August 28, 2013 Seattle District Corps Of Engineers Regulatory Branch .

below). It may occur over a longer duration in order to facilitate the ongoing shipping schedule at the berth. Ongoing shipping activities will be a consideration for scheduling. The combi-wall will be installed as follows in pile units, each consisting of one pipe pile and one sheet pile pair (pipe pile in the center with one sheet pile panel attached to either side). Installation of the combi-wall will commence by first installing the pipe pile, with a vibratory hammer, to a specific depth, at which point the sheet pile panels will be placed into the grooves (on the side of the pipe pile). The pipe pile and sheet pile panels will then be sequentially vibrated in until they reach the desired depth or until resistance is met. It is assumed that the pipe pile will hit resistance within 40 ft of the final depth. It is anticipated that the sheet pile will not encounter resistance due to the fact that with this design the sheets are approximately 20 ft long. Once resistance is met (pipe pile only), an auger will be placed within the pipe pile to predrill a hole to the desired depth (tillings will be collected, stored on the work barge or on Pier 2, and disposed of in a similar manner as the dredged material; material will not be allowed to reenter Guemes Channel during augering). Once the hole has been pre-drilled, the pipe pile will then be impact driven into place. Based on boring data, it is anticipated that the auger and impact pile driver will be required for the final 40 ft of the pipe pile installation. The project engineer estimates that, at the high end, each pile unit may require 100 strikes to set into place, with strikes occurring non-continuously over 15 minutes per unit. By pre-drilling the holes (augering) the pile will not require a significant amount of blows to advance the pipe pile. In fact, it is anticipated that approximately half of the strikes will be required to install the pipe pile the initial 30 ft. The remaining strikes will occur over less than 5 minutes as the pipe pile unit is embedded the final 10 feet. The combi-wall will be sequentially installed using an installation template accommodating 12 pile units (approximately 80 feet in length). Each installation segment (12 pile units) will be fully installed to or below the mudline (final depth) prior to moving on to the next segment. Once the pile units have been driven to resistance with the vibratory hammer and pre-drilled with the auger, the project engineer anticipates that it will take 1.5 days to complete embedment with the impact driver. Typically, eight (8) pile units would be driven on the first day (800 strikes, 120 minutes) and 4 pile units driven on the second day (400 strikes, 60 minutes); 8 pile units would be the upper limit per day. Because the pile units in an active installation segment will be interlocked above the mudline during installation, during impact pile driving/proofing of any part of that unit the entire segment will be enclosed within a long ( 80 ft), rectangular bubble curtain (see proposed bubble curtain details enclosed with this letter). Each installation segment (12 pile units) will occur over an approximately 5-day cycle consisting of set up (including fender unit removal/replacement), vibratory driving, augering, and impact work. The combi-wall consists of 8 installation segments (96 pile units), and will require 40 days total to construct. The City outfall will be temporarily removed prior to the installation of the combi-wall and the combi-wall will need to be completed prior to dredging in any one area along the face of the berth. All combi-wall work may occur prior to all dredging, or they may be done in alternating phases, depending on the needs of the Port during construction. Re. Addendum 2 to the Pier 2 Berth Dredge and Dolphin Relocation/Upgrade Biological Evaluation, Corps Ref. NWS 2013-00056 Page 4 of 27 Prepared by Grette Associates, August 2013

If the City utilizes precast concrete anchors for the sewer outfall, the only change in construction methods will be the placement of sand and underwater grout within the piles. The placement of sand will occur by placing a pipe (or tube) on the mouth of the installed pile and pouring the sand down the pipe. Clean sand will be placed to within approximately 6 ft from the top of the pile. Underwater grout will then be installed using the same method. Underwater grout will contain only inert elements (no contaminants) and will be approved for inwater use (ex. Fox Industries FX-225 underwater grout). Following the placement of sand and grout, the steel hooks will be placed within the pipe. The remainder of the work (existing outfall removal, pile installation, etc) will all occur as described in Addendum 1. The installation and attachment of the concrete blocks or the steel beams to the piles and outfall pipe will still occur by divers and will have little impact on the aquatic environment. The size of the concrete base and cap blocks are larger than the steel beams; however, they will be located at or below -35 ft MLLW and will not result in a decrease to habitat. 2.4 Construction Timing The Port proposes to commence construction activities at the beginning of the 2014 in-water work window. Based on permits received for similar projects in Guemes Channel, the anticipated work window would likely be July 15 through March 14. Construction is anticipated to require one construction season to complete if the permits are received on time and the construction is not delayed (either shipping or ESA protection), but may be spread over multiple seasons if necessary. In order to minimize potential effects of underwater noise on listed marine mammals, specifically Southern Resident killer whales, the Port will conduct marine mammal monitoring during all impact driving of pipe and sheet pile driving that occurs during the project. This will ensure that Level A harassment (injury) of marine mammals is avoided during project construction. Please see attached Marine Mammal Monitoring Plan. 5.1 Direct Effects of the Project 5.1.1 Elevated Sound during Pipe and Sheet Pile Work The following updates the language in BE Section 5.1.1 and also incorporates elevated sound described in Addendum 1. Project engineers anticipate that combi-wall installation will require both vibratory (sheet pile and pipe pile) and impact (pipe pile) hammering. Most of the dolphin replacement/realignment can be completed with a vibratory hammer; however, the installation of the plumb pile (vertical pile) will be installed using a vibratory hammer to resistance and then an impact hammer will be utilized to install the plumb pile (estimated that the final ten feet will be impact driven). The batter piles will be installed using a vibratory hammer; the impact driving of the plumb pile will allow the project engineer to estimate the bearing capacity for the batter piles. Outfall realignment (existing pile removal and pile installation) can be completed with a vibratory hammer only. Therefore, the analysis below addresses elevated sound from both vibratory and impact hammers. Re. Addendum 2 to the Pier 2 Berth Dredge and Dolphin Relocation/Upgrade Biological Evaluation, Corps Ref. NWS 2013-00056 Page 5 of 27 Prepared by Grette Associates, August 2013

