Addendum Three .pdf

COMMONWEALTH OF KENTUCKY

DEPARTMENT FOR FACILITIES AND SUPPORT SERVICES

DIVISION OF ENGINEERING AND CONTRACT ADMINISTRATION

INVITATION TO BID NO: RFB-90-25

FOR: Bullitt County Historic Landfill Leachate Management Energy and Environmental Cabinet Bullitt County, Kentucky

DATE: October 24, 2024

RFB-785-2500000178

ADDENDUM NO. Three (3)

BIDDER SHALL CONFORM TO THE FOLLOWING CHANGES AS SAME SHALL BECOME BINDING

UPON THE CONTRACT TO BE ISSUED IN RESPONSE TO THIS INVITATION TO BID.

Item 1: Refer to addendum to be distributed by Lynn Imaging for all additions, deletions, and/or changes to specifications and/or drawings.

Item 2: Official Bid Date has been moved to October 31, 2024 at 1:30 P.M. Eastern Time

END OF ADDENDUM

Invitation to Bid No. RFB-90-25 For: Bullitt County Historic Landfill Leachate Management Energy and Environmental Cabinet Bullitt County, Kentucky

Susan Ward, Statewide Procurement Analyst II Division of Engineering and Contract Administration

26 Village Plaza • Shelbyville, Kentucky 40065 • office 502.633.7585 • fax 502.633.7513

331 Townepark Circle, Suite 100B • Louisville, Kentucky 40243• office 502.645.3788 400 E 2nd St • Owensboro KY 42303 • office 270.9842923

October 22, 2018

Mr. Mike Davis, PE Senior Associate Strand 1525 Bull Lea Rd # 100 Lexington, KY 40511

Subject: Geotechnical Borings and Soundings Proposed Transmission Main and Pump Stations Old Landfill Site Shepherdsville, Kentucky

Vector Proposal Number 16-2842A

Dear Mr. Davis, Vector Engineers, Inc. has completed the soil test borings and rock soundings along the alighment of the proposed transmission main. Our services were conducted in general accordance to our proposal 18-466 dated July 24, 2018. This report discusses the results of our findings and our recommendations. Due to utility access issues, we deleted one of the soil test boring and adjusted several sounding locations.

Project Informaton

Project information was obtained from a document entitled, “Report for

Commonwealth of Kentucky, Finance and Administration Cabinet, Bullitt County

Historic Landfill, Leachate Management”, dated October 2017. In the document several options were provided for treating the leachate from the landfill. The selected option was to construct a pump station(s) at the existing landfill and pipe the leachate through a force main to the Shepherdsville Waste Water Treatment Facility. The force main will consist of a 6-inch pipeline extending from a new pump station, at the old landfill to where it will tie into an exiting pipe along highway 61 (Preston Highway) just north of highway 149. The alignment generally will extend from the existing pipe along Preston

Highway, south along Highway 61 to Highway 251 (Belmont Road). At Highway 251, the pipeline will head west to Collings Hill Road where it will tie into the leachate collection system of the old landfill. The entire length of the proposed force main will be

Proposed Transmission Main about 5 miles (25,300 linear feet). The depth of the pipe will be a minimum of 3 ½ feet and a maximum of 8 feet. The alignment generally follows existing roadways. In addtion to the force main, two pump stations will be constructed on the landfill property.

Findings

Site Surface Conditions

The general alignment of the proposed pipeline extending from the landfill to the connection to the existing pipeline was along existing roadways. The area from the landfill to about Collings Hill Road consists of hills with valleys and ridges (Figure 1 and

2). The area along Collings Hill Road and Belmont Road was in a generally rolling valley plain and the area along Preston Highway is generally flat and gently sloping (Figures 3 and 4).

Figure 1: View of the pump station site at the back of the old landfill.

Figure 2: View along Collins Hill Road

Figure 3: Intersection of Preston and Belmont looking at Belmont

Figure 4: Along Preston Highway looking south.

Published Geological and Soil Survey Information

Figure 5: General Geological Map along Alignment (Red line is the approximate force main alignment.

