Within the zoning districts established herein, accessory uses or accessory buildings are permitted, provided that any such use or building is customarily incidental to, subordinate to and on the same lot as the principal use it serves except as otherwise provided for herein.
The following accessory uses are permitted, provided that a special permit is first obtained from the Board of Appeals:
In residential zoning districts, accessory uses and structures on a lot adjoining or immediately opposite and across a road from the lot on which the principal use it serves is located, provided that both lots are retained in identical ownership with respect to both fee and nonfee interests.
Uses accessory to permitted scientific research or scientific development or related production only if the Board finds that such accessory use does not substantially derogate from the public good. Such accessory use need not be located on the same lot as the principal use it serves.
Other accessory uses requiring special permit authorization are provided for within the various zoning districts established herein.
[Added 6-14-2007 by Order No. 2007-082]
Purpose and intent. It is the express purpose of this section to accommodate distributed wind energy conversion facilities in appropriate land-based locations, while minimizing any adverse visual, safety and environmental impacts of the facilities. The section enables the review of wind energy conversion facilities by the Town's special permit granting authority, clarifying the criteria for siting such a facility. This section is intended to be used in conjunction with other regulations adopted by the Town, including historic district regulations, site plan review and other local ordinances designed to encourage appropriate land use and environmental protection. Further, it is the express intent of this section that any special permit granted hereunder run with the land and that any subsequent owner of said land be bound by the terms and conditions of said special permit.
Definitions. As used in this section, the following terms shall have the meanings indicated:
- CLEAR AREA
- The distance from the lowest point of the blade tip to the ground.
- Height is measured from the grade at the base of the tower to the top of the fixed tower (moveable blades are not included).
- Wholly located on upland including any guy wires as may be required.
- SPECIAL PERMIT GRANTING AUTHORITY (SPGA)
- Shall be the Planning Board, for this section.
- WIND ENERGY CONVERSION FACILITY (WECF)
- All equipment, machinery and structures utilized in connection with the conversion of wind to electricity. This includes, but is not limited to, all transmission, storage, collection and supply equipment, substations, transformers, site access, service roads and machinery associated with the use. A wind energy conversion facility may consist of one or more wind turbines.
- WIND-MONITORING OR METEOROLOGICAL (TEST OR MET) TOWERS
- Tower used for supporting anemometer, wind vane and other equipment to assess the wind resource at a predetermined height above the ground.
- WIND TURBINE
- A device that converts kinetic energy of the wind into rotational energy to turn an electrical generator shaft.
All wind energy conversion facilities or wind-monitoring towers shall require a building permit and may be permitted only as an accessory use to permitted uses in all zoning districts.
Wind energy conversion facility and wind-monitoring or meteorological towers. The construction of any wind energy conversion facility or wind-monitoring/meteorological tower shall be permitted in all zoning districts, subject to issuance of a special permit and provided the proposed use complies with all dimensional and special permit regulations set forth in § 240-125C (unless waived by the SPGA). Any subsequent change or modification of wind energy equipment shall be subject to review by the Building Commissioner.
Type. Tilt-up towers, fixed-guyed towers, freestanding towers or other designs may be considered for approval by the SPGA. Towers may not be attached to any residence or habitable structures.
Setback. The base of any WECF shall be set back from any property line or road layout line by not less than 120% of the proposed height of the tower if abutting residentially zoned properties and 80% of the proposed height of the tower, if abutting nonresidentially zoned properties. Guy wires or any WECF related construction not wholly below grade, as may be required by the proposed design, shall be set back at least 20 feet from property lines, and 30 feet from road layout lines if located on, or adjacent to, residentially zoned property. If located on nonresidentially zoned property and not abutting residentially zoned property, guy wire setbacks may be reduced to five feet. Other setbacks shall conform to the yard setbacks of the zone in which the subject property is located. The SPGA may allow the setback to be reduced as part of the special permit process if the project proponent can demonstrate that additional height is needed and that the additional benefits of the higher tower outweigh any increased adverse impacts.
Special permit regulations. The SPGA shall grant a special permit only if it finds that the proposal complies with the provisions of this Zoning Ordinance (unless waived) and is consistent with the applicable criteria for granting special permits.
General. Proposed wind energy conversion facilities shall be consistent with all applicable local, state and federal requirements, including, but not limited to, all applicable electrical, construction, noise, safety, environmental and communications requirements.
