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HomeMy WebLinkAboutResponse to pre-app notes T ECHNICAL M EMORANDUM Date: August 8, 2016 To: Rocale Timmons From: Kenny Booth, Andy Noone Pre-Application Number PRE 16-000406 TWC Project Number: 150809 Project Name: Southport Shoreline Modifications Subject: Response to June 23, 2016 pre-application notes and questions All fill and excavation waterward of the OHWM not associated with ecological restoration, flood control or approved shoreline stabilization shall require a Shoreline Conditional Use Permit. Response: The small amount of concrete (approximately 66 cubic yards) that is proposed waterward of the OHWM is associated with repair of the existing approved shoreline stabilization structure (bulkhead). WDFW may also mandate the placement of clean gravel/sand in areas where piles are extracted. No other fill is proposed waterward of the OHWM. A geotechnical report is required for proposed shoreline stabilization projects. The geotechnical analysis pursuant to this Section that addresses the need to prevent potential damage to a primary structure shall address the necessity for shoreline stabilization by estimating time frames and rates of erosion and report on the urgency associated with the specific situation. The geotechnical analysis shall evaluate the need and effectiveness of both hard and soft armoring solutions in preventing potential damage to a primary structure. Consideration should be given to permit requirements of other agencies with jurisdiction. Response: Please see the SECO Development Bulkhead Structural Observation Report, CG Engineering, 2016. It is unclear the scope of abandoning the recently removed log boom. Please provide additional detail and note this log boom provides shoreline protection by minimizing wave action to Coulon Park. Response: The log boom was previously removed from the site approximately ten years ago. This item was included in the scope to indicate that the log boom will not be put back in place. The shoreline that the log boom protected is entirely bulkhead. Since its removal, no significant impacts associated with its removal have been documented. Gene Coulon Memorial Beach Park has a separate log boom that serves to protect the swimming area from wave action. This log boom will remain. Southport Shoreline Modifications Response to pre-application notes August, 2016 Page 2 With increased boat traffic, please prepare a wave analysis, describing potential impacts to Coulon Park around Bird Island and the west side of Coulon Park that abuts the Southport property (vicinity of location of Log Boom to be abandoned). Response: All boats in Lake Washington are restricted to 7 knots/ 8 miles per hour within 100 yards of the shoreline, pier, restricted area, or shoreline installation (King County Code 12.44.090). This speed limit requires most boats to travel at idle speed when near the shoreline. At idling speed, boats are producing as little wake as possible. Additionally, the 100-yard requirement would extend outward from Bird Island and the Boeing property which would provide even greater protection for the inner harbor area where the floats are proposed. Any wake and wave action within the Southport area would not result in erosion impacts, since the shoreline in that area is entirely bulkheaded. Additionally, if any wake was created from accessing the proposed floats, that wake would be interrupted by Bird Island, and would not reach the swimming area. Significantly more boat traffic, and wave impacts to the Gene Coulon swimming area would occur from ongoing operation of the 8-lane boat launch ramp in Gene Coulon Memorial Beach Park. This existing facility is not separated from the swimming beach area like the Southport site is, rather it is directly adjacent to the beach. Lastly, the park’s swimming area is protected by a log boom, a floating dock area and a swimming line, all of which will reduce or eliminate wave impacts on the shoreline and prevent boats from entering the swimming area. The west side of Gene Coulon Memorial Beach Park that is in the vicinity of the proposed project is bulkheaded, and therefore protected from any wave action that might result from small motorized vessel access. While some erosion on Bird Island may be possible, Bird Island has a natural, vegetated shoreline that serves to prevent significant erosion. The Watershed Company Technical Memorandum August 2016 Page 3 Figure 1. The western portion of Gene Coulon Memorial Beach Park in the vicinity of the proposed floats. Note the bulkheaded shoreline and the natural shoreline of Bird Island. Turtles currently utilize the pilings and log booms to rest. Be sure to identify species and describe impacts if any. Response: A turtle that appeared to be an invasive red-eared slider was observed and documented by Kenny Booth, Senior Planner, on August 10th, 2015. This turtle was observed on the pilings towards the eastern shoreline area of the proposed project. The pilings in this area are proposed to remain. A discussion of turtles and species can be found in the Lake Study, in Section 2.2 Critical Areas and Habitat – Wildlife. Dolphins/Piles have been identified as creosote-based. Will pilings be cut or removed? If removed, will soil be tested and removed? Describe removal methods to be utilized, protection measures and environmental impacts if any. Response: All dolphins and piles will be pulled using a vibratory pile extraction method. Piles that cannot be removed using this method will be cut 2 feet below the mudline. Pile and finger removal could produce temporary, localized sediment plumes that would dissipate following cessation of activity. To minimize construction impacts Southport Shoreline Modifications Response to pre-application notes August, 2016 Page 4 associated with increased turbidity and the potential for release of toxic chemicals during construction, the following timing restrictions and conditions are proposed: • No in-water construction activity will occur at a minimum from January 1st through July 15th and August 1st through November 15th for protection of fish. • A floating sediment curtain will be installed and maintained around the work area for the duration of in-water work. • The contractor will stockpile any debris on the barge pending off-site disposal. • No hazardous materials will be mixed or stored in or near the water. No cleaning of materials will be performed in or near the water. • A Spill Prevention Plan will be developed and implemented. In addition, a Spill Kit will be maintained and secured on the barge at all times. • The barge will not be allowed to ground. • All debris will be properly disposed of on land in such a manner that they cannot enter into the waterway or cause water quality degradation (Section 13, Rivers and Harbors Act).