3. MARINE HABITAT RESTORATION

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1 Feasibility Study for Restoration of Titlow Lagoon Fish Passage South Puget Sound Salmon Enhancement Group 3. MARINE HABITAT RESTORATION Marine habitat restoration at Titlow Park could include restoration of the south beach, dredging the lower lagoon, and restoration of the lagoon shoreline and upper/lower lagoon connection. Design concepts and costs for these actions are described in this section. Appendix D provides detailed cost estimates for design, permitting, BNSF coordination, construction, and other items. Costs noted below include all of these project elements. Table 3-1 summarizes project costs and provides a comprehensive cost for three potential restoration alternatives. Table 3-1. Summary and Compilation of Estimated Project Costs Construction Element Interim Action for Existing Fish Passage Pipe Fish Passage Rail Bridge Fish Passage CONSTRUCTION COST Enhancing Existing Fish Passage $42,000 Dredging Lagoon $228,000 $228,000 $228,000 Upper/Lower Lagoon Connection Channel $133,000 $133,000 $133,000 Off-Site Disposal of Lagoon Sediment $1,023,000 $1,023,000 $1,023,000 Pipe Fish Passage $1,153,000 Rail Bridge Fish Passage $2,969,000 Total: $1,426,000 $2,537,000 $4,353,000 OPTIONAL/CONTINGENCY WORK ELEMENTS South Beach Restoration/Fill $520,000 $520,000 Off-Site Disposal of Lagoon Sediment $760,000 $760,000 $760,000 Total: $1,286,000 $3,817,000 $5,633, BEACH RESTORATION Figure 3-1 shows a beach restoration concept. Beach restoration is included in this Feasibility Study for completeness, but was not an element of the preferred alternative in the Master Planning process. The north beach appears to provide satisfactory intertidal habitat and does not require restoration. Ongoing beach nourishment from eroding shoreline bluffs is apparently maintaining the beach in good condition. The existing sediment delta offshore of the lagoon outlet pipe provides high quality intertidal habitat directly adjacent to lagoon connection. Restoration of the south beach would provide a slight increase in additional habitat value. Restoration of the south beach area by shoreline softening or pull-back is not possible due to the presence of the existing BNSF railroad embankment. Restoration of the south beach could be accomplished by placing approximately 27,000 cubic yards (cy) of sand and gravel in the existing intertidal zone in a wedge approximately 1,000 feet long by 160 feet wide by 8 feet deep at the revetment to create a beach extending above the intertidal zone and having a slope of approximately 8 horizontal to 1 vertical to seaward. The cost for this beach fill is estimated at approximately $800,000 to $1,000,000, if material is procured from upland sources. Clean dredged sediment from a source such as the Port of Tacoma could be obtained and used for the bulk of the fill; however, dredged material would likely be predominantly sand, which would be finer grained January (01/0202) 3-1

2 Feasibility Study for Restoration of Titlow Lagoon Fish Passage South Puget Sound Salmon Enhancement Group and more prone to erosion than the preferred material (sand and gravel). The beach fill could be constructed primarily with dredged material, and then capped with gravel from an upland source. Using this approach, the cost for the beach fill is estimated at approximately $520,000. Maintaining the restored south beach would likely require periodic replacement of beach material lost by natural beach processes and transported offshore by the lagoon outflow. However, the replenish volume and schedule cannot be reliably estimated. Appendix B provides additional discussion of site geomorphology and beach restoration. 3.2 LAGOON RESTORATION Several actions are recommended to restore the Titlow Lagoon: Dredge the lower lagoon deeper to provide improved habitat for juvenile salmon during low water conditions (see Section 3.3). Replace the narrow wood drainage channel between the upper and lower lagoons with a broad natural channel (see Section 3.4). Modify the lower lagoon shoreline to increase its length and complexity; grade the shoreline to create salt marsh habitat; and soften the shoreline through removal of riprap, placement of woody debris and plants, and other restoration methods. Enhance the shoreline of the southeast portion of the upper lagoon between the existing pedestrian bridge and the creek. The remainder of the upper lagoon appears to provide good quality habitat that does not need restoration. This Feasibility Study addresses the first two actions noted above (see Sections 3.3 and 3.4). Figure 3-2 illustrates a lagoon restoration concept that addresses the latter two actions. The specific lagoon shoreline configuration and elevations will be determined during final design. The size and elevation of the lower lagoon bottom allows for dredging part of the lagoon without requiring excavation or setback of the lagoon shoreline; therefore, these two goals can be accomplished independently for the most part. The estimated cost to restore the lagoon shoreline is $1.0 million. This cost includes $300,000 to demolish the pool and pool building. This cost of pool demolition is a preliminary order of magnitude estimate. Preparation of a detailed pool demolition cost estimate was not part of the scope of work for this feasibility study Lower Lagoon Dredging Dredging the lower lagoon approximately 8 feet deeper (from -1 foot to -9 feet NGVD20 [+5 feet MLLW to -3 feet MLLW]) to provide improved habitat for juvenile salmon during low water conditions is one of the recommendations. The lagoon, but not the lagoon fish passage, would be deepened to maintain a deeper pool in the lagoon during low water conditions to provide improved water conditions (i.e., temperature, quality) in the lagoon and less bird predation. Figure 3-3 shows a possible scenario for dredging area and contours. Dredging to these contours would generate approximately 9,100 cubic yards of sediment. Dredging of the lagoon is expected to be subject to Puget Sound Dredge Disposal requirements and would require characterization, even if the sediment is excavated in the dry and disposed of on-site. In general, this means a sediment sampling and analysis plan must be negotiated with the Washington State Department of Natural Resources and the U.S. Corps of Engineers, and sampling protocols (including number of samples, sampling methods, and analyses) must 3-2 January (01/0202)

