Environmental Scientists and Engineers, LLC an … · Environmental Scientists and Engineers, LLC...

Environmental Scientists and Engineers, LLC

an ecology and environment company

820 16th Street, Suite 400 Denver, Colorado 80202 Phone (303) 573-5545 FAX (303) 573-5525

May 30, 2012 Mr. Mike Havens, P.E. Colorado Parks and Wildlife Rocky Mountain Region Office 361 32 Road P.O. Box 700 Clifton, Colorado 81520 RE: Highline Dredging Project – Site Characterization Letter Report, Highline Lake State Park, CO Dear Mr. Havens, Walsh Environmental Scientists and Engineers, LLC (Walsh) has prepared this letter report for Colorado Parks and Wildlife (CPW) to describe the activities and results related to the site characterization portion of the Highline Lake State Park Reservoir (Site) dredging project near Grand Junction, Colorado. The fieldwork was performed from April 16 through April 20, 2012. This letter report is a contract deliverable under Task 1 of the Statement of Work included as Exhibit A of the Professional Services Contract executed between Walsh and CPW on March 1, 2012. The work was done in general accordance with Walsh’s work plan dated April 5, 2012. A daily field report was prepared for each day in the field and is provided in Attachment A. Figure 1 shows a map of the Site identifying the three areas that were characterized: the Outlet Gate (OG) Area, the East Bay (EB) Area, and the potential Sediment Disposal (SD) Area. Walsh was assisted in the field by Mike Beardsley, P.E. of Green Globe Environmental, Inc. (GGE). GGE provided the boat and operator to perform the sonar surveying and sampling. Topographic Mapping All equipment and personnel were mobilized on Monday, April 16, hereafter referred to as Day 1. Single beam (Hydrolite) sonar mapping began on Day 1 in the OG Area. Sonar mapping of the EB Area was accomplished on Day 2. Topographical maps of the top of sediment for the OG and EB Areas are included as Figures 2 and 3, respectively. During the sonar mapping of the OG Area, CPW opened the outlet gate releasing bubbles to the surface that were used to map the location of the outlet gate structure. A topographical map of the SD Area was surveyed using conventional global positioning satellite (GPS) equipment on Day 5 and is included as Figure 4. Sub-bottom Profile Mapping Midway through Day 2, the process of setting up the BSS+ Sub-Bottom Profiler (hereafter referred to as the “BSS+”) began. The BSS+ performs a type of sonar survey that generates a profile (cross section) shows layers and other objects of different acoustical density. Numerous BSS+ profiles of the OG Area were obtained on Day 3. There was not enough water in the EB Area to operate the BSS+. The BSS+ was used to identify a bottom of sediment layer in the OG Area and to identify whether any significant sized debris (e.g., car bodies) is present in the

Mike Havens, P.E. Colorado Parks and Wildlife May 30, 2012


sediment. No significant debris was identified by the BSS+. An attempt was made to use the BSS+ profiles performed in OG Area to generate a bottom of sediment surface for the OG Area but due to acoustical interference from the face of the dam and the outlet structure, a discernible bottom of sediment figure could not be generated. Vibracore and Test Pit Sample Collection The second half of Day 3 was used to setup the coring equipment on the boat. Day 4 and the first half of Day 5 were spent obtaining core samples in the OG and EB Areas. The core samples were collected using a 3-inch diameter aluminum tube attached to a Vibracore sampling apparatus; which was attached to an A-frame and winch system mounted on the boat. The tube lengths were 20 feet for the OG Area and 10 feet for the EB Area. The Vibracore apparatus and tube are lowered into the water and sediment. The Vibracore operates by vibrating the core tube through the sampling media (e.g., sediment). The more consolidated or dense the material being sampled, the more time consuming and difficult it is to collect a sample. OG Area The work plan called for core samples to be attempted to be collected from five locations in the OG Area. Three of the five planned core samples were collected from the OG Area at the locations shown on Figure 2. The planned southwest core encountered refusal within the first two feet of coring. When the core was raised to the surface, it was discovered that the core tube had separated from the Vibracore. It is hypothesized that the core became wedged in the face of the dam and the attempt to remove it broke the core tube from the Vibracore. The core tube was left in the ground at the southwest location shown on Figure 2. It was decided that the southeast core would not be attempted to avoid a similar loss. The northeast (Sample OGNE), northwest (Sample OGNW), middle (Sample OGM) locations in the OG Area were all successfully sampled. A total of 9.5 feet of core sample was obtained in OGNE, 12.6 feet in OGNW, and 11.5 feet in OGM. The tubes were advanced until they couldn’t be vibrated any deeper. Sample OGNE did not penetrate the entire sediment thickness so at least 9.5 feet of sediment is present at that location. Samples OGNW and OGM showed 11.6 and 10.0 feet sediment present, respectively, for those locations. The BSS+ profiles correlated well with these depths. The native material noted in OGNW and OGM was observed to be a distinctive highly consolidated weathered shalestone or claystone. Logs and photographs of OGNE, OGNW, and OGM are included as Attachment B. The OG Area sediment generally consisted of 2-3 feet of very loose, highly saturated low plasticity silt and clay at the top. The sediment became less saturated and more consolidated (denser) with depth. The sediment was consistently very fine-grained in texture and generally grayish in color with varying interbedded layers of different shades of black, brown, and red. Plasticity appeared to vary throughout each core from low to high plasticity.