[Four paragraphs addressing standard method and models for sound analysis are not repeated. Note that the thresholds for marbled murrelet have changed since the BE was completed: the threshold and calculator results for sound above 183 dBSELcum no longer apply (M. Jensen, pers. comm.) See updated analysis below.] The applicant proposes to: remove seven (7) 12-inch creosote treated timber pile (outfall realignment); install four (4) new 12-¾-inch steel pile (outfall realignment) extract up to fourteen (14) 12- to 18- inch timber pile and three (3) 20-inch steel pipe pile (dolphin repair); install (or re-install) eight (8) 12- to 18-inch timber pile, three (3) 20-inch and two (2) new 24-inch steel pipe pile (dolphin repair); adjust up to twenty-four (24) 18-inch steel pipe pin pile (if necessary, fender system temporary removal); install 610 linear feet of combi-wall, including approximately ninety-six ( 96) 20-inch steel pipe pile and 96 sheet pile pairs. Pile used for outfall support, fender pin pile (if necessary), timber pile, and sheet pile all will be installed using a vibratory hammer. Five (5) steel pile used for the dolphin will be done using a vibratory and impact hammer (only the plumb pile will be installed to final depth using impact hammer). Approximately ninety-six ( 96) pile used on the combi-wall will be installed as much as possible using a vibratory hammer, followed by augering and impact driving/proofing as needed. Pile work is expected to occur over approximately 54 work days of construction; 40 work days for combi-wall pile and pin pile (if needed) work, 10 work days for dolphin relocation and upgrade, and 4 days of work for outfall realignment. There may be some overlap of effort, which could reduce the total number of days. [Assumptions for sound modeling not repeated here, as 20-inch steel pile have already been included in this analysis, with two exceptions as follows]. Use of a bubble curtain will result in at least 9 dB of sound attenuation at the source. The original BE incorrectly specified a confined bubble curtain; the intent was to be nonspecific. Sound analysis was completed both with and without this assumption in order to illustrate both scenarios for context during review (Table 1). o A standard single-pile bubble curtain will be used during impact work required during dolphin construction (vertical plumb pile). Re. Addendum 2 to the Pier 2 Berth Dredge and Dolphin Relocation/Upgrade Biological Evaluation, Corps Ref. NWS 2013-00056 Page 6 of 27 Prepared by Grette Associates, August 2013

o A rectangular bubble curtain, similar to that used by WSDOT during installation of an interlocking sheet and pile wall at Cape Disappointment (WSDOT 2006) will be used to fully enclose each active section (12 pile units, up to 80-ft-long) of combi-wall during impact driving/proofing. The proposed bubble curtain would fully encompass the entire 80 ft long section of combi-wall being installed (forming a complete rectangle around the perimeter of the 80 ft long section). Sound will travel, largely unattenuated, through all of the interlocked sections of the combi-wall previously installed during both impact and vibratory work. Because the already installed sections of combi-wall will be installed to or below the mudline, the sandy substrate will provide attenuation comparable to the bubble curtain as it is transmitted away from the combi-wall itself (J. Laughlin, pers. comm.). With the number of pile required to construct the combi-wall, the Port can no longer reasonably limit impact strikes to 100 per day (anticipated 1 pile). For the combi-wall, it is assumed that contractor will install up to 8 pile units per day, or 800 strikes per day (upper-range estimate, see Section 2.3 above), after pre-drilling with the auger. Impact work for the dolphin (vertical plumb pile) will be limited to 600 strikes per day. The plumb pile is the only pile that will be installed with an impact hammer and will be installed in a single day (anticipated that plumb pile will be driven with impact hammer the final ten (10) feet over approximately 15 minutes); the batter pile will be installed with a vibratory hammer. Dolphin pile will not be pre-drilled. Re. Addendum 2 to the Pier 2 Berth Dredge and Dolphin Relocation/Upgrade Biological Evaluation, Corps Ref. NWS 2013-00056 Page 7 of 27 Prepared by Grette Associates, August 2013

