Response to Comments

2014 Revised Shelby County Maintenance Plan

The Pollution Control Section of the Shelby County Health Department (Department)

prepared a draft revision of the federally approved 2010 Maintenance Plan (Federal 

Register/Vol.75, No. 1/Monday, January 4, 2010) for public review and comment prior to

submission for approval by the Tennessee Air Pollution Control Board and subsequent

submission to the United States Environmental Protection Agency (EPA) for their

consideration and approval. The required 30-day public comment period was formally

opened on January 31, 2014 with the publication of a notice in the Memphis Daily News. 

In accordance with the Department’s public notice protocol, electronic notice was sent to a

list of interested individuals and local elected bodies on January 29, 2014. In addition, 

electronic notice was sent to local members of the Metropolitan Planning Organization 

(MPO) and the MPO distributed an electronic message on February 3, 2014. A press

release was made by Shelby County Government on January 31, 2014, announcing the

availability of the plan for review and comment.

Two public hearings were scheduled and held. One was held at the Benjamin L. Hooks 

Central Library in Memphis, Tennessee on Tuesday, March 4, 2014 at 6:00PM. The

second public hearing was held at the Baker Community Center in Millington, Tennessee 

on Thursday, March 6, 2014 at 6:00PM. The comment period ended at the close of 

business on Friday March 14, 2014, although comments were accepted that were dated and 

post-marked for the following Monday, March 17, 2014.

The Department received comments from the Environmental Protection Agency, Region 4 

(EPA), the Tennessee Department of Environment and Conservation (TDEC) and from 

the Memphis Metropolitan Planning Organization (MPO). A listing of those comments

and the Department’s response (in italics) follows.

Commenter 1 - EPA

The EPA submitted a letter dated March 6, 2014 by the United States Postal Service and 

electronically on March 10, 2014. The letter contained six (6) numbered comments.

EPA 1. Phase 3 of the Contingency Plan: For clarity, please specify that the regulatory 

programs that will be implemented to correct a monitored violation will be adopted and 

implemented within eighteen to twenty-four months of the trigger.

Shelby County Response to EPA 1. - Because of the nature of rulemaking in Tennessee, it 

is not possible to ‘pre-adopt’ this contingency plan. However, the language for Phase 3 of 

the plan has been changed to more clearly indicate the steps and timing the Department 

will take in response to the trigger.

EPA 2. On page 9-11 the Motor Vehicle Emissions Budget (MVEB) Section: In Table III 

Shelby County has provided a great deal of detail on how the base year inventories with the 

safety margins have been prepared for Volatile Organic Compounds (VOC) and Nitrogen 

Oxides (NOx). However, this may be confusing to the general public. The EPA suggests 

that a Table IV be created to reflect MVEBs for years 2006 and 2021.

Shelby County Response to EPA 2. - EPA offered an example Table IV for use by Shelby 

County. That table has been utilized, in part, in the revised maintenance plan.
EPA 3. Please include a discussion on the methodology (MOVES2010b) used to calculate 

the mobile source emissions. The discussion can be included in attachments III through VI. 

A discussion on Temperatures, Reid Vapor Pressure, and Humidity used as inputs will be 

helpful. Also a statement on how these planning assumptions were agreed on by

interagency consultation should be included.

Shelby County Response to EPA 3. – Information can be found in the document, 

“Methodology Used for MOVES Runspec”, which describes the various parameters 

required to set up the MOVES Run Specification file for the MOVES2010b model. 

Information concerning methodology used to calculate mobile source emissions, 

temperatures, Reid Vapor Pressure, and humidity can be found in the document titled

“Methodology Used to Develop MOVES Inputs”. Both documents are located in 

Attachment VIII - Supplemental Support Documents of the maintenance plan revision. 

These assumptions were agreed upon and are as iterated in the May 17, 2013 IAC 

memorandum found in Attachment II – Intergovernmental Consultation.

EPA 4. On page 6 it clearly describes the attainment status for particulate matter. Doing the 

same for Lead, Nitrogen Dioxide and Sulfur Dioxide would enhance the non-interference 

showing.

Shelby County Response to EPA 4. - Changes have been made to clearly define the area’s 

current status with regard to these pollutants.

EPA 5. When submitting the final plan, please ensure the MOVES input/output files are 

included in the submission. An electronic copy on CD may be substituted for a hard copy 

(input/output files only). Please ensure the files are unzipped and in excel format.

Shelby County Response to EPA 5. - An electronic copy (CD) of the MOVES input/output 

files are included in the submission. The files are unzipped and are in excel format.

EPA 6. On page 3 the second paragraph under section 5 Emissions Reduction 

Requirements, please clarify the current ozone nonattainment status for the 2008 8-hour 

ozone standard.

Shelby County Response to EPA 6. - Language has been added to improve clarity.

Commenter 2 – TDEC

The TDEC submitted a letter dated March 17, 2014 by the United States Postal Service 

and electronically on March 17, 2014. The letter contained twelve (12) numbered

comments.

