DEPARTMENT OF TRANSPORTATION...Subbase: 14” Aggregate Base Material, Type I, Size No. 21B. The subbase should be extended 1 foot behind the curb and gutter and connected to a standard

DEPARTMENT OF TRANSPORTATION 4975 Alliance Drive Fairfax, VA 22030

VirginiaDot.org WE KEEP VIRGINIA MOVING

GREGORY A. WHIRLEY

COMMISSIONER OF HIGHWAYS

March 22, 2013

MEMORANDUM

TO: Ms. Susie Lue, P.E.

SUBJECT: Soil Survey and Pavement Design Recommendations

for Evergreen Mills Road (Route 621) at Ryan Road (Route 772)

From: 0.17 miles S. of Ryan Road (Route 772)

To: 0.24 miles N. of Ryan Road (Route 772)

Length: 0.379 miles

Project No.: 0621-053-913, C-501; UPC: 84358

A soil survey has been performed for the referenced project, consisting of 51 standard

penetration test (SPT) borings in the existing pavement and in the areas of proposed pavement

widening. This project will widen the existing north and south bound travel lanes on Route 621

north and south of Ryan Road (Route 772)/Red Hill Road (Route 617) by widening into the

existing gravel shoulders. Also, Routes 772 and 617 will be widened to accommodate the

proposed improvements on Evergreen Mills Road. The purpose of this investigation was to

determine the existing pavement structure on Routes 621, 772 and 617 and to investigate the

soils in the areas of the proposed new pavements. The results indicate that the project soils

consist primarily of red brown clayey SAND (SC), sandy lean CLAY (CL) and sandy SILT

(ML) with varying amounts of gravel, typical of the Culpeper Basin. Copies of the soil boring

logs and boring location plans are attached for reference. Eight bulk samples of soils were tested

at locations R-1A, R-8, R-9A, R-16A, R-17A, R-20, R-22, and R-23A. The soaked CBR values

ranged from 7 to 34.3 with a resiliency factor of 2. The CBR value and resiliency factor used for

pavement design are 10 and 2, respectively. A minimum CBR value of 10 shall be specified for

all off-site borrow material.

Existing Pavement

Based upon the results of the soil survey, the existing pavement on Route 621 ranges in thickness

from 1.5” to 7.6” of asphalt concrete, average 5.7”, over 10.2” to 68.4”, average 27.7” of plain

aggregate. An asphalt concrete layer with a thickness of 4.8” was encountered beneath the plain

aggregate at location R-1. A mixture of soil and crushed aggregate with a thickness of 6” was

encountered beneath the crushed aggregate at location R-9. The cores at locations R-6A, R-8A,

Soil Survey and Pavement Design Recommendations for Evergreen Mills Road at Ryan Road

March 22, 2013

Page 2

R-10, R-10A and R-10B were performed in the existing turn lanes. These confirm that the

existing turn lane pavement is not adequate for mainline traffic. The cores at locations R-11A

and R-13A were performed in the outer limits of the north bound lane and encountered only 1.5”

to 3.5”, average 2.7”, of asphalt concrete over 13.2” to 67.2”, average 31.7”, of plain aggregate.

There is alligator cracking indicative of structural failure in the outer 2 to 3 feet of the north

bound lane between approximately sta. 113+00 and sta. 123+00. The existing pavement on

Route 617 ranges in thickness from 2.5” to 3”, average 2.8”, over 2.5” to 7.4”, average 4.7”of

plain aggregate. A mixture of soil and crushed aggregate with a thickness of 6” was encountered

beneath the asphalt concrete at location R-17A. The existing pavement on Route 772 ranges in

thickness from 1.4” to 7.4”, average 4”, over 2” to 18”, average 6.3” of plain aggregate. There is

significant alligator cracking indicative of structural failure in the outer 3 to 4 feet of the west

bound lane between approximately sta. 205+00 and sta. 214+00. Detailed descriptions and

photographs of the asphalt layers encountered are included on the attached boring logs.

Pavement Recommendations

Pavement design followed VDOT's "Pavement Design Guide for Subdivision and Secondary

Roads in Virginia". Traffic information was provided by NOVA Transportation Planning section

in a memorandum dated May 30, 2008 and is summarized in Table 1, below.