Demonstrated utility. The proponent shall demonstrate that the proposed WECF efficiently generates electrical power.
Maintenance. A written maintenance plan shall be submitted with the application for a special permit for review and approval by the SPGA and shall be made a condition of said special permit.
Visual impact. The proponent shall demonstrate through project siting and proposed mitigation that the wind energy conversion facility minimizes any impact on the visual character of surrounding neighborhoods and the community. This may include, but not be limited to, information regarding site selection, turbine design, buffering, lighting. All electrical conduits shall be underground.
Color. Wind energy conversion facilities shall be painted nonreflective muted colors that blend with the sky, without graphics or other decoration.
Equipment shelters. All equipment necessary for monitoring and operation of the wind energy conversion facilities should preferably be contained within the turbine tower. If this is infeasible, ancillary equipment may be located outside the tower, provided it is contained either within an underground vault, or enclosed within a separate structure or behind a year-round landscape or vegetated buffer.
Lighting and signage.
Wind turbines shall be lighted only if required by the Federal Aviation Administration (FAA). The proponent shall provide a copy of the FAA's determination to establish the required markings and/or lights for the structure.
Lighting of equipment structures and any other facilities on site (except lighting required by the FAA) shall be shielded from abutting properties.
No signage allowed.
Guy wires. Guy wires as may be utilized in the construction of the tower shall be left totally unadorned. Nothing shall be hung from or attached to said wires. To prevent unintended contact by persons who may be on-site, landscaping or other approved methods may be implemented. Exception: On nonresidentially zoned properties, not abutting residential property, guy wires may be wrapped with a colored sleeve only, to prevent unintended contact. Such sleeve shall extend to a height not greater than 10 feet above grade.
The wind energy conversion facility and associated equipment shall conform to the provisions of the Department of Environmental Protection's Division of Air Quality Noise Regulations (310 CMR 7.10). A source of sound will be considered to be violating these regulations if the source:
"Ambient" is defined as the background A-weighted sound level that is exceeded 90% of the time measured during equipment hours. The ambient may also be established by other means with consent from DEP. The ambient noise level shall be measured at the property line when the WECF is located on a lot adjacent to residentially zoned property. Otherwise, the special permit granting authority, in consultation with the Department, shall determine whether such violations shall be measured at the property line or at the nearest inhabited residence.
Upon complaint of an abutter, ambient and maximum permitted decibel measurements shall be performed by an agent designated by the SPGA. The report shall be submitted to the SPGA for review. The fee for this service shall be paid by the complainant unless the maximum permitted decibel level has been exceeded in which case the owner of the system shall pay the fee.
If the maximum decibel readings are exceeded, the installation shall be considered a nuisance. The nuisance violation must be corrected within 90 days from notification of the violation, and if the violation cannot be corrected, the wind energy system shall be removed or relocated at the expense of the owner.
Shadowing/flicker. Wind energy conversion facilities shall be sited in a manner that does not result in significant shadowing or flicker impacts. The proponent has the burden of proving that this effect does not have significant adverse impact on neighboring or adjacent uses either through siting or mitigation.
No hazardous materials or waste shall be discharged on the site of any wind energy conversion facility. If any hazardous materials or wastes are to be used on site, there shall be provisions for full containment of such materials or waste.
Climbing access to tower shall be limited by placing climbing apparatus no lower than 10 feet from the ground.
The clear area shall be no less than 10 feet.
The wind turbine shall conform to FAA safety standards, as amended.
Upon a finding by the Building Commissioner that the WECF has been abandoned or has been left in disrepair or has not been maintained in accordance with the approved maintenance plan, the owner of said WECF shall be notified in writing by certified mail that the WECF shall be brought up to standard. If required repairs or maintenance are not accomplished within 45 days, the WECF shall be deemed condemned and shall be removed from the site within 90 days thereafter at the expense of the property owner. The aforementioned periods of time may be extended at the request of the owner and at the discretion of the Building Commission. "Removed from site" shall mean:
Removal of the wind turbine and tower, all machinery, equipment, equipment shelters, security barriers and all appurtenant structures from the subject property;
Proper disposal of all solid or hazardous materials and wastes from the site in accordance with local and state solid waste disposal regulations;
Restoration of the location of the wind energy conversion facility to its natural condition, except that any landscaping, grading or below-grade foundation may remain in the after condition.
