What Decision-Makers Should Evaluate Before Choosing Sustainable Surface Systems

Sustainable surface systems — permeable pavements, subsurface stormwater storage, SuDS, sponge park infrastructure — are increasingly specified in Indian infrastructure projects. But not all systems are equal, and not all specifications are correct for every site. Decision-makers need a structured evaluation framework. This article provides exactly that, drawing on Stone Hands' experience designing and implementing Eco Bloc-based SuDS systems across India.

The Problem — Uninformed Specification Leads to Poor Outcomes

Decision-makers frequently encounter: vendors proposing standard systems without site-specific design; specifications copied from other projects without adapting to local soil conditions; systems designed to minimum regulatory requirement rather than functional performance; cost comparisons that ignore lifecycle costs; marketing claims not backed by measurable performance data.

 The Evaluation Framework — 6 Dimensions

1. Site Hydrological Assessment
Has the vendor conducted or reviewed actual rainfall data and soil permeability testing for this site? A system sized without site-specific data will be undersized or incorrectly configured.

2. Design Storm Return Period
What design storm is the system designed for — 1-in-10 year? 1-in-30 year? The appropriate return period depends on risk tolerance and downstream drainage context. It must be justified for the specific project.

3. Full Catchment Analysis
Does the system capture runoff from ALL contributing hard surfaces — roofs, roads, car parks, pavements? A system capturing only parking area runoff while roof downpipes discharge to drain is capturing a fraction of available catchment.

4. System Technology and Void Ratio
• Gravel soakaway: ~30–35% void ratio
• Concrete ring system: ~50–60% void ratio
• Recycled Polypropylene modular (Eco Bloc): ~95% void ratio
Higher void ratio = more storage per cubic metre = smaller footprint, lower excavation cost, better performance.

5. Load Rating and Surface Compatibility
Can the system support the loads it will experience? Car park installation requires minimum 60-ton rated system. Specifying inadequately rated system beneath loaded surface risks structural failure.

6. Maintenance and Lifecycle
What is the maintenance protocol? Who is responsible? What is the system lifespan?
Concrete pit: 5–8 years, difficult to maintain, no inspection access.
Eco Bloc HDPE: 50+ years, inspection chambers, accessible, maintainable.

https://stonehands.in/solutions

What Stone Hands Provides

• Hydrological assessment and design calculations
• System sizing and layout design
• Regulatory compliance documentation (RERA, municipal approval)
• Material specification and supply
• Installation coordination
• O&M protocol documentation
• Post-installation inspection report

FAQs

Q1: How do I compare quotes from different vendors? 

A: Ensure all quotes are based on same design storm return period, same catchment area, same system storage volume. Different assumptions produce incomparable prices.

Q2: Should I choose infiltration or storage as primary function? 

A: Depends on soil permeability. Stone Hands recommends based on site-specific testing.

Q3: What regulatory documentation will I need? 

A: Catchment area map, runoff calculation, system design drawing, material specifications, compliance statement. Stone Hands provides all of these.

Q4: Is there a minimum project size? 

A: Stone Hands works across project scales — from individual plot systems to large municipal infrastructure contracts.

Q5: How long does a project assessment take? 

A: Initial site assessment and preliminary design: typically 5–10 working days.

Q6: What is the cost per cubic metre of Eco Bloc storage versus conventional options? 

A: Higher unit cost, but higher void ratio means fewer cubic metres needed for same storage volume — typically comparable or lower total system cost with significantly better performance.

CTA: If you are evaluating stormwater systems for a current project, contact Stone Hands for a site assessment and independent recommendation.
→ https://stonehands.in/solutions