FINAL MARINE GEOPHYSICAL INVESTIGATION MARINE OUTFALL

Marine Geophysical Investigation

Final; March 2001

FINAL

MARINE GEOPHYSICAL INVESTIGATION

MARINE OUTFALL SITING STUDY

March 2001

Submitted to:

King County Department of Natural Resources201 South Jackson StreetSeattle, Washington 98104

Submitted by:

Golder Associates18300 NE Union Hill Road, Suite 200Redmond, WA 98052-3333

Parametrix, Inc.5808 Lake Washington Blvd. NE, Suite 200Kirkland, WA 98033-7350


Final; March 2001 ii

Table of Contents1.0 INTRODUCTION 1

2.0 REGIONAL AND GEOLOGIC SETTING 3

3.0 METHODOLOGY, INSTRUMENTATION AND FIELD OPERATIONS 4

3.1. Survey Vessel 4

3.2. Navigation 4

3.3. Instrumentation 5

3.3.1 Precision Echosounder 5

3.3.2 Side Scan Sonar Instrumentation 5

3.3.3 Subbottom Profiler (SBP) and Seismic Reflection Instrumentation 6

3.4. Survey Coverage 7

4.0 DATA ANALYSIS AND SELECTION CRITERIA 8

5.0 RESULTS OF GEOPHYSICAL DATA INTERPRETATION 10

6.0 SUMMARY AND CONCLUSIONS 12

7.0 ADDENDUM: POST EARTHQUAKE SURVEY 13

7.1. Site 1 13

7.2. Site 8 13

LIST OF TABLES

Table 1 Summary of Site Characteristics

LIST OF FIGURES

Figure 1 Survey Site Location Map

Figure 2 Interpreted Seismic Stratigraphy (1A, 2A)



Figure 5 Interpreted Seismic Stratigraphy (7A, 7B)


Final; March 2001 iii

Figure 6 Interpreted Seismic Stratigraphy (7C, 7D)

Figure 7 Interpreted Seismic Stratigraphy (8A, 8B)

LIST OF SHEETS

Sheet 1 Tracklines

Sheet 2 Bathymetry

Sheet 3 Bathymetry North Region

Sheet 4 Bathymetry South Region


Final; March 2001 1

1.0 INTRODUCTION

In November of 1999, the Metropolitan King County Council approved theRegional Wastewater Services Plan, a $1.2 billion plan to upgrade King County’sexisting wastewater system. Included in this plan is the construction of a newregional wastewater treatment plant somewhere in northern King or southernSnohomish County. The new treatment plant will have a marine outfall todischarge treated effluent to Puget Sound. This report presents the results of themarine hydrographic and geophysical investigation conducted in July and August2000, to assist the Department of Natural Resources of King County in theselection of a site for the proposed marine outfall. This report is not intended tobe the only report to aid decision-makers in finding a suitable location for themarine outfall; geophysics is one part of a comprehensive Marine Outfall SitingStudy (MOSS) being conducted by King County.

The area of geophysical investigation is located on the eastern shore of PugetSound between Pt. Partridge to the south and the entrance to Possession Soundnear Mukilteo to the north; a distance of 14 miles (Figure 1). The onshoreboundary was the 20-foot depth contour and the offshore boundary was thebottom of the slope, 600-foot depth contour, a distance of approximately 4,000 to5,000 feet. The study area was selected as that area within which the marineoutfall seemed likely to be sited based on current knowledge at the time thegeophysical investigation was conducted. The study area for other aspects of theMOSS extends to the north, south and west of the geophysical investigationstudy area.

The overall objective of the geophysical survey was to provide detailedcharacterization of the physical features of the sea floor and the subsurfacegeology. This information was used to identify and recommend a number ofpotentially acceptable sites, based on engineering/geophysical considerations, forthe placement of the marine outfall and diffuser. The specific objectives of thehydrographic and geophysical investigation were to:

• Identify a number of alternative corridors, or sites, for the marine outfall,having gradual slopes and consistent and regular contours.

• Locate relatively flat zones for placement of a diffuser.

• Characterize the lateral and vertical extent of the surficial sediment andsubsurface geology.

• Identify possible surficial and subsurface geohazards, or geologic conditions,that might impact the construction or operation of the outfall and diffuser.

