Lutes, C.C., H. Schuver, R. Truesdale, I. Hers, D. Folkes and J. Minchak Non-residential building vapor intrusion lifecycle cost analysis Presented at AEHS/EPA 2015 workshop on Long-Term Evidence-Based Protection & Sustainability; in Residential, Commercial and Industrial Buildings; San Diego

1. Nonresidential Building: Vapor Intrusion
Lifecycle Cost Analysis
Chris Lutes, CH2M HILL, Raleigh N.C.
Presented at EPA Workshop at AEHS 2015: Long-Term
Evidence-Based Protection & Sustainability in
Residential, Commercial, and Industrial Buildings

2. Hypothetical Base Case Building Assumptions
 Commercial building: 7,200 square ft, 30 years old, Northern California,
major metropolitan area
 Slab on grade, one floor, three tenants; single style of construction; no
open bay doors
 Not believed to be the primary release location
 Overall site is reasonably well understood – PCE in gw at 500 µg/l at 15 ft
bls (aerobic case, TCE not expected to be driver). Source treatment just
beginning 200 ft. upgradient, expected to require 30 years to reach VISLs
 Previous data on this specific building consists of one round of 24 hour
indoor air sampling, at two locations, in summer. Results gave compound
ratios potentially suggestive of vapor intrusion.
 Indoor air concentrations observed in one round of sampling were
substantially greater then ambient concentrations.
 Indoor air concentrations in one round of sampling (normal HVAC
conditions) were at roughly 50% of the value at which state would definitely
require long term mitigation.

3. Alternate Scenarios' For Cost Analysis in this Same Building
 Scenario 1: Mitigation Early
– Implement vapor intrusion mitigation with SSD immediately,
– Monitor effectiveness sufficiently to verify adequate performance for
chronic risk protection over all climatic conditions.
– Long term monitoring for 30 years.
– No change to building HVAC system.
 Scenario 2: Primarily Monitoring
– Multiple rounds of monitoring to better define seasonal variability;
– Intensive building survey to locate and eliminate potential indoor
sources.
– Mitigate if necessary.

4. Scenario 1 Mitigation – General Requirements Based
on DTSC Vapor Intrusion Mitigation Advisory (2011)
 Preemptive mitigation is an option available to PRP; CA guidance allows
possible next actions between 10-4 and 10-6:
– Additional data collection
– Monitoring
– Additional Risk Characterization
– Mitigation
– Source Remediation
 Assumption - action level in practice 10-5; initial one round result here 5x10-6
 Minimum monitoring requires pressure gauge with optional visual alarm; no
telemetry required
 VI design must be submitted for DTSC for review and approval; including
submitting building inspection and diagnostics results
 Response action implementation report required after install
 O&M plan required, public participation plan required

5. Scenario 1 Mitigation - Monitoring Requirements Based on
DTSC Vapor Intrusion Mitigation Advisory (2011)
 Subslab sampling required for baseline (if not already installed)
 Pressure data baseline pressure field, followed by demonstration of
the presence of a negative pressure field below the entire footprint,
ensure continuous operation of mitigation system
 VOC Monitoring – assume 3 rounds over 1.5 years to establish SSD
seasonal effectiveness (based on negotiation from the six rounds called for “high
risk” sites”)
 Routine system inspection; including monitoring vent risers for flow
rates and gas concentrations (Quarterly for first year, then annual)
 Long term sampling of indoor and outdoor air every 5 years
 Requires an enforceable mechanism, with DTSC cost recovery and
financial assurance.

6. Scenario 1: Key Base Case Cost Assumptions
 Consulting firm within 25 miles of site; 30 years of turn key services,
subcontracts mechanical and electrical aspects of full scale system
 Project pays for electricity and an allowance for loss of conditioned air.
 System requires 1 HP blower; 3 extraction points; Requires about 45 ft ROI
 No significant shallow groundwater/surface water concerns for system
operations
 Maintenance allowance :
– Minor events like squirrel nest or tripped breaker every 3 years, and
– Blower replacement every 10 years (conservative per Folkes and Kurtz, 2014);
 New Source Allowance:
– Assumes 10% chance per sampling year that an indoor source will have been introduced
– Instrumental inspection and resampling will then be required to resolve problem
– Cost $10K per occurrence (assumed, parameter to be varied in sensitivity study).