3 Feasibility Study for Restoration of Titlow Lagoon Fish Passage South Puget Sound Salmon Enhancement Group meet Puget Sound Dredged Disposal Analysis (PSDDA) requirements. The characterization is expected to consist of two to three core samples (10 feet long) from the lagoon in the area of the proposed dredging. The cores would be segmented into sediment above and below the proposed dredging limit, and the sediment analyzed for physical properties (e.g., gradation) and chemical contaminants. Sediment characterization results from below the dredging limits would be indicative of sediment quality that would remain after dredging. Sediment characterization results from the dredging zone would be indicative of the material to be used as fill elsewhere in the park or requiring disposal. The estimated cost for dredging the lagoon is $230,000. This cost estimate assumes that dredged sediment would be disposed of on-site in the lawn area to the south of the lagoon. Historically, this area reportedly drains poorly, and the dredged sediments could be used as fill to provide more slope to the area to promote better drainage. If off-site disposal at a landfill is required due to lack of opportunity to re-use the material as on-site fill, or due to elevated contaminant concentrations, the estimated cost for sediment disposal is approximately $760,000. If disposal is required, the dredging prism would likely be reduced in depth and size so as to reduce dredging and disposal costs Upper/Lower Lagoon Reconnection Improvement of the upper/lower lagoon connection channel is not expected to have substantial benefit to juvenile salmonids because the lower lagoon will provide adequate habitat for juvenile salmon entering the lagoon from the Narrows, and little or no salmon spawning is believed to occur in the streams feeding the upper lagoon. Figure 3-4 provides a concept for reconnection of the upper and lower lagoon. The sill elevation of the existing wood weir would be maintained at the same elevation, but the new channel would be broader and have a natural gravel/cobble substrate. The estimated cost for the reconnection channel is $130,000. Due to the wider channel, the rate of water flow between the lagoons would be substantially increased compared to the present condition. The upper lagoon would drain and fill faster than at present; however, the minimum water level in the upper lagoon would not change. Due to the higher rates of flow between the lagoons, water in the upper lagoon would be more saline than at present. Combining the effects of the enlarged channel with the new fish passage structure (which would increase tidal exchange between the Narrows and the lower lagoon) would further intensify these effects. The upper lagoon currently has some salt tolerant vegetation. After construction of the new fish passage and re-connection channel, an increase in salt tolerant vegetation, along with a corresponding decrease in non-salt tolerant vegetation, can be expected. January (01/0202) 3-3

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5 Parametrix 0 DATE: Dec 01, 2009 N SCALE IN FEET 200 Figure 3-1 Beach Restoration Concept Titlow Park Tacoma, Washington

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7 Parametrix DATE: Dec 04, 2009 N SCALE IN FEET Water Dredging Zone Salt Marsh Tidal Channel Upland Source: Site Workshop 12/03/09 Figure 3-2 Lagoon Restoration Concept Titlow Park Tacoma, Washington

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