TDEC 1. The emissions in Table 1 reflect tons/day. The discussions references tons/year. 

How were the tons/year derived? Was a model run conducted to generate the emissions in 

tons/year?

Shelby County Response to TDEC 1. – A model run was conducted to obtain VOC and 

NOx in tons/day. These numbers were then multiplied by 365 days/year to achieve 

tons/year. The document has been corrected to explain and show consistency between the 
numbers.

TDEC 2. Does the point source inventory for 2021 reflect all changes to the point source 

sector (other than Cleo Inc.) that have occurred since the second half of the maintenance 

plan was originally submitted? Have other industries expanded or shutdown since this 

maintenance plan was last submitted? If so, are those changes to the emission inventory

reflected here? If not, why not?

Shelby County Response to TDEC 2. – The point source sector of the 2021 emissions 

inventory only reflects the reductions that have occurred due to the shutdown of Cleo Inc. 

Other industries relevant to the point source sector have shutdown. None have expanded 

and no new sources have been constructed. The reductions from these closures are a 

weight of evidence as to the continued progress of the overall plan to maintain air quality 

that attains the 1997 national ambient air quality standard for ozone, but are not necessary 

to demonstrate an offset of the emissions that occur with the shutdown of the vehicle 

inspection and maintenance (I/M) program by the City of Memphis. Further, until history 

proves otherwise, it is not known what emission reductions may or may not occur in the 

years ahead and until 2021 occurs. Consequently, the main issue of the entire revision is to 

assure the offset of emissions that occur with the shutdown of the I/M program.

TDEC 3. Page 11, 1

st paragraph, the third sentence seems to indicate that there are 

reductions of NOx and VOCs from point sources, which is not borne out by the tables. In 

the second paragraph, the safety margins allocated to the MVEB do not appear to match the 

information in Table III.

Shelby County Response to TDEC 3. – The third sentence in the first paragraph has been 

corrected to reflect the figures in Table III. The safety margins discussed in the second 

paragraph have been corrected to match the information in Table III.

TDEC 4. The emissions inventory does not show interim emissions estimates between 

2006 and 2021.

Shelby County Response to TDEC 4. – In early proposals by the Department to revise the 

2010 Shelby County Maintenance Plan, several interim years were discussed with the IAC. 

In an October 31, 2013 IAC teleconference, “ . . . it was agreed by those on the call that 

the SIP would consist of a base analysis year of 2006 and a final year of 2021. MVEB’s 

will be established for 2006 and 2021.” Reasons for this determination were summarized 

in the original minutes for the October 31 teleconference in a memorandum dated 

November 1, 2013. After review of the memorandum by the agencies attending the call, the 

memorandum was finalized and redistributed on November 18, 2013, by email, to the call 

attendees. This memorandum can be found in Attachment II – Intergovernmental 

Consultation of the proposed 2014 Revised Maintenance Plan and is entitled “SIP Revision 

Budget Years and Memphis MPO Conformity” in the Subject line.

TDEC 5. The documentation lacked information on how the inputs for the MOVES model 

were developed.

Shelby County Response to TDEC 5. – Documentation titled “Methodology Used to 

Develop MOVES Inputs” is included in the maintenance plan revision in Attachment VIII -

Supplemental Support Documents.
TDEC 6. What was the source of the vehicle miles traveled VMT used? What are the VMT 

for each of the analysis years?

Shelby County Response to TDEC 6. – Vehicle miles traveled (VMT) were provided by the 

MPO and were generated by the Memphis Urban Area Travel Demand Model (TDM). The 

VMT for 2006 and 2021 are displayed in the tables below.

Shelby County Annual VMT by Source Type and by Year

Source Type

Source 

Type 

ID

Source Type VMT

2006 2021

Motorcycle 11 25,604,577 30,597,047

Passenger Car 21 6,116,293,396 7,308,869,710

Passenger Truck 31 1,393,265,928 1,664,929,980

Light Commercial Truck 32 465,466,353 556,224,433

Intercity Bus 41 3,712,127 4,873,218

Transit Bus 42 1,942,992 2,309,079

School Bus 43 25,201,662 32,497,370

Refuse Truck 51 2,897,462 2,074,341

Single Unit Shorthaul Truck 52 198,308,587 249,731,833

Single Unit Longhaul Truck 53 25,487,609 39,169,765

Motor Home 54 45,859,407 59,508,279

Combination Short-haul Truck 61 166,694,865 222,336,742

Combination Long-haul Truck 62 199,421,654 316,912,033

Total 8,670,156,620 10,490,033,832

TDEC 7. What version of the MOVES database was used?

Shelby County Response to TDEC 7. - MOVES2010b.

TDEC 8. How was the source type population developed and adjusted over time?

Shelby County Response to TDEC 8. - The MOVES Technical Guidance offers direction 

on how to leverage default population and VMT data alongside local VMT data to arrive at 

an estimate of the local population. This guidance suggests comparing the ratio of default 

source type population to default VMT to the local VMT to arrive at an estimate of local 

source type population. This methodology was applied for all analysis years. A growth rate 

was not applied, since growth is inherently built in through this methodology.

