DREDGING AND DISPOSAL REPORT for the PORT OF BROOKINGS PORT OF BROOKINGS HARBOR, OREGON

Transcription

1 DREDGING AND DISPOSAL REPORT for the PORT OF BROOKINGS PORT OF BROOKINGS HARBOR, OREGON Attn: Mr. Ted Fitzgerald, Port Director PO Box 848 Brookings, OR By Jack Akin, EMC, Engineers/Scientists, LLC 2/15/13 TABLE OF CONTENTS 1.0 INTRODUCTION POST-TSUNAMI DREDGE AND DISPOSAL DREDGING MAJOR DREDGING EQUIPMENT LIST SEDIMENT DISPOSAL PROJECT DESIGN DESCRIPTION OF WORK PROCEDURE DREDGE OPERATION FIELD MEASUREMNT CHECKS ENVIRONMENTAL PROTECTION HORIZONTAL/VERTICAL CONTROL OF DREDGING EQUIPMENT SEDIMENT DISPOSAL LOCATION MONITORING ENVIRONMENTAL PROTECTION REQUEST TO DECANT DREDGE AREAS PROTECTION AGAINST TURBIDITY-RELATED POLLUTANTS WORKING HOURS POSITIONING & PROGRESS SURVEYS DREDGE NAVIGATION VESSEL TRAFFIC AND SECURITY PROTECTION OF PORT FACILITIES... 9 ATTACHED DRAWINGS FIGURE 1 NOTES, PAGE 3; FIGURE 1, PAGE 2; DETAIL B1, PAGE 21; DETAIL H1, PAGE 37; FIGURE 1.6, PAGE 13; FLUID CALCULATIONS FOR 14 INCH, SDR 17 HDPE PIPE SYSTEM, PAGES 4 AND 5 OF 5; PORT OF BROOKINGS POST DREDGING VOLUMES, SHEET 1 OF 1

2 1.0 INTRODUCTION This 2/15/13 Dredge Report is submitted by EMC - Engineers/Scientists, LLC (PE), on behalf of the Port of Brookings, Harbor, Oregon. The PE was contracted by the Port of Brookings (Port) to propose for permits, and to provide engineering, labor, materials and equipment to conduct post-tsunami dredging and disposal of about 31,000 yds 3 of sediment within the North and South Basins (Basin 1 and Basin 2), and within the Ice House/Fueling Dock Inlet, Port of Brookings Harbor, Oregon. This work was conducted under a Joint Permit (Permit # /3) to remove accumulated sediments. In addition to the plan view of the proposed dredging areas shown in the Dredge & Disposal Plan (DDP), cross-sectional views (prisms) have been constructed at key locations, which have been provided to the USACE, and are available to particular regulatory reviewers of this report upon request (Jack Akin, Engineer of Record, Work Phone: , Ext. 1. If Jack is not at his desk, calls are auto-transferred to Akin s cell phone. address is emc@emcengineersscientists.com). 2.0 POST-TSUNAMI DREDGE AND DISPOSAL 2.1 DREDGING A permit to dredge the Port basins was received from the USACE on March 6 th, 2012 (Permit # /3). However, since the in-water work window at this harbor has been from November 15 th to February 15 th, the Port would have been unable to dredge until November 15 th, The Port therefore petitioned for an earlier date to begin, and eventually was informed in late August that a start-date to begin September 1 st was approved by the Program Review Group (PRG). The Port proceeded after annual boating events on September 6 th, and completed by October 10 th, the dredging of about 27,000 yds 3 via FEMA/OEM and Oregon State matching funding, and about 4000 yds 3 via Oregon State Marine Board funding, of port harbor basin sediments that had been shifted by the 3/11/11 tsunami. The dredging was accomplished by hydraulic suction dredge with cutter head as described below. The Port employed equipment for this project as described within the Section below entitled Major Dredging Equipment List for Plan. 1

