§ 25.138.1. Pre-design site evaluation.

Infiltration structures can present some practical design problems. When planning for an infiltration structure that provides stormwater quality treatment, consideration should be given to soil characteristics, depth to the groundwater table, sensitivity of the region, and runoff water quality. Specifically, infiltration structures must not be used in the following locations:

•

Industrial and commercial areas where solvents and/or petroleum products are loaded, unloaded, stored, or applied or pesticides are loaded, unloaded, or stored.

•

Areas where hazardous materials are expected to be present in greater than "reportable quantities" as defined by the U.S. Environmental Protection Agency in the Code of Federal Regulations at 40 CFR 302.4.

•

Areas where infiltration structure use would be inconsistent with an NJDEP-approved remedial action work plan or landfill closure plan.

•

Areas with high risks for spills of toxic materials such as gas stations and vehicle maintenance facilities.

•

Areas where industrial stormwater runoff is exposed to "source material." "Source material" means any material(s) or machinery, located at an industrial facility that is directly or indirectly related to process, manufacturing, or other industrial activities, that could be a source of pollutants in any industrial stormwater discharge to groundwater. Source materials include, but are not limited to raw materials, intermediate products, final products, waste materials, by-products, industrial machinery and fuels, and lubricants, solvents, and detergents that are related to process, manufacturing, or other industrial activities that are exposed to stormwater.

•

Areas where their installation would create a significant risk for basement seepage or flooding, cause surficial flooding of groundwater, or interfere with the operation of subsurface sewage disposal systems and other subsurface structures. Such adverse impacts must be assessed and avoided by the design engineer.

Infiltration structures must be configured and located where their construction will not compact the soils below the structure. In addition, an infiltration structure must not be placed into operation until the contributing drainage area is completely stabilized.

Minimal Setback Requirements for Infiltration Structures:

Soil Absorption Systems for septic:	50 ft.
Private wells:	100 ft.
Public wells:	150 ft.
Public reservoir, surface water sources for public water systems and their tributaries:	400 ft.
Other surface waters:	50 ft.
Property lines:	10 ft.
Building foundations:	>10 to 100 ft., depending upon soil types and Infiltration Structure type

 

Soils are perhaps the most important consideration for site suitability. In general, County Soil Surveys can be used to obtain necessary soil data for the planning and preliminary design of infiltration structures. For final design and construction, soil tests are required at the exact location of a proposed structure in order to confirm its ability to function without failure.

Tests should include:

•

determination of the textural classification.

•

permeability of the subgrade soil at and below the bottom of the proposed infiltration structure.

The recommended minimum depth for subgrade soil analysis is five (5) feet below the bottom of the structure or to the groundwater table. Soil permeability testing can be conducted in accordance with the Standards for Individual Subsurface Sewage Disposal Systems.