1133.1 – 1 

(Adopted January 10, 2003)(Amended July 8, 2011) 

RULE 1133.1 CHIPPING AND GRINDING ACTIVITIES 

(a) Purpose 

 The purpose of this rule is to prevent inadvertent decomposition occurring during 

chipping and grinding activities, including stockpile operations. 

(b) Applicability 

This rule applies to operators of chipping and grinding activities to produce 

materials other than active or finished compost, unless otherwise exempted under 

subdivision (f) of this rule. The requirements of Rule 403 – Fugitive Dust, also 

apply to these activities. 

(c) Definitions 

For the purposes of this rule, the following definitions shall apply: 

(1) ACTIVE COMPOST is material that is in the process of being rapidly 

decomposed and is biologically unstable. Active compost is generating 

temperatures of at least 122 degrees Fahrenheit during decomposition. 

Active compost includes, but is not limited to, pathogen-reduced mulch. 

(2) AGRICULTURAL CHIPPING AND GRINDING is any chipping and 

grinding activity conducted at an agricultural site where organic waste 

material is generated on-site by the production and/or processing of farm 

products, and the chipped and ground organic waste material is used onsite. 

(3) CHIPPING AND GRINDING is any activity that mechanically reduces 

the size of greenwaste, woodwaste, and/or foodwaste. 

(4) COMPOSTING is a process in which solid organic waste materials are 

decomposed in the presence of oxygen under controlled conditions 

through the action of bacteria and other microorganisms. 

(5) COMPOST OVERS are the oversized woody materials that do not 

decompose in a typical composting cycle and are screened out of finished 

product at the end of composting. Compost overs have been through the 

pathogen reduction process outlined in Title 14, Section 17868.3 of the 

California Code of Regulations. 
Rule 1133.1 (cont.) (Amended July 8, 2011) 

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(6) CURBSIDE GREENWASTE is greenwaste that is collected from 

receptacles designated for residential household greenwaste. Curbside 

greenwaste also includes screened curbside greenwaste containing only 

grass clippings, leaves, and/or twigs that is not considered non-curbside 

greenwaste as defined in paragraph (c)(13). 

(7) FINISHED COMPOST is a humus-like material and/or compost overs 

that result from the controlled biological decomposition of organic waste 

materials and is biologically stable. 

(8) FOODWASTE is any food scraps collected from the food service 

industry, grocery stores, or residential food scrap collection. Foodwaste 

also includes food scraps that are chipped and ground. 

(9) GREENWASTE is any organic waste material generated from gardening, 

agriculture, or landscaping activities including, but not limited to, grass 

clippings, leaves, tree and shrub trimmings, and plant remains. It includes 

curbside, non-curbside, and mixed greenwaste. 

(10) INADVERTENT DECOMPOSITION is decomposition of greenwaste 

and/or foodwaste associated with stockpiling greenwaste and/or foodwaste 

for an extended period of time, and is not considered part of normal 

chipping and grinding operations. 

(11) LANDCLEARING is an activity where trees and plants grown at the site 

are cut, then chipped or ground and removed from the site to clear the site. 

(12) MIXED GREENWASTE is curbside greenwaste that is mixed with noncurbside greenwaste. 

(13) NON-CURBSIDE GREENWASTE is any greenwaste that is not collected 

from receptacles designated for residential household greenwaste. 

(14) PALM CHIPPING AND GRINDING is any activity that mechanically 

reduces the size of palm trees waste. 

(15) PORTABLE CHIPPING AND GRINDING is chipping and grinding 

utilizing equipment with a manufacturer's rating of 170 brake horsepower 

or less. 

(16) RAINY DAY is any day with at least 0.05 inches of rain reported by the 

National Weather Service or a cooperative weather reporting station for 

the site closest to where the chipping and grinding activity occurs. 
Rule 1133.1 (cont.) (Amended July 8, 2011) 

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(17) STOCKPILE is a supply of raw material tipped and stored prior to being 

utilized on-site or removed from the site. Raw materials before and after 

chipping and grinding are also included. 