Table 1: Summary of Design Traffic Data

Route ADT2008 ADT2024 Trucks

Route 621, South of Ryan Rd 8,000 vpd 13,000 vpd 7%

Route 621, North of Ryan Rd 12,000 vpd 19,000 vpd 3%

Route 772 (Ryan Road) 6,000 vpd 10,000 vpd 4%

Route 617 (Red Hill Road) 1,000 vpd 2,000 vpd 3%

The following pavement section is structurally adequate for the projected traffic volume based

upon a design CBR value of 6.7 and a resiliency factor of 2. The subbase thicknesses have been

designed to match the subbase thickness in the existing mainline pavement in order to provide

for lateral drainage of the existing subbase.

Evergreen Mills Road Widening

Surface: 2” Asphalt Concrete, Type SM-9.5D estimated at 224 lbs/yd2

Base : 6” Asphalt Concrete, Type BM-25.0A Subbase: 14” Aggregate Base Material, Type I, Size No. 21B. The subbase should be

extended 1 foot behind the curb and gutter and connected to a standard UD-4 edgedrain, in accordance with UD-4 standard details. For widening on the high side of the pavement cross-slope, use 8” Aggregate Base Material, Type I, Size No. 21A pugmill mixed with 4% hydraulic cement by weight.

The existing pavement should be saw cut full depth a minimum 1’ from the existing edge of pavement prior to widening except north of Ryan Road in the NB lane where it should be sawcut

Soil Survey and Pavement Design Recommendations for Evergreen Mills Road at Ryan Road

March 22, 2013

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3’ from the existing edge of pavement. The existing turn lanes that will be located beneath future mainline travel lanes should be demolished up to the curb return of the connecting streets and reconstructed with the pavement section identified above. The remaining pavement should be milled to a depth of 2” and replaced with asphalt concrete, type SM-9.5D. Ryan Road Road Widening

Surface: 2” Asphalt Concrete, Type SM-9.5A, estimated at 224 lbs/yd2

Base: 6” Asphalt Concrete, Type BM-25.0A Subbase: 8” Aggregate Base Material, Type I, Size No. 21B. The subbase should be

extended 1 foot behind the curb and gutter and connected to a standard UD-4 edgedrain, in accordance with UD-4 standard details. For widening on the high side of the pavement cross-slope, use 8” Aggregate Base Material, Type I, Size No. 21A pugmill mixed with 4% hydraulic cement by weight.

The existing pavement should be saw cut full depth a minimum 1’ from the existing edge of pavement prior to widening except in the WB lane where it should be sawcut 4’ from the existing edge of pavement. The existing pavement should be milled to a depth of 2” and replaced with asphalt concrete, type SM-9.5D. Red Hill Road Road Widening

Surface: 2” Asphalt Concrete, Type SM-9.5A, estimated at 224 lbs/yd2

Base: 3” Asphalt Concrete, Type BM-25.0A Subbase: 8” Aggregate Base Material, Type I, Size No. 21B. The subbase should be

extended 1 foot behind the curb and gutter and connected to a standard UD-4 edgedrain, in accordance with UD-4 standard details. For widening on the high side of the pavement cross-slope, use 8” Aggregate Base Material, Type I, Size No. 21A pugmill mixed with 4% hydraulic cement by weight.

The existing pavement should be saw cut full depth a minimum 1’ from the existing edge of pavement prior to widening. The existing pavement should be milled to a depth of 2” and replaced with asphalt concrete, type SM-9.5D. Add the following note to the plans: “When liquid asphalt is used as a curing material for the

cement stabilized course, it shall be liquid asphalt CRS-1, CRS-1h or CMS–2 applied at a rate of

0.2 gal/sq.yd. Where necessary for maintenance of traffic, cover material consisting of No. 10

Aggregate or Grading B Sand shall be applied at a rate of 10 lb/sq.yd. All costs for such curing

and materials shall be included in the bid price for the cement stabilized course.”

Unsuitable Materials

Based upon the results of the soil survey, areas that contain wet soils should be expected to be

encountered on this project, especially in the existing wet weather ditches on Evergreen Mills

Road north of Ryan Road. Table 2 lists areas of unsuitable soils which will require removal and

replacement. All unsuitable materials should be specified for disposal off-site at no additional

cost to the Department. Unsuitable materials and methods of treatment shall be identified on the

plans and cross-sections.

Soil Survey and Pavement Design Recommendations for Evergreen Mills Road at Ryan Road

March 22, 2013

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(a) Excavate unsuitable material, replace with Select Material, Type I, Minimum CBR-30,

placed on a woven geotextile subgrade stabilization fabric.

