### CLARK COUNTY

AIR QUALITY REGULATIONS

S E C T I O N 9 0

- FUGITIVE DUST FROM OPEN AREAS AND VACANT

LOTS

90.1 F UGITIVE D UST From O PEN A REAS AND V ACANT L OTS

90.1.1 Purpose: To limit the E MISSION of P ART I CULAT E M A TTE R into the A MBIENT
A IR from O PEN A REAS A ND V ACANT L OTS

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90.1.2 Applicability : The provisions of this Regulation shall apply to O PEN A REAS
A ND V ACANT L OTS which are located in the PM 10 N ONATTAINMENT A REA (H YDROGRAPHIC B ASIN 212) and the Apex Valley (H YDROGRAPHIC B ASINS 216 and 217). Nothing in Section 90 of thes e Regulations shall be construed to prevent enforcement of Se ction 40 (Prohibition of N UISANCE Conditions) of these Regulations. The provisions of this Regulation shall not apply to

Normal Farm Cultural Practices or t he raising of fowl or animals. The provisions of this Regul ation shall not apply to S T A T IONARY S OURCES as defined in Section 0, exc ept that these control m easures shall be considered as part of a BACT determination.

90.1.3 Effective Date Of This Regulation:

90.1.3.1 S e cti on 90, adopted by the Clark County Board of County Commissioners on June 22, 2000, shall be effective in H YDROGRAPHIC B ASIN 212 o n January 1, 2001, except as otherwise provided herein.

90.1.3.2 Section 90 s hall be ef f e c t iv e in H YDROGRAPHIC B ASINS 216 and 217 o n A p r i l 1, 2002, except as ot herwise provided herein.

90.2 Requirements:

______________________________________________________________________ Amended 07/01/04 90-1 CC Air Quality Regulations 90.2.1 O PEN A REAS A ND V ACANT L OTS : If O PEN A REAS A ND V ACANT L OTS are 5,000 square feet or lar ger and are disturbed by any means, including use by M OTOR V EHICLES and/or O FF -R OAD M OTOR V EHICLES or material dumping, then the O WNER A ND /O R O PERAT OR of such O PEN A REAS A ND
V ACANT L OTS shall implement one or more of the C ONTROL M EASURES described in Subsection 90.2.1.1 of this Regulation within 30 calendar days following the initial discovery of disturbance or vehicle use on O PEN
A REAS A ND V ACANT L OTS . The O WNER A ND /O R O PERAT OR shall implement all control measures necessary to limit the disturbanc e of open areas and______________________________________________________________________ Amended 07/01/04 90-2 CC Air Quality Regulations vacant lots in accordance with the requirements of this regulation. Advisory Notice: In order to conserve water to the greatest extent practicable, the use of R ECLAIMED W AT ER is highly encouraged.

90.2.1.1 C ONTROL M EASURES :

(a) Where there is evidence of soil disturbance by M OTOR V EHICLES and/or O FF -R OAD V EHICLE use, prevent M OTOR V EHICLE and/or O FF

R OAD V EHICLE trespassing, parking, and/or access, by installing barriers, curbs, fences, gates, posts, signs, shrubs, trees, or other

effective traffic Control Measures . A stable surface area shall be

established and maintained by using one of the C ONTROL
M EASURES set forth in Subsections 90. 2.1.1(b) or (c) or by the effective application of water in compliance with the stabilization

standards set forth in Subsection 90.2.1.2. Where measures to prevent vehicular trespassing and mo vement are not effective, the application of water will not be utilized for surface stabilization. For the purposes of this Subsecti on, use of or parking on O PEN A REAS
A ND V ACANT L OTS for noncommercial and non-institutional purposes by the O WNER A ND /O R O PERAT OR of such O PEN A REAS A ND V ACANT
L OTS shall not be considered vehicle use under this Subsection. In addition, vehicle use related to landscaping maintenance shall not

be considered vehicle use under this Subsection. For the purpose of this Regulation, landsc ape maintenance does not include grading, trenching, or any other mechanized surface disturbing activities performed to establish initial landscapes or to redesign existing landscapes; or