The geophysical methods used to accomplish these objectives included:

• Precision single and multibeam echosounding;

• Side scanning sonar;


Final; March 2001 2

• Subbottom profiling;

• High-resolution seismic reflection profiling; and,

• Deep-penetration seismic reflection profiling.

This report presents:

• An overview of the regional and geologic setting of the geophysicalinvestigation area;

• A description of the methodology, instrumentation and field operations;

• Data analysis and site selection considerations;

• Results of the geophysical data interpretation; and,

• Summary and conclusions.


Final; March 2001 3

2.0 REGIONAL AND GEOLOGIC

SETTING

The geomorphology and geology of the Puget Sound region has been shaped bythe advance and retreat of the Cordilleran Ice Sheet. The Puget Lobe of thisglobal glaciation advanced and retreated at least four times the most recent beingthe Frazer Glaciation approximately 10,000 years ago. The advances and retreatsof this ice sheet, 1,000 to 3,000 feet thick, resulted in the erosion, transportation,and deposition of massive amounts of rock and sediment. Following the lastretreat of the Puget Lobe sea level rose and marine waters filled the scouredchannels and troughs. The combination of glacial and marine processes hasresulted in the accumulation of glacial, riverine, deltaic, lacustrine, and marinedeposits over nearly all of the Puget Lowlands. The stratigraphy and geologyresulting from these events consist of recent deposits of fine- to medium-grainedmarine sediment overlying medium-grained glacial outwash sediment andcoarse-grained glacial till. Other glacial and post-glacial features within thesedeposits include buried stream channels, cobbles and large boulders, and lateralvariations in sediment types.

Geophysical surveys have shown that from 800 to 1500 feet of post-glacialdeposits partially fill the original scour depression created by the Puget Lobe.This accumulation of sediment, the surface of which forms the floor of PugetSound, has resulted in considerable modification of the original scour surfacecreated by the southward moving ice. In some places, the unconsolidated post-glacial sediment fill, as well as the older glacial deposits along the margins of thebasin have been involved in slope failures and submarine landslides. Locatingthese areas of possible slope instability was of particular interest in thisinvestigation.


Final; March 2001 4

3.0 METHODOLOGY,

INSTRUMENTATION AND

FIELD OPERATIONS

The investigation used several marine acoustic instruments to obtain bathymetric,surface and subsurface geologic information. The selection and operatingparameters of the instruments varied depending on the survey area (shallow ordeep water) and the information required. However, during most of theinvestigation, the three primary acoustic systems; the echosounder, thesubbottom profiler (SBP), and the seismic reflection system; were operatedsimultaneously. The side scan sonar was run with the multibeam echosounderand high-energy seismic reflection system was run on selected transects parallelto the slope.

3.1. Survey Vessel

The geophysical instruments were installed on the research vessel R/VHydrohawk, operated by CRA Northwest, Lynnwood, Washington. The vessel isoutfitted with transducer mounts, cable deployment systems, and a geophysicalinstrument lab specifically designed for conducting multi-system marinegeophysical investigations. Mobilization of the survey vessel was done at theEdmonds Marina, Edmonds, Washington. When the installation of theequipment was completed, a test and calibration run was conducted outside of themarina. The backup navigation and geophysical instruments were also tested atthis time.

During the duration of the geophysical survey, no time was lost because ofequipment malfunctions or adverse weather or sea conditions.

3.2. Navigation

The position of the survey vessel was determined with differential globalpositioning system (dGPS) using the Omni Star satellite to provide differentialcorrections. The navigation data were acquired with a Trimble Model Ag132dGPS interfaced with CRA-NW HP navigation software. The shipboard receiverand navigation software provided differentially corrected WGS 84 latitude andlongitude values every second with sub-meter accuracy. WGS 84 positions wereprojected in real-time to Washington North, Zone 4601, in US feet. The positionof the survey vessel was plotted on a vessel track plot and displayed in real-timeon a color monitor that also provided additional navigation parameters to thehelmsman. This display enabled piloting the survey vessel along predeterminedsurvey lines. In addition, this system made it relatively easy to relocate the


Final; March 2001 5

vessel in areas of interest and run additional lines. This capability was used on anumber of occasions when preliminary analysis of the data identified areas ofconcern. The navigation system transmitted a fix or event mark to the seismicrecorders and digital acquisition system at a fixed time interval providing a timeand geographical reference for the data.

