Why Watertight Design Matters

Filter Treatment Systems

Water entering these systems is considered contaminated and assurances need to be made where the water is treated (filtered) as designed. Each compartment of the system that the water travels through needs to be made watertight so the water does not short circuit and bypass the treatment process. Liability for the owner can exist over time if the local agencies discover that the water has not been treated properly and is polluting tributaries.

Housing Water Quality Storage

Water entering these systems is considered contaminated and assurances need to be made where the water stored before a filter does not leak out and contaminate the soils surrounding the BMP storage vault.

Near Building Foundations and Retaining Walls and Underground Aquifers

Water stored in these BMP systems can create problems for foundations through migration when stored water escapes through the wall, and floor joints. This problem can increase the lateral earth pressure on a foundation wall or destabilize the soil.

Water stored in a BMP system near an underground aquifer can pollute the ground and aquafer water through migration when stored water escapes through the wall, and floor joints. The untreated water stored in the BMP should be considered contaminated.

Hydrostatic pressure increases with taller structures and accelerates the migration process, making this a particularly troublesome issue for tall systems. In addition, BMP systems backfilled with stone will also accelerate the migration process as well as the destabilization of the soil around the system.

Groundwater Above the Invert

Exterior ground water will migrate through the wall, and floor joints carrying sediment from the outside. The sediment removal can be a significant problem over time to the stability of the BMP structure. With the presence of a high groundwater table, the groundwater can infiltrate into the structure causing a reduction of storage capacity as well as reducing the groundwater supply by allowing the external water to enter the storm drain system

Area that Contains Contaminated Soils

Water stored in a BMP system that has contaminated soils around it can become contaminated through migration when stored water escapes and reenters through the wall, and floor joints. The contaminated water can then contribute to downstream pollution.

The Value of Watertight Design

A watertight solution isn’t just a feature; it’s an insurance policy for your project’s success. At a minimal cost—typically about 10% of the total basin cost—you gain:

• Peace of Mind: Meet regulatory standards and environmental obligations.

• Long-Term Savings: Avoid costly repairs and legal liabilities.

• Sustainability Leadership: Promote responsible and forward-thinking design practices.