Former ravine SMWP Addendum Three Final_3.18.13

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March 18, 2012

Addendum Three to the

SOILS MANAGEMENT WORK PLAN

SOUTHSIDE EAST REDEVELOPMENT PROJECT
(FORMER ROLLING HILLS SITE)
BROWNFIELDS PROJECT #:
URS – NORTH CAROLINA PROJECT NO. 38854599
March 18, 2013

A. Overview Approximately 22,000 tons of impacted soil has been removed from the former ravine at
Southside East and shipped for off-site disposal. Consistent with requirements of the
“Former Ravine Area Addendum Two to the Soils Management Work Plan, Southside
East Redevelopment Project (Former Rolling Hills Site)” dated December 21, 2012 approximately 9,800 cubic yards of impacted soil were removed and temporarily stockpiled to the south of the former ravine. Stockpiling was performed to facilitate the
construction schedule in the former ravine. The stockpiled material is divided as follows:

• 3,500 cubic yards that are relatively high in entrained inert debris.
• 6,300 cubic yards that are relatively low in entrained inert debris.

B. Background
Initial geotechnical and site assessment activities at the City of Durham’s Southside East development identified a possible former ravine in the northeast section of the property
that had been infilled with:

• Soils contaminated with polyaromatic hydrocarbons (PAHs) and lead above North Carolina’s Department of Environment and Natural Resources (DENR)
Hazardous Sites Branch Residential Preliminary Residential Health-Based Soil
Remediation Goals (PSRGs).
• Building rubble to include:
o Concrete
o Brick
o Concrete block
o Entrained steel rebar o Cinder block

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March 18, 2012
o Masonry mortar
o Rock
• Asbestos containing building materials.
North Carolina’s restrictions on landfill disposal of petroleum hydrocarbon impacted soil (petroleum hydrocarbons often contain PAHs) prompted an in-depth evaluation of the
likely origin of the contamination. In a correspondence to DENR dated February 22
2012, a forensic evaluation of the former ravine materials was made by comparison of the
ravine materials to known petroleum-hydrocarbon impacted materials elsewhere on-site at Southside East.
Presented below are chromatograms generated from known petroleum hydrocarbon
contaminated soils (left) and the former ravine material (right), both located on the
Southside East site.

Based on comparisons between the two contamination types, the February 22 correspondence concluded that the contamination in the former ravine is consistent with
“construction material buried prior to burial.” The presence of lead is readily attributed
to the presence of lead-based paints in construction materials typically used in the 19th
and 20th centuries.
Approximately 22,000 cubic yards of soil and rubble were shipped off-site for disposal.
However, an unexpectedly large volume of contaminated soil and rubble remained.
These materials have been managed with approval from DENR:

• As geotechnically engineered fill within the former ravine.
• In temporary stockpiles in the southeast corner of the site. Stockpiling was
necessary to facilitate construction schedule within the former ravine.

The production of an unexpectedly large volume of stockpiled material during site preparation activities prompted a re-assessment of this material for use as geotechnically

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March 18, 2012
engineered fill outside of the former ravine, beneath parking lots on the southeast corner
of the site.

A North Carolina Accredited Asbestos Inspector was present during all ravine excavation
activities. No suspect Asbestos Containing Materials (ACMs) were identified in the stockpile, indicating that ACMs that had been initially observed in the former ravine were
isolated in extent and had been shipped off-site.

To address the potential of PAHs and heavy metals in these materials to impact the site,
additional stockpile characterization was performed. The sampling had these objectives:
• Determine the exposure potential to future residents, if left on the surface, by
comparing results to the July 2012 PSRGs.
• Determine the exposure potential to groundwater, using 10X (a default Dilution Attenuation Factor [DAF] criterion) North Carolina’s 15A NCAC 2L.0202
Groundwater Standards and the Safe Drinking Water Act’s Maximum
Contaminant Levels (MCLs) for drinking water.
• As much as practicable, determine the exposure potential to soil gas, which have the potential to infiltrate overlying structures.

Observations by URS in its February 7, 2013 stockpile Soil Sampling report to DENR are
paraphrased below.
Soil Results

• Arsenic, although present at 1.5 mg/kg to 5.3 mg/kg and above the North Carolina
PSRG, is within typical background levels for the Durham area. It is concluded that the measure arsenic levels are naturally occurring and warrant no further
action.
• Total Chromium was detected above the PSRG for Chromium VI. If the total
Chromium results contained Chromium VI then SPLP test for Chromium would
have yielded a higher concentration than 15.5 ug/L (which is the highest detected concentration of Chromium SPLP in SP-3). Given the low concentrations of
Chromium SPLP relative to the total Chromium detected concentrations, the total
Chromium results should be compared to the Chromium III PSRG (24,000
mg/kg). All of the detected total Chromium results are less than the Chromium III
PSRG.
• PAH exceedances of their respective PSRGs is present in almost all soil samples
tested, particularly for the high molecular weight PAHs such as benzo(a)pyrene
(BAP) with a PSRG of 15 parts per billion (ppb) by weight. However, most BAP
exceedances are relatively low in concentration, with 16 out of 18 less than 1.0 mg/kg, and only 2 out of 16 exceed 1.0 mg/kg.