EB Area The work plan anticipated five core samples to be collected in the upper six feet of sediment in the EB Area. Four samples were attempted to be collected at the locations shown on Figure 3. In order for the Vibracore to effectively create the vacuum needed to capture the core samples, the Vibracore head needed to be completely submerged. The water in the majority of the EB Area was too shallow for this to occur. Thus no recovery was achieved at the EB1 location. The EB2 location resulted in only one foot of recovery. The EB3 location was in too shallow of water to even attempt to collect the sample. Only EB4 (7.2 feet) and EB5 (8.3 feet) resulted in substantial sediment recovery. Attachment C contains logs and photographs of the EB Area samples. The EB Area sediment generally consisted of 1-2 feet of very loose, highly saturated non-plastic silt at the top. The sediment became less saturated and more consolidated (denser) with depth. The sediment was consistently fine-grained non-plastic silt and generally dark brown in color with some interbedded layers of different shades of brown and black. SD Area Two test pits were excavated in the SD Area on Day 5 to collect geotechnical samples. The test pits were dug approximately 4-feet deep at the locations shown on Figure 4. The test pits consisted of white-gray weathered shale/silt with low moisture, little to no organics, and little to no gravel. Sample Analyses Agricultural, analytical and geotechnical tests were performed on OG and the EB Area sediment on two samples from each area. Soil classification tests were performed on both of the SD Area test pit samples. Composite laboratory specimens were collected from the entire length of the core or from a mixture of test pit spoil. The agricultural analyses are summarized on Table 1. The detected analytes are summarized on Table 2. The geotechnical analyses are summarized on Table 3. The individual laboratory test results are included as Attachment D. Agricultural Test Results Overall the sediment is described as “moderately suitable” as a vegetative growth medium. Salt levels are acceptable. The pH is somewhat high, but typical for that region and organic content is on the low end of acceptable. Both of these are manageable if compost can be added as an amendment and appropriate native plants are chosen. Available nutrients, especially nitrogen and phosphorus, are low and the high excess lime rating ties up the major and micro nutrients’ availability to plants. The small grain size of the sediment will be prohibitive to root growth, but could be mixed with larger grained (sandier) soils to make a more suitable grain size distribution. Analytical Test Results The only analyte of concern that was detected was arsenic of 2 and 1.9 mg/kg in the OG Area. The Colorado Soil Evaluation Value (CSEV) worker protection limit for arsenic is 1.6 mg/kg. However, background concentrations of arsenic in the area are consistent with the levels found in the analyses.


820 16th

Street, Suite 400 Denver, Colorado 80202 Phone (303) 573-5545 FAX (303) 573-5525

Geotechnical Test Results

The geotechnical tests showed the sediment to contain, not surprisingly, large percentages of fines. The OG Area contained over 99 percent fines with a majority of clay size particles. The EB Area contained over 97 percent fines with a majority of silt size particles. This means that the

OG area will cloud more heavily when the sediment is disturbed and take longer to clear than the EB area. The SD Area samples contained 70-80 percent fines and classified as a silt material.

Volume of Sediment to be Removed

The volume of sediment to be removed was estimated for both the OG Area and the EB Area by

generating an anticipated bottom of sediment removal surface and comparing it the top of sediment surface topography generated by the single beam sonar survey described above.