3.3. Instrumentation

3.3.1 Precision Echosounder

Precision bathymetric data were acquired with an Odom Echotrack precisionechosounder. A Reson Model 9001 multibeam echosounder was used to obtainswath bathymetric data. This system generates 60; 1.5-degree acoustic beams ina fan-shaped pattern that is perpendicular to the survey trackline. The width ofthe footprint, or area of coverage on the sea floor, is equal to two times the waterdepth. The single-beam depth data were displayed on an analog recorder andacquired digitally on the navigation computer. The multibeam depth data weredisplayed on a color monitor and recorded digitally on the Reson digitalacquisition system.

A SeaTec model MRU-5 heave, pitch, and roll compensator was interfaced to thenavigation computer to correct the depth data for motion of the transducer due toswells and waves. Vessel heave, roll, and pitch motion data, recorded at a rate of5 times per second, were used to correct the depth measurements during post-processing. In addition, a KVH-1000 continuously calibrating fluxgate compasswas used to provide heading information. Calibration of the echosounder wasdone using a standard bar check. The velocity of sound in seawater, determinedwith the bar-check and the transducer draft were entered into the echo sounderprocessor. During final data processing the soundings were reduced to depthsbelow mean lower low water (MLLW) using data acquired from the NOAA tidegauges located in Elliott Bay, Seattle and Port Townsend, Washington.

3.3.2 Side Scan Sonar Instrumentation

The surficial features of the sea floor were mapped with an EdgeTech ModelDF-1000 side scan sonar. This system produces a plan view image of the seafloor to the left and right of the survey trackline. Reflections from targets orfeatures on the sea floor appear as shades of varying intensity (white to black) onthe sonogram record. High intensity reflections (dark image on the sonogram)represent coarse-grained material, such as cobbles, boulders, or rock outcrop.Low intensity reflections (light gray to white) represent fine-grained sediment,such as silt and fine sand. Eelgrass, or other macrophytes, produces acharacteristic pattern that is quite distinctive from the acoustic signature or imageproduced by sediment, cobbles and rock, or cultural artifacts. Additional featuresthat can be identified on side scan sonar data as possible geohazards aresubmarine slides, faulting, and localized zones of subsidence.

Depending on the depth of the water, and the frequency of the transducer selected(100 kHz or 500 kHz), the graphical display was set for a swath width that variedfrom 450 to 600 feet. The data were displayed on an EPC Model 1086 graphic


Final; March 2001 6

recorder and archived on a Sony Model PC208A DAT recorder. The graphicaland digital recording systems were interfaced with the shipboard navigationsystem that placed event mark on the data at 20-second intervals.

3.3.3 Subbottom Profiler (SBP) and Seismic ReflectionInstrumentation

Subbottom and seismic reflection profiling use acoustic pulses, emitted at regularintervals by a transducer or energy source, to image subsurface strata or geologicfeatures. The acoustic pulses, or sound waves, are reflected from the sea floorand underlying geology or sediment layers. The reflected signals are received bythe transmitting transducer (subbottom profiler, SBP) or a surface-towedhydrophone (high-resolution seismic reflection profiler) and converted intoelectrical signals. The electrical signals are processed and then displayed, in realtime, on a graphic recorder. This display, the subsurface reflection record, is anacoustical profile of the sea floor and subbottom stratigraphy, or sediment layers,along the survey trackline.

Information on the shallow subsurface sediments was obtained with a DatasonicModel 5000 SBP, interfaced with two 5 kHz transducers. The transducer arraywas mounted on the port side of the vessel immediately opposite of thenavigation antenna. The data were processed using time variable gain amplifiersand displayed on an EPC Model 1086 thermal graphic recorder and archived on aSony DAT recorder. Position fixes were marked on the record at a 20-secondinterval.

In fine-grained sediment (silt and clay) this system provided subsurfaceinformation to a depth of 5 to 15 feet. Subsurface penetration was limited in thenearshore, shallow water areas by the presence of coarse-grained sediment. Onthe slope and in deep-water subsurface penetration increased to a maximum of 30feet.

