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→Four Step Process
'''4. Design Considerations'''
'''4. Design Considerations'''
*Determination of a suitable infiltration rate for design calculations; and
*Determination of a suitable infiltration rate for design calculations; and
*Consideration of desired BMP drawdown period.
*Consideration of desired BMP [[drawdown time]].
===Background Evaluation===
===Background Evaluation===
The number of test pits or soil borings varies depending on site conditions and the proposed development plan. General guidelines are as follows:
The number of test pits or soil borings varies depending on site conditions and the proposed development plan. General guidelines are as follows:
*For infiltration BMPs with footprint surface areas from 50 to 900 square metres, a minimum of two test pits or one test pit and two soil borings are required at, or within 10 metres of the proposed location to determine the suitability and distribution of soil types present;
*For infiltration BMPs with footprint surface areas from 50 - 900 m<sup>2</sup>, a minimum of two test pits or one test pit and two soil borings are required at, or within 10 m of the proposed location to determine the suitability and distribution of soil types present;
*For infiltration BMPs with footprint surface areas greater than 900 square metres, a minimum of one test should be conducted for each 450 square metres of footprint surface area. Tests should be conducted equidistant from each other to provide adequate characterization of the area;
*For infiltration BMPs with footprint surface areas > 900 m<sup>2</sup>, a minimum of one test should be conducted for each 450 m<sup>2</sup> of footprint area. Tests should be conducted equidistant from each other to provide adequate characterization of the area;
*For linear infiltration BMPs a minimum of one test should be conducted within each soil mapping unit present along the proposed BMP location. Soil borings should be conducted every 50 metres and a test pit should be conducted every 450 metres; and
*For linear infiltration BMPs (e.g. [[bioswales]], [[enhanced grass swales]], [[infiltration trenches]], [[exfiltration trenches]]) a minimum of one test should be conducted within each soil mapping unit present along the proposed BMP location. Soil borings should be conducted every 50 m and a test pit should be conducted every 450 m; and
*For sites with multiple infiltration BMPs, each with footprint surface areas less than 50 square metres, a minimum of one test pit is required and one soil boring per infiltration BMP location is recommended.
*For sites with multiple infiltration BMPs, each with footprint surface area < 50 m<sup>2</sup>, a minimum of one test pit is required and one soil boring per infiltration BMP location is recommended.
===Infiltration Testing===
===Infiltration Testing===