06_South 18th Avenue Sanitary Sewer Exploration Report.pdf

Soilogic, Inc.

3522 Draft Horse Court • Loveland, CO 80538 • (970) 535-6144

March 28, 2024

Professional Engineering Consultants 351 Linden Street, Suite 100 Fort Collins, Colorado 80524

Attn: Kent Bruxvoort, P.E.

Re: Geotechnical Subsurface Exploration Report Proposed Sanitary Sewer Line South 18th Avenue, between S. Bridge Street & E. Egbert Avenue Brighton, Colorado Soilogic Project # 24-1018

Mr. Bruxvoort:

Soilogic, Inc. (Soilogic) personnel have completed the geotechnical subsurface exploration you requested for the proposed sanitary sewer line to be constructed on S. 18th Avenue between S. Bridge Street & E. Egbert Avenue in Brighton, Colorado. The results of our subsurface exploration and pertinent geotechnical engineering recommendations are included with this report.

We understand the proposed sewer line will consist of 8-inch diameter PVC pipe connecting precast concrete manholes and installed at depths ranging from approximately 7 to 9 feet below ground surface. We anticipate the sewer installation will be completed utilizing conventional cut and cover (open trench) construction procedures.

The purpose of our exploration was to describe the subsurface conditions encountered in the completed site borings and develop the test data necessary to provide geotechnical recommendations concerning design and installation of the proposed sewer line.

SITE DESCRIPTION

The proposed sewer line will connect to the existing City of Brighton sanitary sewer system at a point within the S. 18th Avenue right-of-way approximately 210 feet north of E. Egbert Street, and will extend to the north within S. 18th Avenue ROW for a distance of approximately 520 feet, where it will connect to another existing City of Brighton sanitary

Geotechnical Subsurface Exploration Report Proposed Sanitary Sewer Line – S. 18th Avenue between S. Bridge Street & E. Egbert Avenue Brighton, Colorado sewer line. The proposed sewer alignment is located within S. 18th Avenue, which is a 2-lane asphaltic concrete-paved public roadway. The ground surface in this portion of the sewer line alignment was relatively level, with the difference in ground elevation across this area estimated to be approximately 5 feet or less based on review of available USGS topographic maps of the area.

EXPLORATION AND TESTING PROCEDURES

To develop subsurface information for the proposed sewer line, two (2) soil borings were drilled along the proposed alignment to a depth of approximately 15 feet below present site grade. The boring locations were established in the field by Soilogic personnel based on a proposed sewer alignment plan provided by the client, the presence of existing underground utilities, and by pacing and estimating angles and distances from identifiable site references. A diagram indicating the approximate boring locations is included with this report. The boring locations outlined on the attached diagram should be considered accurate only to the degree implied by the methods used to make the field measurements.

Graphic logs of each of the auger borings are also included.

The test holes were advanced using 4-inch diameter continuous-flight auger, powered by a truck-mounted CME-45 drill rig. Samples of the subsurface materials were obtained at regular intervals using California barrel sampling procedures in general accordance with ASTM specification D-1586. Penetration resistance measurements were obtained by driving the standard sampling barrel into the substrata using a 140-pound hammer falling a distance of 30 inches. The number of blows required to advance the sampler a distance of 12 inches is recorded and helpful in estimating the consistency, relative density or hardness of the soils/bedrock encountered. In the California barrel sampling procedure, lesser disturbed samples are obtained in removable brass liners. Samples of the subsurface materials obtained in the field were sealed and returned to the laboratory for further evaluation, classification and testing.

The samples collected were tested in the laboratory to measure natural moisture content and dry density where applicable and were visually and/or manually classified in accordance with the Unified Soil Classification System (USCS). The USCS group symbols are indicated on the attached boring logs. An outline of the USCS classification system is

Brighton, Colorado included with this report. Classification of bedrock was completed through visual and tactual observation of disturbed samples. Other bedrock types could be revealed through petrographic analysis.