(18) WET WEATHER CONDITIONS are weather conditions following a 

rainy day not to exceed 10 days. 

(19) WOODWASTE is lumber, and the woody material portion of mixed 

demolition wastes and mixed construction wastes. Woodwaste also 

includes large wood materials of curbside greenwaste or mixed 

greenwaste that is screened or unscreened, such as tree trimmings, 

branches, tree trunks, stumps, and limbs exceeding 2 inches in any 

dimension. 

(d) Requirements 

The operator of a chipping and grinding activity shall comply with the following 

requirements: 

(1) Foodwaste shall not be taken at the facility, unless otherwise allowed by 

the Local Enforcement Agency to handle foodwaste. 

(2) Chip or grind and utilize on-site or remove curbside, non-curbside, or 

mixed greenwaste from the site within 48 hours of receipt, excluding 

observance of official federal and state holidays, or up to seven days 

maximum, with approval from the Local Enforcement Agency. 

(3) Maintain all the operational records for the prior five years of operation, 

with the most recent two years retained at the facility, which shall be 

immediately available upon request by the Executive Officer. The 

remaining three years of records shall be made available to the Executive 

Officer within one week of request. 

(4) Maintain the following records, as applicable, on-site for two years: 

(A) A copy of the facility’s AQMD registration and annual updates 

submitted in compliance with Rule 1133; 

(B) Records of date, type, and amount of greenwaste received; 

(C) Records of date, type, amount of greenwaste removed from the 

site, and location where they are transferred to; 

(D) Records of dates of rainy days and wet weather conditions and 

description of specific conditions that limited normal operations; 
Rule 1133.1 (cont.) (Amended July 8, 2011) 

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(E) Records of temperature or moisture content measurements; and 

(F) Records of dates and amount of curbside greenwaste chipped and 

ground. 

(5) The time requirements specified in paragraph (d)(2) may be extended by 

the number of rainy days and wet weather conditions that impede normal 

chipping and grinding operations provided that records are maintained in 

accordance with subparagraph (d)(4)(D). 

(e) Moisture Content Measurement 

 Moisture content will be determined by collecting at least 10 samples of chipped 

and ground greenwaste from various locations of the pile at a depth of at least 12 

inches below pile surface. The samples shall then be mixed thoroughly and 

analyzed for moisture content by ASTM method D4442 (December 2007), ASTM 

method D4444 (May 2008) or ASTM method E871-82 (December 2006). 

(f) Exemptions 

(1) Chipping and grinding activities of greenwaste derived from the site and 

utilized on-site shall be exempt from the requirements of paragraphs 

(d)(2), (d)(3), and (d)(4), provided less than 1,000 cubic yards of materials 

are either sold or given away. 

(2) Portable chipping and grinding, agricultural chipping and grinding, land 

clearing chipping and grinding, woodwaste chipping and grinding, and 

palm chipping and grinding activities shall be exempt from the 

requirements of paragraphs (d)(2), (d)(3), and (d)(4). 

(3) Chipped and ground curbside greenwaste shall be exempt from the 

requirements of paragraph (d)(2) provided that the moisture content is less 

than 30%, measured in accordance with subdivision (e) and the 

temperature or moisture content measurements are maintained on-site in 

accordance with subparagraph (d)(4)(E). 

(4) A biomass power generation facility or a facility processing material as a 

biomass fuel for a biomass power generation facility shall be exempt from 

the requirements of paragraph (d)(2) provided that the material 

temperature is maintained at below 122 degrees Fahrenheit or the moisture 

content is less than 30%, measured in accordance with subdivision (e) and 

the temperature or moisture content measurements are maintained on-site 
Rule 1133.1 (cont.) (Amended July 8, 2011) 

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in accordance with subparagraph (d)(4)(E). This exemption shall not 

apply to material processed for purposes other than biomass fuel. 

(5) The operator of a landfill or biomass power generation facility shall be 

exempt from the requirements of paragraph (d)(4), provided that the 

operator does not perform chipping and grinding of greenwaste on-site.