Geological Survey

Review of the Kentucky Geological Survey published information reveals that the alignment is underlain by a few geological formations. The majority of the force main alignment is underlain by alluvium and lacustrine deposits. This includes most of the alignment along Preston Highway, all of the alignment along Belmont Road, and about half of the alignment along Collings Hill Road. These Quaternary lacustrine deposits and alluvium consist of silty, calcareous clays that become increasingly silty towards the base.

Two sections of the alignment along are underlain by the New Albany Shale; one section is approximately 4,500 feet along Preston Highway south of Clermont Road and north of Belmont Road and the other section includes the northern portion of the landfill and the front pump station and extends west and north approximately 3,000 feet along

Collings Hill Road. The New Albany Shale is a Middle Devonian to Lower Mississippian silty, olive-black to grayish-black shale that weathers as light as pale yellowish brown or very light gray. It is massive, dense where fresh and fissile in thin brittle chips where weathered.

The southern portion of the landfill and back pump station are underlain by the

Borden Formation. The Borden Formation is a Mississippian age formation of silty shale and siltstone. Coloration varies from pale-olive to grayish-yellowish-green or light-gray and may be iron stained.

National Resource Conservation Service (NRCS)

A brief review of the NRCS website indicates that several soil types exist along the proposed force main alignment. From the north side of the force main extending south, the soils generally are classified as McGary Silt Loam (Mc), Caveyville Silt Loam (CaB) and Crider Silt Loam (CrB) extending to Belmont Road. Along Belmont Road the soils are classified as Newark Silt Loam (Ne) and the Lawrence Silt Loam (La and Le). From

Belmont along Collings Hill Road, Newark Silt Loams are mapped with the Nolan Silt

Loam (No) at lower elevations. As the alignment rises in elevation, the soils become the

Otwood Silt Loam (OtC) and some areas of the Nolan Silt Loam. The NRCS web site indicates that the majority of the soils are high in corrosivity to uncoated steel.

Therefore, the ductile iron pipe must be coated to protect it from corrosion. The soils are generally silty clays extending to bedrock.

Subsurface Exploration

After researching the readily available published geological information, a preliminary subsurface profile is formulated. The soil boring program is a means to substantiate the assumptions made in our preliminary profile and assist us in developing a representative subsurface profile of the site. The subsurface conditions will vary between borings thereby making the development of a representative and reliable profile dependent upon the number of borings or data points obtained during the field operations. The following discusses our interpretation of the subsurface profile on the site based on the published information and the results of our borings. The individual Boring Logs attached to this report will have specific details at the location of the boring.

Field Exploration and Laboratory Testing Methods

The procedures used by Vector Engineers for field and laboratory sampling and testing are in general accordance with ASTM procedures and established engineering practice. A brief summary of the field and laboratory procedures is included in the attachments.

We drilled a total of 17 soil test borings and 32 soundings to explore the subsurface conditions across the site. Mr. Barnett, Geologist contacted the applicable utility companies for drilling clearance, directed the drilling operations and logged the soil specimens and boring depths. The boring and sounding locations were located in the field based on utility locations and the approximate location of the proposed pipeline.

In some cases, the boring or sounding was on the opposite side of the road to miss utilities. One boring was deleted due to utility issues and a boring and a sounding were deleted due to property owner denying access. Boring surface elevations have not been obtained at the time of this report. We understand that Strand will be surveying the alignment and will obtain the elevations. Because of the methods used, the soil boring and sounding locations shown on the Boring and Sounding Location Plan are approximate. The stratification lines shown on the Boring Logs represent the approximate boundaries between soil or rock types. The transitions may be more gradual than shown.

We obtained soil samples using a split-barrel sampler driven by a manual hammer assembly in general accordance with ASTM D1586. The soundings were planned to be conducted using the truck mounted drill rig, however, at the time of drilling the ground was saturated. Therefore, to minimize site disturbance to residents along the alignment, we used a high-pressure water probe. The water probe displaces soil until refusal material is encountered. The depths of the high-pressure water probe can be slightly shallower than the refusal determined by the drill rig, especially in shale bedrock. The shale tends to be soft compared to limestone and the drill rig earth auger can cut into the shale bedrock several feet until refusal is encountered.

