1001 N BROADWAY EVCC 2025-10-03 - Laserfiche WebLink

V. Document BMP implementation and maintenance in the site log book. Compliance with these requirements does not relieve the Permittee from responsibility to maintain continuous compliance with permit benchmarks. D. pH Sampling Requirements—Significant Concrete Work or Engineered Soils If construction activity results in the disturbance of 1 acre or more, and involves significant concrete work (significant concrete work means greater than 1000 cubic yards placed or poured concrete or recycled concrete used over the life of a project) or the use of engineered soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKDj,or fly ash),and stormwater from the affected area drains to surface waters of the State or to a storm sewer system that drains to surface waters of the State, the Permittee must conduct pH sampling as set forth below. Note: In addition, discharges to segments of water bodies on Washington State's 303(d) list (Category 5)for high pH are subject to a numeric effluent limit for pH; refer to Special Condition S8. 1. The Permittee must perform pH analysis on site with a calibrated pH meter, pH test kit, or wide range pH indicator paper. The Permittee must record pH sampling results in the site log book. 2. During the applicable pH monitoring period defined below, the Permittee must obtain a representative sample of stormwater and conduct pH analysis at least once per week. a. For sites with significant concrete work, the Permittee must begin the pH sampling period when the concrete is first placed or poured and exposed to precipitation,and continue weekly throughout and after the concrete placement, pour and curing period,until stormwater pH is in the range of 6.5 to 8.5 (su). b. For sites with recycled concrete where monitoring is required, the Permittee must begin the weekly pH sampling period when the recycled concrete is first exposed to precipitation and must continue until the recycled concrete is fully stabilized with the stormwater pH in the range of 6.5 to 8.5 (su). c. For sites with engineered soils,the Permittee must begin the pH sampling period when the soil amendments are first exposed to precipitation and must continue until the area of engineered soils is fully stabilized. 3. The Permittee must sample pH in the sediment trap/pond(s) or other locations that receive stormwater runoff from the area of significant concrete work or engineered soils before the stormwater discharges to surface waters. 4. The benchmark value for pH is 8.5 standard units. Anytime sampling indicates that pH is 8.5 or greater,the Permittee must either: a. Prevent the high pH water(8.5 or above)from entering storm sewer systems or surface waters of the state; or b. If necessary, adjust or neutralize the high pH water until it is in the range of pH 6.5 to 8.5 (su) using an appropriate treatment BMP such as carbon dioxide (COZ)sparging, dry ice or food grade vinegar.The Permittee must obtain written approval from Ecology before using any form of chemical treatment other than COz sparging, dry ice or food grade vinegar. Construction stormwater General Permit Page 16