7. Scenario 1: Variables for Sensitivity Analysis (Base
Case in Red)
 Long term sampling frequency after passing initial monitoring
– Every 3 years
– Every 5 years
 Reporting
– Full written reporting to occupants and agency after each round
– Brief report (no significant changes) in later rounds
 Building size (scales number of samples, size of fan, extraction
points, capital cost etc.)
– 7,000 sq ft
– 35,000 sq ft
– 175,000 sq ft
 Building Complexity: 1, 3, 10 occupied suites/foundation additions
 System Intensity (based on soils permeability and heterogeneity)
– 45 ft ROI; 0.14 HP of blower per 1,000 sq. ft.
– 15 ft ROI; 0.5 HP of blower per 1,000 sq. ft.
 New source analysis response cost $10K, $1K

8. Scenario 2 Monitoring –Provisions from CA VIG 2011
that Affect Cost
 “Regulatory staff should be present during all building visits”
 “Numerous sampling events may be required within a building
before DTSC would consider “no further action” for the exposure
pathway.”
 “In office buildings, samples should be collected from primary work
areas and near the points of vapor entry (such as sumps, elevator
shafts or floor drains) to help define the potential routes of entry.”
 “It is generally desirable to conduct concurrent sampling of other
media, such as sub-slab soil gas, and/or groundwater, when
sampling indoor air.”
 “DTSC anticipates that numerous documents will be submitted for
agency review and approval during the process of evaluating a
site for vapor intrusion.”

9. Example of Regulatory Guidance on Number of
Sampling Locations – NJ - 2013
For example, a 25,000 ft2
strip mall separated into five
individual tenant spaces that
are separately ventilated may
be best evaluated with 10
samples, where a stand-
alone 25,000 ft2 building that
is mostly warehouse space
with a small office space and
a single ventilation system
may only need 5 IA samples

10. Scenario 2 Monitoring – Costing Assumptions – Base
Case
 Four rounds of sampling – twice a year for two years; including both
subslab and indoor air.
 30% risk of needing mitigation after the first four monitoring rounds
 If Ok after two years, one round every three years thereafter
 Reporting to occupants and agency after each round
 Thirty years of monitoring
 10% risk per monitoring round after the first year of exceedance due
to a new indoor source requiring study to find
 Seven total indoor samples per round in this 7,200 sq ft building:
– 4 breathing zone
– 2 entry point
– 1 ambient
 Four subslab samples per round
 New Source Allowance: same assumptions as scenario 1

11. Scenario 2: Variables for Sensitivity Analysis (Base
Case in Red)
 Initial monitoring period frequency:
– Twice per year for 2 years
– Quarterly for two years
– Monthly for 15 months
 LTM frequency after passing initial monitoring
– Annual
– Every 3 years
– Every 5 years
 Reporting
– Full written reporting to occupants and agency after each round.
– Brief report (no significant changes) in later rounds
 Building size (scales number of samples)
– 7,000 sq ft
– 35,000 sq ft
– 175,000 sq ft
 Building Complexity: 1, 3, 10 occupied suites/foundation additions

12. Base Scenarios, Cumulative Costs; With and Without
Mitigation
$‐
$50,000
$100,000
$150,000
$200,000
$250,000
$300,000
$350,000
$400,000
0 10 20 30
Cost
Year
Cumulative Cost Over Time of Base Scenarios
Scenerio 1 Mitigation Early,
Cumulative ($)
Scenario 2, Primarily
Monitoring, Cumulative,
Never Need to Mitigate ($)
Scenario 2 Try Monitoring,
Then Need to Mitigate,
Cumulative ($)
Scenario 2 Primarily
Monitoring, With 30% Risk
of Mitigation, Cumulative
($)

13. Base Case Annual Costs: With and Without Mitigation
$1,000
$10,000
$100,000
0 10 20 30
Year
Annual Costs by Year of Operation
Scenario 1 Mitigation Early
($)
Scenario 2 Primarily
Monitoring, ($), Never
Need to Mitigate
Scenario 2 Try Monitoring,
Then Need to Mitigate ($)
Scenario 2, Primarily
Monitoring, Predicted Cost
with 30% mitigation risk
($)

14. Sensitivity to Changing Monitoring Frequency in
Scenario 2
$‐
$50,000
$100,000
$150,000
$200,000
$250,000
$300,000
$350,000
$400,000
0 10 20 30
Year
Cumulative Cost Over Time
Effect of Increased Monitoring Frequency in Out Years
Scenario 1, Mitigation Early
Scenario 2, Primarily
Monitoring, Never Need to
Mitigate
Scenario 2 Primarily
Monitoring with 30%
Mitigation Risk
Scenario 2,Continued
Annual Monitoring for 30
Years, Never Mitigate
Scinerio 2, Continued
Annual Monitoring for 30
years, 30% Risk of
Mitigation