As part of the laboratory testing, a calibrated hand penetrometer (CHP) was used to estimate the unconfined compressive strength of essentially cohesive specimens. The CHP also provides a more reliable estimate of soil/bedrock consistency than tactual observation alone. Atterberg limits, -200 wash/gradation and swell/consolidation tests were completed on selected samples to help establish specific soil/bedrock characteristics. Atterberg limits tests are used to determine soil/bedrock plasticity. The percent passing the #200 size sieve (-200 wash)/gradation tests are used to determine the percentage of fine-grained soils (clay and silt) and grain-size distribution of a sample. Swell/consolidation tests are performed to evaluate soil/bedrock volume change potential with variation in moisture content. Water Soluble Sulfates (WSS) tests were completed on two (2) selected soil samples to evaluate corrosive soil characteristics with respect to buried concrete and results will be provided under separate cover when they become available.

SUBSURFACE CONDITIONS

The subsurface conditions encountered in the completed site borings can be generalized as follows. Approximately 6 inches of asphalt pavement and 4 to 6 inches of apparent aggregate base course was measured as the in-place pavement section at each of the boring locations. The composite asphalt pavement section was underlain by dark brown/brown sandy lean clay which varied to clayey sand and containing trace to minor amounts of gravel. The lean clay/clayey sand varied from medium stiff to stiff in terms of consistency or was loose in terms of relative density, exhibited no swell potential at in-situ moisture and density conditions, and extended to depths of approximately 9½ and 3½ feet below ground surface at the locations of borings B-1 and B-2, respectively, where it was underlain by brown/beige sand with varying amounts of silt and gravel. The silty sand varied from loose to medium dense in terms of relative density, would be expected to be non-expansive based on the physical properties and engineering characteristics of the material, and extended to the bottom of boring B-1 at a depth of approximately 15 feet below ground surface, or to a depth of about 7 feet below ground surface at the location of boring B-2, where it was underlain by gray/olive/brown sandstone/siltstone/claystone bedrock. The

Brighton, Colorado bedrock varied from firm to hard in terms of relative density and extended to the bottom of boring B-2 at a depth of about 15 feet below present site grade.

The stratigraphy indicated on the included boring logs represents the approximate location of changes in soil and bedrock types. Actual changes may be more gradual than those indicated.

Groundwater was measured in both borings at a depth of approximately 9 feet below ground surface when checked upon completion of drilling, and the borings were backfilled and patched prior to leaving the site such that no subsequent groundwater level measurements could be made. Groundwater level information is indicated in the upper right-hand corner of the attached boring logs.

Groundwater levels will vary seasonally and over time based on weather conditions, site development, irrigation practices and other hydrologic conditions. Perched and/or trapped groundwater conditions may also be encountered at times throughout the year. Perched water is commonly encountered in soils overlying less permeable soil layers and/or bedrock. Trapped water is typically encountered within more permeable zones of layered soil and bedrock systems. The location and amount of perched/trapped water can also vary over time.

ANALYSIS AND RECOMMENDATIONS

General

We expect the proposed sewer line will be constructed utilizing conventional cut and cover "open trench" excavation procedures (using trench boxes where necessary). Sewer line excavations in the area of boring B-1 are expected to expose overburden lean clay/clayey sand. Excavations completed in the area of boring B-2 are expected to expose overburden lean clay/clayey sand, silty sand and sandstone/sandstone/claystone bedrock. Based on the materials observed in boring B-2, we anticipate the bedrock materials in this area could be excavated using conventional excavating equipment.

Brighton, Colorado

Due to the presence of comparatively shallow groundwater and soft/loose nature of the lean clay/clayey sand and silty sand soils encountered in the completed site borings, instability of the trench sides and bottoms should be expected in some areas. In unstable areas, it may be necessary to remove unstable materials and/or place granular backfill soils to develop a stable trench bottom. Care will be needed to ensure utilities are not placed on or above disturbed or sloughed materials. Bedding around utility pipelines should be placed in accordance with recommendations from the pipeline designer.

Special care will be required in developing stable excavation slopes. The soft and saturated clay and less cohesive and loose clayey to silty sand soils would be particularly susceptible to sloughing and caving during excavation. Deeper-lying caving soils which undermine overburden soils can result in larger slope failures. As such, we expect temporary shoring, bracing, or cutting of shallow slopes will be necessary for utility excavations in this area.

All excavations should be sloped or shored in the interest of safety following local and federal regulations, including current OSHA excavation and trench safety standards. As a safety measure, it is recommended that vehicles and soil stockpiles be kept to a minimum lateral distance from the top edge of utility excavations greater than or equal to the depth of the adjacent utility excavation.

