The URL can be used to link to this page

Home My WebLink AboutEX_26_M_Field_Design_Narrative_220920_v1 1450 – 114TH Ave SE Page 1 of 5 p. 206‐285‐0400 Suite 225 f. 206‐285‐0480 Bellevue, WA 98004 www.dahogan.com MEMORANDUM To: Tom Proebstle, AIA Generator Studio Cc: For Distribution From: Eric Gold Date: July 27, 2022 Re: Seattle Sounders FC Fields & Landscape Program & Design Narrative Project Design Program Summary This document describes generally and in detail proposed exterior improvements including the athletic surfaces (fields/pitches), circulation, player parking lot, fencing, and landscaping including parking lot and building vicinity. Proposed Site Build‐Out (north is to the right) 1450 – 114TH Ave SE Page 2 of 5 p. 206‐285‐0400 Suite 225 f. 206‐285‐0480 Bellevue, WA 98004 www.dahogan.com There will be two distinct field types – sand‐based natural grass and synthetic turf. Fields 1 and 2, along with an adjacent “utility” or goal keeper space will be sand‐based natural grass. Fields 3‐5, and additional adjacent utility spaces, will be synthetic turf. Detailed information about the design and function of the fields follows. Field sizes are as determined by FIFA/International Soccer Rule, matching the club’s Competition Facility (Lumen Field), generally 75y x116y with 10’ of safety clearance / runout on all sides. All interior pedestrian/service/emergency circulation is proposed as concrete, although both of the playing surfaces are also part of the interior circulation plan. The Players’ Parking Lot is created through modification of the existing parking lot, and is secured with a proximity card or phone‐based‐application entry and a 10’ perimeter security fence. Parking within the secure perimeter includes 9’ x20’ spaces and curb. Fencing, generally, will consist of color‐clad galvanized steel chain link fencing , black, with 2”mesh woven fabric. There will be a hierarchy of fence types within the development, including perimeter security (10’), interior partitioning (4’), and ball control, which will consist of 15’ of nylon netting (black) above 10’ chain link. Additional detail is included below. Landscaping includes parking lot landscape per RMC 4‐4‐070.F.6.b, including the addition of 10 new “street” trees, Carpinus caroliniana / American Hornbeam (20’‐30’ ht. x20‐‘‐25’ canopy spread), mass plantings of Prunus laurocerasus / Otto Luyken Laurel, and Vinca minor / Periwinkle groundcover. All parking spaces are within 50’ of plantings. All plantings are consistent with code. Note that accessible parking is provided within the existing parking lot, immediately adjacent to the player/staff entry on the south façade of the building. American Hornbeam, summer & fall foliage 1450 – 114TH Ave SE Page 3 of 5 p. 206‐285‐0400 Suite 225 f. 206‐285‐0480 Bellevue, WA 98004 www.dahogan.com Landscaping around the building perimeter, within the secure perimeter, includes hardscape (concrete paving), synthetic turf, and a small area of accent landscaping including on‐grade with aggregate mulch and a large planter / series of planters. DETAIL: Natural Grass Fields The natural grass fields will be sand based, with a pea gravel drainage cavity and subsurface drainage collected and discharged to site civil infrastructure. 12” of Sand growing medium (“root zone sand”) will be consistent with USGA Standards, as will be the 6” pea gravel drainage cavity. 4” perforated corrugated polyethylene drainage tubing laterals spaced 15’ on center will conduct stormwater to ridged dual‐wall corrugated polyethylene pipe for conveyance to the Civil Stormwater infrastructure for treatment and detention. Typical Natural Grass Field/Pitch Section Grass species will be a blend of perennial rye gras (“PRG”) and Kentucky bluegrass (“KBG”) varieties, sod, grown in a like root zone sand for a minimum 12 months and cut to between 3/4Z” and 1” immediately prior to installation. This species blend provides for three seasons of active growth and wear recovery ‐ PRG breaks dormancy in early spring when soil temperatures reach 50°F sustained, and goes mostly dormant when soil temps hit 70‐75°F in summer. KBG requires around 70°F sustained to break dormancy, and so “takes over” in the heat of summer. As fall progresses, the KBG goes dormant and the PRG takes over until soil temperatures decline below 50°F. DETAIL: Synthetic Turf Fields Resilient infill synthetic turf product, ideally complying with FIFA Quality Program for Football Turf, will be selected as part of a later process. The field section will consist of an 8” lift of base course permeable aggregate and a 2” leveling course of top course permeable aggregate. With the depth of the turf system, this usually results in a standard 12” section. The permeable aggregate section specification requires that both aggregate products be free‐draining, with a relatively small percentage of fines, and be stable. To accomplish this, the base course must be a crushed product with a minimum of 75% fractured faces. The top course must be a full‐fracture product, generally ledge rock, with 100% fracture. All of this allows for vertical movement of stormwater, and lateral movement along a 0.50% sloped subgrade, to a gallery of flat/panel drains which conduct drainage to a traditional perforated collector for conveyance to the Civil Stormwater infrastructure for treatment and detention. 1450 – 114TH Ave SE Page 4 of 5 p. 206‐285‐0400 Suite 225 f. 206‐285‐0480 Bellevue, WA 98004 www.dahogan.com Typical Synthetic Turf Field Section including subsurface drainage Two of the three synthetic turf fields are proposed as described above (fields 4 and 5). These will include a permeable liner, to reliably separate the field stormwater from proposed flood mitigation designed below (refer to Civil). Field 3 will be constructed above the site stormwater detention facility, where stormwater will be detained prior to treatment. Because of this, the vertically draining character of the field section will not require a subsurface drainage system. That simplified field section will simply drain directly to the detention system. Field 3 Section over Civil Stormwater Detention Considerations in the selection of the synthetic turf product will include fiber and infill types. There are several fiber configuration options available, and more infill varieties to choose from including granular cork, TPE, coated SBR, and several proprietary blended and extruded materials with an organic component. Many of these lack the necessary resiliency, and require that a supplemental pad or underlayment be incorporated. Here again, there are several options. We expect this will be determined during the Design Development phase. Note that a third area of synthetic turf is proposed, in more of a landscape / pedestrian application adjacent to the main building. This surface will be a very dense, low pile height, non‐infilled product that is not permeable and so requires sheet‐flow treatment as for any hard surface. This material is adhered directly to a concrete or asphalt base, and drains directly to a common stormwater inlet, in this case a trench drain. Non‐Infilled synthetic landscape turf for select pedestrian areas adjacent to the building 1450 – 114TH Ave SE Page 5 of 5 p. 206‐285‐0400 Suite 225 f. 206‐285‐0480 Bellevue, WA 98004 www.dahogan.com DETAIL: Fencing: Security & Ball Control There will be a clear hierarchy of perimeter and interior fencing ranging from 4’ (interior “partitioning” and ball control) to 10’ (perimeter security) and 25’ (ball control fence/net systems) heights throughout the site. Again, all fencing components will be color‐clad black. 4’ fences are intended only to partition the fields from each other to prevent balls from rolling from one field to an adjacent field. A 10’ chain link fence will encircle the entire perimeter. Behind each goal and extending the length of the goal box, a 10’ fence with an additional 15’ of nylon netting will protect adjacent fields (and the site perimeter) from errant shots on goal. Between the goal box and the outside of the penalty box, a 10’ fence will protect against errant crossing passes and lower‐trajectory crossing shots on goal. From the penalty box to the corner kick a 4’ fence will stop balls from rolling onto adjacent fields. Most 10’ fencing will include a visual screen with team branding, described elsewhere. Various openings will allow pedestrians and service vehicles to freely access throughout the interior of the site. Strategically located security gates will control access to the site and maintenance yard. Example Ball Control Fence/Net system. Finish will likely be black powder coat (shown in galvanized).