If an applicant fails to remove a wind energy conversion facility in accordance with this section of this chapter, the Town shall have the authority to enter the subject property and physically remove the facility. The SPGA may require the applicant to provide a form of surety (i.e., post a bond, letter of credit or establish an escrow account or other) at the SPGA's election at the time of construction to cover costs of the removal in the event the Town must remove the facility. The amount of such surety shall be equal to 150% of the cost of compliance with this section. The applicant shall submit a fully inclusive estimate of the costs associated with removal. The amount shall include a mechanism for a cost of living adjustment every five years.
[Added 10-7-2010 by Order No. 2011-006]
This section promotes the creation of new large-scale, ground-mounted solar photovoltaic installations by providing standards for the placement, design, construction, operation, monitoring, modification and removal of such installations that address public safety, minimize impacts on scenic, natural and historic resources and for providing adequate financial assurance for the eventual decommissioning of such installations. This section ordinance is adopted pursuant to the Commonwealth of Massachusetts Green Communities Act.
The provisions set forth in this section shall apply to the construction, operation, and/or repair of large-scale, ground-mounted solar photovoltaic installations.
Applicability. This section applies to large-scale (250 kW), ground-mounted solar photovoltaic installations proposed to be constructed after the effective date of this section. This section also pertains to physical modifications that materially alter the type, configuration, or size of these installations or related equipment.
District established. A Ground-Mounted Solar Photovoltaic Overlay District (GMSPOD) is hereby established, and shall be considered as superimposed over any other districts established by this chapter, and is shown as an overlay on the Official Zoning Map established pursuant to § 240-6, Zoning Map
Definitions. These definitions shall apply to § 240-44.2 exclusively:
- AS-OF-RIGHT SITING
- The ground-mounted solar photovoltaic installation may proceed without the need for a special permit, variance, amendment, waiver, or other local discretionary approval. As-of-right development is subject to Article IX, Site Plan Review. As-of-right solar photovoltaic installations that are consistent with the Zoning Ordinance and applicable state and federal law can be reasonably regulated and approved by the Building Commissioner.
- GROUND-MOUNTED SOLAR PHOTOVOLTAIC INSTALLATION
- A large-scale solar photovoltaic (PV) system that is structurally mounted on the ground, not roof-mounted, and has a nameplate capacity of at least 250 kW DC.
- OFF-GRID SYSTEM
- A solar photovoltaic installation where all energy generated on the installation site is consumed on that site and does not send any energy into the electrical grid for distribution.
- RATED NAMEPLATE CAPACITY
- The maximum rated output of electric power production of the photovoltaic system in direct current (DC).
Application and review.
Ground-mounted, large-scale solar photovoltaic installations with 250 kW or larger of rated nameplate capacity shall undergo site plan review pursuant to Article IX, Site Plan Review, prior to construction, installation or modification as provided in this section. All plans and maps shall be prepared, stamped and signed by a professional engineer licensed to practice in Massachusetts.
Required documents. In addition to the requirements of § 240-102, Contents of site plan, the project proponent shall provide the following documents:
A site plan showing:
Property lines and physical features, including roads, for the project site;
Proposed changes to the landscape of the site, grading, vegetation clearing and planting, exterior lighting, screening vegetation or structures. The square footage of each disturbed area shall be identified on a plan, and details of any site alteration, including number and species of trees to be removed, shall be provided.
[Amended 8-17-2017 by Order No. 2018-04]
Blueprints or drawings of the solar photovoltaic installation signed by a professional engineer licensed to practice in the Commonwealth of Massachusetts showing the proposed layout of the system and any potential shading from nearby structures;
One- or three-line electrical diagram detailing the solar photovoltaic installation, associated components, and electrical interconnection methods, with all National Electrical Code compliant disconnects and overcurrent devices;
Documentation of the major system components to be used, including the PV panels, mounting system, and inverter;
Name, address, and contact information for proposed system installer;
Name, address, phone number and signature of the project proponent, as well as all co-proponents or property owners, if any;
The name, contact information and signature of any agents representing the project proponent; and
Documentation of actual or prospective access and control of the project site (See also Subsection G below.);
Zoning district designation for the parcel(s) of land comprising the project site (submission of a copy of a Zoning Map with the parcel(s) identified is suitable for this purpose);
Site control. The project proponent shall submit documentation of actual or prospective access and control of the project site sufficient to allow for construction and operation of the proposed solar photovoltaic installation.
