Swope Campus Parking Lot and Entry Plaza

Challenge

Project designers were challenged to aesthetically revitalize the parking lot and entry approach to the Kansas City Water Services building while creating an “in-situ” laboratory to test the effectiveness of sustainable stormwater management practices. The goal was for the Water Services campus to serve as a model demonstration project for the Midwest, provide convenient access to measure ongoing performance, and promote sustainable practices to people who visit the campus daily. Over 325 parking spaces and heavy equipment vehicle parking had to be provided while achieving a goal of zero runoff from a 10-year, 24-hour storm event (5.7 in). For performance monitoring, there was a desire to install and isolate different products and strategies so that they could be compared. It was also important to improve the overall attractiveness of the campus, provide better pedestrian connectivity between parking and the building, enhance the entry experience, and create new outdoor gathering spaces for employees and visitors alike.

Solution

While not immediately apparent to first-time visitors to the Water Services campus, the site supports a sophisticated system to eliminate potable water for landscape use and treat stormwater runoff above and below ground. Above ground, bioswales, rain gardens, bioretention basins, and porous paving filter and infiltrate stormwater. Parking lots, which typically generate large runoff quantities, were constructed to test runoff reduction efficiency through 4 types of permeable surfacing: bays 1 and 2 use different types of permeable pavers, the third bay is surfaced with porous asphalt, and the fourth bay uses pervious concrete. Beneath the parking bays, aggregate-filled water storage basins hold water for infiltration. Isolation valves provide independent flow monitoring and water quality sampling between parking bays. However, the most obvious and visible improvements have been the inclusion of a new entry plaza, associated amenities, and the promotion of a native landscape aesthetic that visitors and employees can experience when approaching and leaving the building each day and across seasons.

• The parking lot contains 4 pervious parking bays: 2 bays with permeable pavers (23,566 sf), 1 bay with porous asphalt (11,783 sf), and 1 bay with pervious concrete (11,783 sf) to collect and filter stormwater.
• Underground water storage is provided by up to 36 in of aggregate beneath the parking bays, which detain stormwater before releasing it to a surface tributary. The storage system is designed for a 10-year, 24-hour storm event, with the capacity to hold 350,000 gallons of water. Aggregate materials were locally quarried.
• Underground storage cells are drained with 6-in pipes that have valves and cleanouts which allow independent measurements for comparative performance testing.
• Over 25,000 native plants of various species were planted in 6 vegetated islands within the parking lot, around the lot perimeter, and in the entry plaza. Key species include white-tinged sedge, ‘The Blues’ little bluestem, prairie dropseed, sideoats grama, blue flag iris, marsh blazing star, and brown-eyed susan. 
• The new entry plaza and building entry sequence features include a bosque of 14 trees, a third type of permeable paver (7,860 sf) and subdrainage system which visibly drains to a rain garden, and an 80-ft long artistic glass canopy at the building entrance. The canopy captures rainwater and directs it to the adjacent rain garden.
• The entry plaza contains 7 aluminum lighting fixtures, 10 aluminum bollards/bike racks, 4 benches, and 7 stainless steel moveable tables with 28 chairs that are aesthetically integrated, appropriately scaled, and contribute to user comfort and safety.
• High-performance LED lights improve luminaire efficacy by 75% as compared to a typical High Pressure Sodium source.
• A 0.4-mile, ADA-compliant sidewalk around the periphery of the site encourages healthy walking and enjoyment as employees pass native plantings.

The distinguishing feature of this project is the various types of pervious paving/stormwater storage used in the parking lot to detain and reduce peak stormwater runoff. The installed pervious paving cost $10.65 per sf for pervious concrete, $10.92 per sf for porous asphalt, and an average of $15.16 per sf for pervious pavers. All of the pervious material costs include 12-36 in of rock base, which serves to temporarily store stormwater runoff.

A standard concrete parking lot with a 7-in thickness costs $9 per sf. The premium for the pervious concrete, porous asphalt and pavers averages $3.97 per sf for the additional stormwater storage.

