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Title: Final Supplemental Environmental Assessment : San Juan Harbor, Puerto Rico Seagrass Mitigation, Additional Sand Source
Authors: United States. Army. Corps of Engineers. Jacksonville District
Keywords: San Juan (P.R.)
Environmental protection
Aquatic plants
Publisher: United States. Army. Corps of Engineers. Jacksonville District.
Abstract: The project study area includes San Juan Harbor (SJH), and surrounding areas as identified in the Recommended Plan in the 2018 San Juan Harbor Puerto Rico Integrated Feasibility Report & Environmental Assessment (2018 IFR/EA) and the 2015 San Juan Harbor, Puerto Rico Submerged Aquatic Vegetation Mitigation Environmental Assessment (2015 Mitigation EA). The Puerto Nuevo Channel widening portion of the 2001 SJH expansion dredging project impacted an estimated 1.2 acres (ac) of shoal grass (Halophila decipiens) and marine macro-algae. Subsequently the USACE completed the 2015 Mitigation EA and in a March 2, 2015 Finding of No Significant Impact (FONSI), USACE approved compensating for the submerged aquatic vegetation (SAV) impacts by filling 4 ac using suitable sandy material in artificial depressions in Condado Lagoon (Figure 1-1) to reach the target mitigation of 1.2 ac at -12 to -15 ft. Although construction of this mitigation was included in advertisements for past SJH Operation & Maintenance dredging (O&M) events, contract bids have consistently exceeded the awardable thresholds and the mitigation remains unconstructed. The 2018 IFR/EA for navigation improvements at SJH analyzed a beneficial use of dredged material option to fill approximately 18-ac of the artificial depressions in Condado Lagoon for seagrass restoration. The beneficial use option would fill a greater acreage of artificial depressions in Condado Lagoon then the required previous mitigation plan (2015 EA). Filling the depressions, with depth contours of -12 to -15 ft, would restore the natural bathymetry and improve the overall marine ecology within the Lagoon. The Recommended Plan from the 2018 IFR/EA, including the beneficial use option, was recommended in the Chief of Engineers’ Report dated August 23, 2018, authorized by Congress in Section 1401(1) of the Water Resources Development Act (WRDA) of 2018 (Public Law 115-270), and approved in the USACE Finding of No Significant Impact (FONSI) dated November 5, 2018. This project is referred to as the “SJHNI Project” in this SEA. Section 1122 of the WRDA of 2016 required the USACE establish a pilot program to recommend ten projects for the beneficial uses of dredged material. In a FONSI dated December 4, 2018, the Assistant Secretary of the Army (Civil Works) selected ten projects for the Section 1122 pilot program, including a project to restore the degraded aquatic ecosystem in Condado Lagoon by using dredged material from the San Juan Harbor, Puerto Rico navigation project to reestablish historic lagoon bathymetry. However, updated geotechnical investigations indicate there is less material suitable for beneficial use (coarse grain size) within the authorized channel expansion footprint for the San Juan Harbor, Puerto Rico project than anticipated in the 2018 IFR/EA. This Supplemental Environmental Assessment (SEA) evaluates only the dredging of a new area outside the Federal channel west of Cut-6 (Figure 1-3) as an additional sand source for the seagrass mitigation. The effects of dredging Cut-6 and the other channel expansion areas, and the effects of placement into Condado Lagoon for seagrass habitat restoration were previously evaluated in the 2018 IFR/EA and 2015 Mitigation EA. All discussions, consultations, effects determinations, and conclusions contained in the 2018 IFR/EA and 2015 Mitigation EA are hereby incorporated by reference into this SEA.
Description: Supplemental Environmental Assessment
Rights: Approved for Public Release; Distribution is Unlimited
Appears in Collections:Environmental Documents

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