(b) Where a D IST U RBED S URFACE A REA exists (including disturbed surfaces caused by M OTOR V EHICLES ), uniformly apply and maintain surface gravel or D UST P ALLIAT IVES to all areas disturbed by M OTOR
V EHICLES in compliance with one of the stabilization standards described in Subsection 90.2.1.2 of this Regulation; or

(c) Where a D IST URBED S URFACE A REA exists (including disturbed surfaces caused by M OTOR V EHICLES and/or O FF -R OAD M OTOR
V EHICLES ), apply and maintain an alternative C ONTROL M EASURE approved in writing by the C ONTROL O FFICE R and the Region IX

A DMINISTRATOR of the Environmental Protection Agency (EPA).

90.2.1.2 Stabilization Standards:

(a) A visible crust shall be established, as determined by

Subsection 90.4.1.1 (The Drop Ba ll/Steel Ball Test) of these Regulations; or,______________________________________________________________________ Amended 07/01/04 90-3 CC Air Quality Regulations (b) A percent cover that is equal to or greater than 20% for nonerodible elements shall be es tablished, as determined by Subsection 90.4.1.2 (Rock Test Me thod) of these Regulations; or,

(c) A threshold friction velocity, corrected for non-erodible elements of 100 cm/second or higher, shall be established, as determined by Subsection 90.4.1.3 (Determination Of Threshold Friction Velocity) of this Regulation; or,

(d) An alternative test met hod approved in writ ing by the C ONTROL O FFICE R and the Region IX A DMINISTRATOR of the EPA.

90.2.2 D u s t M i t i g a t i o n P l a n s R e q u i r e d : Any O WNER A ND /O R O PERAT OR of O PEN
A REAS A ND V ACANT L OTS having a cumulative area of 10,000 acres or greater must submit a dus t mitigation plan to the Department of Air Quality and Environmental Management for approval by March 31, 2003, in a format prescribed by the C ONTROL O FFICE R

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90.2.3 Mechanized Weed Abatemen t and/or Trash Removal: If machinery is

used to clear weeds and/or trash from O PEN A REAS A ND V ACANT L OTS of 5,000 square feet or lar ger, then the following Cont rol Measures set forth

in Subsection 90.2.3. 1 shall be applied. Advisory Notice: In order to conserve water to the greatest ex tent practicable, the use of R ECLAIMED
W AT ER is highly encouraged.

90.2.3.1 C ONTROL M EASURES

(a) Pre-wet surface soils before me chanized weed abatement and/or trash removal occurs; and,

(b) Maintain dust control measur es while mechanized weed abatement and/or trash removal is occurring; and,

(c) P AVE , apply gravel, apply water, or apply a suitable D UST
P ALLIATIVE , in compliance with the stab ilization standards set forth

in Subsection 90.2.1.2 of this R egulation, after mechanized weed

abatement and/or trash removal occurs.

90.3 Record Keeping Requirements

90.3.1 Record Keeping: Any P ERSON subject to the requirements of this Regulation shall compile and retain re cords that provide evidence of

C ONTROL M EASURE application, by indicati ng type of treatment or C ONTROL
M EASURE , extent of coverage, and dat e applied. The records and supporting documentation shall be made available to the C ONTROL O FFICE R within 24 hours of a written request.______________________________________________________________________ Amended 07/01/04 90-4 CC Air Quality Regulations 90.3.2 Record Retention: Copies of the records r equired by Subsection 90.3.1 (Record Keeping Requirements) of this Regulation shall be retained for at least one year.

90.4 Test Methods

90.4.1 Stabilization Standards For O PEN A REAS A ND V ACANT L OTS : The test

methods described in Subsections 90.4. 1.1 through Subsections 90.4.1.3 o f this Regulation shall be used to determine whether an O PEN A REA or a V ACANT L OT has a stabilized surface. Should a disturbed O PEN A REA or V ACANT L OT contain more than one type of disturbance, soil, or other characteristics which are visibly distinguishable, each representative surface must be tested separately for st ability in an area th at represents a random portion of the over all disturbed conditions of the site, utilizing the appropriate test methods in S u b s e c t i o n s 9 0

. 4

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. 1 t h r ough Subsections

9 0

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. 3 of this Regulation. Depending upon test method results, include or eliminate each representat ive surface from the to tal size assessment of

the D IST U RBED S URFACE A REA ( S ).