Compared to traditional detention basin construction at $4.04 per sf, pervious concrete/porous asphalt represents a 55.7% reduction in costs. Similarly, pervious concrete and porous asphalt provides a 59.5% cost reduction compared to a $4.42 per sf treatment train of forebays, sand filter, and wetlands.

Conversely, the average $6.16 per sf stormwater retention costs for the permeable pavers represent a 52.48% cost increase compared to a traditional detention basin, and 39.37% increase compared to a treatment train system. Even though they are more expensive, permeable pavers may still be the best option when open space for traditional stormwater detention is not available.

• Demolition required saw cutting of pavement and application of fly ash, which were dusty operations that had the potential to impact indoor air quality. Consequently, gravel subgrade in 2 of 4 phased areas was substituted for fly ash to minimize dust generation. Additional recommendations included specifying that fly ash installation be completed on weekends to reduce the number of building occupants exposed to particulates. For similar projects, project managers might consider putting adjacent building HVAC systems in the “positive” mode to protect building openings from dust.

• It was difficult to match the elevation of porous asphalt near adjacent concrete curb gutters. With slopes under 2%, ridges and low spots were created resulting in a relatively uneven surface.

• Rain garden soil was wet at the time that sediment needed to be removed and grading operations completed. Placing and working wet soil damages soil structure and can lead to slower final infiltration rates. As a result, additional time was required to allow the soil to dry, and in a few places time and weather made drying impossible. When getting ready to build green infrastructure, project managers should try to divert rain/runoff to the greatest extent possible. If needed, they should pump out excess water and provide enough time to dry out soil prior to working.

• Having a pervious concrete expert on the team at the time of installation allowed the team to make efficient changes in the field to install a high-quality product.

• Composite lumber becomes slippery in humid or dewy conditions and generated user complaints concerning the parking lot boardwalk. Handrails were added along the boardwalk to address safety concerns.

• More shade, either through mature trees or a shade structure, would increase plaza use further.

Perennials and Shrubs: Bohn’s Farm and Greenhouse 
Shortleaf Pines: Forest Lawn Nursery
Hillspire Junipers: Kat Nurseries
Deciduous Trees: Loma Vista
Permeable Pavers-Type 1: Pavestone, “Eco-Venetian, Ashlar pattern”
Permeable Pavers-Type 2: Belgard, “Aqua Roc II in Herringbone 90”
Permeable Pavers-Type 3: Unilock, “Eco-line”
ADA Pavers: Endicott Clay Products Company
Asphalt/Porous Asphalt: Vance Brothers
Pervious Concrete: Mega Industries
Grasscrete: The Bomanite Company
Zero Ice Melter (MgCl, KCl, & NaCl): Howard Johnson’s Enterprises
Parking Lot Infiltration Aggregate: Quarried by ESI
Parking Lot Light Standards: Philips Gardco “SlenderForm” SCFA-Dual LED
Pedestrian Light Standards: BEGA
Plaza Light Fixture: BEGA, “77 844”
Plaza Light Standards: Landscape Forms
Plaza Tables: Forms + Surfaces
Bike Racks/Bollards: Forms + Surfaces, “Capitol Bike Rack”
Trash/Recycling: Landscape Forms

Project Team

Client: Kansas City Water Services (KCMO)
Landscape Architect: BNIM
Civil Engineer: SK Design
Structural Engineer: KH Engineering Group
Electrical and Plumbing Engineer: BGR Consulting Engineers
Irrigation Consultant: Landworks Studio
Special Inspections: Solid Ground Environmental
Testing: PSI
General Contractor: Mega Industries
Asphalt/Porous Asphalt Contractor: Vance Brothers
Pervious Concrete Contractor: Mega Industries

Role of the Landscape Architect

The landscape architect was the lead designer and project manager responsible for all planning and design services associated with the WSD campus improvements. Complete tasks included development of the site master plan, design of all site improvements, oversight of all civil and electrical engineering scope, construction administration services, and material testing.