Module 7: Water and the Built Environment - Comprehensive Study Notes

Foundations of Sustainable Development: Water and the Built Environment

• Instructor: Prof. Jason Von Meding, Florida Institute for Built Environment Resilience, M.E. Rinker, Sr. School of Building Construction.
• Module: Module $7$: Water and the Built Environment (IDS $2935$).

Water Systems and Green Infrastructure

• Water Management Focus: While discussions often center on water conservation, sustainable systems must also prioritize water treatment.
• Role of Green Infrastructure: This infrastructure type provides significant benefits by integrating natural processes into urban water management.
• Alternative Terminology: Green infrastructure is also referred to as:     * Low Impact Development (LID).     * Blue-Green Infrastructure.
• Definition and Scope of Green Infrastructure:     * It describes how infrastructure systems—including water delivery, electricity grids, telecommunications networks, and transportation/parking—can minimize material and energy consumption, waste generation, and product development.     * It represents a shift from "hard engineering" (mechanical) toward "soft engineering" (biological).     * It aims to provide "ingredients" for solving urban and climatic challenges by building with nature, leveraging ecosystem services refined over millions of years of "R&D."

The $17$ Ecosystem Services Provided by Soft Engineering

Low Impact Development (LID) transforms hard engineering to function like soft engineering by offering the following $17$ ecosystem services:

1. Atmospheric regulation.
2. Climate regulation.
3. Disturbance regulation.
4. Water regulation.
5. Water supply.
6. Erosion control and sediment retention.
7. Soil formation.
8. Nutrient cycling.
9. Waste treatment.
10. Pollination.
11. Species control.
12. Refugia/habitat.
13. Food production.
14. Raw material production.
15. Genetic resources.
16. Recreation.
17. Cultural enrichment.

Principles and Processes of Low Impact Development (LID)

• Primary Management Goal: LID/Green infrastructure is planned and managed primarily for storm-water control.
• Two Core Design Principles:     1. Conserve Natural Areas: Preserve natural areas wherever possible and avoid paving over the entire site if it is not necessary.     2. Control Runoff: Manage the rate and duration of runoff from the site to prevent water from leaving the site.
• Integration of Engineering Approaches:     * Mechanical (Hard Engineering): Focuses on managing flow through structures.     * Biological (Soft Engineering): Focuses on nature-based solutions.
• Functional Progression (Slow, Spread, Soak):     * Slow (Flow Control): The regulation of stormwater runoff flow rates.     * Spread (Detention and Retention):         * Detention: The temporary storage of stormwater runoff in underground vaults, ponds, or depressed areas to allow for metered discharge that reduces peak flow rates.         * Retention: The storage of stormwater runoff on-site to allow for the sedimentation of suspended solids.     * Soak (Filtration, Infiltration, and Treatment):         * Filtration: The sequestration of sediment from stormwater runoff through a porous media such as sand, a fibrous root system, or a man-made filter.         * Infiltration: The vertical movement of stormwater runoff through soil, which recharges groundwater.         * Treatment: Processes that utilize phytoremediation or bacterial colonies to metabolize contaminants specifically found in stormwater runoff.

Porous (Permeable) Pavements

• Functional Benefits:     * Reduces stormwater runoff.     * Increases groundwater recharge.     * Provides freezing resistance.     * Reduces the need for salt use (for ice management).
• Applications: Residential roads, driveways, sidewalks, and parking lots.
• Structural Layers (Top to Bottom):     1. Permeable Pavers: Designed with larger joint spaces to allow stormwater to percolate through the surface.     2. Small Aggregate ($2.5-10\,mm$): Filters out contaminants and debris from rainwater.     3. Medium Aggregate ($5-28\,mm$): A transition layer that provides further filtration of pollutants.     4. Large Aggregate ($40-80\,mm$): A reservoir layer used for rainwater harvesting and the evacuation of excess water via a drain pipe.
• Runoff Comparison: An impervious surface property will generate $2$ to $6$ times more runoff than a natural surface.