A Datasonic Model 1200 Bubble Pulser seismic reflection system was used toobtain deeper subsurface penetration in the marine and glacial sediment as wellas through coarse-grained sediment in the nearshore area that could not bepenetrated by the SBP. The maximum subsurface penetration observed on thedata was approximately 600 feet. In some nearshore areas, subsurfacepenetration was limited to several feet by the presence very coarse-grainedsediment.

An Applied Acoustic Engineer CSP 2000 power supply, using a sparkertransducer, was used for deep subsurface penetration. This instrument haslimited resolution in the near surface but was able to achieve up to 1000 feet ofpenetration. The primary objective of this system was to detect possible faults inthe deeper, more competent sediment.

The acoustic energy sources were towed astern from the port side and thehydrophone receiver was towed astern from the starboard side. The data wereprocessed and filtered (band-pass 450 to 1000 Hz, and 100 to 800 Hz) and thendisplayed on an EPC Model 1086 graphic recorder and archived on a Sony DAT


Final; March 2001 7

recorder. The graphic record was annotated by the navigation system at a 20-second interval.

3.4. Survey Coverage

The primary survey transects ran perpendicular to the shoreline from as shallowof water as possible to the base of the slope (Sheet 1). The interval betweentransects varied from 200 to 400 feet. A secondary set of transects ran parallel tothe slope; the interval between these lines was also 200 to 400 feet. A total of250 miles of primary transects and 65 miles of secondary transects werecompleted for this investigation.

The quality of the data ranged from very good to excellent. The poorest qualitydata resulted during the late afternoons when wave conditions increased orbecause of acoustic noise from passing survey vessels. Both events occurred forperiods of less than 1 hour each day.


Final; March 2001 8

4.0 DATA ANALYSIS AND

SELECTION CRITERIA

The following QA/QC procedures were undertaken prior to analysis andinterpretation of the data.

• Editing of the trackline data, and correcting for position errors.

• Editing of the bathymetric data, correcting for sound velocity and forchanges in elevation due to tides.

• Plotting the bathymetric soundings and checking for errors in depths at linecrossings.

• Reprocessing and replaying of selected side can sonar, subbottom profiler,and seismic reflection data.

Upon completion of these QA/QC steps a set of geophysical criteria were usedfor identifying regions or zones that would possibly be acceptable for routing apipeline and locating a diffuser. Site selection considerations, referred to as“detailed evaluation questions” (DEQs) were developed for each aspect of theMOSS project to ensure that sufficient data were available to support policycriteria approved by the Metropolitan King County Council. These DEQs weredeveloped at a number of meetings with the King County marine outfall sitingteam. The DEQs addressed bathymetric conditions, potential geohazards such assubmarine slides, faults, and sediment type. Using these DEQs, a number of siteswere identified that are potentially acceptable pipeline corridors or diffuser sites.In summary, the engineering/geophysical DEQs considered the followingconditions as being potentially acceptable.

• Gradual slope of less than 20° (30%) for pipeline corridor.

• Diffuser sites with 2° (3%) slope or less in water depth of greater than 100feet.

• Consistent and regularly spaced bathymetric contour lines.

• Sand and gravel sediment.

• No evidence of recent slides, slumping, subsidence or shallow faulting.

• No evidence of buried channels or lateral changes in stratigraphy that mightimpact directional drilling in the nearshore area.

The bathymetry data were evaluated first since the bathymetric criteria have thegreatest significance for selecting acceptable pipeline corridors and diffuser sites.Furthermore, the high density, detailed bathymetric data made this evaluation a


Final; March 2001 9

relatively time efficient task since contour maps of the slope angles could beproduced and irregular contours were easily identified.

The side scan sonar data were then analyzed for evidence of geohazards, unusualsediment conditions (large boulders for example), and the presence of culturalartifacts (cables, miscellaneous debris, sunken vessels, etc.). The results of thebathymetric and side scan sonar analysis were used to select the most likely areasor regions for pipeline corridors and diffuser sites.