The soil samples were sealed in the field and returned to our laboratory where

Mr. Barnett assigned the applicable laboratory tests. The soil samples were visually classified according to the Unified Soil Classification System (USCS, ASTM D2487). We conducted moisture contents and Atterberg limits tests on several soil samples.

Atterberg limits tests were performed on selected soil samples to determine the engineering properties of the soil. The laboratory data and descriptions of these tests are included in the attachments.

Subsurface Conditions

The subsurface conditions discussion is separated into three areas; The back pump station, the front pump station and the proposed force main alignment.

Proposed Back Pump Station

Two soil test borings (B1 and B2) were drilled in the approximate location of the proposed pump station. The borings were located as shown on Figure 5. Beneath about 3 to 4 inches of topsoil, the borings encountered what we interpreted to be previously placed fill. The fill consisted of stiff to very stiff gray to orange brown lean clay with crushed stone and shale particles. On Boring B1, a trace of plastic was found.

In boring B2, weathered shale was encountered from about 4 feet to 6 feet. Below the fill in Boring B1 and the weathered shale in Boring B2, hard dark brown shale and hard lean clay with shale was encountered to the earth auger refusal depths of 12 ½ in Boring

B1 and 17 ½ in Boring B2. The laboratory tests conducted on a specimen of the fill soils in Boring B1 indicated a liquid limit of 49 and a plasticity of 21 which, according to the Unified Soil Classification System (USCS) indicates a borderline lean silt to lean clay. Visually the soils appear to be a lean clay. The borings were both dry after completion of drilling.

Figure 6: Approximate location of the soil test borings in the back pump station area.

Proposed Front Pump Station and Start of the Force Main

The proposed front pump station is near the current location of the leachate collection pit. Two borings (B3 and B4) were drilled in the generally vicinity of the pump station and one boring (B5) was drilled just off the road where the force main will begin.

The approximate boring locations are shown on Figure 7. There was a crushed stone vehicle access pad in the area of Boring B3, where our boring encountered 2 ½ of crushed stone. Boring B4 encountered a thin layer (1 inch) of topsoil at the surface.

Both pump station borings encountered what we interpreted as previously placed fill material below the upper crushed stone and topsoil. The fill consisted of stiff gray lean clay with traces of glass and other small organic materials. The fill extended to weathered shale at depths of 9 ½ to 14 ½ in Boring B3 and B4 respectively. The boring closest to Collings Hill Road encountered what we interpreted as previously placed fill from the surface to a depth of about 4 ½ feet. Below the fill, very stiff to hard weathered shale was encountered to earth auger refusal at 12. 2 feet. Refusal to the earth auger was encountered at 11.9 feet in Boring B3 and 15.3 feet in Boring B4. Groundwater was encountered in both pump station borings on the sampling tools at depths of 3 ½ feet in Boring B3 and at 13 ½ feet in Boring B4. Boring B5 was dry at the completion of drilling. There is a creek near the area where the borings were drilled. An Atterberg limits test on a soil specimen from Boring B4 indicated a liquid limit of 41 with a plasticly index of 14. The USCS classification is a borderline lean silt/clay. Visually the soils appear to be a lean clay.

Figure 7: Approximate location of the soil test borings for the front pump station and the start of the force main (B3, B4 and B5)

Proposed Force Main

The proposed force main extends from the front pump station to an existing pipeline on Preston Highway just north of Highway 1494. Twelve soil test borings and

32 soundings were conducted along the alignment. The soil test borings are numbered

B6 through B19 with two borings; B13 and B17 omitted due to access issues with soft ground or utility concerns. The soil test borings were generally drilled along side the road and therefore encountered an upper layer of crushed stone, small amounts of previously placed fill (as a part of the road construction) or topsoil. Below the upper soils, the borings generally encountered firm to stiff lean clays extending to a weathered shale layer before encountering refusal material. In the northern few borings along

Preston Highway, the bedrock formation changes from shale to limestone. At the time of our drilling, a gas line was being installed along Preston Highway, near soundings

S26.