Table 1. Sound impact threshold and distance to threshold summary by species. Species Effect type Threshold Distance to Effect Threshold Vibratory Hammer Operation (extraction and installation) Southern Resident Behavioral disruption (continuous): 120 dBRMS 5.86 mi (9.43 km) killer whales, extract and/or drive 24 18-inch inch humpback whale steel pin pile, and Steller sea lion extract and drive 3 20-inch steel dolphin pile, drive 2 24-inch steel dolphin pile, drive 4 12¾-inch steel outfall support pile; and drive 96 20-inch steel pipe pile for 610 lineal feet of combi-wall Behavioral disruption (continuous): 120 dBRMS 760 ft (232 m) extract up to 14 timber pile (up to 18inch) Behavioral disruption (continuous): 120 dBRMS 5.86 mi (9.43 km) insert 8 timber pile (up to 18-inch) Behavioral disruption (continuous): 120 dBRMS 2.88 mi (4.64 km) sheet pile for 610 lineal feet combiwall Impact Hammer Operation, with 9 dB attenuation from a bubble curtain2 All listed fish Injury, cumulative sound ( 2 g) 187 dBSEL 282 ft (86 m), 800 strikes 233 ft (71 m), 600 strikes 177 ft (54 m), 400 strikes Injury, cumulative sound ( 2 g1) 183 dBSEL 522 ft (159 m), 800 strikes 430 ft (131 m), 600 strikes 328 ft (100 m), 400 strikes Injury, single strike 206 dBpeak N/A: below threshold at source Behavior 150 dBRMS 3,280 ft (1,000 m) Steller sea lion Injury, pulsed sound 190 dBRMS N/A: below threshold at source Behavioral disruption, pulsed sound 160 dBRMS 707 ft (215m) Southern Resident Injury, pulsed sound 180 dBRMS 33 ft (10 m) killer whale, humpback whale Behavioral disruption, pulsed sound 160 dBRMS 707 ft (215m) 2 Marbled murrelet Barotrauma 208 dBSEL 10 ft (3 m), 800 strikes 10 ft (3 m), 600 strikes 6 ft (2 meters), 400 strikes Auditory Injury 202 dBSEL 30 ft (9 m), 800 strikes 23 ft (7 m), 600 strikes 16 ft (5 meters), 400 strikes Re. Addendum 2 to the Pier 2 Berth Dredge and Dolphin Relocation/Upgrade Biological Evaluation, Corps Ref. NWS 2013-00056 Page 8 of 27 Prepared by Grette Associates, August 2013

Impact Hammer Operation, with no attenuation from a bubble curtain2 All listed fish Injury, cumulative sound ( 2 g) 187 dBSEL 1,125 ft (343 m), 800 strikes 929 ft (283 m), 600 strikes 709 ft (216 m), 400 strikes Injury, cumulative sound ( 2 g1) 183 dBSEL 2,080 ft (634 m), 800 strikes 1716 ft (523m), 600 strikes 1,309 ft (399 m), 400 strikes Injury, single strike 206 dBpeak N/A: below threshold at source Behavior 150 dBRMS 2.47 mi (3,981 m) Steller sea lion Injury, pulsed sound 190 dBRMS N/A: below threshold at source Behavioral disruption, pulsed sound 160 dBRMS 2,813 ft (858m) Southern Resident Injury, pulsed sound 180 dBRMS 131 ft (40 m) killer whale, humpback whale Behavioral disruption, pulsed sound 160 dBRMS 2,813 ft (858 m) 2 Marbled murrelet Barotrauma 208 dBSEL 46 ft (14 m), 800 strikes 36 ft (11 m), 600 strikes 30 ft (9 meters), 400 strikes Auditory Injury 202 dBSEL 112 ft (34 m), 800 strikes 92 ft. (28 m), 600 strikes 72 ft (22 meters), 400 strikes 1 Given the Project location and adherence to the in-water work window all salmonids in the Action Area during construction are assumed to be 2 grams and only the 187 dBSEL threshold is applicable for salmonids. 2 Combi-wall would be 800 or 400 strikes per day (not more than 100 strikes per pile, if needed); dolphin (vertical plumb pile) estimated at 600 strikes per day. 3 Change from prior sound analysis to reflect current guidance on marbled murrelets to address only the injury thresholds (M. Jensen, pers. comm.) 5.1.2 Construction Related Turbidity Turbidity associated with pile driving is already addressed under BE Section 5.1.2. The pipe pile will act as a drill casing during augering, and the contractor will be required to capture drilled material without allowing it to enter surface waters, and disposed of in a similar manner as the dredged material. There are no additional effects of construction-related turbidity to address. 5.2.1 Direct Effects on Salmonids: Injury or Disturbance due to Impact Pile Driving/Proofing The following updates the language in BE Section 5.2.1 specific to impact driving and/or proofing. Impact driving and/or proofing will be needed to install 96 steel pipe pile for the combi-wall, following pre-drilling holes with the auger. This will require up to 800 strikes (120 minutes) or 400 strikes (60 minutes) per day. Impact driving and/or proofing will also be required to install the one (1) 20-inch pipe pile during dolphin relocation (plumb pile). This will be limited to 600 strikes (approximately 15 minutes) per day. The results for sound modeling are shown in Table 1 above. Re. Addendum 2 to the Pier 2 Berth Dredge and Dolphin Relocation/Upgrade Biological Evaluation, Corps Ref. NWS 2013-00056 Page 9 of 27 Prepared by Grette Associates, August 2013

