Upgrading Civic Drainage for Denver’s 16th Street Mall Project
Quick Facts
- Location: Denver Colorado
- Customer: PCL
- Design firm: Martin & Martin
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Timeline: 13 phase project over 28 months.
First phase shipped Nov. 2022, Final phase shipped Feb. 2025 - Amount: Over 7650 feet of Slot Drain.
- Load Requirements: Designed to meet AASHTO M 306-10 HS-20.
- Maximum Flow Rate: 1290 GPM (at the deepest flange of drain)
- Maximum Surface Drainage: 70,000 GPM
- Materials: T304 & T316 stainless steel
- Special Requirements: Heel Proof and ADA Compliant
- Supplied Product: Slot Drain Systems, 11,000 Series with paver extension.
Project Scope and Drivers
In the 2010s The 16th Street Mall in Denver had a problem. Deteriorating conditions in the granite paver system and inadequate subsurface drainage were resulting in frequent disruptions to the transit system. On top of this maintenance costs related to this deterioration had ballooned to $1M annually. Spiraling costs were creating an unsustainable situation for local stakeholders and decisions had to be made about the future of the Mall.
The 16th Street Mall has been a fixture of Downtown Denver since its construction in 1982. It serves as an economic engine for the area drawing locals and tourists alike. Boasting 1.25 miles of dense walkable neighborhood, it features over 200 shops and restaurants. The Mall has national renown as the “premiere pedestrian environment in the rocky mountain region,” according to the Downtown Denver Partnership.
The Mall has national renown as the “premiere pedestrian environment in the rocky mountain region,”
Downtown Denver Partnership.
Based on its historic, economic and civic importance the decision was made to improve surface drainage and secure the sustainable future of the 16th Street Mall. This led to the creation of the 16th Street Mall Project. This multi-phase project called for the excavation of the mall to regrade the land, replace the pavers and upgrade the underground drainage system. Global Drain Technologies was honored to be selected to supply the stainless steel drainage required to achieve this generational project.
Supplying Storm Water Drainage
Civic spaces like the 16th Street Mall require storm water drainage. Storm water drainage is infrastructure that drains excess rainwater or snowmelt from hard surfaces like roads, parking lots, transitways and pedestrian walkways and diverts it through storm sewers away from dense urban areas.
Storm water drainage has a huge impact on the longevity of an urban space and is a key component of urban planning and civic design. If rainwater is not properly drained it eventually seeps down between the pavers or under the concrete and slowly erodes the stone or sand base.. This can result in the formation of depressions or potholes. These depressions then collect water leading to even more erosion. This vicious cycle can result in ever increasing maintenance costs for civic spaces with inadequate storm water drainage.
Today’s storm water drainage has evolved to a minimalist aesthetic that blends with its surroundings. The 16th Street Mall project features innovative drainage design that moves away from traditional curbside inlets to nearly invisible slot drains that seamlessly blend beauty and functionality.
Preventing Flooding
Storm water drainage combats standing water and the resulting erosion during normal precipitation but must also accommodate the influx of water during a significant rainfall event. For the 16th Street Mall Project Global Drain Technologies deployed our 11,000 Series Slot Drain System. The 11,000 Series is a heavy duty industrial slot drain reserved for large civil projects or spaces that will see heavy industrial use.
Slot Drain Systems are seeing increased use because they are less prone to blockages than traditional area drains. In an area drain system, water is diverted towards multiple point drains or openings within a large paved area. This design requires that complex slopes be incorporated during the installation of the paver system to ensure water reaches the drains. If one of the drain openings becomes blocked then the entire area it serves cannot drain. A Slot Drain spreads out storm water collection over the entire length of the drain. This approach to drainage requires less complex slopes in the paver system and helps to prevent blockages.
The linear design of a Slot Drain System also presents advantages in surface drainage capacity. Surface drainage for a Slot Drain System is calculated by taking the entire length of installed drain and multiplying it by the amount of water each section of drain can accept in a minute. This is also known as the drain’s intake discharge.
