All uses and activities established after the effective date of this chapter shall comply with the following performance standards.
A. 
The sound level of any operation (other than the operation of motor vehicles or other transportation facilities, operations involved in the construction or demolition of structures, emergency alarm signals or time signals) shall not exceed the decibel levels in the designated octave bands and center frequency as stated below. The sound pressure level shall be measured with a sound level meter and an octave band analyzer that conforms to specifications published by the American National Standards Institute, Inc. [American National Standard Specification for Sound Level Meters, S1. 4-1971, American National Standards Institute, Inc., New York and the American Standard Specification for Octave, Half-Octave and Third-Octave Band Filter Sets, S1. 11-1966 (R 1971), American Standards Association, Inc., New York, New York], shall be used. Such levels shall be measured at the property boundary of the sound source.
B. 
The maximum permissible sound-pressure levels for smooth and continuous noise shall be as follows (all of the decibel levels stated below shall apply in each case):
Octave Band
(cycles per second)
Center Frequency Maximum
Permitted Sound-Pressure Level
(A-weighted decibels-dBA)
10 to 599
63 Hz
50
125 Hz
250 Hz
500 Hz
600 to 2,399
1,000 Hz
38
2,000 Hz
2,400 to 4,799
4,000 Hz
35
8,000 Hz
32
C. 
If the noise is not smooth and continuous or is radiated during sleeping hours (between the hours of 10:00 p.m. and 7:00 a.m.), one or more of the corrections below shall be added to or subtracted from each of the decibel levels given in Subsection B above:
Type of Operation or Character of Noise
Correction in A-weighted Decibels
(dBA)
Noise occurring between the hours of 10:00 p.m. and 7:00 a.m.
-3
Noise occurring less than 5% of any 1-hour period
+5
Noise being of periodic character (hum, scream, etc.), or being of impulsive character (hammering, etc.). In the case of impulsive noise, correction shall apply only to the average pressure during an impulse, and impulse peaks shall not exceed the basic standards given above
-5
No smoke shall be emitted from any chimney or other source of visible gray opacity greater than No. 1 on the Ringlemann Smoke Chart as published by the United States Bureau of Mines, except that smoke of a shade not darker than No. 2 on the Ringlemann Smoke Chart may be emitted for not more than four minutes in any thirty-minute period.
A. 
The emission of dust, dirt, fly ash, fumes, vapors or gases which can cause any damage to human health, to animals or vegetation or to other forms of property or which can cause any soiling or staining of persons or property at any point beyond the lot line of the use creating the emission is herewith prohibited.
B. 
No emission of liquid or solid particles from any chimney or otherwise shall exceed 0.3 grains per cubic foot of the covering gas at any point beyond the lot line of the use creating the emission. For measurement of the amount of particles in gases resulting from combustion, standard correction shall be applied to a stack temperature of 500° F. and 50% excess air in stack at full load.
There shall be no transmission of heat or heated air in quantities discernible above ambient levels at the lot line without instruments by a healthy observer such as the Zoning Officer or a designee. This requirement applies to all land uses and activities, except that this standard shall not apply to heat created during the construction of the use on the subject property, or by incidental traffic, parking, loading, or maintenance operations.
No use shall emit odorous gases or other odorous matter in such quantities as to be offensive at any point on or beyond its lot lines. The guide for determining such quantities of offensive odors shall be the 50 Percent Response Level of Table 1 (Odor Thresholds in Air), Research on Chemical Odors: Part I - Odor Thresholds for 53 Commercial Chemicals, October 1968, Manufacturing Chemists Association, Inc., Washington, D.C.
A. 
General standards: Outdoor lighting for all residential and nonresidential uses shall be designed to minimize undesirable off-premises effects.
(1) 
No use shall produce glare off the premises by illumination originating on the premises. Glare is defined as the sensation produced by light within the visual field that is sufficiently greater than the light to which the eyes are adapted and which causes annoyance, discomfort, or loss in visual performance or visibility, for any period of time, no matter how short in duration.
(2) 
No bare or direct light source shall be visible beyond the lot lines. All lights shall have a full cutoff fixture, which is defined as a light fixture with light distribution pattern that results in no light being projected at or above a natural plane located at the bottom of the fixture. This applies to all pole-mounted lights, building-mounted lights, sign lights, walkway lights, and any other type of illumination. No light shall shine directly into windows or onto streets and driveways off the premises. These standards shall not apply to holiday lights that are temporarily displayed during holiday seasons.