90.4.1.1 Soil Crust Determination ( The Drop Ball Test): Drop a steel ball with a diameter of 15.9 millimeters (0. 625 inches) and a mass ranging from 16- 17 grams from a distance of 30 centim eters (one foot) directly above the soil surface. If blowsand is present, clear the blowsand fr om the surfaces

on which the soil crust test method is conducted. Blowsand is defined as thin deposits of loose uncombined grai ns covering less than 50% of an

O PEN A REA or V ACANT L OT which have not originated from the representative O PEN A REA or V ACANT L OT surface being tested. If material covers a visible crust, which is not blowsand, apply the test method in Subsection 90.4.1.3 (Determination Of Thre shold Friction Velocity) of this Regulation to the loose mate rial to determine whether

the surface is stabilized.

(a) A sufficient crust is defined under the following conditions: once a ball has been dropped according to S ubsection 90.4.1.1 of this Regulation, the ball does not sink in to the surface, so that it is partially or fully surrounded by l oose grains and, upon removal of the ball, the surface upon which it fell has not been pulverized, so that loose grains are visible.

(b) Randomly select each representative D IST URBED S URFACE for the drop ball test by using a blind “over the shoulder” toss of a throwable object (for example, a metal weight with survey tape attached). Using the point of fall as the lower left hand corner, measure a 1-foot square area. Dr op the ball three times within the 1-foot by 1-foot square survey area, using a consistent pattern______________________________________________________________________ Amended 07/01/04 90-5
CC Air Quality Regulations across the survey area. The survey area shall be considered to have passed the Soil Crust Determinati on Test if at least two of the three times the ball was dropped, t he results met the criteria in Subsection 90.4.1.1(a) of this Regulat ion. Select at least two other survey areas that represent a random portion of the overall disturbed conditions of the site, and repeat this procedure. If the

results meet the criteria of Subsection 90.4.1.1( a) of this Regulation for all of the survey areas tested, then the site shall be considered to have passed the Soil Crust Determination Test and shall be considered sufficiently crusted.

(c) At any given site, the existence of a sufficient crust covering one portion of the site may not represent the existence or protectiveness of a crust on another portion of the site. Repeat the

soil crust test as often as necessa ry on each portion of the overall conditions of the site using the r andom selection method set forth in Subsection 90.4.1.1(b) of this Regulation for an accurate

assessment.

90.4.1.2 Rock Test Method: The Rock Test Method, which is similar to Subsection 90.4.1.3 (Determination Of Threshold Fric tion Velocity) of this Regulation,

examines the wind-resistance effe cts of rocks and other non-erodible

elements on disturbed surfaces. Non-er odible elements are objects larger than 1 centimeter (cm) in diameter t hat remain firmly in place even on windy days. Typically, non-erodible elements include rocks, stones, glass fragments, and hardpacked cl umps of soil lying on or embedded in the surface. Vegetation does not count as a non-erodible element in this method. The purpose of this test met hod is to estimate the percent cover of non-erodible elements on a given surface to see whether such elements take up enough space to offe r protection against windblown dust. For simplification, the following te st method refers to all non-erodible

elements as “rocks.”

(a) Randomly select a 1 meter by 1 meter survey area within an area that represents the general rock di stribution on the surface (a 1 meter by 1 meter area is slightly greater than a 3 foot by 3 foot area). Use a blind “over the s houlder” toss of a throwable object (for example, a metal weight with survey tape attached) to select the survey surface and using the point of fall as the lower left hand corner, measure a 1 meter by 1 meter survey area. Mark-off the survey area by tracing a straight, visible line in the dirt along the edge of a measuring tape or by plac ing short ropes, yard sticks, or other straight objects in a square around the survey area.