TDEC 9. How were the compliance factors in the IM inputs calculated?

Shelby County Response to TDEC 9. – The compliance factors for the revised ozone 

maintenance plan for Shelby County were developed as discussed in the document titled 

“MOVES2010b Compliance Factor for Shelby County Tennessee” found in Attachment 

VIII - Supplemental Support Documents.
TDEC 10. Why is the endModelYear 2002 in the 2006 IM input file? Did the 4 year 

exemption apply then? When did the change to the ordinance for the 4 year exemption take 

effect?

Shelby County Response to TDEC 10. – 2002 should not be used as the endModelYear in 

the 2006 IM input file, MOVES has been rerun to correct this using 2005 as the end year. 

The 4 year exemption should not be used in the 2006 IM input file, MOVES has been rerun 

to correct this using 2005, a one-year exemption. The 4 year exemption took effect January 

3, 2011, however this was an incorrect application of this exemption and should not have 

been used in the MOVES I/M input for 2006.

TDEC 11. The last paragraph on page 9 seems to indicate that the MVEBs did not change 

as provided in the 2010 ozone maintenance plan. Is this true? Table III and subsequent 

discussion do not agree with this statement.

Shelby County Response to TDEC 11. – the second sentence of the referenced paragraph 

has been restructured to provide clarity.

TDEC 12. Table III has a column indicating ‘On-Road Allocation Percent’ – these values 

appears to be a fraction, not a percent. The last column states that this is the “On-Road 

Safety Margin”; the safety margin identified in 40 CFR 93.101 indicates that any safety 

margin is not explicitly for on-road – it is the overall safety margin, some of which (95% in 

this case) is being applied towards the MVEB. The column headings are somewhat 

confusing.

Shelby County Response to TDEC 12. – The values referenced in Table III have been 

corrected to show percent.

The Code of Federal Regulations (CFR), 40 CFR 93.101, defines “safety margin” to mean 

“the amount by which the total projected emissions from all sources of a given pollutant 

are less than the total emissions that would satisfy the applicable requirement for . . .

maintenance.” Subpart 93.101 also states that the “motor vehicle emissions budget”

(MVEB) is that “ . . . portion of the total allowable emissions defined in the submitted or 

approved . . . maintenance plan for a certain date for the purpose of . . . demonstrating . . . 

maintenance of the NAAQS, for any criteria pollutant or its precursors, allocated

(emphasis added) to highway and transit vehicle use and emissions.” As used in Table III

(which has been restructured to add clarity), the “safety margin” is the difference between

“baseline” emissions in 2006 and “total” emissions in 2021, which has occurred in the 

summation of the increases and decreases in emissions from the five categories of area, 

non-road, on-road, point, and Cleo, Inc Offsets at 1.1 to 1, in Table III. Considering VOC 

emissions specifically, as the method would be the same for NOx emissions, “Total” 

emissions of 93.433 tpd in 2021 evidence a reduction of emissions from 2006 (98.061 tpd)

of 4.628 tpd (98.061 tpd minus 93.433 tpd) which is the “safety margin”. Ninety-five 

percent (95%) of the “safety margin”, 4.396 tpd, which is termed the “motor vehicle safety 

margin”, is allocated to the MVEB (as provided for by the definition of MVEB in 40 CFR 

93.100) which is a summation of the emissions expected to occur in 2021 from on-road 

sources plus the “motor vehicle safety margin” of 4.396 tpd. To further clarify the intent 

and use of Table III, a column has been added which is labeled “Safety Margin” and, the

former “On-Road Safety Margin” column has been repositioned and is now termed “Motor 

Vehicle Safety Margin”. As was discussed and implemented in response to EPA 2., a Table 
IV has been added to the revised maintenance plan to better clarify the MVEBs for VOC 

and NOx.

Commenter 3 – MPO

The MPO submitted a letter dated March 6, 2014 by email on March 10, 2014. The letter

contained two (2) numbered comments.

MPO 1. Under Section 11 Public Comment,please list the public hearing that will be held

on March 6, 2014. The draft document only lists the public hearing on March 4, 2014.

Shelby County Response to MPO 1. - March 6, 2014 has been added to the document.

MPO 2. Under Section IIA, Regulatory Portion: Revised Maintenance Plan Projects, if

discontinuing the I/M program resulted in 129 tpy of VOCs and if 224.4 tpy are available

from the closure of the Cleo plant, the remaining emission bank would seem to be

104.94 when the two are subtracted and multiplied by 1.1. Under the section it states

that there would be 105.5 tpy in banked emissions. We would like to get a clarification

on the remaining banked emissions.

Shelby County Response to MPO 2. - The actual emissions increase that must be offset is 

128.48 tons per year (tpy) (0.352 tons per day times 365 days per year) of VOC. This has 

been corrected in the document.