(3) 
Outdoor light fixtures lawfully installed prior to and operable on the effective date of this amendment to the zoning chapter are exempt from all requirements of this chapter. There shall be no change in use or lamp type, or any replacement (except for same-type and same-output lamp replacement) or structural alteration made, without conforming to all applicable requirements of this chapter. Further, if the property is abandoned, or if there is a change in use or ownership of the property, the provisions of this chapter will apply when the abandonment ceases or the new use or ownership commences.
B. 
Types of pole-mounted lights permitted: Lighting shall be provided by fixtures with a height not more than 18 feet above finished grade in all zoning districts. Height shall be measured from the ground to the uppermost point of the light fixture. Light fixtures shall be fully shielded fixtures where the light source is not visible from the property line. Borough Council may consider other type of light fixtures, provided that the intent of this chapter is met.
C. 
Lighting plan required: Any outdoor lighting such as pole-mounted, building, sign, canopy, or sidewalk illumination, and driveway lights, shall be shown on the lighting plan in sufficient detail to allow determination of the effects to adjacent properties, traffic safety, and overhead sky glow.
D. 
Light at the property line: Illumination from light originating on the site shall not exceed 0.5 footcandles at the lot line. Overhead light pollution caused by unshielded or bright lights shall not be permitted.
E. 
Maximum lighting levels: The maximum lighting level at areas within each Borough property shall not exceed five footcandles at building entrances and three footcandles elsewhere on the lot.
No use shall cause earth vibrations or concussions detectable beyond its lot lines without the aid of instruments, with the exception of that vibration produced as a result of construction activity.
A. 
Buffering serves to soften the outline of buildings, to screen glare and noise and to create a visual and/or physical barrier between conflicting land uses. Except in cases of lot line adjustments, buffer yards are required between various land uses and along existing and proposed streets. The extent of buffering required shall be determined by the type of use proposed and the adjacent uses or streets surrounding the proposed development. The impact of the proposed use on adjoining properties is the basis for establishing buffer yard standards.
(1) 
The standards of this section are minimum design requirements. The Borough reserves the right to request that the minimum requirements listed herein be exceeded if conditions so warrant. All landscape plans shall be prepared by a landscape architect familiar with this section to promote the proper use and arrangement of plant materials.
B. 
To determine the required buffer yard and planting schedule, a three-step procedure shall be followed:
(1) 
Step 1: site analysis and determination of buffer yard class.
(2) 
Step 2: selection of the planting option for the buffer class.
(3) 
Step 3: selection of the plant materials from the plant materials list.
C. 
Step 1: site analysis and determination of buffer yard class.
(1) 
For each property boundary, the applicant shall determine the adjacent land use or road classification. Land use information shall be determined by an on-site survey, and this chapter shall be utilized to determine road classifications. Table 1 below specifies the buffer yard class for each boundary.[1]
[1]
Editor's Note: Said table is included is an attachment to this chapter.
(2) 
The applicant shall match his proposed land use with the corresponding adjacent land use or road classification for each property boundary. The letter indicates the buffer yard class.
(3) 
If other uses are determined to be potential conflicts or where unique site conditions warrant, the applicant shall provide a buffer class as specified by Borough Council, upon recommendation by the Borough Planning Commission.
D. 
Step 2: selection of the planting option for the buffer class.
(1) 
After determining the buffer class, the applicant shall select a planting option from Table 2 to meet the buffer yard requirement for each boundary. The Borough may consider an alternate planting option which shall have a screening capability equal to or greater than any of the available options.
(2) 
Table 2: Planting options. The options below indicate the amount of plant material that is required per linear foot of property line. Plantings aligned on property or right-of-way boundaries shall be located one foot to five feet inside of the boundary line. Plantings are not required to be aligned on property or right-of-way boundaries and may be sited on any portion of the buffer yard for buffering purposes. The Borough may permit staggering or grouping of plant materials if a satisfactory buffer is achieved.
Class
Option
A
Within a 10-foot buffer yard: 1 canopy tree per 40 feet of boundary; or 1 flowering tree per 30 feet of boundary.
B
Within a 15-foot buffer yard: 1 canopy tree per 40 feet and 1 flowering tree per 60 feet of boundary; or 1 canopy tree per 40 feet and 1 evergreen tree per 30 feet; or a 4-foot high opaque fence and 1 flowering tree per 40 feet.