(b) Without moving any of the rocks or other elements, examine the survey area. Since rocks greater t han 3/8 inch (1 cm) in diameter______________________________________________________________________ Amended 07/01/04 90-6 CC Air Quality Regulations are of interest, measure the diamet er of some of the smaller rocks to a get a sense of which rocks need to be considered.

(c) Mentally group the ro cks greater than 3/8 inch (1cm) diameter lying in the survey area into small, m edium, and large size categories. If the rocks are all approximately the sa me size, simply select a rock of average size and typical shape. Without removing any of the rocks from the ground, count the number of rocks in the survey area in each group and write dow n the resulting number.

(d) Without removing rocks, select one or two average-size rocks in each group and measure the length an d width. Use either metric units or standard units. Using a calcul ator, multiply the length times the width of the rocks to get the average dimensions of the rocks in each group. Write down the results for each rock group.

(e) For each rock group, multiply t he average dimensions (length times width) by the number of rocks c ounted in the group. Add the results from each rock group to get the total rock area within the

survey area.

(f) Divide the total rock area, calcul ated in Subsection 90.4.1.2(e) of this Regulation, by two (to get fr ontal area). Divide the resulting number by the size of the survey area (make sure the units of measurement match), and multiply by 100 for percent rock cover. For example, the total rock area is 1,400 square centimeters, divide 1,400 by 2 to get 700. Divide 700 by 10,000 (the survey area is 1 meter by 1 meter, which is 100 c entimeters by 100 centimeters or 10,000 centimeters) and multiply by 100. The result is 7% rock

cover. If rock measurements ar e made in inches, convert the survey area from meters to inches (1 inch = 2.54 centimeters).

(g) Select and mark-off two additional survey areas and repeat the procedures described in Subsection 90.4.1.2(a) through Subsection 90.4.1.2(f) of this R egulation. Make sure the additional survey areas also represent the general rock distribution on the site. Average the percent cover results fr om all three survey areas to estimate the average percent of rock cover.

(h) If the average rock cover is gr eater than or equal to 20%, the surface is stable. If the average rock cover is less than 20%, follow the procedures in Subsection 90.4. 1.2(i) of this Regulation.

(i) If the average rock cover is less than 20%, the surface may or may not be stable. Follow the proc edures in Subsection 90.4.1.3 (Determination Of Threshold Fricti on Velocity) of this Regulation______________________________________________________________________ Amended 07/01/04 90-7 CC Air Quality Regulations and use the results from the rock te st method as a correction (i.e., multiplication) factor. If the rock cover is at least 1%, such rock cover helps to limit windblown dust. However, depending on the soil’s ability to release fine dust parti cles into the air, the percent rock cover may or may not be sufficient enough to stabilize the surface. It is also possible that the soil itself has a high enough Threshold Friction Velocity (TFV ) to be stable without accounting

for rock cover.

(j) After completing the procedures de scribed in Subsection 90.4.1.2(i) of this Regulation, use Table 2 of this Regulation to identify the appropriate correction factor to the TFV, depending on the percent rock cover. Multiply the correcti on factor by the TFV value for a

final TFV estimate that is co rrected for non-erodible elements.

90.4.1.3 Determination Of Threshold Friction Velocity (TFV): For D IST U RBED S URFACE A REAS that are not crusted or vegetated, determine TFV according to the following sieving field procedure (based on a 1952 laboratory procedure published by W. S. Chepil).

(a) Obtain and stack a set of si eves with the following openings: 4 millimeters (mm), 2 mm, 1 mm, 0. 5 mm, and 0.25 mm, or obtain and stack a set of standard/commonly available sieves. Place the sieves in order according to size openings, beginning with the largest size opening at the top. Place a collector pan underneath the bottom (0.25 mm) sieve. Collect a sample of loose surface

material from an area at least 30 cm by 30 cm in size, to a depth of approximately 1 cm using a brus h and dustpan or other similar device. Only collect soil samples from dry surfaces (i.e., when the surface is not damp to the touch) . Remove any rocks larger than 1 cm in diameter from the sample. Pour the sample into the top sieve (4 mm opening) and cover the sieve/ collector pan unit with a lid. Minimize escape of particles into the air when transferring surface soil into the sieve/collector pan unit. Move the covered sieve/collector pan unit by hand using a broad, circular arm motion in the horizontal plane. Complete twenty circular arm movements,