16th Street Mall Drainage at a Glance :
- 7650’ of Slot Drain was installed
- 5648’ is standard riser slot drain with an intake of 11 GPM
- 944’ is heel proof slot drain with an intake of 8 GPM
- The remaining 1965’ is a slot cover drain which was buried and accepts no discharge
- This gives us a total intake discharge of 70068 GPM
Engineers at Global Drain Technologies were able to plan for and deliver drainage that accounted for extreme rainfall events including a “once in a hundred year event” as stipulated by project managers. The 16th Street Mall’s storm water drainage system was delivered with a maximum surface drainage of over 70,000 GPM.
The 16th Street Mall’s storm water drainage system was delivered with a maximum surface drainage of over 70,000 GPM.
Underground the 11,000 Series Slot Drain System has a maximum discharge capacity of 1290 gallons per minute (GPM) at the deepest flange of the drain. This means that one section of the 11,000 Series Slot Drain System could drain a 15’ x 30’ inground pool in about 10 minutes. This underground capacity allows for the free flow of water from the surface into the drain body and ultimately into the City of Denver’s storm sewer system. This massive drainage capacity will ensure the safe and dry operation of the 16th Street Mall for decades to come by protecting it from flooding and erosion.
Cleaning and Maintenance
The 11,000 Series Slot Drain System features presloped stainless steel design which makes the drain body effectively self-cleaning. The 11,000 series also features a tapered throat extending above the drain body for surface drainage. Catch basins were placed along the length of the drain during the design phase. Catch basins temporarily store and transfer water either between runs of surface drainage (inline) or between surface and subsurface drainage (termination). Catch basins act as an access point to clear debris from the drainage system and/or to access the inside of the plumbing system.
The tapered throat is engineered to prevent the accumulation of ice and snow, a requirement of the Mall’s project management team. “We tested and iterated multiple designs,” says Chad Kaatz VP of Engineering and Product Management at Global Drain Technologies. “The final product allowed ice and snow to fall into the drain body rather than remaining in the tapered throat.” While the engineering details of this design are proprietary, the finished product impressed project leaders and proved that Slot Drain Systems could function without issue in Denver’s cold weather climate.
“The final product allowed ice and snow to fall into the drain body rather than remaining in the tapered throat.”
Chad Kaatz, VP of Engineering, Global Drain Technologies
Maintenance and cleaning of the 11,000 Series are performed by city crews using existing tools like pressure washing systems. Cleaning crews can easily access the entire drain body due to its slotted opening and inclusion of catch basins. This makes cleaning and maintenance easy and requires less use of expensive specialists to clear underground drain lines saving the city on cleaning and maintenance costs.
Heel Proof Design and Paver Integration
The 16th Street Mall Project specified heel proof and ADA compliant requirements for the supplied storm water drainage. Heel proof drains are designed with narrow openings to prevent high heels, or other small items from becoming trapped in the drain. ADA compliance requires that drains have openings no larger than 0.5” perpendicular to the direction of travel. Slot Drain Systems like the 11,000 Series are designed to fit flush to the surrounding paver system. This allows wheelchairs and other mobility aides to operate freely without encountering obstructions ensuring the safe and equitable use of the Mall by all visitors.
The 11,000 Series supplied to the 16th Street Mall Project was delivered with an ADA compliant design and heel proof sections. High traffic areas like crosswalks were delivered with a heel proof design. Lower traffic areas integrated the drainage as a 0.5” slot between paving stones.
These design requirements are achieved on the 11,000 Series Slot Drain System through the inclusion of a paver extension. The paver extension allows the body of the slot drain to be positioned well underground while a tapered throat extends above the drain and integrates with the surrounding paving stone.
Beyond being designed for accessibility and durability this design also integrates seamlessly with aesthetics of the mall to meet architectural requirements.