Operation and maintenance plan. The project proponent shall submit a plan for the operation and maintenance of the ground-mounted solar photovoltaic installation, which shall include specific measures for maintaining safe access to the installation, a stormwater management plan, and general procedures for and frequency of operational maintenance of the installation.
Utility notification. No ground-mounted solar photovoltaic installation shall receive a building permit until an executed interconnect agreement with EVERSOURCE, the utility company operating the electrical grid, has been submitted to the Building Commissioner. Off-grid systems are exempt from this requirement.
[Amended 8-17-2017 by Order No. 2018-04]
Dimensional requirements. Ground-mounted solar photovoltaic installations are subject to the front, side and rear yard setbacks as set forth in the underlying zoning district(s).
Lighting. Lighting of solar photovoltaic installations shall be consistent with local, state and federal law. Lighting of other parts of the installation, such as accessory structures, shall be limited to that required for safety and operational purposes, and shall be reasonably shielded from abutting properties.
Signage. Signs on large-scale, ground-mounted solar photovoltaic installations shall comply with Article VII, Sign Regulations. A sign shall be required to identify the owner and provide a twenty-four-hour emergency contact phone number. Solar photovoltaic installations shall not be used for displaying any advertising.
Accessory structures. All structures accessory to ground-mounted solar photovoltaic installations shall be subject to reasonable regulations concerning the bulk and height of structures, lot area, setbacks, open space, parking and building coverage requirements. To avoid adverse visual impacts, all such accessory structures, including but not limited to, equipment shelters, storage facilities, transformers, and substations, shall be architecturally compatible with each other, multiple accessory structures shall be clustered to the greatest extent feasible and views of such structures to residential properties and roadways shall be screened with landscaping.
Utility connections. Reasonable efforts, as determined by site plan review, shall be made to place all utility connections from the solar photovoltaic installation underground, depending on appropriate soil conditions, shape, and topography of the site and any requirements of the utility provider. Electrical transformers for utility interconnections may be above ground if required by the utility provider.
Safety and environmental standards.
Emergency services. The large-scale solar photovoltaic installation owner or operator shall provide a copy of the project summary, electrical schematic, and site plan to the local Fire Chief. Upon request the owner or operator shall cooperate with local emergency services in developing an emergency response plan. All means of shutting down the solar photovoltaic installation shall be clearly marked. The owner or operator shall identify a responsible person for public inquiries throughout the life of the installation.
Land clearing, soil erosion and habitat impacts. Clearing of natural vegetation shall be limited to what is necessary for the construction, operation and maintenance of the large-scale, ground-mounted solar photovoltaic installation or otherwise prescribed by applicable laws, regulations, and bylaws.
[Amended 8-17-2017 by Order No. 2018-04]
Land clearing is prohibited within 800 feet from the outer boundary of any Zone I protective radius around a public water supply well or wellfield established by 310 CMR 22.
Land clearing in excess of two contiguous acres in connection with any single installation is prohibited.
Monitoring and maintenance.
Solar photovoltaic installation conditions. The large-scale, ground-mounted solar photovoltaic installation owner or operator shall maintain the facility in good condition. Maintenance shall include, but not be limited to, painting, structural repairs, and integrity of security measures. Site access shall be maintained to a level acceptable to site plan review. The owner or operator shall be responsible for the cost of maintaining the solar photovoltaic installation.
Modifications. All material modifications to a solar photovoltaic installation made after issuance of the required building permit shall require site plan review approval.
Abandonment or decommissioning.
Removal requirements. Any large-scale, ground-mounted solar photovoltaic installation which has reached the end of its useful life or has been abandoned consistent with this section shall be removed. The owner or operator shall physically remove the installation no more than 150 days after the date of discontinued operations. The owner or operator shall notify the Building Commissioner by certified mail of the proposed date of discontinued operations and plans for removal. Decommissioning shall consist of:
Physical removal of all large-scale, ground-mounted solar photovoltaic installations, structures, equipment, security barriers and transmission lines from the site.
Disposal of all solid and hazardous waste in accordance with local, state, and federal waste disposal regulations.