Dewatering

Based on discussion with the project engineer, we understand the utility trench/manhole excavations may extend close to or below the observed level of groundwater at this site. In this case, dewatering procedures would be required to facilitate proper construction. Based on the observed depth to groundwater and proposed depth of the sewer utility, some limited dewatering of utility trench/manhole excavations should be expected along the proposed alignment. Based on the soils encountered and depending on the time of year when construction occurs and bury depth of the sewer utility, we expect dewatering of the utility trench excavations could be completed through open pumping procedures fed from sumps and ditches.

For open pumping dewatering procedures, care should be taken to construct a suitable sump outside of the improvement area. Fine-grained materials can be drawn to the sump

Brighton, Colorado area, creating unsuitable bearing conditions. A sump should consist of a slotted pipe large enough to house a submersible pump, extended deep enough such that when it is pumped out, the entire excavation will be drained. Pumps are typically suspended a minimum of 12 inches above the bottom of the pit in order to provide room for sediment. The slotted pipe should be surrounded by a much larger mass of free-draining gravel. A ¾-inch screened rock could be considered to develop the sedimentation zone. A larger sedimentation zone will reduce water velocities, allowing fines to settle out prior to entering the slotted pipe and mechanical pump. Periodic cleaning and maintenance of the sump should be anticipated.

Drainage ditches should be constructed outside of the immediate work area to allow for collection of the infiltration waters and feeding of the sump. It may be necessary to construct shallow ditches around the perimeter of the basement excavation in order to help intercept any infiltration water before it enters and flows laterally across the excavation to reach the drains. Ditches should be filled with free-draining gravel to reduce the potential for erosion and sloped to provide positive gravity drainage to the sump. For larger water infiltration rates, socked perforated pipe could be installed within the free draining aggregate in the collection ditches in order to facilitate drainage to the sump.

Careful observation of seepage waters should be completed at the start of pumping. If excessive fines are observed being transported up from the bottom or out of the sides of any excavation, pumping should be stopped and the excavation flooded until methods to reduce soil migration can be employed.

Sewer Line Construction

We anticipate the sewer line will be bedded in select granular fill. Above the minimum recommended bedding depth, compacted soil backfill could be used. The materials used for sewer utility backfill should consist of approved fill, free from organic matter, debris and other objectionable materials. Based on results of the completed laboratory testing, it is our opinion the site lean clay, clayey to silty sand soils and thoroughly-processed bedrock material could be used as backfill for the proposed sewer line, provided care is taken to develop the proper moisture content in those materials at the time of placement and compaction. Bedrock fragments should be processed to less than 3 inches in any dimension

Brighton, Colorado prior to use as backfill. At current moisture levels, we expect native site lean clay/clayey sand and sand with silt and gravel soils near current groundwater level will require fairly substantial drying back of these materials or mixing with dry materials prior to use as backfill.

For that portion of open trench within S. 18th Avenue and any other anticipated surface improvement locations, we recommend suitable backfill soils be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted to at least 95% of the materials standard Proctor maximum dry density for backfill depths of less than 10 feet.

Backfill for utility excavations deeper than 10 feet in structural areas should be compacted to at least 98% of the materials standard Proctor maximum dry density. The moisture content of the backfill soils should be adjusted to within ±2% of standard Proctor optimum moisture content at the time of placement and compaction.

Pavement Design

Pavement subgrades underlying S. 18th Avenue along the sewer alignment are expected to consist of reconditioned site lean clay/clayey sand and silty sand with no to low swell potential. An in-place pavement section of approximately 6 inches of asphalt overlying 4 to 6 inches of possible aggregate base course was measured at the locations of our borings.

The new pavements constructed along S. 18th Avenue should match the existing pavement section, or should meet minimum pavement thickness design criteria for the roadway designation as required by City of Brighton design standards.

Depending on the in-place moisture content of the subgrade soils, time of year when construction occurs and other hydrologic conditions, stabilization of site pavement subgrades may become necessary to develop a suitable paving platform. At current moisture levels, and based on the soils anticipated to be present at subgrade elevation, we expect stabilization of the pavement subgrade soils may be required. If stabilization does become necessary, we recommend consideration be given to stabilization of the pavement subgrades with Class C fly ash or Portland cement (pending results of WSS testing currently being completed). Chemical stabilization can also eliminate some of the uncertainty associated with attempting to pave during periods of inclement weather.