ten clockwise and ten counterclockwis e, at a speed just necessary

to achieve some relative horizont al motion between the sieves and the particles. Remove the lid fr om the sieve/collector pan unit and disassemble each sieve separatel y, beginning with the largest sieve. As each sieve is removed, examine it for loose particles. If loose particles have not been sifted to the finest sieve through which they can pass, reassemble and cover the sieve/collector pan unit and gently rotate it an additional ten times. After disassembling the sieve/collector pan unit, slightly tilt and gently tap each sieve, and the collector pan, so that mate rial aligns along one side. In______________________________________________________________________ Amended 07/01/04 90-8 CC Air Quality Regulations doing so, minimize escape of particl es into the air. Line up the sieves and collector pan in a row and visibly inspect the relative quantities of catch in order to determine which sieve (or whether the collector pan) contains the gr eatest volume of material. If a

visual determination of relative volumes of catch among sieves is difficult, use a graduated cylinder to measure the volume. Estimate TFV for the sieve catch with the gr eatest volume using Table 1 of this Subsection, which provides a correlation between sieve opening size and TFV.

Table 1. Determination Of Threshold Friction Velocity

Tyler Sieve No. ASTM 11 Opening TFV

Sieve No. (mm) (cm/s)

_____ 5 5 4 135

9 10 2 100

16 18 1 76

32 35 0.5 58

60 60 0.25 43

Collector Pan

⎯ ⎯ 30

(b) Collect at least three soil samp les which represent random portions

of the overall conditions of t he site, repeat the above TFV test method for each sample and aver age the resulting TFVs together

to determine the TFV uncorrected for non-erodible elements. Nonerodible elements are di stinct elements, in the random portion of the overall conditions of the site, that are larger than 1 cm in diameter, remain firmly in place during a wind episode, and inhibit soil loss by consuming part of the shear stress of the wind. Nonerodible elements include stones and bulk surface material but do not include flat or standing vegetat ion. For surfaces with nonerodible elements, determine corrections to the TFV by identifying the fraction of the survey area, as viewed from directly overhead, that is occupied by non-erodibl e elements using the following procedure. For a more detailed de scription of this procedure, see Subsection 90.4.1.2 (Rock Test Method) of this Regulation. Select a survey area of 1 meter by 1 meter that represents a random portion of the overall conditions of the site. Where many nonerodible elements lie within the survey area, separate the nonerodible elements into groups accord ing to size. For each group,

calculate the overhead area for the non-erodible elements according to the following equations:______________________________________________________________________ Amended 07/01/04 90-9 CC Air Quality Regulations Eq. 1: (Average length) x (Average width) = Average Dimensions. Eq. 2: (Average Dimensions) x (Num ber of Elements) = Overhead Area. Eq. 3: Overhead Area Of Group 1 + Overhead Area Of Group 2 (etc.) =

Total Overhead Area. Eq. 4: Total Overhead Area/2 = Total Frontal Area. Eq. 5: (Total Frontal Area/Survey Area) x 100 = Percent Cover Of NonErodible Elements.

Note: Ensure consistent units of measurement (e.g. square meters or square inches when calculating percent cover).

Repeat this procedure on an additional two di stinct survey areas that represent a random portion of the overall conditions of the site and aver age the results.

Use Table 2 of this Subsection to identif y the correction factor for the percent

cover of non-erodible elements. Mult iply the TFV by the corresponding

correction factor to calculate the TFV corrected for non-erodible elements.

Table 2. Correction Factors For Threshold Friction Velocity

Percent Cover Of Non-Erodible Elements Correction Factor

Greater than or equal to 10% 5 Greater than or equal to 5% and less than 10% 3 Less than 5% and greater than or equal to 1% 2

Less than 1% None

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - History : Initial adoption: June 22, 2000

A m en d e d : No v e mb er 16, 2000; No v e mb er 20, 2001; Decemb e r 17, 2002; Ju n e 3, 2003; Ju ly 1,

2004.