Stabilization or revegetation of the site as necessary to minimize erosion. The Building Commissioner may allow the owner or operator to leave landscaping or designated below-grade foundations in order to minimize erosion and disruption to vegetation.
Abandonment. Absent notice of a proposed date of decommissioning or written notice of extenuating circumstances, the solar photovoltaic installation shall be considered abandoned when it fails to operate for more than one year without the written consent of the Planning Board. If the owner or operator of the large-scale, ground-mounted solar photovoltaic installation fails to remove the installation in accordance with the requirements of this section within 150 days of abandonment or the proposed date of decommissioning, the Town may enter the property and physically remove the installation.
Financial surety. Proponents of large-scale, ground-mounted solar photovoltaic projects shall provide a form of surety, either through escrow account, bond or otherwise, to cover the cost of removal and disposal in the event the Town must remove the installation and remediate the landscape, in an amount and in a form acceptable to the Town Attorney but in no event to exceed more than 125% of the cost of removal and compliance with the additional requirements set forth herein, as determined by the project proponent. Such surety will not be required for municipally or state-owned facilities. The project proponent shall submit a fully inclusive estimate of the costs associated with removal, prepared by a qualified engineer. The amount shall include a mechanism for pro rating removal costs as they may be affected by inflation or changes to disposal regulations.
Editor's Note: Section 3 of this order reads as follows: "A building permit shall be issued by the Building Commissioner within one year from the date an application submitted is deemed complete by the Building Commissioner. Failure to issue a building permit within one year shall not result in a constructive grant."
[Amended 2-22-1996 by Order No. 95-194]
A mobile home may be stored in a garage or other accessory building or on the rear half of a lot owned or occupied by the owner of the mobile home. The location of the mobile home shall comply with the yard requirements of the zoning district in which it is located.
[Added 8-17-1995 by Order No. 95-195]
Intent. It is the intent of this section to allow the residents of the Town of Barnstable to operate a home occupation within single-family dwellings, subject to the provisions of this section, provided that the activity shall not be discernible from outside the dwelling; there shall be no increase in noise or odor; no visible alteration to the premises which would suggest anything other than a residential use; no increase in traffic above normal residential volumes; and no increase in air or groundwater pollution.
After registration with the Building Commissioner, a customary home occupation shall be permitted as of right subject to the following conditions:
The activity is carried on by the permanent resident of a single-family residential dwelling unit, located within that dwelling unit.
The activity is a type customarily carried on within a dwelling unit.
Such use is clearly incidental to and subordinate to the use of the premises for residential purposes.
Such use occupies no more than 400 square feet of space.
There are no external alterations to the dwelling which are not customary in residential buildings, and there is no outside evidence of such use.
The use is not objectionable or detrimental to the neighborhood and its residential character.
No traffic will be generated in excess of normal residential volumes.
The use does not involve the production of offensive noise, vibration, smoke, dust or other particulate matter, odors, electrical disturbance, heat, glare, humidity or other objectionable effects.
There is no storage or use of toxic or hazardous materials, or flammable or explosive materials, in excess of normal household quantities.
Any need for parking generated by such use shall be met on the same lot containing the customary home occupation, and not within the required front yard.
There is no exterior storage or display of materials or equipment.
There are no commercial vehicles related to the customary home occupation, other than one van or one pickup truck not to exceed one-ton capacity, and one trailer not to exceed 20 feet in length and not to exceed four tires, parked on the same lot containing the customary home occupation.
No sign shall be displayed indicating the customary home occupation.
If the customary home occupation is listed or advertised as a business, the street address shall not be included.
No person shall be employed in the customary home occupation who is not a permanent resident of the dwelling unit.
Customary home occupations shall not include such uses similar to, and including the following:
Barber- and beauty shops.
Real estate or insurance office.
The sale of retail or wholesale merchandise from the premises.
The sale of antique or secondhand goods.
Service or repair of vehicles, and gasoline or diesel powered machinery.
Contractors storage yards.
The manufacture of goods using heavy machinery.
Medical or dental practice.
Fortune-telling or palm reading.
Home occupation by special permit. A home occupation may be permitted in the RC-1 and RF Single-Family Zoning Districts, provided that a special permit is first obtained from the Zoning Board of Appeals subject to the provisions of § 240-125C herein, and subject to the specific standards for such conditional uses as required in this section:
There is no more than one nonilluminated wall sign not exceeding two square feet in area, listing only the occupants' name and occupation.