(b) Excavate unsuitable material, replace with Select Material, Type I, Minimum CBR 30.

(c) Excavate unsuitable material, replace with regular embankment (min. CBR 10)

Table 2: Unsuitable Materials at, or below, Subgrade

Boring

Number

Boring

Location

(station)

Depth of

Unsuitable/

Treatment

(inches)

Estimated

Limits

Direction Comments/Reason

R-4 105+90

18” (b) Sta. 105+00

to 106+50

SB Wet, cut only

R-6A 108+29 18” (a) Sta. 107+50

to 109+50

NB Wet, cut only

R-8A 110+17 18” (b) Sta. 109+50

to 111+50

NB Wet, cut only

R-9A 111+95 18” (b) Sta. 111+50

to 123+00

NB and SB Wet, cut only

R-10 114+05

R-12 117+81

-- -- 18” (c) Sta. 113+00

to 123+00

NB and SB Exist. ditch, prior to

embankment fill

R-17A 203+23 24” (b) Sta. 202+75

to 203+75

WB Wet, cut only

R-22 209+00 24” (a) Sta. 208+00

to 210+00

EB Wet, cut only

R-24 212+96 24” (b) Sta. 212+75

to 213+75

EB and WB Wet, cut only

R-24A 213+21

Underdrains

Standard UD-4 edgedrains should be installed beneath the curb and gutter or beneath the outside edge of paved shoulder. The UD-4 should be lowered a minimum of 4" below the bottom of the plain aggregate subbase course and below the base of the Select Materials, Type I, Minimum CBR 30 identified in Table 2, above. Alternatively, a standard cross-drain (CD-1 or CD-2) may be installed at the low end of the areas listed in Table 2 and extended to daylight.

Shrinkage Factor

For estimating earthwork quantities, use an average shrinkage factor of 18% for the clayey

sands/sandy clays/silts encountered on-site.

Soil Survey and Pavement Design Recommendations for Evergreen Mills Road at Ryan Road

March 22, 2013

Page 5

Shallow Rock

Although bedrock consisting of diabase was encountered at shallow depths across the project

limits we do not anticipate any significant conflicts based upon the currently proposed grades for

the roadway and storm drains. However, the surface of the diabase rock is typically highly

variable so rock removal may be required at isolated locations.

Sources of Materials

Aggregate materials for this project may be obtained from the following sources:

Chantilly Crushed Stone, Chantilly, with an average truck haul of approximately 6.6 miles.

The average unit weights of materials are:

Plain Aggregate, Type I, Size No. 21B: 161.4 pcf plus 4.9% moisture correction.

Cement Treated Aggregate (CTA): 160.9 pcf plus 5.2% moisture correction.

Select Material, Type I, Min. CBR 30: 161.4 pcf plus 4.9% moisture correction.

Luck Stone, Leesburg, with an average truck haul of approximately 7.2 miles.

The average unit weights of materials are:

Plain Aggregate, Type I, Size No. 21B: 161.8 pcf plus 5.8% moisture correction.

Cement Treated Aggregate (CTA): 159.7 pcf plus 5.1% moisture correction.

Select Material, Type I, Min. CBR 30: 161.8 pcf plus 5.8% moisture correction.

Asphalt concrete for this project may be obtained from the following sources:

Virginia Paving, Chantilly, with an average truck haul of approximately 7.7 miles.

Virginia Paving, Herndon, with an average truck haul of approximately 9.1 miles.

If you have any questions, please contact Kyana Jennings at (703) 259-2917.

Prepared by: For:

Kyana Jennings David P. Shiells, P.E.

Geotechnical Engineer District Materials Engineer

Attachments: Pavement Photographs

Boring Location Plans (6)

Boring Logs (51)

Summary of Soils Laboratory Test Data

Soil Survey and Pavement Design Recommendations for Evergreen Mills Road at Ryan Road

March 22, 2013

Page 6

Soils Laboratory Test Results

cc: Ms. H. L. Cuervo, P.E.

Mr. S. L. Bates, P.E.

Mr. C. M. Pruitt, P.E.

File

Q:\Mat\RECOMMENDATIONS & REPORTS\Soil Survey Reports\0641-053-913, C501\0641-053-913, C501 Final Report with letterhead.doc

Soil Survey and Pavement Design Recommendations for Evergreen Mills Road at Ryan Road

March 22, 2013

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