HomeMy WebLinkAbout04.20.2020_Weatherly_Inn_CTB.pdf
April 30, 2020
Mr. Joe Wilhite
Accrete Construction LLC
801 Valley Ave NW Suite A
Puyallup, WA 98371
Sent via email: jchavez@rentonwa.gov
Re: Surface Water Adjustment Request – Weatherly Inn
Use of Detention Vault for Storage of CTB Runoff (C18005810)
Dear Mr. Wilhite:
We have reviewed your request for approval of a Surface Water Adjustment to Applicable Standard #5
under D.2.2.9 USE OF HIGH PH SOIL AMENDMENTS ON CONSTRUCTION SITES, for the proposed Weatherly
Inn project on Talbot Road S. The request is for an adjustment to allow the use of the permanent detention
vault for storage of Cement Treated Based (CTB) runoff. The adjustment request for the Weatherly Inn
project is in accordance with the City adopted 2017 City of Renton Surface Water Design Manual
(RSWDM). The Planning Division of the City of Renton has determined that the subject application is
complete according to submittal requirements and, therefore, is accepted for review. Based on the
information provided, the requested adjustment is approved, subject to conditions.
The adjustment request for this specific development situation is as follows:
1. Section D.2.2.9, Applicable Standard #5 of the 2017 Renton Surface Water Design Manual:
Collection of stormwater (see BMP #5 in Table D.2.2.9.A):
• Stormwater from the application area shall be kept separate from and prevented from
comingling with uncontaminated stormwater.
• During the application of CKD/CTB, stormwater runoff shall be collected in temporary
collection systems and shall not be allowed to enter the permanent facilities. Permanent
drainage systems shall be capped to prevent contact stormwater from entering the inlets of
the catch basins. Stormwater from the application area shall not be collected in the
temporary/permanent detention ponds, even if the underlying soils are ‘impermeable.’
2. Adjustment Request: Allow for the use of the permanent detention vault to store CTB runoff.
3. Proposed Mitigation: plug the outlet pipe to ensure no water from the vault enters the public storm
drain system. In addition, the collected CTB runoff will be pumped into baker tanks, where it will be
treated and discharged to the storm drain system after the water has met NPDES permit water quality
parameters.
Based on these understandings, and Section 1.4 of the 2017 Renton Surface Water Design Manual, the
adjustment request is approved under the following conditions:
1. The outlet for the detention vault must be plugged/disconnected to eliminate any potential of water
entering the storm system without proper treatment.
2. All storm water within the detention vault must be routed through the baker tanks and treated to
meet NPDES permit water quality parameters, prior to any discharge into the public storm system.
3. Stormwater readings shall be taken at the top and bottom of the baker tanks to ensure that the water
is consistently meeting NPDES permit water quality parameters.
4. The detention vault shall be cleaned prior to uncapping the outlet pipe and connecting to the public
storm system. The use of pressure washers and vactor trucks will be required to breakup and remove
any CTB sediment in the vault.
This decision to approve the Surface Water Adjustment for the Weatherly Inn project on Talbot Road S is
subject to a fourteen (14) day appeal period from the date of this letter. Any appeals of the administrative
decision must be filed with the City of Renton Hearing Examiner by 5:00 pm, May 14th, 2020.
Sincerely,
Brianne Bannwarth
Development Engineering Manager
cc: Jennifer Henning, CED Planning Director
Joe Farah, Utility Engineering Manager – Surface Water
Justin Johnson, Assistant Development Engineering Manager
Jonathan Chavez, Plan Reviewer
Tom Main, Inspector