Impact driving and/or proofing is anticipated to take up to 15 minutes per pile unit (combi-wall) or pipe pile (dolphin), and may occur on up to 17 days (16 for combi-wall, 1 for dolphin pile). Pile work, including impact work, would occur within the approved in-water work window (anticipated to be July 15 through March 14). During combi-wall installation, assuming up to 800 strikes per day, the area of potential cumulative injury is very small: 522 feet or 282 feet from pile driving for fish 2 grams or 2 grams, respectively (Figure 1). On days with only 400 strikes, these distances are even smaller, 328 feet and 177 feet, respectively. Based on beginning pile work even later than the typical inwater work period (not before July 15), it is assumed that salmonids in the Action Area would be 2 grams. For the most part, areas within 282 feet (or less) of active pile driving and the combiwall alignment are in deep water to the north of Pier 2, well below -20 feet MLLW. Juvenile salmonids may pass through this area, but they are not likely to rear within it. Exceptions occur at the ends of the combi-wall, where sound may extend east or west as well as south into shallower areas; these areas may experience elevated sound during impact driving/proofing. However, because pile work would occur within the in-water work window, which is past the peak outmigration period for juvenile salmonids, it is unlikely that any juveniles would be present during pile driving. Impact pile driving would occur within 4 to 8 discontinuous 15minute periods (60 to 120 minutes total) on each of up to 16 days. In order to sustain cumulative injury from underwater sound, fish must be exposed to impact driving as it happens throughout the work day. As described above, based on project timing it is extremely unlikely that juveniles would be rearing within areas of potentially elevated sound, even where that includes shallower habitat areas near the ends of the combi-wall. While subadults and adults may be present in the Action Area, they are unlikely to be present in substantial numbers in Guemes Channel, and are extremely unlikely stay within 282 feet (or less) the combi-wall installation alignment (Figure 1) for an entire day. Based on project timing, the relatively small area of potentially injurious sound during pile driving, and the relatively short, discontinuous nature of that sound over the course 16 working days ( 15 minutes per pile or pile unit, 4 to 8 times per day), it is discountable that any juvenile, subadult, or adult salmonids would experience cumulative sound sufficient to cause injury. During dolphin pile installation the distances (and areas) for cumulative injury is 233 feet from the dolphin for fish 2 grams (Figure 1). This sound will occur for up to 15 minutes on a single day. Based on the small area and short duration of this sound, as well as project timing, it is discountable that either juvenile, subadult, or adult fish would sustain cumulative injury during this work. The Port proposes to use a bubble curtain during all impact pile work, and anticipates 9 dB attenuation from that bubble curtain. Assuming no attenuation from a bubble curtain, the distance to cumulative injury for fish 2 grams increases to as much as 1,125 feet per day (see Table 1). This is the maximum possible distance to cumulative injury, assuming the bubble curtain is completely ineffective throughout the entire day. There is no expectation of this situation, however it is considered in order to evaluate the worst-case scenario with respect to cumulative injury. This area is still relatively small (for reference, it is over 4,000 feet across the Re. Addendum 2 to the Pier 2 Berth Dredge and Dolphin Relocation/Upgrade Biological Eva

vibratory hammer to install the entire sheet pile proposed cut-off wall was not feasible. The Port's engineer has developed an alternative system; a combination pipe pile and sheet pile wall ("combi-wall"), which consists of -six (ninety96) 20-inch steel pile with sheet pile supported between each pair of pile.