C
Within a 20-foot buffer yard: 1 evergreen tree per 20 feet and 1 flowering tree per 60 feet of boundary; or a hedge or large shrub (4 foot centers) along property boundary and 1 evergreen tree per 25 feet of boundary; or an opaque fence 4 feet high and 1 flowering tree per 40 feet and 1 shrub per 20 feet.
D
Within a 50-foot buffer yard: 2 staggered rows of evergreen trees spaced no more than 20 feet apart; or a combination of trees and shrubs which achieve a similar level of vegetative density; or an opaque fence 6 feet high and 1 canopy tree per 40 feet.
E. 
Step 3: selection of plant materials from the plant materials list.
(1) 
Each planting option may utilize any of the plant materials outlined in Table 3. Minimum plant size, given either in height or caliper, is indicated on this table. The Borough may permit other planting types if they are hardy to the area, are not subject to blight or disease, and are of the same general character and growth habit as those listed in Table 3. All planting material shall meet the standards of American Nursery and Landscape Association (ANLA).
(2) 
Where vegetation, topography, or man-made structures exist which can meet the objectives of the buffer requirements, they may be preserved and may be used to meet the buffer and planting requirements. Quantities, size, species, and locations of existing plant materials and other features must be shown on plans and verified by the Borough. Where the Borough allows existing vegetation and features to be counted toward meeting the buffer requirements of this chapter, the vegetation or features shall not be removed and shall be protected by recorded plan note to insure that it remains as a part of the subdivision or land development.
(3) 
Table 3: Plant Materials List.
(a) 
Canopy trees, including columnar trees (minimum 2 1/2 inch caliper).
Acer rubrum (red maple)
Acer saccharum (sugar maple)
Cercidiphyllum japonica (katsura tree)
Gleditsia triacanthos 'Inermis' (thornless honeylocust)
Liquidambar styraciflua (sweetgum)
Phellodendron amurense (Amur cork tree)
Platanus acerifolia (London planetree)
Quercus alba (white oak)
Quercus rubra (red oak)
Quercus coccinea (scarlet oak)
Quercus palustris (pin oak)
Sophora japonica (Japanese pagodatree)
Tilia-linden (all species hardy to the area)
Zelkova serrata (Japanese zelkova)
Columnar Trees
Acer rubrum 'Bowhall' (Bowhall red maple)
Acer rubrum 'Karpick' (Karpick red maple)
Acer saccharum 'Goldspire' (Goldspire sugar maple)
Acer x freemanii 'Jaffersred' (Autumn Blaze freeman maple)
Acer x freemanii 'Armstrong' (Armstrong freeman maple)
Carpinus betulus 'Fastigiata' (fastigate European hornbeam)
Ginkgo biloba; male only (Ginkgo; 'Princeton Sentry' or other cultivars)
Quercus robur 'Fastigiata" (columnar English oak)
Quercus robur 'Skyrocket' (skyrocket English oak)
Taxodium distichum (bald cypress)
(b) 
Flowering trees (minimum 8 feet high).
Amelanchier canadensis (shadblow serviceberry)
Cornus florida (flowering dogwood)
Cornus kousa (kousa dogwood)
Cornus mas (cornelian cherry dogwood)
Crataegus species (hawthorn)
Koelreuteria paniculata (goldenrain tree)
Laburnum vossi (golden chain tree)
Magnolia soulangiana (saucer magnolia)
Magnolia virginiana (sweetbay magnolia)
Malus species (disease resistant)
Malus baccata 'Jackii' (Siberian crabapple)
Malus floribunda (Japanese flowering crabapple)
Oxydendrum arboreum (sourwood)
Prunus kwanzan (Kwanzan cherry)
Prunus subhirtella 'Pendula' (weeping Japanese cherry)
(c) 
Evergreens (minimum 5 feet high).
Ilex opaca (American holly)
Picea abies (Norway spruce)
Picea omorika (Serbian spruce)
Picea pungens (Colorado spruce)
Pinus strobus (white pine)
Pseudotsuga menziesii (Douglas fir)
Tsuga canadensis (Canada hemlock)
x Cupressocyparis leylandii (Leyland Cypress)
(d) 
Deciduous shrubs (30-inch minimum height, 24-inch minimum spread).