15. Sensitivity Analysis: Scenario 1 Mitigation Early
Case Description $K total
cost over
30 years
% Change
From Base
Case
Base case 314
LTM increased to every three from every five years 341 +9
Reporting in outyears brief letter only if no significant
changes
299 -5
Building complexity decreased to one suite/foundation
from three
289 -8
Building complexity increased to ten suites/foundations
from three
457 +46
New indoor source analysis response cost decreased
from $10K to $1K per event (still with 10% likelihood)
307 -2

16. Sensitivity Analysis: Scenario 1 Mitigation Early
Case Description:
Building Size
$K total
cost over
30 years
%
Change
From
Base
Case
Multiple
of Base
case
cost
30 Year
Mitigation
Cost Per
Sq. Ft ($)
First Year
Cost Per
Sq. Ft.
Base case 7000 sq. ft.
and 45’ ROI
$314K $44 $14
Increase size from 7,000
to 35,000 sq. ft. (5x)
$523K 67% 1.67x $15 $5
Increase size from 7,000
to 175,000 sq. ft. (25x)
$1,337K 425% 4.25x $8 $2
Increase size from 7,000
to 35,000 sq. ft. (5x) and
tighter soil – 15’ ROI
$1,006K 320% 3.20x $28 $12

17. Sensitivity Analysis: Scenario 2 Monitoring Only
(assumed on this slide that no mitigation occurs)
Case Description:
Building Size
$K total
cost over
30 years
%
Change
From
Base
Case
Multiple
of Base
case
cost
30 Year
Monitoring
Cost Per Sq. Ft
($)
Base case: 7000 sq. ft.;
3 suites/foundations
$159K $22
Increase size from 7,000
to 35,000 sq. ft. (5x)
$196K 23% 1.23x $6
Increase size from 7,000
to 175,000 sq. ft. (25x)
$234K 47% 1.47x $1
Increase number of
suites/foundations to 10;
still at 7,000 sq. ft.
$238K 50% 1.5x $34

18. Mitigation Early vs. Monitoring Only – By Building
Size; 30 Year Cumulative Total Cost
0
200
400
600
800
1000
1200
1400
1600
0 50 100 150 200
30YearCost($K)
Building Area (thousands of sq. ft.)
Early Mitigation Compared to Monitoring With 30%
Chance of Mitigation - By Building Size
Scenario 1: Mitigation
Early
Scenario 2:
Monitoring Never
Needed to Mitigate
Scenario 2:
Monitoring With 30%
Chance of Mitigation

19. How Much Do You Save on Mitigation and Monitoring
If Remediation Is Eventually Effective?
 Assumption: Remediation eliminates need for system operation for VOCs after 10
years. Systems turned over to building owner for use for radon if desired.
 Remediation costs and close out costs not quantified here.
Scenario Year 11-30
Total Cost $K
Year 11 – 30
Annual Cost $K
Scenario 1: Mitigation Early; Base Case, Sq. Ft. $145K $7K
Scenario 1: Mitigation Early, 35,000 Sq. Ft. Building $250K $13K
Scenario 1: Mitigation Early, 35,000 sq. ft. and tighter
soil – 15’ ROI
$402K $20K
Scenario 1: Mitigation Early, 175,000 Sq. Ft. Building $652K $32K
Scenario 2: Monitoring Only; Base Case $80K $4K
Scenario 2: Monitoring Only: If Still Annual $229K $11K

20. Conclusions – Part 1
 There are cases, like the hypothetical, but realistic one illustrated -
where the economic tradeoff between a “mitigation early” and
“monitoring until you have to mitigate” strategy is a close one.
 Going to mitigation early can raise the ultimate life cycle cost if there
is a reasonable chance that monitoring will lead to a decision not to
mitigate. But if you are almost certain to have to mitigate anyway,
then several rounds of monitoring plus mitigation is more expensive.
 Monitoring and mitigation have very different annual cash flows.
 If you have to monitor annually for the long term without mitigation,
then mitigation is less expensive in the long term.
 The cost advantage of trying monitoring first is greater for larger,
simple buildings (few suites/foundations)

21. Conclusions – Part 2
 Reducing LTM time from 30 to 10 years can save $140K - $650K
building.
 For mitigation the most cost sensitive variables are complexity of the
building (# of foundations/suites), size and soil type.
 Mitigation cost per square foot drops considerably in large, but
simple, relatively open buildings.
 Cost should not be the only consideration in selecting an option – for
how to weigh other considerations along with cost see poster:
A Life Cycle and Cost Analysis of Preemptive Mitigation, Site Characterization,
and Vapor Source Reduction Strategies at Industrial VI Sites with Multiple
Buildings by Loren Lund

22. Acknowledgements
 Henry Schuver, EPA ORCR
 Robert Truesdale, RTI
 Ian Hers, Golder
 Dave Folkes, Geosyntec
 Jeff Minchak, CH2M HILL

23. Discussion