Comparison of Paving Systems

• Porous Asphalt:     * Usage: Mostly parking lots.     * Process: Water drains through the surface into a stone recharge bed and infiltrates below.     * Heat Island Mitigation: Low.     * Initial Cost: $+10\%$ above conventional.     * Maintenance: Vacuuming.     * Durability: $10-30\text{ years}$.
• Pervious Concrete:     * Process: Eliminates the need for retention ponds/other Best Management Practices (BMPs), lowering project costs.     * Heat Island Mitigation: Low to Moderate (color dependent).     * Initial Cost: $+10\%$ above conventional.     * Maintenance: Vacuuming.     * Durability: $10-30\text{ years}$.
• Interlocking Paver Systems:     * Materials: Pre-cast concrete, natural stone, or brick units.     * Heat Island Mitigation: Low to Moderate (color dependent).     * Initial Cost: High.     * Maintenance: Vacuuming.     * Durability: $10-50\text{ years}$.
• Alternative Paving Systems (e.g., Recycled Rubber):     * Formats: Modular pavers or poured-in-place.     * Heat Island Mitigation: Moderate.     * Initial Cost: Medium.     * Maintenance: Vacuuming.     * Durability: $10-50\text{ years}$.
• Gravel Systems:     * Structure: Injection molded ring and grid structure underlain by geotextile fabric and sandy gravel base.     * Heat Island Mitigation: Moderate to High (color dependent).     * Initial Cost: Medium to High.     * Maintenance: Adding gravel.     * Durability: $10-20\text{ years}$.
• Grass Concrete and Turf Pavers:     * Benefit: High load-bearing strength while protecting root systems; allows excellent water storage capacity.     * Heat Island Mitigation: High.     * Initial Cost: High.     * Maintenance: Watering.     * Durability: $20-40\text{ years}$.
• Void Space Considerations:     * Systems with $15\%$ void space require frequent vacuuming.     * Systems with $90\%$ void space (gravel and vegetated) allow for greater infiltration but may require mowing and sediment removal.

Parking Lot Design Strategies via Storm Event Scale

• One to Ten-Year Storm Events (Slow and Soak):     * Remove curbs and sink tree islands in parking stalls to receive and filter stormwater as it enters treatment landscapes.     * Construct rain gardens in the center of parking modules to treat the "first flush" and infiltrate the most contaminated runoff.
• Ten to Twenty-Five-Year Storm Events (Spread):     * Use underground storage (Underground Detention or Wet Vaults) if soils are poorly drained or land area is limited.
• Ten to Fifty-Year Storm Events (Spread):     * Convey water through oversized perforated pipes from rain gardens to treatment facilities.
• Twenty-Five to Fifty-Year Storm Events (Soak):     * Use oversized pipes to connect bioswales to an infiltration basin or retention pond to retain and infiltrate runoff.     * Use residual spaces as large treatment meadows to eliminate contaminants as infiltration occurs.
• General Note: Provide perforated overflow pipes to manage runoff during large storm events, particularly in poorly drained soils.

Benefits of Green Infrastructure Practices

Methods such as Green Roofs, Tree Planting & Infiltration, Bioretention, Permeable Pavement, and Water Harvesting contribute to various benefits:

• Direct Water Benefits: Reduces stormwater runoff, improves water quality, reduces flooding, increases available water supply, increases groundwater recharge, and reduces water treatment needs.
• Infrastructure/Economic Benefits: Reduces grey infrastructure needs, reduces salt use, and reduces energy use.
• Environmental/Climate Benefits: Improves air quality, reduces atmospheric $CO_2$, and reduces the Urban Heat Island effect.
• Social/Community Benefits: Improves community livability, aesthetics, recreational opportunity, and community cohesion; reduces noise pollution; improves habitat; and cultivates public education (especially via Urban Agriculture).

Urban Heat Island Effect and Albedo

• Temperature Differential: Cities can be $3^{\circ}C$ to $10^{\circ}C$ hotter than rural areas.
• Rural Dynamics: Characterized by less heat absorption, greater plant transpiration, and greater water penetration.
• Urban Dynamics: Characterized by greater heat absorption and retention.
• Albedo Definition: A measure of reflective power ranging from $0$ (total absorption/no reflexivity) to $1$ ($100\%$ completely reflective).
• Satellite Observations (NASA Data): NASA data shows a direct correlation between vegetation density and temperature. Areas with dense vegetation (dark green on satellite maps) appear significantly cooler (dark purple) than areas with sparse vegetation which appear hot.
• Mitigation: White roofs can help cool cities by increasing albedo.

Controlling Runoff: Urban vs. Natural Surface Coverage

• Highly Developed Areas (e.g., Seattle, WA):     * $30\%$ Evapotranspiration.     * $55\%$ Runoff (flows directly into surface waters).     * $10\%$ Shallow Infiltration.     * $5\%$ Deep Infiltration.     * Total soaking capacity: only $15\%$.
• Natural Areas (e.g., Upper Tillamook Bay, OR):     * $40\%$ Evapotranspiration.     * $10\%$ Runoff.     * $20\%$ Shallow Infiltration.     * $25\%$ Deep Infiltration.     * Nearly half ($45\%$) of rainfall soaks into the soil.

