1. Scope

1.1 This specification covers the particle size distributions (PSDs) of silica-based sediments to be used in the laboratory performance testing of stormwater treatment devices as well as criteria defining an acceptable error range of the target PSDs. 1.2 Silica sand is used as a surrogate material for performance and scour determinations for some manufactured stormwater treatment devices such as hydrodynamic separators and filters. These data are used to gain regulatory approvals within certain jurisdictions. 1.3 The following precautionary caveat pertains only to the Test Methods portion, Section 9, of this specification. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Keywords

particle size distribution; gradation; silica sand

Rationale

Agencies that regulate the use of stormwater treatment technologies frequently require laboratory testing of the devices using silica-based surrogate sediment. The objective of these studies is to test the sediment removal rate as a function of flow, particle size removal , particle resuspension, and washout. In some agencies, a standard manufactured silica sediment product is specified, whereas in other agencies, a custom particle size distribution (PSD) is specified and the testing organization is tasked with mixing commercially available materials to approximate the specified PSD. Recently, several manufactured silica sediment products, which have served as the standard contaminants specified by many agencies, have been discontinued. This change has occurred faster than regulatory agencies have been able to address the void. Subsequently, laboratories have been relying on rapidly diminishing stockpiles or attempting to recreate the products through sieving other products. In addition, prior research has shown that these standardized materials can have a significant variance in the PSD from published data. Manufactured for the purpose of foundry casting sand, the preciseness of the specification relative to the needed precision for testing in stormwater devices does not have a range of acceptable error. Since the use of these materials is for technology verification and these verifications are being conducted by different individuals, in different laboratories, using different lots or admixtures, standards are needed to ensure that devices are tested using material within the specification such that there is a level of confidence the same materials are being used.

The title and scope are in draft form and are under development within this ASTM Committee.