SS Credit: Rainwater Management

The best stormwater system is the one you don’t notice—because it behaves like nature.

What is the Intent of this Credit?

The goal is to:

👉 reduce runoff volume
👉 improve water quality
👉 replicate natural hydrology of the site

🎯 Big Picture

Rainwater is not waste—it is a resource.

🌍 Why This Matters

Typical development:

• increases impervious surfaces
• sends stormwater to drains quickly
• causes flooding and pollution

💡 LEED Approach

👉 Manage rainwater:

• on-site
• close to source
• like natural land conditions

🌱 How LEED Achieves This

Using:

👉 Green Infrastructure (GI)
👉 Low Impact Development (LID)

📌 Common Techniques

• vegetated roofs
• bioretention areas
• porous paving
• rain gardens
• rainwater harvesting
• pervious decking
• reduced hardscape
• restored natural landscape

🎯 Key Idea

Manage water where it falls

🧩 Two Compliance Options

✅ Option 1: Percentile of Rainfall Events

What Does This Mean?

👉 Design the system to manage:

👉 a percentage of rainfall events

📊 Common Thresholds

• 85th percentile
• 95th percentile

💡 Example (Very Important)**

👉 85th percentile means:

• system captures runoff from 85% of storms
• only largest 15% overflow

🎯 Exam Insight

Percentile = % of storms managed
(not % of rainfall volume)

⚙️ Steps to Implement

Step 1: Collect Rainfall Data

• minimum 10 years preferred
• include seasonal variation

Step 2: Calculate Runoff Volume

👉 For selected percentile

Step 3: Manage That Volume On-Site

👉 Using GI + LID strategies

🏙️ Path 3: Zero Lot Line Projects

❓ What is a Zero Lot Line Project?

👉 Building footprint ≈ site boundary

📏 Eligibility Requirement

👉 Surrounding density must be:

👉 FAR ≥ 1.5

(within ¼ mile)

⚠️ Important

👉 If FAR < 1.5 → NOT eligible