Figure 8 and 9: Gas line installation exposing limestone bedrock near sounding S26.

The following table lists each soil test boring and sounding with the refusal depths.

Table 1: Soil Test Boring and Sounding Refusal Depths

Boring or Sounding

Number

Type of Borehole Refusal depth (feet)

Comments

B1 STB 12.5

B2 STB 17.5

B3 STB 11.9

B4 STB 15.3

B5 STB 12.2

B6 STB 14.5

B7 STB 7.7

S1 Sounding 10.5 Used drill rig

S2 Sounding 8.3 Used drill rig

B8 STB 8.8

B9 STB 7.3

S3 Sounding 10+ Used drill rig -No refusal

S4 Sounding 6.8 Used drill rig

B10 STB 9.8

S5 Sounding 7.1 Used drill rig

B11 STB 10.5+ No refusal

B12 STB 10.5+ No refusal

S6 Sounding 10+ Used drill rig – No refusal

B13 STB Not completed Property owner denied access

B14 STB 10.5+ Used drill rig - No refusal

S7 Sounding 10.5

S8 Sounding 12.2

S9 Sounding 10+ Drill rig – no refusal

S10 Sounding 4

B15 STB 7.3

S11 Sounding 6.5 Used drill rig

S12 Sounding 7.4

S13 Sounding 4.4

S14 Sounding 5.7

S14A Sounding 3.6

B16 STB 7.3

B17 STB Not completed Location was over gas main along

Preston Highway

S15 Sounding 8.9 Used drill rig

S16 Sounding 7 Used drill rig

S17 Sounding 5.9

S18 Sounding 5.3 Used drill rig

S19 Sounding 5.5 Used drill rig

S20 Sounding 6

S21 Sounding 4.9

S22 Sounding 10+ Used drill rig – no refusal

S23 Sounding 8.9 Used drill rig

S24 Sounding 9

B18 STB 5.9

S25 Sounding 2.9

S26 Sounding Not completed Owner denied access, but gas line repair showed limestone bedrock

(Figure 7)

S27 Sounding 6.1

S28 Sounding 5.9

S29 Sounding 6.4

S30 Sounding 10+ Used drill rig – no refusal

S31 Sounding 4

S32 Sounding 5.5

S33 Sounding 10+ Used drill rig -No refusal

B19 STB 10.5+ Used drill rig -No refusal

STB – Soil Test Boring drilled with Mobile B47

Soundings were either drilled using the Mobile B47 as indicated or with a high-pressure water sounding rod. The sounding rod typically hits refusal a few inches or more before the mechanical drill due to a much higher down pressure on the mechanical drill.

The approximate locations of the borings and soundings along the force main route are shown in the following figures. We understand the actual locations will be surveyed by Strand to obtain locations and elevations.

Figure 10: Approximate boring and sounding locations from landfill along Collings Hill

Road

Figure 11: Approximate boring and sounding locations along Collings Hill Road

Figure 12: Approximate boring and sounding locations along Collings Hill Road

Figure 13; Approximate boring and sounding locations along Collings Hill Road and Belmont Road

Figure 14: Approximate boring and sounding locations along Belmont Road

Figure 15: Approximate boring and sounding locations along Belmont and Preston Highway

Figure 16: Approximate boring and sounding location along Preston Highway

Figure 17: Approximate boring and sounding location along Preston Highway

Figure 18: Approximate boring and sounding location along Preston Highway

Figure19: Approximate boring and sounding location along Preston Highway

Figure 20: Approximate boring and sounding location along Preston Highway

Figure 21: Approximate boring and sounding location along Preston Highway

Groundwater

Groundwater was not encountered in any of the borings at the completion of soil borings. However, in several of the borings, water was noted on the sampling tools at various depths. In boring B3, drilled in the front pump station location, water was encountered on the sampling tools at about 3 ½ feet below the top of ground. In addition, in Boring B11, along Belmont Road had water on the sampling tools at about

4 ½ feet and in Boring B15 on Preston Highway just north of the intersection of Belmont, we encountered water on the sampling tools at about 4 feet. All other borings were dry at the completion of the drilling.

