Make Sponge City Tangible – Kaifeng Science Popularization Plaza Rainwater Harvesting Case | Zhengzhou Yayuan Technology

Project Positioning: Turning Sponge Facilities into Exhibits for Science Outreach

Kaifeng Science Popularization Plaza serves as a key public venue for science education and themed events, featuring high foot traffic and extensive hard paving. Rainwater systems in conventional plazas are usually buried underground, invisible and difficult to interpret. Unique to this science plaza, the rainwater harvesting system must be functional and interpretable. It translates the abstract concepts of infiltration, retention, storage, purification, reuse and discharge into physical scenes that visitors can observe, understand and even engage with.

Zhengzhou Yayuan Technology addressed this dual challenge for the project: mitigating flooding risks caused by concentrated runoff peaks from large hard-surfaced areas, and integrating the underground rainwater harvesting system organically into the plaza. This aligns with Kaifeng’s urban development strategy of combining sponge city construction with public science education. Drawing on prior experience from projects such as Kaifeng Railway Station Front Square, Yayuan’s PP module system has proven reliable for sites with complex underground utility layouts.

System Design: PP Modules as the Core — Underground Water Storage Supporting Above-Ground Science Communication

The project adopts Yayuan’s PP rainwater harvesting modules as the main water storage body. Each module features a honeycomb hollow 3D structure with a void ratio of over 95% and bearing capacity up to 60kN/㎡. Assembled on-site, the modules form an underground cistern. After backfilling and soil covering, the surface can still support plaza paving and green landscapes without occupying extra ground space. This characteristic is critical for the science plaza: the underground zone functions as a rainwater detention tank, while the ground level fully retains space for exhibitions, public assembly and landscaping.

The system follows a closed loop: Collection → Pre-treatment → Storage → Purification → Reuse. Rainwater falling on the plaza and adjacent hard surfaces flows through inlets into pipelines. It first passes through trash screens to intercept leaves and debris. An initial flush diverts heavily polluted first-flush runoff to the municipal sewer. Cleaner rainwater then flows into the PP module cistern. Sedimentation structures at the tank inlet reduce silt accumulation inside the modules, and backwash pipelines are installed inside for routine maintenance. After filtration and disinfection, stored rainwater is reused for plaza irrigation, pavement washing and landscape water replenishment. This traceable rainwater cycle provides real operational data to support on-site science interpretation.

Construction Highlights: Underground Works Restricted by a Live Science Popularization Plaza

Constructing within a science plaza differs from standard municipal squares: work zones sit adjacent to existing exhibits, paving and active public areas. Construction windows are limited, with strict controls on dust, noise and surface restoration. Yayuan prioritized three key phases in construction management.

First, precision control for foundation excavation and base preparation. Excavation is carried out by machinery with manual finishing to the designed elevation. The tank base is built with a 2%–3% drainage gradient sloping toward the collection end. Once the base passes inspection, impermeable geomembrane is laid. Overlap width and anchoring spacing follow formal specifications to prevent groundwater ingress or stored rainwater leakage. After casting the bedding concrete, elevation and flatness are rechecked to ensure even load distribution across PP modules.

Second, PP module assembly and tank enclosure. Modules are stacked in staggered layers according to tank dimensions, fixed with connectors between adjacent and vertical layers for structural stability. The tank perimeter is wrapped with impermeable membrane and geotextile. Soft backfill soil is compacted in lifts around the module array to avoid sharp aggregates puncturing liners. Lift thickness and compaction passes are strictly controlled during backfilling. Overburden depth above the tank ranges from 30cm to 90cm, balancing surface pavement loads and the residual bearing capacity of modules.

Third, coordination between electromechanical installation and surface reinstatement. Water pump sets, liquid level control units and filtration equipment are pre-installed and piping reserved before tank enclosure to avoid re-excavation later. Permeable paving and science exhibit foundations are reinstated only after backfill settlement stabilizes. This guarantees proper elevation matching and unbroken drainage gradients between concealed underground works and above-ground educational displays. All concealed works undergo sectional acceptance and photo documentation before covering, preserving records for underground cross-section exhibits in future science outreach.

Integration with Science Outreach: Turning Invisible Infrastructure into an Outdoor Classroom

The differentiated value of this project lies not in system complexity, but its embedding within a public space dedicated to sponge city literacy. Kaifeng Sponge City Planning Exhibition Hall already uses interactive installations, digital sand tables and physical cutaways to demonstrate how permeable landscapes absorb and hold water. The rainwater system at Science Popularization Plaza acts as its outdoor extension. The permeable pavements, sunken green spaces and rain gardens visitors see sit directly above Yayuan’s PP module cisterns. During rainfall, plaza runoff flows underground for storage; after rain, harvested water feeds irrigation. This complete cycle can be labelled, demonstrated and explained to the public.

From a delivery perspective, Yayuan supplies more than underground rainwater harvesting equipment. It delivers a system built for science interpretation: tank liquid level variation, pump activation cycles and filter maintenance points all serve as data sources and talking points for exhibits. While meeting runoff detention requirements, the system transforms “sponge city” from a policy term into a traceable process for visitors to follow — where rain comes from and where it goes.

Integration with Science Outreach: Turning Invisible Infrastructure into an Outdoor Classroom

The differentiated value of this project lies not in system complexity, but its embedding within a public space dedicated to sponge city literacy. Kaifeng Sponge City Planning Exhibition Hall already uses interactive installations, digital sand tables and physical cutaways to demonstrate how permeable landscapes absorb and hold water. The rainwater system at Science Popularization Plaza acts as its outdoor extension. The permeable pavements, sunken green spaces and rain gardens visitors see sit directly above Yayuan’s PP module cisterns. During rainfall, plaza runoff flows underground for storage; after rain, harvested water feeds irrigation. This complete cycle can be labelled, demonstrated and explained to the public.

From a delivery perspective, Yayuan supplies more than underground rainwater harvesting equipment. It delivers a system built for science interpretation: tank liquid level variation, pump activation cycles and filter maintenance points all serve as data sources and talking points for exhibits. While meeting runoff detention requirements, the system transforms “sponge city” from a policy term into a traceable process for visitors to follow — where rain comes from and where it goes.