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March 18, 2012
• Lead was not measured above its PSRG, but two out of 16 samples had a total
lead level over 100 mg/kg with the maximum being 207 mg/kg. These two
samples were evaluated by TCLP and the results (AD-4 – 2.42 mg/l; AD-6 –
BDL) confirmed both were below the Hazardous Waste Level for lead (5.0 mg/l). Although these different regulatory levels were not exceeded, capping of these soils to
prevent future contact by residents is warranted.

In managing these soils on-site, leachability testing through SPLP testing was conducted to evaluate the potential for groundwater impacts. The SPLP test results show:
• No PAH exceedances of North Carolina’s groundwater 2L action levels were
observed.
• No heavy metal exceedances of 10X the 2L values were observed.
• No exceedances of federal MCLs were observed.

The SPLP results support the conclusion that these materials are not expected to contaminate groundwater above either North Carolina or Federal drinking water standards.

• Materials removed from the stockpile because they are not inert debris need not
be managed as characteristic hazardous wastes for lead.
Implications for soil gas

An additional consideration for evaluation of the stockpile data is the
contaminants’ potential impacts to site soil gas, and thus, contaminant impacts to overlying structures.

Unlike groundwater and soil contaminant levels, the profound variables in soil
types, thicknesses, and chemical properties, has resulted in a general lack of
consensus within the environmental community regarding the interpretation of soil contaminant levels and impacts to overlying structures. Given this
uncertainty, it is prudent to pre-emptively install engineering controls whenever
soil gas issues are a concern to Brownfield stakeholders.

Current site designs place stockpiled soils derived from the former ravine at Southside East outside of proposed building footprints. If this design is changed
in the future, and these soils may be used beneath building footprints, DENR will
be consulted prior to design finalization. Construction of appropriate engineering
controls, such as vapor mitigation systems as required by the Brownfields Agreement, would be expected to adequately mitigate any soil-gas hazard created by the stockpile’s impacts by PAHs.

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March 18, 2012
C. Specific Requirements
Environmentally impacted geotechnically engineered fill may contain inert debris, which
is limited to concrete, brick, concrete block, entrained steel rebar, cinder block, masonry
mortar, rock, sand, silt, and gravel only. ‘Environmentally impacted’ is defined as soils with lead or polyaromatic hydrocarbon contamination above North Carolina’s PSRGs.

Materials that are not inert debris will be removed as specified below and subsequently
managed off-site as solid waste, to be disposed of at a fully lined RCRA Subtitle D
landfill facility.
1. The receiving area in need of geotechnically engineered fill is outlined as a plan
view in Figure 1 and a cross-sectional view on Figure 2 (attached).

2. For all areas to be constructed using environmentally impacted, geotechnically engineered fill, current grades higher than the final grade specified in the site
development plan shall be removed to achieve an adequate subgrade.

3. Materials will be visually inspected by an Environmental Professional who is also a
North Carolina Accredited Asbestos Inspector. Materials that are not inert debris shall be removed by excavator/track hoe or, if the volumes/sizes/weights are sufficiently small, by
hand picking.

4. Visual inspection will be performed:
a. When the stockpile is disassembled. b. As the material is placed and processed for geotechnically engineered fill.

5. The geotechnically engineered fill shall be placed in lifts not to exceed 12 inches
and be compacted with a Caterpillar 815 or similar sized piece of equipment. Lifts of this
thickness will facilitate inspection, and identification of materials that are not inert debris shall prompt removal prior to placement of the next lift.

6. Concrete, brick, concrete block, entrained steel rebar, cinder block, and masonry
mortar greater in size than twenty-four inches shall be size reduced to less than twenty
four inches prior to placement.
7. The geotechnically engineered fill shall be placed to an elevation that would:
a. Allow approximately six inches of clearance for asphalt and base courses as
required under project specifications for any roadway or parking area.
b. If necessary and in accordance with the Brownfields Agreement, allow a minimum of four feet of suitable structural fill to be placed beneath any
structure.

8. Areas of geotechnically engineered fill will be surveyed per the current witness
barrier specifications.

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March 18, 2012
9. A witness barrier consistent with specifications for the former ravine's witness
barrier shall be placed over all areas of environmentally impacted geotechnically
engineered fill.

10. Areas of environmentally impacted geotechnically engineered fill will be recorded on the property deed as required by North Carolina's Brownfield Program.

