Changes

| Materials || Plastic or Metal || Concrete || Plastic || Plastic

| Materials || Plastic or Metal || Concrete || Plastic || Plastic

|-

|-

| Footprint || Medium || Small || Large || Small

| Footprint || Medium || Small || Medium || Small

|-

|-

| Stackable || Yes || No || Yes || Yes

| Stackable || Yes || No || Yes || Yes

|-

|-

| Porosity || 60-65% || 75-85% || 50-65% || 95%

| Effective Porosity (n') || 0.60 - 0.65 || 0.75 - 0.85 || 0.50 - 0.65 || 0.95

|-

|-

| Maintenance access || Moderate || Excellent || Moderate || Difficult

| Maintenance Access || Moderate || Excellent || Moderate || Difficult

|-

|-

| Standard strength || H-20  || H-25 || H-20 || H-20 to H-25

| Standard Strength || H-20  || H-25 || H-20 || H-20 - H-25

|}

|}

==Planning Considerations==

==Planning Considerations==

All types of modular systems require a bedding of angular clear stone to permit infiltration, and provide a foundation for the installation:  

All types of modular infiltration systems require a bedding of angular clear stone to permit infiltration, and provide a foundation for the installation:  

*Plastic modules usually have a parabolic shape to support the load above. The spaces between the rows of modules are filled with clear stone to support overlying structures.

*Plastic chambers usually have a parabolic shape to support the load above. The spaces between rows of plastic pipes or chambers are filled with clear stone to support overlying structures.

*Concrete vaults are often rectangular-shaped and can, in some circumstances, be employed without any additional cover. However, a minimum of 20 cm cover is recommended for most applications. Where this cover is planting soil this can support turf grass. Greater planting soil depths are required to support more deeply rooting plants like perennials and shrubs (45 to 60 cm) and trees (85 to 100 cm).

*Concrete vaults and plastic crates are often rectangular-shaped. Concrete vault systems can, in some circumstances, be employed without any additional cover. However, a minimum of 20 cm cover is recommended for most applications. Where this cover is planting soil this can support turf grass. Greater planting soil depths are required to support more deeply rooting plants like perennials and shrubs (45 to 60 cm) and trees (85 to 100 cm).

==Design==

==Design==