Cotoneaster species
Daphne species
Azalea species (deciduous)
Deutzia species
Eleagnus species
Enkianthus species
Erica species
Forsythia species
Hamamelis vernalis (Vernal witch hazel)
Hamamelis virginiana (Common witch hazel)
Ilex verticillata (winterberry holly and other deciduous hollies)
Potentilla species
Pyracantha species
Viburnum species
(e) 
Evergreen shrubs (24-inch minimum height, 18-inch minimum spread).
Azalea species (evergreen)
Rhododendron species (evergreen)
Ilex crenata (Japanese holly species and other evergreen shrub hollies)
Juniper species
Leucothoe species
Taxus species (Yew)
Vaccinium species
(4) 
General requirements.
(a) 
Location of buffer yard.
[1] 
The buffer yard shall be measured from the property line or the near street line where the street serves as a property line.
[2] 
The buffer yard may overlap the required front, side, or rear yards and, in case of conflict, the larger yard requirements shall apply. The lot shall provide a minimum of 10 feet of usable, nonbuffer yard between the rear of the principal structure and the required buffer yard setback line.
[3] 
The buffer yard may be part of the lot area assigned to a dwelling unit. A deed restriction conforming to the dimensions of the buffer yard shall be placed on the lot.
[4] 
All buffer yards shall be maintained and kept clean of all debris, rubbish, and weeds.
[5] 
No structure, play structure, driveway, sign, stormwater detention facility, manufacturing or processing activity, commercial activity, parking, storage or display of materials shall be permitted in the buffer yard, except that a driveway may cross a required buffer area in order to connect the street with a parking area or driveway lying outside the buffer area. Fences are permitted when part of a required buffer yard as specified in this section.
[6] 
Required plant materials shall be permanently maintained and any plant material which dies shall be replaced.
(b) 
Planting requirements near overhead utility lines. Where trees are to be planted near overhead power lines, the following requirements shall be met:
[1] 
If trees are to be planted within 15 feet of a utility pole or line, measured along the ground from the base of the pole, only trees which grow no taller than 25 feet shall be planted.
[2] 
If trees are to be planted within 15 feet to 25 feet of a utility pole or line, measured along the ground from the base of the pole, only trees which grow no taller than 40 feet shall be planted.
(c) 
Guarantee: All plant material shall be guaranteed for 18 months from the day of final approval of the landscape installation by the Borough in accordance with the provisions of the Borough's developer's agreements, escrow agreements, and maintenance agreements. Any plant material 25% or more of which is dead shall be considered dead. A tree shall be considered dead when the main leader has died or 25% or more of the crown is dead. Any dead plant material shall be replaced and installed according to the approved planting practices.
(d) 
Berming shall be provided where the Borough determines that, due to topography or other factors, the buffer classes in Table 1[2] do not provide an adequate buffer between adjoining incompatible uses.
[2]
Editor's Note: Said table is included as an attachment to this chapter.
(e) 
In general, to prevent the planting of a monoculture, at least two different genus of each type of plant should be specified.
F. 
Supplemental regulations. The minimum buffer requirement to be provided by either Open Space Preservation Performance Subdivision 1 or Open Space Preservation Performance Subdivision II shall be a Class C twenty-foot buffer yard. Notwithstanding any contrary provisions of this chapter, the required buffer yard for an Open Space Preservation Performance Subdivision I and Open Space Preservation Performance Subdivision II may be permitted within the rear or side yards of individual lots and may be included in the area of required open space. Any portion of the required buffer yard located on an individual lot shall be subject to a restriction prohibiting disturbance of or construction within the buffer yard.
[Added 10-6-2014 by Ord. No. 978]
A. 
Requirement for transportation impact study. A transportation impact study shall be required for all rezoning applications and in all applications for a zoning variance, special exception and conditional use to enable the Borough and/or the Zoning Hearing Board to assess the impact of a proposed rezoning or zoning application on the local transportation systems, both highways and public transportation. The purpose of the study is to ensure that the proposed rezoning or zoning application does not adversely affect the transportation network and to identify any traffic problems that may be created in the existing highway network as a result of the rezoning or zoning relief and to delineate solutions to potential problems and to present improvements to be incorporated into the proposed rezoning or zoning relief or to the highway and/or public transportation systems within the designated study area. The study shall assist in the protection of air quality, the conservation of energy and the encouragement of public transportation use.
B. 