OG Area The top of the outlet gate structure was verified between the sonar data, the release by CPW, and

the sub-bottom profile information. This data was checked against the CPW as-built information to verify elevations and the outlet gate location and the surrounding area bottom of sediment

topography. A grading design was then developed for the OG Area assuming a circular area of sediment will be removed around the outlet gate. The sediment will be removed to the original dam face surface on the south side. All sediment will be removed in front of the outlet gate

within a 15-foot 180 degree arc around the north side of the outlet gate. Sediment outside the 15-foot radius would be sloped upward at an approximate 25 percent slope, which is assumed to

be the angle of repose of the sediment. The excavation topography is shown on Figure 5. The estimated volume of sediment to be removed in the OG Area is approximately 2,200 cubic yards.

EB Area For the EB area, it was assumed that an approximate 6-foot deep by 50-foot wide area of

sediment will be removed as shown on Figure 6. The angle of repose of the sides of the 50-foot wide removal area was again estimated as approximately 25 percent. The estimated volume of sediment to be removed in the EB Area is approximately 5,100 cubic yards.

Dredging Challenges

Several potential challenges will be faced by a dredging contractor. These include:

Removing sediment from above and around the outlet gate structure and its components without damage to the outlet gate and its appurtenances. This includes the air vent pipe

running from the structure to the top of the dam. Hand dredging of the sediment in direct contact with the outlet gate may be required.

Removing sediment from the required areas without additional sediment sloughing in.

Our estimated volumes assumed an average stable angle of repose of 25 percent (4:1) of the sediment slope based on the amount of consolidation seen in the core samples, Mr.

Beardsley’s experience, and our research. In reality, this angle of repose may vary



Enclosures: Table 1 – Agricultural Analyses Summary Table 2 – Chemical Analyses Summary Table 3 – Geotechnical Analyses Summary Figure 1 – Overall Area Map Figure 2 – Outlet Gate Area Top of Sediment Topography Figure 3 – East Bay Area Top of Sediment Topography Figure 4 – Disposal Area Surface Topography Figure 5 – Outlet Gate Area Bottom of Sediment Removal Topography Figure 6 – East Bay Area Bottom of Sediment Removal Topography Attachment A – Daily Field Reports Attachment B – Outlet Gate Area Core Logs and Photographs Attachment C – East Bay Area Core Logs and Photographs Attachment D – Laboratory Test Results

Analyte EB5‐120420 EB4‐120420 OGM‐120419 OGNW‐120419

1:1 Soil pH 8.3 8.2 8.3 8.2

WDRF Buffer pH 7.2 7.2 7.2 7.2

1:1 S Salts mmho/cm 0.35 0.38 0.57 1.03

Excess Lime HIGH HIGH HIGH HIGH

Texture No 2 2 2 2

Organic Matter LOI % 2 2.3 1.7 2

Nitrate‐N ppm N 0.4 0.3 0.5 0.4

lbs N/A 1 1 2 2

Potassium ppm K 121 106 245 210

Sulfate‐S ppm S 15 20 35 42

Zinc ppm Zn 2.65 3.53 3.48 3.46

Iron ppm Fe 215.3 220 269 256.2

Manganese ppm Mn 13.5 15.9 23.2 22.4

Copper ppm Cu 5.55 4.94 8.17 7.07

Calcium ppm Ca 4278 4152 4616 4601

Magnesium ppm Mg 412 345 693 583

Sodium ppm Na 121 130 180 168

Boron ppm B 0.81 0.86 0.65 0.59

CEC/Sum of Cations 25.7 24.5 30.3 29.1

%H Sat 0 0 0 0

%K Sat 1 1 2 2

%Ca Sat 83 85 76 78

%Mg Sat 13 12 19 17

%Na Sat 2 2 3 3

Mehlich P‐III ppm P 6 7 2 2

Loaction

Table 1

Agricultural Analysis

Highline State Park

Sediment Characterization

CSEV

Analyte EB5‐120420 EB4‐120420 OGM‐120419 OGNW‐120419 Detection Limit Units Method Worker

pH 6.9 6.9 7.4 7.2 su 9045D

Mercury BDL BDL 0.024 0.021 0.02 mg/kg 7471 160

Arsenic 1.1 1.3 2 1.9 1 mg/kg 6010B 1.6

Barium 130 140 100 86 0.25 mg/kg 6010B 160000

Cadmium 0.46 0.47 BDL BDL 0.25 mg/kg 6010B 770

Chromium 9.4 9.4 16 14 0.5 mg/kg 6010B 1500000

Lead 12 11 13 12 0.25 mg/kg 6010B 800

Location Result

Table 2

Chemical Analysis

Highline State Park


Analysis EB2‐120420 EB5‐120420 EB4‐120420 OGM‐120419 OGNW‐120419 SDN‐120420 SDS‐120420