“The curbless drainage system on the rehabilitated mall is designed to be “hidden in plain sight. The system offers efficient access to maintenance, but for many will be relatively imperceptible as an infrastructure element.”
Matt Schlageter, director of civil engineering for Martin/Martin.
Source: enr.com
Load Class Rated Drains
The 16th Street Mall Project called for the removal of the center boulevard and the repurposing of that space as a transitway for city buses. The drains running along the transitway are designed to structurally integrate with the surrounding pavement and last for decades under the load of daily heavy vehicle traffic.
The 11,000 Series Slot Drain is designed to meet AASHTO M 306-10 HS-20. “In layman’s terms the drain must not show any signs of cracking or deformation when loaded with a 40,000 lb test load and held for 1 minute. The 40,000 lb. test load is applied to a plate that is 9″x9″ that sits on the center of the drain/test block;” says Chad Kaatz VP of Engineering and Product Management at Global Drain Technologies.
To learn more about purchasing drains that are load rated to your specific needs please talk to our sales staff. Our engineering department is available to custom design and test drains to meet any weight rating specification.
Managing a Staged Timeline
The 16th Street Mall Project laid out an ambitious phased timeline. The first phase called for the relocation of utilities including electric, gas, telecom, storm and sanitary sewer. This phase was planned to take 13-14 months and broke ground in April of 2022. However, as with many such projects both unknown unknowns in the form of buried historic utilities and supply chain issues caused delays.
Global Drain Technologies worked closely with PCL on this project to ensure on time delivery of the Slot Drain Systems matched with the realities of the project on the ground. Our phased delivery approach began with our first drain delivery in November of 2022 and ended with our final delivery in February of 2025.
Clear Communication ensured smooth progress of the project regardless of operational delays. Material was made to order and delivered just in time to the project to prevent early or late material deliveries that could lead to delays or unacceptable staging of materials. Our sales, engineering, manufacturing, shipping and service staff all worked together to ensure this went off without a hitch. We would like to thank each and every one of them for their tireless efforts without which this project would not have been possible.
The Future of Drainage in Civic Spaces
As landscape and civic design continue to evolve, the future of drainage is to seamlessly integrate with the aesthetic of public spaces like the 16th Street Mall. Our goal at Global Drain Technologies is to blend form and function. Our drains are built to embrace the key concepts discussed in this article:
- Providing flow rates adequate for extreme rainfall events
- Creating accessible designs
- Integration with paver or concrete systems
- Load class rated designs
- Project integration with timelines and staged delivery
Global Drain Technologies is proud to have participated in this generational project. We thank PCL, the City of Denver and all the stakeholders who made this project a success. We will see you all in 50+ years when time comes due to renew the Mall for another generation.
About Global Drain Technologies (GDT)
Global Drain Technologies (GDT) is a leading manufacturer of drainage products and systems, offering innovative, industry-specific solutions. As the inventor of the Slot Drain we offer unmatched expertise in integrated drainage solutions for new construction and drainage upgrades.
Through its divisional brands: FoodSafe Drains and Landscape Drains as well as our Slot Drain Systems product division GDT provides specialized drainage solutions for customers in North America and internationally.
Slot Drains Systems Product Division offers a wide and expanding range of commercial and residential drainage options.
FoodSafe Drains provides hygienic drainage solutions for the Food & Beverage sector including Slot Drain Systems products as well as drainage design and consulting services.
Landscape Drains delivers a comprehensive range of interior and exterior drainage solutions for residential and commercial applications including Slot Drain Systems products
With a focus on value-added design, manufacturing, and product delivery, GDT ensures its products are hygienic, easy to clean, and maintain. Committed to excellence, GDT provides industry-leading service, support, and engineering.
Brands:
- FoodSafe Drains – www.foodsafedrains.com
- Slot Drain Systems – www.slotdrainsystems.com
- Landscape Drains – www.landscapedrains.com