3 2.2 MAJOR DREDGING EQUIPMENT LIST 1) Dredge - 12x12 DSC Shark 2) Tug boat with A- Frame 3) 2 Connex boxes of tools and supplies 4) Work skiff 5) Misc. equipment anchors, cables, etc. 6) C-15 Caterpillar 650 hp engine, driving a 36 impeller booster 7) A total of about 10,500 feet of 14 SDR 17 HDPE pipe 8) HDPE pipe welder with 10, 12 and 14 dies. 9) Specialized HDPE floats, buoys and lighting 10) Silent monitor 3.0 SEDIMENT DISPOSAL The sediment, after removal by a hydraulic dredge (see photo below), was pumped through direct piping from the hydraulic dredge through the booster to the Chetco ODMDS. According to the above-referenced EPA EIS, the average depth of this disposal area is feet. The dumping site is about a mile off-shore in and is called the Chetco ODMDS (see attached drawing FIGURE 1 Notes, Page 3), and is described, for example, in the EPA document entitled Chetco Ocean Dredged Material Disposal Site Designation, Draft Environmental Impact Statement, (1999). The four corners of the 1800 X 1800 sediment disposal area are located via four geographic points in that EIS. A pipeline (14 diameter, plastic, welded, see footnote) was constructed, laid out and towed to location, and anchored to the ocean floor as shown on attached drawing FIGURE 1, Page 2. 12x12 DSC Shark, with Work Skiff Alongside The pipe outlet was mounted to a platform (see photo on next page) and equipped with location monitoring. Dredged sediment was thence pumped directly from the hydraulic suction dredge to the disposal location. 2

4 4.0 PROJECT DESIGN 4.1 DESCRIPTION OF WORK - The sediments were transported via hydraulic dredge from the harbor, through a designed piping and pumping system, and disposed in the Chetco ODMDS. The Port completed the dredging of post-tsunami moved sediments on October 10 th, Anchored Platform Supporting Silent Monitor 4.2 PROCEDURE - The Port completed the dredging of about 27,000 yds 3 via FEMA/OEM and Oregon State matching funding, and about 4000 yds 3 via Oregon State Marine Board funding, of port harbor basin sediments that had been shifted by the 3/11/11 tsunami, via a 12x12 DSC Shark hydraulic suction dredge, equipped with a cutter head. A rock guard was welded to the cutter head to limit rock size to 8 diameter. The dredge operated in the harbor only, and pumped sediment-slurries ranging from about 10% - 40% solids, through a maximum of 3500 feet, to a C-15 engine driven, 36 impeller mounted booster pump. The booster pump drove the slurry thence a maximum of about 7000 to the sediment disposal area, described in Section 3.0. All piping was 14 SDR 17 HDPE. The harbor piping was submerged during operations. Piping from the dredge was laid underwater (when containing slurry), until reaching land, and thence upland to the booster pump. Piping from the booster pump outlet was not attached to floats to a point out to sea just beyond the nose of the adjacent jetty, in order remain beneath breaking waves, after which the pipe was floated to the anchored platform supporting the silent monitor. The floating pipe was kept aloft by in-house designed and built floats, constructed of older HDPE pipe that had been determined by the PE to be less safe for pressures required for this dredging project. 25 lengths of 14 SDR 17 and 12 SDR 17 of this piping were cut and caps welded thereon. The sealed floats were then strapped to the piping to be floated, spaced as directed by the PE (see attached drawing DETAIL B1, Page 35). The decision to float the pipe from a point beyond the surf to the disposal site was made at the PE s recommendation, in order to avoid collisions with vessels moving at higher speeds during accidentally surfacing of pipe sections which were not visible out at sea. 3