The transportation impact study shall be performed in accordance with the provisions set forth in Chapter 164, Article III, § 164-41.2, titled, "Transportation impact study."
C. 
The transportation impact study shall be submitted as part of all rezoning applications and zoning applications that have the potential of generating 250 or more trips per day. Where doubt exists as to the need for the study, the applicant shall seek guidance from the Borough Engineer or his/her designee. The application shall not be considered complete until the transportation impact study is submitted to the Borough in accordance with the provisions of this section and § 164-41.2. Council may, at its discretion, require any other application to be accompanied by a transportation impact study, provided that Council notifies the applicant immediately following Council's first meeting to consider the proposal. Such notification shall specify the reason for the requirement, citing the proposal's particular location or existing problems or type of use (e.g., generation of heavy truck traffic).
D. 
Submission procedures and implementation.
(1) 
Time of submission. The transportation impact study shall be submitted to the Borough of Perkasie or the Zoning Hearing Board with the rezoning or zoning application. In the case of rezoning applications, a copy of the study shall also be submitted to the Bucks County Planning Commission.
(2) 
Implementation. The Perkasie Borough Planning Commission, the Bucks County Planning Commission (in the case of rezoning applications only), the Perkasie Borough Engineer and the Perkasie Borough Council or the Zoning Hearing Board shall review the transportation impact study to analyze its adequacy in identifying solutions to traffic problems that may occur either totally, or in part as a result of the application. Transportation improvements required in order to eliminate deficient conditions may be required. These necessary improvements may be attached to the conditions of approval set forth by the Borough or the Zoning Hearing Board prior to approval.
Each site is unique. It has physical features which are rarely precisely duplicated on another site. Portions of some sites may not be usable, and a minimum amount of buildable land should be retained for recreation. The purpose of this section is to determine the appropriate intensity of use to which a specific tract may be put. For each tract that is five acres or larger in R-1A and R-1B Residential Districts, the developer shall include the following calculation with the initial plan submission.
A. 
Base site area: Certain portions of tract may not be usable for the activities proposed for the site; these shall therefore be subtracted from the site area to determine base site area.
(1) 
Site area as determined by actual on-site survey (acres).
(2) 
Subtract: land within ultimate right-of-way of existing roads or utility rights-of-way or easements (acres).
(3) 
Subtract: land which is not contiguous, i.e., a separate parcel which does not abut or adjoin nor share common boundaries with the rest of the development, and/or land which is cut off from the main parcel by a road, railroad, existing land use or major stream so as to serve as a major barrier to common use or so that is isolated and unavailable for building purposes (acres).
(4) 
Subtract: land which in a previously approved subdivision was reserved for resource reasons, such as flooding or recreation (acres).
(5) 
Subtract: land used or zoned for another use, i.e., land which is used or to be used for commercial or industrial uses in a residential development, or land in a different zoning district than the primary use (acres).
(6) 
Equals base site area (acres).
B. 
Resource protection land: All land within the base site area shall be mapped and measured for the purpose of determining the amount of open space needed to protect it.
(1) 
The resource protection land equals, for each resource, the acres of land in the resource multiplied by the open space ratio for that resource. The open space ratios are as follows:
[Amended 3-16-2015 by Ord. No. 985]
Resources
Open Space Ratio
Floodplain district
1.00
Soils on floodplain
1.00
Watercourses, waters of the commonwealth
1.00
Steep slope (25% or more)
0.85
Steep slope (15% to 25%)
0.70
Steep slope (8% to 15%)
0.60
Wetlands
1.00
Wetland buffer
0.80
Woodlands
Environmentally sensitive
0.80
Other
0.50
(2) 
The total land with resource restrictions equals the total of all the acres of land in each resource.
(3) 
The total resource protection land equals the total of all the lands resulting from the calculation in § 186-56B(1).
C. 
Determination of site capacity: Individual site capacity is based on net buildable site area. For single-family cluster or performance standard subdivisions, the number of allowable dwelling units is determined by multiplying the density by net buildable site area. The calculations are as follows:
(1) 
The base site area (acres) multiplied by the open space ratio [see § 186-20A(3), 186-20B(4), and 186-20B(5)] equals the minimum required open space.
(2) 
The base site area (acres) minus the total resource protection land or minimum required open space, whichever is greater (acres) equals the net buildable site area.