Groundwater levels fluctuate with seasonal and cyclical climatic variations in precipitation and may be either higher or lower at other times. In that Alluvial soils along the alignment, the water levels can vary considerably depending on rainfall.

Typically, water conditions affecting construction projects in the site area are related to trapped or perched water which occurs in irregular, discontinuous locations within the soil overburden, or near the soil/rock interface. When these water bearing strata are exposed in excavations, such as cut slopes, utility or footing trenches, they can produce widely varying seepage durations and rates depending on recent rainfall activity and other site-specific characteristics of the area.

Discussion

The proposed force main will be embeded into the ground about 3 ½ to as much as 8 feet deep. Based on the data from our soundings and borings (Table 1), there will be areas that will encounter bedrock in the bottom of the trench excavation. The force main alignment in the areas underlain by shale bedrock, the excavation should be able to be conducted with a trackhoe, provided excavation into the shale is no more that 2 to 3 feet. In areas where the excavation encounters limestone bedrock, the use of a hoe ram will be required to remove the limestone. Based on our observations of the gas line excavation, the surface of the bedrock is very irratic (Figures 8 and 9) and will be difficult to excavate with earth excavation equipment.

Although we did not encounter groundwater in the borings, we do expect that some groundwater will be encountered, partically along Belmont Road during the trench excavation. The groundwater, if an issue, can be removed using pumps.

Based on our soil borings, the soil removed from the trench excavation can be used as backfill material provided large rock fragments are taken out of the backfill material. In the shale bedrock areas, the shale can typically break down under equipment loading, however, the limestone bedrock is more durable and will remain as rock fragments. In the limestone bedrock area, the backfilled excavation material should be free of limestone fragments. We anticpate that a crushed stone or clay bedding material will be utilized to provide a uniform bearing surface for the pipe. The pipe should not be founded directly on the shale or limestone bedrock due to risk of point loading which could eventually damage the pipe.

The two pump stations will be located in areas that are underlain by previously placed fill material. Typically, we do not recommend supporting new buildings on previously placed fill due to the unknowns associated with the placement of and the quality of the fill. However, our borings indicated that the previously placed fill is stiff to very stff and provided the owner understands and accepts that there is a risk of settlement, the pump station can be supported on the old fill. However, Vector must be involved with the evaluation of the foundation bearing materials by observing and testing the bearing soils before the foundations are poured. If the owner does not desire to take the risk of settlement, we recommend that the pump stations be supported on foundation bearing on the shale bedrock. The foundation can consist of either spread footings bearing on the shale bedrock or the foundation excavation can be backfilled with flowable fill and the spread footing bearing on the flowable fill. We do not recommend using crushed stone to backfill the foundaiton excavtion due to the risk of collecting water within the stone. The depth to competent bedrock (Shale) was found to be 6 to 7 feet in the back pump station and about 9 ½ to 15 feet in the front pump station.

The floor slabs may be supported on the previously placed fill provided the subgrade is evalated by the geotechnical engineer. For budgeting purposes, we recommend utilizing an about 1 ½ feet undercut in the pump building footprint and backfilling with propertly placed and compacted crushed stone fill or clean clay fill.

LIMITATIONS OF RECOMMENDATIONS

This report has been prepared for the exclusive use of Strand Associates, Inc. for specific application to the project site. Our recommendations have been prepared using generally accepted standards of geotechnical engineering practice in the Commonwealth of Kentucky. No other warranty is expressed or implied. This company is not responsible for the conclusions, opinions, or recommendations of others based on these data. Additionally, our conclusions and recommendations are based on the information provided to us, the data obtained from our subsurface exploration, and our experience.

They do not reflect variations in the subsurface conditions which are likely to exist between borings and in unexplored areas of the site. These variations result from geologic variability of the subsurface conditions. If conditions are different than those encountered in our exploration, it will be necessary for us to re-evaluate our conclusions and recommendations based upon on-site observation of the conditions.