Brighton, Colorado

GENERAL COMMENTS

This report was prepared based upon the data obtained from the completed site-specific exploration, laboratory testing, engineering analysis and any other information discussed.

The completed borings provide an indication of subsurface conditions at the boring locations only. Variations in subsurface conditions can occur in relatively short distances away from the borings. This report does not reflect any variations which may occur across the site or away from the borings. If variations in the subsurface conditions anticipated become evident, the geotechnical engineer should be notified immediately so that further evaluation can be completed and when warranted, alternative recommendations provided.

The scope of services for this project does not include either specifically or by implication any biological or environmental assessment of the site or identification or prevention of pollutants or hazardous materials or conditions. Other studies should be completed if concerns over the potential of such contamination or pollution exist.

The geotechnical engineer should be retained to review the plans and specifications so that comments can be made regarding the interpretation and implementation of our geotechnical recommendations in the design and specifications. The geotechnical engineer should also be retained to provide testing and observation services during construction to help determine that the design requirements are fulfilled.

This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with the generally accepted standard of care for the profession. No warranties express or implied, are made. The conclusions and recommendations contained in this report should not be considered valid in the event that any changes in the nature, design or location of the project as outlined in this report are planned, unless those changes are reviewed and the conclusions of this report modified and verified in writing by the geotechnical engineer.

Brighton, Colorado

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning the enclosed information or if we can be of further service to you in any way, please do not hesitate to contact us.

Very Truly Yours, Soilogic, Inc. Reviewed by:

Darrel DiCarlo, P.E. Alec Kaljian, P.E.

Senior Project Engineer Project Engineer

03/28/2024 03/28/2024

LOG OF BORING B-1

1/1 CME 45

4" CFA

Automatic

MR / AK

Estimated Swell % Passing SOIL DESCRIPTION Depth "N" MC DD qu % Swell @ Pressure # 200 Sieve

(ft) (%) (pcf) (psf) 500 psf (psf) LL PI (%)

±6" ASPHALT PAVEMENT -

±4-6" AGGREGATE BASE COURSE 1

3 CS 8 13.7 106.9 7000 None <500 24 9 27.8%

CL-SC SANDY LEAN CLAY to CLAYEY SAND -dark brown, brown 5 CS 12 25.3 97.6 5500 - - - - -medium stiff to stiff / loose -trace to minor GRAVEL 6

10 CS 6 15.2 - - - - - - -

SP-SM SAND with SILT and GRAVEL 12 brown, beige -loose to medium dense 13

15 CS 31 21.3 - - - - - - -

BOTTOM OF BORING @ 15.0' -

PROPOSED SANITARY SEWER LINE

S. 18TH AVENUE BETWEEN S. BRIDGE ST AND E. EGBERT AVE, BRIGHTON, COLORADO

Project # 24-1018 March 2024

Sheet Drilling Rig: Water Depth Information Start Date 3/19/2024 Auger Type: During Drilling 9.0'

Finish Date 3/19/2024 Hammer Type: After Drilling 9.0'

U

SC

S

Sa m pl er

Atterberg Limits

Surface Elev. - Field Personnel: 24 Hours After Drilling Backfilled

LOG OF BORING B-2

1/1 CME 45

4" CFA

Automatic

MR / AK

Estimated Swell % Passing SOIL DESCRIPTION Depth "N" MC DD qu % Swell @ Pressure # 200 Sieve

(ft) (%) (pcf) (psf) 500 psf (psf) LL PI (%)

±6" ASPHALT PAVEMENT -

±4-6" AGGREGATE BASE COURSE 1

CL-SC SANDY LEAN CLAY to CLAYEY SAND -dark brown, brown 2 medium stiff / loose -trace to minor GRAVEL 3 CS 9 18.5 103.2 4000 None <500 - - -