(3) 
The net buildable site area (acres) multiplied by the density [see § 186-20A(3), § 186-20B(4), and § 186-20B(5)] equals the number of dwelling units (do not round up).
A. 
Floodplains: All such lands shall remain as permanent open space, except that roads and utilities may cross the floodplain where design approval is obtained from the Pennsylvania Department of Environmental Protection and where other applicable ordinances, regulations and statutes are complied with.
B. 
Soils on floodplain: All such land shall remain as permanent open space, except that roads may cross these soils where design approval is obtained from the Pennsylvania Department of Environmental Protection and that recreational, conservation or agricultural open space uses shall be permitted. Where floodplains are defined, they shall be used rather than soils on floodplain.
[Amended 3-16-2015 by Ord. No. 985]
C. 
Steep slopes: In areas of steep slopes, the following standards shall apply:
(1) 
No more than 40% of steep slopes (8% to 15%) shall be altered, regraded, cleared or built upon. The remaining 60% shall permanently remain undisturbed in existing natural cover and as permanent open space.
(2) 
No more than 30% of steep slopes (15% to 25%) shall be altered, regraded, cleared, or built upon. The remaining 70% shall permanently remain in existing natural cover and as permanent open space.
(3) 
No more than 15% of steep slopes (25% or more) shall be altered, regraded, cleared, or built upon. The remaining 85% shall permanently remain in existing natural cover and as permanent open space.
D. 
Watercourses, waters of the commonwealth: These areas shall be left as permanent open space and free flowing. Such areas shall not be altered, regraded, filled, piped, diverted or built upon, unless design approval is obtained from the Borough and the Pennsylvania Department of Environmental Protection as required.
E. 
Wetlands.
(1) 
All such lands shall remain as permanent open space. No development, grading, filling, piping, diverting, or disturbance of any kind shall be permitted in wetlands except that bridges, roads, and utilities may cross wetlands where design approval is obtained from the Pennsylvania Department of Environmental Protection and the United States Army Corps of Engineers or their successor agencies, and where other applicable ordinances, regulations and statutes are complied with.
(2) 
All wetland determinations shall be performed by the Army Corp of Engineers or by an independent party certified by the Army Corp of Engineers to be expert in wetland delineations, in which case a copy of such certification shall be provided with the subdivision or land development application and all wetland delineations shall be attested to and sealed.
(3) 
At the time of application, the applicant shall file for review a wetlands report that shall identify and delineate all wetlands on the plan set in sufficient detail as to make on-site verification possible. All wetland areas shall be clearly staked at the time of application and throughout the review period to allow the entire perimeter of the wetland area(s) to be located.
F. 
Wetlands buffer: In addition to the wetlands preservation, a buffer of 100 feet shall be maintained from the limits of any wetland as delineated through the requirements in § 186-57E, in order to minimize hydrologic modifications and potential for pollution. Within the buffer area, an eighty-percent existing natural cover must be undisturbed and maintained as permanent open space. The remaining 20% of the buffer area may be disturbed. Any permanent wetland crossing in the buffer area shall be part of the twenty-percent maximum allowable encroachment.
G. 
Woodlands: In areas of woodlands, the following standards shall apply:
(1) 
No more than 20% of a woodland area associated with another environmentally sensitive resource shall be altered, regraded, cleared, or built upon. The remaining 80% shall permanently remain in existing natural cover. For the purposes of this section (§ 186-57G), an environmentally sensitive resource shall include floodplains, soils on floodplain, steep slopes (15% and greater), wetlands, and wetland buffers.
[Amended 3-16-2015 by Ord. No. 985]
(2) 
No more than 50% of a woodland area not associated with another environmentally sensitive resource shall be altered, regraded, cleared or built upon. The remaining 50% shall permanently remain in existing natural cover.
H. 
Tree protection zone: Such areas shall be 100% open space. No land within the tree protection zone shall be altered, regarded, compacted, or built upon or used for storage or parking of vehicles.
[Added 10-6-2014 by Ord. No. 978]
On any site developed for an Open Space Preservation Performance Subdivision I or Open Space Preservation Performance Subdivision II development, naturalized stormwater management facilities in accordance with the Pennsylvania Department of Environmental Protection BMP Manual and approved by the Borough Engineer, shall be permitted in the required open space. Additional stormwater management facilities, including retention basins, shall be limited to 20% of the required open space area on a site, at the discretion of the Borough Engineer.