5 A floating pipeline, lit by flashing solar lights and buoys (see attached drawing DETAIL H1, Page 37), helped to prevent such collisions. Additionally, since some of the pipe was not new, and because the Port did not have knowledge of the quality of old welds, pipe breaks were more easily detected and repaired. All pipeline out to sea was stayed from drift via anchoring. All piping in the harbor was fully visible, when floating, to the dredge operator deckman, as well to the workers on the work skiff and tender vessel, at all times. Therefore piping in the harbor was sunk via maintaining adequate sediment in the piping. No pipe anchoring was used within the harbor. On several occasions during the project the piping in the harbor surfaced accidentally. However, with personnel and vessels available, the slow-moving vessels in the harbor were piloted away from the floating pipeline. 4.3 DREDGE OPERATION - First, pipe lengths were welded (and flange-bolted at convenient pipe segment joints) into 1000 and 2000 lengths, and staged either on land nearby or along the east bank of the Chetco River. All pipe welding was performed by Port employees, after adequate certifying training for each welder was completed. The pipe fuse-welding unit utilized was leased from the company performing the training. The welded lengths were then flange-bolted together at sea as needed. The leased dredge and assistance vessels were at the same time lowered into the harbor by the boat lift located at the south end of Basin 2 (South Basin). Pipe lengths were then flange-bolted to the dredge pipe outlet, and to the inlet and outlet of the booster pump (see attached drawing FIGURE 1.6, Page 13). The dredge operated by utilization of a cutter, a C-15 engine-driven centrifugal pump (the cutter head is also powered by an estimated hp from the engine), and a combination of winches, anchors, and spuds. The cutterhead broke the material free from the bottom, and pulled it to the suction zone in solution for pumping. This slurry was then pumped by means of a centrifugal pump through a pipeline towards the disposal location. The dredge swings from side to side using winches pulling on anchors while pivoting on spuds, one at a time as it swings from side to side, and is piloted by the skiff and/or workboat. With the combination of swing anchors and winches, and by alternating spuds in staggering positions, the dredge walked forward into the banks of post-tsunami shifted material. The swing anchors, located off to the sides of the work zones, are marked by buoys. Dredging began in the west side of the South Basin (Docks C K), thence to the east side (Docks P & Q), thence to the Ice House Inlet, thence to the east side of the North Basin (Docks A H), and completed the project at the Sports Transient Dock near the northwest corner of the North Basin. 4

6 4.4 FIELD MEASUREMENTS CHECKS Pipe and Pumping System Fluid calculations were submitted within drawing notes (see attached drawings entitled FLUID CALCULATIONS FOR 14 INCH, SDR 17 HDPE PIPE SYSTEM, Pages 4 of 5 and 5 of 5) 1 with the Dredge and Disposal Plan. Therein design power requirements were calculated using Hazen-Williams pipe friction, confirmed by Darcy-Weisbach. The friction factor in Darcy Weisbach was calculated via Swamee-Jain exponentials, and tested using Colebrooke-White. The most conservative of the two was used in the total dynamic head calculations for power determinations. A spreadsheet was constructed for various pipe lengths, pipe diameters and dimensional ratios, and efficiency factors, also included within the design drawings. Additionally, other dependant characteristics, including buoyancies, spans and production rates, were presented. These fluid calculations within the drawing notes corroborated closely with field observations. For example, the PE observed the 650 hp C RPM enginedriven-booster pump, while running at 1500 rpm, drove the fluid in the id HDPE pipe at feet/second (measured via Greyline Doppler flow-meter) through 6000 feet of pipe, with an inlet pressure of psi and outlet pressure of psi. At 1500 rpm, fluid laws indicated that the booster pump was operating at or under 50% capacity Turbidity measurements were taken by the PE each day. During the first two days turbidity was measured once each hour during dredging. When measurements provided the PE with adequate sense of predictability, two sample events, randomly selected, were conducted each day for the ten days, and then one per day, randomly selected, was conducted for the remaining project period. Depths of samples collected ranged from two feet beneath the water surface to within one foot from basin floor, feet from the cutter head. At no time did turbidity measurement readings exceed 15 NTUs, and 90% read between 5 and 10 NTUs. An Omega Portable turbidity unit was used for the project, calibrated by the PE each day (range NTUs). 4.5 ENVIRONMENTAL PROTECTION The pipeline was inspected initially by the PE, and subsequently, at the least, daily when dredging was taking place Only sound pipeline was used. The PE reviewed the pipe and application. Net maximum pressure on the piping material is internal, created by flow requirements, and is greatest at maximum hydrostatic conditions (at water surface). 1 These and all calculations shown in this Report are for the use of the PE referred to in this Report, are specific to this project, and any use by outside persons are at their own risk. The Port and the PE does not support or protect or guarantee the use of any of the design details or parameters for any use outside of this particular project. 5