11. An approximate / average clean soil six-inch cap of structural fill shall cover the
witness barrier wherever future hardscape (parking lots, driveways, sidewalks, curbing) is
planned. A minimum of two feet of clean compacted soil shall cover the witness barrier where softscape (grass, shrubbery) will be installed in the final construction.

12. The receiving area will be inspected by URS once per month in the period
between completion of cap installation and eventual hardscape installation in the final
construction. DENR will receive updates or reports of all such inspections. Erosion damage to the clean soil cap will be promptly repaired.

13. Utilities (to include storm water, sewerage, electrical, telecommunication, and
drinking water) shall not be installed through the environmentally impacted
geotechnically engineered fill.
Attachments (3)

Richard Lesser, CHMM Slosky & Company, Inc. Mike Fulkerson URS Corporation Kevin Arnold, PG URS Corporation

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B&G SUNBELT INVESTMENTS, LLC
DB 5070, PG 711
PB 144, PG 144
PIN: 0821-16-93-7895
PARCEL NO. 119332
N/F
ZURI AND ASSOCIATES, INC
DB 2560, PG 95
PB 144, PG 144
PIN: 0821-16-93-6463
PARCEL NO. 119328
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HOUSING
IMPROVEMENTS AND
ASSOCIATED
INFRASTRUCTURE
PHASE 1 INFRASTRUCTURE
LIMITS OF ENVIRONMENTALLY
IMPACTED GEOTECHNICALLY
SUITABLE FILL (TYPICAL)
ZONE TO BE PREPARED WITH ENVIRONMENTALLY IMPACTED,
GEOTECHNICALLY ENGINEERED FILL HARVESTED FROM THE
FORMER RAVINE AND CURRENTLY STOCKPILED ON SITE.
LEGEND
ZONE "B-1"
6' CAP
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FUTURE IMPROVEMENTS
VOLUMES
- ZONE B1:9,800 CY
NOTE:
THE DEPTH OF THE EXCAVATION
AREAS ARE BASED ON ROCK
DEPTHS OBTAINED FROM SOIL
BORINGS. DEPTHS OF ROCK
BETWEEN BORINGS HAS BEEN
INTERPOLATED. ACTUAL VOLUMES
MAY DIFFER DUE TO LOCATION OF
ROCK IN INTERPOLATED AREAS.
EXTENTS OF FORMER RAVINE
N:\_2010\1010098\CAD\Construction Documents\Soils_Addendum\SOILS_02-01-13.dwg, PLAN, 2/5/2013 11:17:01 AM, krowe, LandDesign, Inc.
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CLEAN SOILS
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PLACE WITNESS BARRIER AT TOP
OF ENVIRONMENTALLY IMPACTED
GEOTECHNICALLY ENGINEERED
FILL AND SURVEY PRIOR TO
BACKFILLING WITH CLEAN SOIL CAP.
LIMITS OF CONTAMINATED DEBRIS AND SOILS BURY AS SHOWN ON SHEET C-10.0
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SECTION B-B (ZONE B)
SCALE: 1" = 10' (HOR)
1" = 5' (VERT)
FUTURE PARKING LOT - 0'-6" CLEAN SOIL CAP
PRE-CONSTRUCTION
EXISTING GRADE
PROP. INTERIM GRADE
ENVIROMENTALLY IMPACTED
GEOTECHNICALLY SUITABLE FILL
(DEPTH VARIES)
BOTTOM OF EXCAVATION VARIES DUE TO THE
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GREATER, TO ALLOW FOR ADDITIONAL FILL
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SCALE: N.T.S.
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NOTE:
BOTTOM OF EXCAVATION VARIES DUE TO THE
LOCATION OF ROCK/GROUNDWATER. THE
CONTRACTOR SHALL EXCAVATE TO EITHER
BEDROCK OR GROUNDWATER, WHICHEVER IS
GREATER, TO ALLOW FOR ADDITIONAL FILL
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LIMITS OF ZONE B ENVIROMENTALLY
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FUTURE IMPROVEMENTS
NOTE:
SPOT ELEVATIONS GIVEN ON THIS SHEET REPRESENT MINIMUM
BOTTOM OF EXCAVATION. WHERE POSSIBLE, THE
CONTRACTOR SHALL EXCAVATE BELOW THE ELEVATIONS
SHOWN ON THIS SHEET TO EITHER BEDROCK OR
GROUNDWATER, WHICHEVER IS GREATER, TO ALLOW FOR
ADDITIONAL FILL.
N:\_2010\1010098\CAD\Construction Documents\Soils_Addendum\SOILS_02-01-13.dwg, ZONE B GRADING, 2/5/2013 11:17:21 AM, krowe, LandDesign, Inc.