(a) If you use a solvent recovery system, you must install, operate, and maintain a weight measurement device to measure the weight of HAP solvent loaded into the solvent mixer and the weight of HAP solvent recovered for each mix batch.

(b) For each weight measurement device required by this section, you must develop and submit for approval a site-specific monitoring plan that addresses the requirements of paragraphs (b)(1) through (6) of this section:

(1) Procedures for installing the weight measurement device;

(2) The minimum accuracy of the weight measurement device in pounds and as a percent of the average weight of solvent to be loaded into the solvent mixer;

(3) Site-specific procedures for how the measurements will be made;

(4) How the measurement data will be recorded, reduced, and stored;

(5) Procedures and acceptance criteria for calibration of the weight measurement device; and

(6) How the measurement device will be maintained, including a routine maintenance schedule and spare parts inventory list.

(c) The site-specific monitoring plan required in paragraph (b) of this section must include, at a minimum, the requirements of paragraphs (c)(1) through (3) of this section:

(1) The weight measurement device must have a minimum accuracy of ±0.05 kilograms (±0.1 pounds) or ±1 percent of the average weight of solvent to be loaded into the solvent mixer, whichever is greater.

(2) An initial multi-point calibration of the weight measurement device must be made using 5 points spanning the expected range of weight measurements before the weight measurement device can be used. The manufacturer's calibration results can be used to meet this requirement.

(3) Once per day, an accuracy audit must be made using a single Class F calibration weight that corresponds to 20 to 80 percent of the average weight of solvent to be loaded into the solvent mixer. If the weight measurement device cannot reproduce the value of the calibration weight within ±0.05 kilograms (0.1 pounds) or ±1 percent of the average weight of solvent to be loaded into the solvent mixer, whichever is greater, the scale must be recalibrated before being used again. The recalibration must be performed with at least five Class F calibration weights spanning the expected range of weight measurements.

(d) You must operate and maintain the weight measurement device according to the site-specific monitoring plan.

(e) You must maintain records of all maintenance activities, calibrations, and calibration audits.