Liquid Limit 41 34 35 51 55 41 35

Placticity Index 14 9 8 22 25 11 10

USCS Classification ML CL ML CH CH s(ML) s(ML)

AASHTO Classisification A‐7‐7(16) A‐4(10) A‐4(9) A‐7‐6(27) A‐7‐6(30) A‐7‐6(8) A‐4(7)


Location Result

Table 3

Geotechnical Analysis

Highline State Park

Approximate Property Lines

Areas of Interest

East Bay Area

Highline Lake

State Park Headquarters

Township 2 North,

Range 3 West,

Section 5

Sediment

Disposal Area

Outlet Gate Area

Utah

Colorado

Site

0500'

100'500'

Figure 1

Project Number:

WA-001680-0001-10

Drawn By:

KDW

Engineer:

BC

NO. DATE REVISION BY CHK

SCALE

Walsh Environmental Scientists and Engineers

4888 Pearl E. Circle, Suite 108

Boulder, CO 80301-2475 USA

P 303.443.3282 F 303.443.0367

Date:

05/18/12

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Area of Interest

Legend

NTS

Contour Major

Contour Minor

Limits of Survey

Outlet Gate Piping

(approximate)

Core Sample Location and Label

040'

80'40'

Figure 2

Project Number:

WA-001680-0001-10

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Outlet Gate Area

Top of Sediment

Topography

Green Globe Environmental

6206 Jefferson Avenue

Denver, Colorado 80235

P (720) 838-7107

Legend

Notes:

1) Topography depicts top of sediment surface contours.

2) Top of Sediment surface contours obtained using Hydrolite

single beam sonar operating at 200kHz.

3) Top of Sediment sonar survey performed by Green Globe

Environmental Inc. on 4/17/12.

4) The outlet gate elevation is approximately 4648.2 feet.

Approximate spillway elevation is 4703.7 feet.

5) Three core samples were obtained as shown hereon. One

core location was not sampled and the last was lost during

the coring. Approximate locations are shown hereon.

060'120'

60'

Figure 3

Drawn By:

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Engineer:

BC


SCALE




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East Bay Area

Top of Sediment

Topography

Legend

Project Number:

WA-001680-0001-10




P (720) 838-7107

Notes:


2) Top of Sediment surface contours obtained using

Hydrolite single beam sonar operating at 200kHz.

3) Top of Sediment sonar survey performed by Green

Globe Environmental Inc. on 4/17/12.

4) Approximate spillway elevation is 4703.7'.

Test Pit

Contour Major

Contour Minor

Limits of Survey

Hiking Trail

060'120'

60'

Figure 4

Drawn By:

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Engineer:

BC


SCALE




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Disposal Area

Surface Topography

Legend

Project Number:

WA-001680-0001-10

Notes:

1) Disposal Area contours obtained using survey

grade RTK GPS.

2) Disposal Area Topographic survey was performed

by Walsh Environmental on 4/20/12.

3) Elevations are based on NAVD 88.

Existing Contour Major

Existing Contour Minor

Limits of Survey

Lost Core Sample Location and Label

Design Contour Major

Design Contour Minor

040'

80'40'

Figure 5

Project Number:

WA-001680-0001-10

Drawn By:

KDW

Engineer:

BC


SCALE




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Outlet Gate Area

Bottom of Sediment

Removal Topography




P (720) 838-7107

Legend

Notes:


2) The outlet gate elevation is approximately 4648.2 feet.

Approximate spillway elevation is 4703.7 feet.

3) All underground features are approximated hereon.

Base Surface Comparison Surface Cut

Top of Sediment Removal Design 2,200 Cu. Yd.

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50'

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060'120'

60'

Figure 6

Drawn By:

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Engineer:

BC


SCALE




P 303.443.3282 F 303.443.0367

Date:

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East Bay Area

Bottom of Sediment

Removal Topography

Legend

Project Number:

WA-001680-0001-10




P (720) 838-7107

Notes:

1) Additional topography shown outside the 'Limits of

Survey' was provided by Mike Havens in an email dated

March 26th, 2012 in a CAD file titled 'HiData20 highline

Topography 07-27-00.dwg .

Base Surface Comparison Surface Cut

Top of Sediment East Bay Design 5,100 Cu. Yd.

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