If the overall design or location of the project is changed, the recommendations contained in this report must not be considered valid unless our firm reviews the changes and our recommendations are modified. When the design is finalized, we should be given the opportunity to provide the additional service of reviewing the grading plan, and applicable portions of the project specifications. This review will allow us to check whether these documents are consistent with the intent of our recommendations.

We may recommend that a supplementary exploration be performed when significant design changes such as movement of the project are incorporated in the final design after the geotechnical exploration has been completed. This supplementary exploration may include obtaining additional soil data along the new alignment to provide specific recommendations.

RECOMMENDATIONS

Earthwork

We understand that the 6-inch force main will be about 3 ½ to 8 feet deep along the alignment. Also, the two pump stations will be located at the base of the old landfill on the north and south sides. The following recommendations are for preparation of the building site(s).

Stripping

Topsoil and debris should be stripped to prepare the site for construction. The stripping should extend 5 feet outside of the proposed pump stations and 2 feet on either side of the pipeline trench. Vector should be contacted if unusual or unexpected subsurface conditions (i.e. – organic pockets, sinkholes or other anomalies) are encountered during stripping operations. There were several low-lying areas along the proposed force main so thick pockets of organic soils may be encountered. In addition, there may be areas of old previously placed fills from the road construction that may be encountered.

Subgrade Evaluation)

Due to the previously placed fill in the proposed pump locations, after stripping, the subgrade should be evaluated by a geotechnical engineer by observing proofrolling.

Proofrolling consists of applying repeated passes (3 to 4 passes) on the subgrade with a fully loaded dump truck or similar rubber-tired vehicle. Any materials judged to deflect excessively under the wheel loads should be undercut to more stable soils or stabilized in-place before placing fill.

Structural Fill Placement (Proposed Pump Stations)

After subgrade evaluation, fill areas may be brought to the planned subgrade elevations with structural fill. At the time of this report, specific finished floor elevations have not been determined, therefore some of these recommendations should be considered general. The onsite previously placed fills may be used as fill material provided Vector observes the soils as they are excavated. Ideally, structural fill is defined as inorganic natural soil with maximum particle sizes of 3 inches and a maximum dry density of at least 95 pounds per cubic foot (pcf) when tested by the standard Proctor method (ASTM D698). Limit the fill materials to a Plasticity Index less than 35. The on-site soils should meet this criterion.

Structural fill should be placed in relatively thin (6 to 8-inch) layers and compacted to at least 95 percent of the soil’s maximum dry density as determined by the standard Proctor compaction test. Additionally, the moisture content of the fill material should be maintained within -2 to 2 percent of its standard Proctor optimum moisture content depending upon the results of the Proctor tests. If fill will come from an off-site borrow source, the fill source should be tested and approved by a geotechnical engineer before it can be used as fill.

Field Density Testing

In-place density testing must be performed as a check that the previously recommended compaction criteria (density and moisture) have been achieved. This allows our project engineer to monitor the quality of the fill construction and verify that his design criterion is being achieved in the field. Performance of slabs-on-grade will depend directly on the quality of the fill construction. The testing frequency for density tests performed on a full-time basis can be determined by our personnel based on the area to be tested, the grading equipment used, and construction schedule. Tests should be performed at vertical intervals of at least each 8-inch lift as the fill is being placed.

We recommend that an engineering technician working under the direction of our project geotechnical engineer perform the density tests. If the previously placed fill is used as new structural fill, the heterogenous nature of the soil may not allow accurate field density testing, therefore, we recommend an experienced geotechnical engineering technician under the direction of Vector observe the fill placement and evaluate the compaction based on the soil’s reaction to the compaction equipment.

Pump Station Building Foundations

Based on the encountered subsurface conditions, we believe spread footings are suitable for the support of the addition. We recommend using a maximum allowable net soil bearing pressure of 3,000 psf (pounds per square foot) to size footings if the footings are bearing within the previously placed fill material.

The exterior foundations should be designed with a minimum 30-inch embedment to protect against frost heave. We also recommend foundations have a minimum footing width of 24 inches to lessen the risk of differential settlement and to reduce the risk of punching failure. This footing width also allows for entry into the excavation to remove loose debris and for placement of the reinforcing steel. Reinforcing steel should be clean and dry prior to concrete placement.