7 As mentioned above, highest pressures in the system were noted at the pressure gage located just after the booster pump to be about 95 psi. 17 SDR HDPE pipe is ASTM-rated at 160 PSI. Since some of the pipe in this system was used, the PE calculated the SDR pressure rating based on the thinnest wall of piping that was pressurized in the project, which was inch wall of a 14 OD HDPE pipe is ASTM rated as an SDR 22 pipe at 120 psi (approximated by 2(1250)/(SDR- 1)). The selected pipe was rated as a function of the hydrostatic strength of the material, the pipe dimensional ratio, and environmental and temperature factors. Affected employees had undergone pipe handling and welding training, as provided by the pipe supplier (3-4 classroom plus 4-hour hands-on training session, to certify employees to set up and weld medium diameter (4 20 ) HDPE pipe via butt fusion. Welded pipe bending radii did not exceed that recommended (usually about 25 pipe diameters). All calculations available upon request The pipeline was positioned, weighted and marked for safe navigation NAME AND TELEPHONE NUMBERS OF REPRESENTATIVES ON- SITE PE (Jack Akin, , Ext. 1) was on site during operations SCHEDULE Dredging prep and mobilization began on September 6 th, Pumping rates required that minimum in-water work period required 25 days, barring unforeseen problems (breakdowns, encountering of unseen debris, garbage, etc. during hydraulic dredging). Dredging flowrates averaged 200 (about 50% capacity of on-site equipment) cubic yards per hour, 10 hours a day, with 10 40% solids pumped, with about 40% debris-clearing loss of efficiency In-water work was completed by October 9 th, SLURRING OF MATERIALS - All dredged materials were pumped utilizing the hydraulic suction dredge QUANTITY OF MATERIAL DREDGED - Approx. 31,000 cubic yards were removed and disposed DREDGE DESIGN DEPTHS - Project depths are as per plans and specs, and are in NAVD. Completed depths were measured by the PE after the dredging was completed, and are presented within the attached, contoured drawing entitled PORT OF BROOKINGS POST DREDGING VOLUMES, SHEET 1 OF CONTROLS FOR DREDGE SITE (Implemented when necessary in the judgment of the PE and dredge operator: otherwise see applicable sections below) Dredge positioning on the Port project was done utilizing DGPS for Dredge positioning, a gyro compass for Dredge direction, a pressure transducer for cutter depth, all linked together in a computer with dredge positioning software. 6

8 The corner point coordinates for the project were entered into the system, and the dredge was positioned accordingly. Horizontal positioning was verified by visual observations, comparing the plans with the dredge location in reference to structures, land, and/or stakes and docks. Ladder depth was verified visually with a ladder scale. Vertical control utilized an auto tide gauge and/or visual tide boards PIPELINE - 14 inch diameter SDR 17 HDPE pipe was used. Only pipeline in sound condition was used, inspected and approved per section by the PE LIMITS & CONTROLS FOR DISPOSAL SITE: Per the USACE-issued Permit # / Detailed drawings and specifications of the centrifugal pump & piping system are attached Dredged quantities were calculated by multiplying the estimated and measured pump rates by the dredge pump time, and recorded on the dredge logs, confirmed by on-site post-dredging depth measurements, conducted and adjusted by MLLW readings by the PE Pipeline Layout diagram was adjacent to cut and parallel cut, from the dredge, and on the side of the channel along jetty. 5.0 HORIZONTAL AND VERTICAL CONTROL OF DREDGING EQUIPMENT When necessary in the judgment of the PE and dredge operator, controls were implemented as described in Section At minimum horizontal positioning was accomplished by using line of sight positioning from the numerous visual reference points in the harbor. This was feasible because all planned dredging occurred within the harbor, where reference landmarks (i.e. boat slips, floating and permanent docks) were readily available. Vertical positioning was accomplished via a ladder gauge on the dredge. This gauge was regularly checked with the tide gauge near the Port fueling station. 6.0 SEDIMENT DISPOSAL LOCATION MONITORING Silent monitoring was provided by an anchored platform vessel that anchored the pipe end (see photo on Page 3 of this Report). 7