Not more than one nonresident of the household is employed.
The Zoning Board of Appeals may permit the home occupation to be located within an accessory structure located on the same lot as the single-family residential dwelling unit.
Approval of site plan review is obtained.
The special permit shall be issued to the applicant only at his or her residence, and shall not be transferable to another person, or to another location.
The Zoning Board of Appeals may grant special permits to allow for the use of structures as shared housing to provide care and shelter for persons with special needs due to age or disability. Said special permits shall be issued only with respect to owner-occupied single-family residences to be occupied by not more than six persons not less than 65 years of age or in approved instances persons of lesser age in need of special care, in addition to the family residents in the dwelling, and shall be conditioned upon the maintenance of proper licensed status as a shared residence under the laws of the commonwealth, and upon such other requirements as the Zoning Board of Appeals deems appropriate with respect to safety, parking, screening and other amenities designed to mitigate the impact of the use upon the neighborhood, and may be conditioned as to time and ownership in the discretion of the Board.
[Added 11-18-2004 by Order No. 2005-026; amended 10-7-2010 by Order No. 2011-010; 3-1-2018 by Order No. 2018-053]
The intent of this section is to allow within all residential zoning districts one temporary family apartment occupied only by the property owner or a member(s) of the property owner's family as accessory to a single-family residence to provide families the ability to live together as a family unit, but not to allow for a separate dwelling for rental purposes to non-family members. A family apartment may be permitted, provided that there is compliance with all the criteria, conditions and procedural requirements herein.
As of right. A family apartment shall be allowed as of right, provided that it complies with Subsection C below and satisfies the following criteria:
The apartment unit shall not exceed 50% of the square footage of the existing single-family dwelling and shall be limited to no more than two bedrooms.
Occupancy of the apartment shall not exceed two family members; occupancy limitations shall not apply to children ages 18 and under.
The family apartment shall be located within a single-family dwelling or connected to the single-family dwelling in such a manner as to allow for internal access between the units. The apartment must comply with all applicable zoning requirements for the zoning district in which it is located.
By special permit. The Zoning Board of Appeals may allow by special permit, subject to the provisions of § 240-125C herein, the following waivers from the requirements of Subsection A above:
A family apartment unit greater than 50% of the square footage of the dwelling.
A family apartment unit with more than two bedrooms.
Occupancy of a family apartment unit by greater than two adult family members.
A family apartment unit within a detached structure, with a finding that the single-family nature of the property and of the accessory nature of the detached structure are preserved.
Conditions and procedural requirements. Prior to the creation of a family apartment, the owner of the property shall make application for a building permit with the Building Commissioner providing any and all information deemed necessary to assure compliance with this section, including, but not limited to, scaled plans of any proposed remodeling or addition to accommodate the apartment, signed and recorded affidavits reciting the names and family relationship among the parties, and a signed family apartment accessory use restriction document.
Certificate of occupancy. Prior to occupancy of the family apartment, a certificate of occupancy shall be obtained from the Building Commissioner. No certificate of occupancy shall be issued until the Building Commissioner has made a final inspection of the apartment unit and the single-family dwelling for regulatory compliance and a copy of the family apartment accessory use restriction document recorded at the Barnstable Registry of Deeds is submitted to the Building Division.
Annual affidavit. Annually thereafter, a family apartment affidavit, reciting the names and family relationship among the parties and attesting that there shall be no rental of the principal dwelling or family apartment unit to any non-family members, shall be signed and submitted to the Building Division.
At no time shall the single-family dwelling or the family apartment be sublet or subleased by either the owner or family member(s). The single-family dwelling and family apartment shall only be occupied by those persons listed on the recorded affidavit, which affidavit shall be amended when a change in the family member occupying either unit occurs.
When the family apartment is vacated, or upon noncompliance with any condition or representation made, including but not limited to occupancy or ownership, the use as an apartment shall be terminated. All necessary permit(s) must be obtained to remove either the cooking or bathing facilities (tub or shower) from the family apartment, and the water and gas service of the utilities removed, capped and placed behind a finished wall surface; or a building permit must be obtained to incorporate the floor plan of the apartment unit back into the principal structure.