Green Roofs

• Historical Context: Sod roofs and walls have been used in Scandinavia for hundreds of years.
• German Implementation: Hamburg implemented a Green Roof Strategy in $2019$; no less than $70\%$ of suitable rooftops must be vegetated. Building owners can receive subsidies covering up to $60\%$ of installation costs ($€\,3\text{ million}$ allocated until the end of $2024$).

Types of Green Roofs

1. Extensive:     * Growing Medium: Generally $6\text{ inches}$ or less.     * Plants: Low diversity (succulents, grasses).     * Soil Composition: $20-30\%$ organic, $70-80\%$ inorganic.     * Roof Slopes: Can be $30\%$ or more.     * Weight: Low saturated weight of $10-35\text{ lbs/sf}$.     * Cost/Maintenance: Relatively low cost and minimal maintenance; often designed for no irrigation; easy to replace and suitable for retrofits.
2. Semi-Intensive:     * Growing Medium: $6-12\text{ inches}$.     * Plants: Slightly greater diversity.     * Soil Composition: $20-30\%$ organic, $70-80\%$ inorganic.     * Roof Slopes: Less than $30\%$.     * Weight: Saturated weight of $35-50\text{ lbs/sf}$.     * Cost/Maintenance: Slightly higher than extensive; good for new construction or major renovations.
3. Intensive:     * Growing Medium: Typically $12\text{ inches}$ or more.     * Plants: Large plant diversity, pools, and garden structures.     * Soil Composition: $50\%$ organic, $50\%$ inorganic.     * Roof Slopes: Usually flat.     * Weight: Saturated weight of $50-300\text{ lbs/sf}$.     * Cost/Maintenance: High cost/maintenance; best insulation and storm water management; usually accessible with high biodiversity potential.

On-Site Water Sources and Harvesting

• Source Definitions:     * Rainwater: Collected directly from roofs/surfaces.     * Stormwater: Runoff from many surfaces.     * Greywater: Wastewater from sinks, washing machines, bathtubs, and showers. Contains lower contamination; easier to treat.     * Blackwater: Wastewater from bathrooms/toilets containing human waste; water from kitchens/dishwashers is often included due to pathogens and grease.
• Rainwater Harvesting Components:     1. Catchment (e.g., roof surface).     2. Conveyance (e.g., gutters, downspouts).     3. Filtration (e.g., leaf screens, sediment traps, debris interceptors).     4. Storage (e.g., on-grade or below-grade cisterns/tanks).     5. Distribution (e.g., irrigation and pressure pumps).     6. Purification (optional based on use).
• Harvesting Metrics:     * $1\text{ inch}$ of rainfall on a $1,000\text{ square-foot}$ roof yields approximately $623\text{ gallons}$ of water.     * Transmission Loss: Expected loss of $10-70\%$ due to absorption, evaporation, and collection inefficiencies.     * First Flush: The initial rainwater after a dry period is contaminated with dust, bird droppings, etc., and should be diverted from the system.

Roof Materials and Harvesting Potential

• Asphalt/Fiberglass Shingle: High pollution; treatment required. Potentially toxic; not for edible landscape or potable needs. Potential: Low.
• Membrane Roof (EPDM, Bitumen, Tar/Gravel): Petroleum-based; high pollutants. Not for edible landscape or potable needs. Potential: Low.
• Wood Shingle: Leaches toxins/carcinogens from treated wood. Cedar is a safer alternative if untreated. Potential: Moderate.
• Clay Tile Roof: High albedo; minor sediment. Potential: High.
• Metal Roof: Very low pollutant levels. Potential: High.
• Vegetated Roof: Treats and retains $60-100\%$ of stormwater. Potential: High.
• Warning: Petroleum-based roofing and treated wood products leach toxins known to cause cancer and mental defects. Harvested water from these surfaces should only be used for ornamental landscape irrigation.

Matching Source to Use

• Source Quality: Must be acceptable for the intended use; treatment may be required.
• Local Governance: Jurisdictions vary in what is legally permitted regarding rainwater harvesting.
• Reclaimed Water: Identified by purple pipes.

iClicker and Questions & Discussion

• Question: What type of green roof do you suspect Rinker (M.E. Rinker, Sr. School of Building Construction) has?     * A. Intensive     * B. Semi intensive     * C. Extensive
• Prompt: There is a green roof in Gainesville mentioned—guesses as to where and what type?
• Next Topic Pre-Spring Break: Net Zero Energy Building.