Office of Air Quality, Permitting & Enforcement Division Mechanical Section Policy Memorandum þÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Date: November 23, 1993 No.: 4 From: Patrick N. Agumadu Approved by: Gary I. Wallin, P.E. Subject: Standard Exemption No. 91 - Interpretation of Intent, Usage and Scope þÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Policy: The intent of Standard Exemption No. 91 is to allow the installation or addition of silos to new or existing operations. Some form of mixing or blending can be authorized under this exemption, provided the operation and movement of materials are performed in enclosed systems and the exhaust air is vented to a fabric filter. There should not be any pollutant other than particulate matter. The exemption may be used in installing one or more cement, sand, or any bulk mineral material silos with all the material conveyed within closed conveyor systems (no front end loading and no stockpiles). The exemption may also be used in dry aggregate handling, blending, bagging, product storage, and shipping provided that none of these operations "sees the light of the day." Background: Standard Exemption No. 91 was originally intended to cover bulk cement handling facilities, but later expanded to cover all bulk mineral products, except asbestos. Examples of such bulk material handling operations are: 1. Standard Exemption No. 91 was approved for Texas Industries, Inc to construct a cement storage and handling, dry aggregate handling, blending, bagging, product storage and shipping operations at their Sakrete Plant in Southeast Travis County. All emissions, including potential fugitive emissions are vented to a bagfilter. 2. Halliburton Energy Service in Fresno also received authorization under Standard Exemption No. 91 to construct a Bulk Material Handling Facility with some blending operation. The blending operation is totally enclosed and vented to a baghouse. In addition, the receiving and loadout operations are vented to bagfilters. Necessary Action: Standard Exemption No. 91 DOES NOT cover the handling of asbestos, stockpiles of any material and any open operation. cc: All Mechanical Section