9 7.0 ENVIRONMENTAL PROTECTION See Section REQUEST TO DECANT Direct piping of dredged sediment from the dredge to the Chetco ODMDS eliminated the need to decant, so this request was removed from the DDP. 9.0 DREDGE AREAS Description Table The following table presents the specific sub-areas within the basins and dock more generally named Basin 1, or North Basin ; Basin 2, or South Basin ; and the Ice House/Fuel dock Inlet. The volumes listed below were calculated from post-dredging depths as measured by the PE, shown on attached drawing entitled PORT OF BROOKINGS POST DREDGING VOLUMES, SHEET 1 OF 1. Area Map Name Estimated Volume Removed (yds. 3 ) Docks A - H Area Ice House/Fuel Dock Area Docks C-Q Areas 3 & PROTECTION AGAINST TURBIDITY-RELATED POLLUTANTS It was proposed that turbidity curtains not be utilized for this project. It was within the DDP noted that all licensed and very experienced operators who have proposed this project, including Dutra Group, Nehalem Dredging and Camenzind Dredging, submitted their proposals assuming, from their knowledge and experience, that hydraulic dredging to direct piping to disposal site does not produce enough turbidity to justify the traffic impedance and expense created by turbidity curtain use. However, conditions within the Permit required that a turbidity curtain be employed. Therefore, a turbidity curtain system was on-site throughout the entire project, and turbidity was measured as described in Section of this report. At no time did turbidity measurement readings exceed 15 NTUs, and 90% read between 5 and 10 NTUs WORKING HOURS Working hours for the duration of the project were 12 hours per day. 8

10 12.0 POSITIONING & PROGRESS SURVEYS When necessary in the judgment of the PE and dredge operator, controls were implemented as described in Section At minimum the Port utilized a survey rod and/or sonar depth finder system to measure and confirm that basin floor design depths had been obtained, but not exceeded. Used in conjunction with the US Coast Guard posted vertical reference marker, frequent measurements and recordings were used to assist. The marker is a tide gauge, or a tide board with markings in tenths of feet, posted near the Port basin entry from the Chetco River. Depth readings were recorded on existing contoured maps of the basin floors. The maps were updated as a result of depth measurements taken after the dredging of each area was completed. Some of these have been referenced and attached to this Report DREDGE NAVIGATION See above Sections and VESSEL TRAFFIC AND SECURITY The Port is a working facility and was able to coordinate with Port management on how to both avoid interference with vessel traffic and complete the project within the permitted time constraints. The Port notified the Coast Guard of activities as required to comply with Coast Guard and Port regulations guiding operations near the Chetco River PROTECTION OF PORT FACILITIES The facilities were returned to the identical condition at project completion as they are found to be at project outset. Sincerely, Jack Akin, MS, PE Environmental Management Consultants, Engineers/Scientists, LLC (on behalf of Port of Brookings Harbor, Oregon) 13 e:\emc\dataemc\pob\basins Dredge\FEMA Budget\Sediment\Regulation & Guidance\Correspondences\Benny Dean\post-tsunami DREDGING REPORT.pdf 9