Proposed Changes To Washington 2015 Construction Stormwater Permit

Written By: Caltha LLP | Published On: 25th January 2017 | Category: Stormwater, Water | RSS Feed

On November 18, 2015, Ecology issued an updated Construction Stormwater General Permit (CSWGP). The permit became effective January 1, 2016. One appeal was filed with the Washington Pollution Control Hearings Board on December 17, 2015. To resolve the case, Ecology has proposed several revisions to the permit and has posted these revisions for public comment. Comments are due by February 10, 2017.

The proposed changes are to dust control (S1.C.3.i), pH sampling requirements (S4.D), engineering calculation requirements (S9.B.1.f), and concrete washout (S9.D.9.h). The proposed changes are:

  • S1.C.3.i – Uncontaminated or potable water used to control dust. Permittees must minimize the amount of dust control water used.
  • S4.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 poured concrete or recycled concrete used over the life of a project ) or the use of recycled concrete or engineered soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD], 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. For sites with significant concrete work, the Permittee must begin the pH sampling period when the concrete is first poured and exposed to precipitation, and continue weekly throughout and after the concrete pour and curing period, until stormwater pH is in the range of 6.5 to 8.5 (su).
    2. 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 and stormwater pH is in the range of 6.5 to 8.5 (su).
  • S9.B.1.f – Engineering calculations for ponds, treatment systems, and any other designed structures. When a treatment system requires engineering calculations, these calculations must be included in the SWPPP. Engineering calculations do not need to be included in the SWPPP for treatment systems that do not require such calculations.
  • S9.D.9.h – Assure that washout of concrete trucks is performed off-site or in designated concrete washout areas only. Do not wash out concrete trucks drums or concrete handling equipment onto the ground, or into storm drains, open ditches, streets, or streams. Do not dump excess concrete on site, except in designated concrete washout areas. Concrete spillage or concrete discharge directly to groundwater or to surface waters of the State is prohibited. Do not wash out to formed areas awaiting LID facilities.

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