SM SILTY SAND -

beige 5 CS 19 1.9 - - - - NL NP 3.5% medium dense -trace GRAVEL 6

10 CS 30 25.6 98.5 9000+ - - - - 68.8%

SANDSTONE/SILTSTONE/CLAYSTONE -

gray, olive, brown, rust 11 firm to hard -

15 CS 50/10 NR NR - - - - - -

BOTTOM OF BORING @ 15.0' -

Sheet Drilling Rig: Water Depth Information

PROPOSED SANITARY SEWER LINE

S. 18TH AVENUE BETWEEN S. BRIDGE ST AND E. EGBERT AVE, BRIGHTON, COLORADO

Project # 24-1018 March 2024

U

SC

S

Sa m pl er

Atterberg Limits

Start Date 3/19/2024 Auger Type: During Drilling 9.0' Finish Date 3/19/2024 Hammer Type: After Drilling 9.0'

Surface Elev. - Field Personnel: 24 Hours After Drilling Backfilled

Liquid Limit 24 Plasticity Index 9

% Passing #200 27.8% Dry Density (pcf) 106.9

PROPOSED SANITARY SEWER LINE

S. 18TH AVENUE BETWEEN S. BRIDGE ST AND E. EGBERT AVE, BRIGHTON, COLORADO

Project # 24-1018 March 2024

SWELL/CONSOLIDATION TEST SUMMARY

Sample ID: B-1 @ 2

Initial Moisture 13.7%

Sample Description: Brown Silty, Clayey Sand (SC-SM)

Final Moisture 14.4%

% Swell @ 500 psf None Swell Pressure (psf) <500

-12

-10

-8

-6

-4

-2

10 100 1000 10000 100000

Applied Load (psf)

Liquid Limit - Plasticity Index -

% Passing #200 - Dry Density (pcf) 103.2

SWELL/CONSOLIDATION TEST SUMMARY

PROPOSED SANITARY SEWER LINE

S. 18TH AVENUE BETWEEN S. BRIDGE ST AND E. EGBERT AVE, BRIGHTON, COLORADO

Project # 24-1018 March 2024

Initial Moisture 18.5%

Sample ID: B-2 @ 2 Sample Description: Dark Brown Sandy Lean Clay (CL)

Final Moisture 18.6%

% Swell @ 500 psf None Swell Pressure (psf) <500

-12

-10

-8

-6

-4

-2

10 100 1000 10000 100000

Applied Load (psf)

UNIFIED SOIL CLASSIFICATION SYSTEM

Criteria for Assigning Group Symbols and Group Names Using Laboratory TestsA Soil Classification

Group Symbol Group NameB

Cu ! 4 and 1 " Cc " 3E GW Well graded gravelF Clean Gravels Less than 5% finesC Cu < 4 and/or 1 > Cc > 3E GP Poorly graded gravelF

Fines classify as ML or MH GM Silty gravelF,G, H

Coarse Grained Soils

More than 50% retained on No. 200 sieve

Gravels More than 50% of coarse fraction retained on No. 4 sieve Gravels with Fines More than 12% finesC Fines classify as CL or CH GC Clayey gravelF,G,H

Cu ! 6 and 1 " Cc " 3E SW Well graded sandI Clean Sands Less than 5% finesD Cu < 6 and/or 1 > Cc > 3E SP Poorly graded sandI

Fines classify as ML or MH SM Silty sandG,H,I

Sands 50% or more of coarse fraction passes No. 4 sieve Sands with Fines

More than 12% finesD Fines classify as CL or CH SC Clayey sandG,H,I

PI > 7 and plots on or above “A” lineJ CL Lean clayK,L,M Silts and Clays Liquid limit less than 50

Inorganic

PI < 4 or plots below “A” lineJ ML SiltK,L,M

Liquid limit - oven dried

Organic clayK,L,M,N

Fine-Grained Soils 50% or more passes the No. 200 sieve

Organic

Liquid limit - not dried

< 0.75 OL

Organic siltK,L,M,O

Inorganic PI plots on or above “A” line CH Fat clayK,L,M Silts and Clays Liquid limit 50 or more

PI plots below “A” line MH Elastic siltK,L,M

Liquid limit - oven dried Organic clayK,L,M,P Organic

Liquid limit - not dried

< 0.75 OH

Organic siltK,L,M,Q

Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat

A Based on the material passing the 3-in. (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name.

C Gravels with 5 to 12% fines require dual symbols: GW-GM well graded gravel with silt, GW-GC well graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay.

D Sands with 5 to 12% fines require dual symbols: SW-SM well graded sand with silt, SW-SC well graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay

E Cu = D60/D10 Cc =

F If soil contains ! 15% sand, add “with sand” to group name.

