based on current Best Available Science, the inner wetland buffer typically
provides water quality functions and buffer beyond that is typically for wildlife functions. This
partial loss of functions is consistent with the partial credit purchase because the wetlands will still
provide hydrologic and water quality functions, but habitat functions will be partially reduced.
7. Include tree removal within the buffer between the edge of the sports fields and existing sidewalk
as shown on the Demo Plan sheets C1.01 and C1.04 as additional buffer impacts. Characterize
these impacts as temporary or permanent, and any tempora l loss from temporary impacts. Per
RMC 4-3-050(H)(2), an approved alteration of the minimum buffer widths must include
demonstration from the application that through enhancing the buffer and use of the low impact
development strategies the reduced buffer will function at a higher level than the standard buffer.
8. Identify the amount of buffer reduction from the proposed sports fields, indirect wetland impacts,
and total buffer enhancement. Include a no net loss statement pursuant to RMC 4-3-050(J)(4)(a).
9. Identify and include temporary buffer impacts in the Mitigation Plan per RMC 4-3-050(H)(2), and
include these areas in the monitoring plans to ensure restoration following construction.
10. Revise buffer impacts and the mitigation credit purchase as necessary.
11. Chapter 7 of the Mitigation Plan should be revised to state that mitigation will be provided for
15,467 SF of indirect impacts to Wetland A. The report currently lists the potential buffer
enhancement area (15,151 SF) requiring the credit purchase. Update the credit purchase
accordingly.
12. The credit purchase and mitigation ratio are determined by the mitigation banking instrument per
RMC4-3-050(J)(4)(e). The applicant has provided clear rationale and justification for the proposed
0.5:1 impact to credit purchase ratio since the mitigation banking instrument does not provide a
standard ratio for indirect wetland impacts.
13. The Mitigation Plan should be updated to address how the habitat logs will be delivered and
installed, identify any potential temporary impacts to existing riparian vegetation, and how any
temporary impacts will be restored if necessary.
14. Consider snagging any hazard trees in the remaining buffers that are recommended to be felled
by a certified arborist following construction. Hazard trees r emoved in the buffers should be
replaced at a minimum mitigation ratio of 3:1.
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15. Add an area qualifier (e.g., square feet) to Performance Standard 1A.
16. A mitigation sequencing statement is provided, and avoidance and minimization measures have
been identified and employed where feasible, including alternative site layouts and designs,
pursuant to RMC 4-3-050(L)(1)(b).
17. The Mitigation Plan prepared by TCI generally meets the independent buffer study criteria per
RMC 4-3-050(G)(9)(d)(ii) that is necessary to authorize approval of alternate buffer widths.
18. The project proposes using natural grass for two of the five sports fields plus the keeper/training
area, and artificial or synthetic turf for the remaining fields. The project site is approximately 1,150
feet from Springbrook Creek, which has documented salmonid presence. The stormwater system
includes a water quality treatment system, but stormwater will discharge untreated at high flows
to Pond B that has a direct surface water connection to Wetland A and Wetland F that discharge
to Springbrook Creek. Synthetic turf fields have related environmental concerns with respect to
using rubber tires as fill, in addition to the recently documented toxic impacts to fish from 6PPD -
quinone associated with rubber tires. The applicant is looking to use environmentally friendly,
non-toxic, materials for the fill. The applicant has not decided on the fill material at this time. If
rubber tires is selected, then the findings in the Habitat Assessment (Chapter 4) should be
updated and effects determinations revisited based on the Best Available Science.
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