If the pump station foundations are bearing on the shale using spread footings foundations, an allowable bearing capacity for the shale of 5000 psf can be used for design.

Floor Slab

We anticipate the existing soil will be supporting the slab-on-grade floor slab in the pump station. We recommend a k-value (modulus of subgrade reaction) of 75 pounds per cubic inch (pci) be used in determining the slab thickness.

Below Grade Wall Recommendations

The pump station below grade walls will act as retaining walls. Where retaining walls are free to deflect or rotate, we recommend that the walls be designed for the "active" earth pressure condition. Where retaining walls are not free to rotate, we recommend using the "at-rest" earth pressure condition.

The soil behind the wall is assumed to exert a triangular stress distribution which can be modeled in terms of an "equivalent fluid" for both the active and at-rest cases. If a uniform area surcharge acts behind the wall, a portion of the surcharge is transferred to the wall in the form of a uniform or rectangular stress distribution. The magnitude of the surcharge load transferred to the wall is a function of the soil's strength and the degree of deflection or rotation permissible and is computed by multiplying the soil's "earth pressure coefficient" by the magnitude of the surcharge. The following table presents values of earth pressure coefficients and equivalent fluid unit weights for both the active and at-rest earth pressure conditions.

Table 2: Earth Pressure Coefficients

Earth Pressure

Condition

Earth Pressure

Coefficient

Recommended

Equivalent Fluid Unit

Weight, pcf

Active, Horizontal

Backfill

0.34 45

At-Rest

Horizontal

Backfill

0.50 65

The recommended earth pressure coefficients assume that there are level ground surfaces on both sides of the walls. The recommended equivalent fluid pressures assume that constantly functioning drainage systems are installed between walls and soil backfill to prevent the build-up of hydrostatic pressures and lateral stresses in excess of those calculated for drained conditions.

Wall drainage systems should consist of a granular backfill such No. 57 size crushed stone. The drainage media should extend to within 2 feet of the ground surface.

Compacted structural cohesive fill should be placed over the drainage media to prevent direct surface water inflow.

Proposed Force Main Backfill and Thrust Blocks

As previously stated, the excavated soils from the force main alignment may be used as backfill provided they are free of man-made debris and large rock fragments over 2 inches in diameter. The trench bottom should be level and support the pipe evenly. Uneven support on limestone or shale bedrock could result in point loading which could damage the pipe. If the bearing surface is uneven compacted soil or crushed stone may be used to provide adequate pipe bedding. The crushed stone can consist of number 9, 11 or 57 stone. The trench width should be wide enough to allow for proper installation and adequate compaction of the backfill. Based on an 8-inch diameter pipe, the trench should be at least 30 inches wide. If bedrock excavation is required, the bedrock must be removed so that it will not be closer than 6 inches to the bottom and sides of the pipe.

The soil backfill must be clean of man-made debris and rock fragments such that the soil backfill can be placed around the pipe in loose 4-inch lifts and compacted.

Typically, the backfill should be placed to at least 95% of the standard Proctor compaction test, however, based on the size of the pipe and the limited space for compaction equipment, we do not believe testing of each lift will be practical. Therefore, we recommend close observation of the installation by a qualified geotechnical under the direction of the geotechnical engineer. If thrust blocks are to be used, the concrete for the block must be of good quality and have a 28-day compressive strength of at least

2500 psi. the size of the thrust block will be dependent on the loading and the angle of the pipe. The soils along the alignment can be assigned a bearing capacity of 1500 psf for design of the thrust blocks. The top 2 feet of the soil should be omitted from the design to allow for the risk of surface soil removal due to future excavation or erosion.

Sincerely

Vector Engineers, Inc.

Wayne A. Karem, PhD, PE, PG, D.GE Principal Engineer Licensed Kentucky 15058

Attachments:

Information about your Geotechnical Report

Individual Boring Logs

Laboratory Data

Field and Laboratory Test Data