Finally, the SBP and the shallow and deep seismic reflection data were analyzedin the areas that had been found potentially acceptable based on the bathymetricand side scan sonar data. These data were analyzed for the presence of fine-grained sediment, geohazards such as active or potential slumps, buried channels,and faulting.

The result of this lengthy analysis and evaluation process was the identificationof eight sites that at present meet the geophysical/engineering DEQs forplacement of a pipeline and diffuser. The general locations of these sites areshown on Sheets 1 and 2. Sheets 3 and 4 show the detailed bathymetry for eachsite. Also shown on these sheets are the locations of the interpreted geologiccross sections that are presented in Figures 2 through 6.


Final; March 2001 10

5.0 RESULTS OF GEOPHYSICAL

DATA INTERPRETATION

This section summarizes the geophysical/geological characteristics of each of thecorridors that are considered potentially acceptable based on thegeophysical/engineering DEQs. The location and associated bathymetry for eachcorridor are shown on Sheets 2 through 4. Representative interpreted geologicsections (technically seismic sections or seismic stratigraphy), based on theseismic subbottom and reflection data, for each of the eight sites are presented inFigures 2 through 7. Sites 7 and 8 have several interpreted cross-sectionsbecause of the possibility for several pipeline routes and diffuser locations. Onthese figures the recent, marine deposited, medium-grained sediment are shaded,and the glacial and glacio-marine sediment have a pattern. The sub-horizontal tohorizontal lines within the deeper sediment represent continuous to discontinuoussediment contacts or horizon identified on the reflection data. These interpretedsketches are intended to be representative of the general characteristics of eachzone. Although not stated in Table 1, it should be noted that there was noevidence of shallow or deep faults, or active slumping at the 8 sites which wouldhave precluded their being included as prospective outfall corridors.



TABLE 1Summary of Site Characteristics

SiteBathymetry Diffuser Site Geophysics/Geology

1Depth 10 to 600 feet; slope9° (16%) consistent slope,several minor slope changes.

.5° (<1%), 20 to 50 feet,fine-grained sediment,4,000 feet offshore.

5 to 10 feet fine to medium grainedsediment on upper slope, nofaulting or slides.

2Depth 10 to 525 feet; slope8.5° (15%), regular andconsistent contour lines.

.5° (<1%), 20-30 feet fine-grained sediment, 2000 feetoffshore.

10 feet medium-grained sedimenton slope. No slump features orfaults.

3Depth 10 to 450 feet and to525 feet, slope angle varies,maximum 12° (20%).

Two sites 8° (1.5%), slope,10 to 15 feet fine-grainedsediment, 4,000 feetoffshore.

10-15 feet medium grainedsediment on upper slope; 10-15feet fine-grained sediment atdiffuser sites.

4Depth 10-475 feet, smooth,continuous and uniformslope of 12° (20%).

.8° (< 1.5%) 10-15 feetfined-grained sediment,3,500 feet offshore.

10-15 feet medium-grainedsediment on upper and mid slope,10-20 feet fine-grained sedimentlower slope.

5Depth 10-420 feet,maximum slope 13° (22%),broad flat shelf, consistentslope.

1° (<2%), 20 feet fine-grained sediment, 4,000feet offshore.

15-20 feet medium-grainedsediment on shelf; glacial sedimenton slope.

6Depth 10-570 feet, slope 11°(20%), consistent, uniformcontours.

1° (<2%), 15-20 feet fine-grained sediment, 3,000feet offshore.

30-50 feet medium-grainedsediment on shelf, 5 to 10 feet onupper, mid and lower slope.

7ADepth 10-120 feet, slope 3°(5%), shallow depth, veryregular contours, broadshelf.

2° (<3%), medium-grainedsediment, 1,700 feetoffshore.

< 5 feet medium-grained sediment

7BDepth 10-600 feet, slope(9°) (15%), uniform andconsistent contours.

.5° (<1%), 15 feet fine-grained sediment, 4,300feet offshore.

20-40 feet medium-grainedsediment on upper slope.

7CDepth 15-280 feet, slope 8°13%, broad shelf, uniformand consistent contours.

1.5° (<3%), 5 feet fine tomedium-grained sediment,2,500 feet offshore.

10-20 feet sediment on midslope

7DDepth 10-600 feet, slope 12°(22%), relatively steep butconsistent and regularcontours.