G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.

HIf fines are organic, add “with organic fines” to group name.

I If soil contains ! 15% gravel, add “with gravel” to group name.

J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay.

K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant.

L If soil contains ! 30% plus No. 200 predominantly sand, add

“sandy” to group name.

M If soil contains ! 30% plus No. 200, predominantly gravel, add

“gravelly” to group name.

N PI ! 4 and plots on or above “A” line.

O PI < 4 or plots below “A” line.

P PI plots on or above “A” line.

Q PI plots below “A” line.

GENERAL NOTES

DRILLING & SAMPLING SYMBOLS:

SS: Split Spoon - 1⅜" I.D., 2" O.D., unless otherwise noted HS:

ST: Thin-Walled Tube – 2.5" O.D., unless otherwise noted PA:

RS: Ring Sampler - 2.42" I.D., 3" O.D., unless otherwise noted HA:

CS: California Barrel - 1.92" I.D., 2.5" O.D., unless otherwise noted RB:

BS: Bulk Sample or Auger Sample WB:

Hand Sample Power Auger Hand Auger Rock Bit Wash Boring or Mud Rotary

The number of blows required to advance a standard 2-inch O.D. split-spoon sampler (SS) the last 12 inches of the total 18-inch penetration with a 140-pound hammer falling 30 inches is considered the “Standard Penetration” or “N-value”. For 2.5” O.D.

California Barrel samplers (CB) the penetration value is reported as the number of blows required to advance the sampler 12 inches using a 140-pound hammer falling 30 inches, reported as “blows per inch,” and is not considered equivalent to the “Standard Penetration” or “N-value”.

WATER LEVEL MEASUREMENT SYMBOLS:

WL: Water Level WS: While Sampling WCI: Wet Cave in WD: While Drilling DCI: Dry Cave in BCR: Before Casing Removal AB: After Boring ACR: After Casing Removal

Water levels indicated on the boring logs are the levels measured in the borings at the times indicated. Groundwater levels at other times and other locations across the site could vary. In pervious soils, the indicated levels may reflect the location of groundwater.

In low permeability soils, the accurate determination of groundwater levels may not be possible with only short-term observations.

DESCRIPTIVE SOIL CLASSIFICATION: Soil classification is based on the Unified Classification System. Coarse Grained Soils have more than 50% of their dry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand.

Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic, and silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are defined on the basis of their in-place relative density and fine-grained soils on the basis of their consistency.

FINE-GRAINED SOILS COARSE-GRAINED SOILS BEDROCK

(CB)

Blows/Ft.

(SS)

Blows/Ft. Consistency

(CB)

Blows/Ft.

(SS)

Blows/Ft.

Relative

Density

(CB)

Blows/Ft.

(SS)

Blows/Ft. Consistency

< 3 0-2 Very Soft 0-5 < 3 Very Loose < 24 < 20 Weathered 3-5 3-4 Soft 6-14 4-9 Loose 24-35 20-29 Firm

6-10 5-8 Medium Stiff 15-46 10-29 Medium Dense 36-60 30-49 Medium Hard 11-18 9-15 Stiff 47-79 30-50 Dense 61-96 50-79 Hard 19-36 16-30 Very Stiff > 79 > 50 Very Dense > 96 > 79 Very Hard > 36 > 30 Hard

RELATIVE PROPORTIONS OF SAND AND

GRAVEL

GRAIN SIZE TERMINOLOGY

Descriptive Terms of

Other Constituents

Percent of

Dry Weight

Major Component of Sample Particle Size

Trace < 15 Boulders Over 12 in. (300mm) With 15 – 29 Cobbles 12 in. to 3 in. (300mm to 75 mm)

Modifier > 30 Gravel 3 in. to #4 sieve (75mm to 4.75 mm) Sand

Silt or Clay #4 to #200 sieve (4.75mm to 0.075mm)

Passing #200 Sieve (0.075mm)

RELATIVE PROPORTIONS OF FINES PLASTICITY DESCRIPTION

Descriptive Terms of

Other Constituents

Percent of

Dry Weight Term Plasticity Index

Trace With

Modifiers

< 5 5 – 12 > 12

Non-plastic Low

Medium High

1-10

11-30 30+

GENERAL COMMENTS