1° (<2%), 10 to 15 feetfine-grained sediment,3200 feet offshore

10-20 feet medium-grainedsediment on upper and midslope.

8ADepth 10 to 400 feet,maximum slope 11° (18%),more gradual upper slope.

.5° (<1%), medium-grainedsediment, 3,000 feetoffshore.

20 feet medium-grained sedimenton upper slope.

8BDepth 75-600 feet, slope, 9°(16%), gradual upper slope,steepens offshore, consistentcontours in each region.

Two sites, .5° (<1%), 20-40 feet fine-grainedsediment, 2,500 and 5,500feet offshore.

10 to 20 feet sediment on upperslope.



6.0 SUMMARY AND CONCLUSIONS

Over 300 miles of marine bathymetric, side scan sonar, subbottom profiler, andseismic reflection data were acquired along the eastern shoreline of Puget Sound.The 14-mile long geophysical investigation study area is located between Pt.Partridge to the south and Mukilteo to the north. The offshore boundaryextended to the base of the slope a distance of approximately 4,000 to 5,000 feet.

The bathymetric and geophysical data were used to map the water depth,characterize the seabed sediment, identify possible geohazards such as submarineslide, faulting, or zones of subsidence, and locate existing cables or other culturalartifacts. This information was used to select possible alternative sites for thelocation of the proposed Brightwater Marine Outfall and Diffuser.

Based on the geophysical and bathymetric data eight sites were identified thatmeet the DEQs to be considered potentially acceptable sites for the outfall anddiffuser. The DEQs used to considered a site to be acceptable were:

• There was no evidence of faults, or submarine slides.

• The bathymetry was gradual and continuous.

• The slopes were less than 12° (20%) for the outfall and 2° (3%) at thediffuser site and water depths of greater than 100 feet.

• The sediment on the slopes should be predominantly sand with no silt.

• No evidence of buried channels in the nearshore area.

It is recommended that after the final proposed route has been selected that thegeophysical data within the selected area or areas be carefully reviewed. It isalso recommended that sediment sampling and a video survey be performedalong the proposed route, particularly along the steepest slopes, for visualevidence of possible unstable conditions.



7.0 ADDENDUM: POST

EARTHQUAKE SURVEY

Following the February 28th earthquake a reconnaissance hydrographicand subbottom survey was conducted within the eight potential pipelinecorridors areas. A profile was run along the location of the interpretedseismic stratigraphic sections (Figures 3 and 4) and also approximately 150feet north and south.

There was no evidence on the bathymetric or subbottom reflection datathat suggested a condition of slope failure in the potential sites with theexception of Sites 1 and Site 8.

7.1. Site 1

On the transect located 100 feet south of the interpreted seismic section(see Figure 3) there is evidence of a possible submarine slide. On thebathymetric and subbottom data, a mound of sediment, located in 375 feetof water, is present on the seabed. This feature was not observed duringthe initial survey.

7.2. Site 8

On the transect located along the interpreted stratigraphic sections (see Figure 4)there is evidence of a slope failure at a depth of 550 feet. On the bathymetric andsubbottom data, it appears that a deposit of sediment, observed on the earlierprofiles at a depth of 520 feet, has moved downslope.


Final; March 2001

FIGURES

PROJECT NO. 003 1139.200 DRAWING NO. 92541 DATE 2/06/01 DRAWN BY ETF

FIGURE 1SURVEY SITE

KING COUNTY/BRIGHTWATER GEOPHYSICS/WA

Golder Associates

Survey Site

PROJECT NO. 003 1139.200 DRAWING NO. 92537 DATE 02/07/01 DRAWN BY JSR

FIGURE 2INTERPRETED SEISMIC STRATIGRAPHY

KING COUNTY/BRIGHTWATER/WA

Golder Associates

1A 1A’0

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Fine to MediumGrained Sediment

Semi-consolidated GlacialMaterial (sand, gravel, clay?)

LEGEND

See Sheet 1 for Location

Vertical Exaggeration 5:1




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Final; March 2001

SHEETS

Site 8

Site 7

Site 6

Site 5

Site 4

Site 3

Site 2

Site 1

SR 104

SR 99

SR 525

SR 524

Holman Rd NW

N 85th St

N 130th St

Auro

ra A

ve N

NE 175th St

.-,5Edwards

Point

PointWells

PicnicPoint

Snohomish CountyKing County

PointJefferson

PresidentPoint

Apple CovePoint

PossessionPoint

Whidby Island

Mukilteo

EdmondsFerry Terminal

RichmondBeach

Loyal HeightsMeadow

Point

P U

G E

TS O

U N

D

POSSE

SSION

SOUND

Norma Beach

1240000

1240000

1250000

1250000

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2600

00260000

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00350000

Legend

3000 0 3000 6000 Feet

0.5 0 0.5 1 Miles

Projection: Washington State Plane, North ZoneUnits: Feet Datum: NAD83

Scale: 1" = 3000'

TRACKLINES

SHEET 1

BRIGHTWATERGEOPHYSICS / WAH:\Projects\003-1139\apr\potential_pipe_corr_map.apr 12Mar01 GE

Bathymetric Survey TracklinesPotential Pipeline CorridorSee sheets 3 - 4 for details

County BoundaryShoreline

FreewaysMajor Roads

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Site 1

SR 104

SR 99

SR 525

SR 524

Holman Rd NW

N 130th St

Auro

ra A

ve N

NE 175th St

.-,5Edwards

Point

PointWells

PicnicPoint

Snohomish County

-500

-400

-300

-200

-100

King County

PointJefferson

PresidentPoint

Apple CovePoint

PossessionPoint

Whidby Island

Mukilteo

EdmondsFerry Terminal

RichmondBeach

Loyal HeightsMeadow

Point

P U

G E

TS O

U N

D

POSSE

SSION

SOUND

Norma Beach

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BATHYMETRY

SHEET 2

BRIGHTWATERGEOPHYSICS / WA

H:\Projects\003-1139\apr\potential_pipe_corr_map.apr 12Mar01 GE

Risk AreasHigher- Slope > 20 degrees- Irregular Contours

- Possible Unstable Sediments- Buried Channels

- Evidence of Submarine Slides or Faults

Potential Pipeline Corridor- Slope < 20 degrees- Smooth, Straight Contours- No Evidence of Submarine Slides or FaultsPotential Diffuser Site- Slope < 2 degrees


FreewaysMajor Roads

NOAA Puget Sound Bathymetry100 Ft Contours20 Ft Contours

Bathymetric Contours - Surveyed100 Ft Contours20 Ft Contours

3000 0 3000 6000 Feet

0.5 0 0.5 1 Miles


Scale: 1" = 3000'

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See Figure 3

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Whidby Island

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3350

00335000

Legend

NORTH REGION

SHEET 3







# #A A'

Location of Interpreted SeismicStratigraphy. See Figures 2 - 7and Sheets 3 - 4.


FreewaysMajor Roads



1000 0 1000 2000 Feet

0.25 0 0.25 Miles


Scale: 1" = 1000'

BATHYMETRY

#

#

#

#

# #

#

#

#

#

#

#

#

#

#

#

-500

-400 -30

0

-200 -10

0

Site 8

Site 7

Site 6

Site 5See Figure 4

See Figure 4

See Figure 5

See Figure 5

See Figure 6

See Figure 6

See Figure 7

See Figure 7

5A

5A'

6A

6A'

7A 7A'

7B'

7B 7C'

7C

7D'

7D

8A

8A'

8B'

8B

SR 104

EdwardsPoint

PointWells

Snohomish County

King County

Edmonds

Ferry Terminal

RichmondBeach

P U

G E

TS O

U N

D

1250000

1250000

1255000

1255000

1260000

1260000

1265000

1265000

2800

00280000

2850

00285000

2900

00290000

2950

00295000

3000

00300000

3050

00305000

Legend

SOUTH REGION

SHEET 4







# #A A'

Location of Interpreted SeismicStratigraphy. See Figures 2 - 7and Sheets 3 - 4.


FreewaysMajor Roads



1000 0 1000 2000 Feet

0.25 0 0.25 Miles


Scale: 1" = 1000'

BATHYMETRY

Documents

FINAL MARINE GEOPHYSICAL INVESTIGATION MARINE OUTFALL