HomeMy WebLinkAboutAgenda - 03-03-2015-13 (4)INFORMATION ITEM
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PLANNING & INSPECTIONS DEPARTMENT
Craig N. Benedict, AICP, Director
Current Planning 131 W. Margaret Lane
(919) 245-2575 1 201
(919) 644 -3002 (FAX) RA1114 3 „� „w O11 1 1\11 FY P. O. Box 8181
www.orangecountync.gov ^KN; (1 4 f C.` I� ( -) JN Hillsborough, NC 27278
MEMORANDUM
TO: Board of County Commissioners
Bonnie B. Hammersley, County Manager
FROM: Michael D. Harvey, Current Planning Supervisor
Wesley Poole, Erosion Control /Stormwater
CC: John Roberts, County Attorney
James Bryan, County Attorney
DATE: March 3, 2015
SUBJECT: INFORMATION ITEM — Response to Petition Impervious Surface
Issues
Please accept the following memorandum responding to a property owner inquiry over
impervious surface allocations within Orange County.
EXECUTIVE SUMMARY: The County is, for the most part, more restrictive than the
State with respect to established impervious surface limits. There are no impervious
surface limit(s) for properties not located within a `protected' or `critical' Watershed
Protection Overlay District.
There has been an increase in requests, both at a staff and elected official level, from
property owners seeking additional impervious surface allotments beyond established
limits. The State allows for the installation /use of a stormwater feature, commonly
referred to as Best Management Practices (BMPs), allowing additional impervious
surface area on a given property in certain circumstances.
The use of a BMP is not, however, universally applicable throughout the County and
can be limited based on soil composition, drainage, and topography. There are
concerns related to establishing a program allowing for additional impervious surface
area through the use of a BMP, as well as the perpetual maintenance costs of such
infrastructure, causing staff to believe the option has limited viability.
2
BACKGROUND: In accordance with NC General Statute 143 Chapter 21, Orange
County adopted watershed management standards in the late 1980's early 1990's
establishing regulations to prevent significant future water quality deterioration in
`existing or potential future drinking water reservoirs'. This included the adoption of
impervious surface limits for properties designated as being located within either
`protected' or `critical' watershed areas.
Impervious surface is defined within Article 10 Definitions of the UDO as:
A surface composed of any material that impedes or prevents the natural
infiltration of water into the soil. Such surfaces include concrete, asphalt, and
gravel surfaces. These include, but are not limited to streets and parking
areas, sidewalks, patios, and structures that cover the land.
Large amounts of impervious surface on a parcel of property impacts water quality by
limiting the availability of undisturbed natural area allowing for the infiltration and
treatment of stormwater runoff. To address this issue, the County adopted limits on the
total cumulative amount of impervious surface(s) that can be developed thereby
encouraging the preservation of natural area and allowing for more on -site infiltration.
Impervious surface limits vary based on a properties location within a Watershed
Protection Overlay District. Please refer to Attachment 1 for a chart breaking down
current impervious surface limits in each district. Please note there are no impervious
surface limits on those properties not located within a `protected' or `critical' Watershed
Protection Overlay District. This includes areas north of Chapel Hill, around the Town of
Hillsborough, and a portion of land area within the Bingham Township. For more
information on the location of various overlay districts, please refer to Attachment 2.
ISSUE: Staff and Board members have received numerous inquiries related to
increasing allowable impervious surface area including:
• Increasing allowable impervious surface percentages in Watershed Protection
Overlay Districts,
• Allow additional impervious surface area on property based on the installation of
a stormwater feature, and
• Exempt gravel from being considered an `impervious surface area'.
The County already has procedures in place, specifically contained Section 4.2.8 of the
Unified Development Ordinance (UDO), allowing for a property owner to modify the
allowable impervious surface area for a parcel, specifically:
a. Applying for a variance
STAFF COMMENT: Obtaining a variance from existing impervious
surface limits is extremely difficult as the property owner has to
demonstrate there is a unique hardship on the property.
b. Proposing the establishment of a conservation easement on an
adjacent parcel of property. This conservation easement would allow
for a defined area to remain in a natural, undeveloped, state while
allowing for the transfer of the impervious surface area to the subject
parcel to facilitate development.
3
It should be noted in 2014 the State Legislature adopted a temporary rule eliminating
certain types of gravel from being classified as an impervious surface. This rule,
however, was rescinded resulting in all forms of gravel being considered an impervious
surface and calculated as same.
STATE ALLOWANCES: The State has produced a stormwater manual, denoting
required design elements, which can be viewed at: http: / /portal.ncdenr.org /web /ir /bmp-
manual. Property owners proposing a certain level of disturbance are required to
comply with established stormwater provisions as detailed within the UDO.
In certain circumstances the State allows the installation of a stormwater feature,
commonly referred to as a Best Management Practice (BMP), providing an opportunity
for the installation of additional impervious surface area. As of the writing of this
memorandum, the State recognizes only one BMP option allowing for additional
impervious surface allocation, specifically:
Permeable pavement - allows stormwater to infiltrate through void spaces
for temporary storage and, ultimately, to be infiltrated into the soil. The
total amount of additional impervious surface allotment is based on the
soil type.
Viability of permeable pavement is determined on a case by case basis
with no guarantee(s).
According to the manual, permeable pavement has the following general
advantages and disadvantages:
Advantages:
• Replaces built upon area with
materials that allow for infiltration
of stormwater.
• Eliminates standing water on
pavement.
• Helps to reduce pollutant runoff
concerns from a parcel of
property.
Disadvantages
• Without proper maintenance it
can become clogged by
sediment, compromising its
effectiveness.
• Not applicable for all site
conditions.
• Higher costs (i.e. installation
and perpetual maintenance)
County regulations, as contained in Section(s) 4.2.5 and 4.2.6 of the UDO, prohibit the
use of BMPs as satisfying, or allowing for an increase in allowable, impervious surface
area.
UPDATE: Staff would like to offer the following:
1. Members of the Planning Department and Erosion Control / Stormwater are
scheduled to review various elements of the existing stormwater program and
possible use of BMPs to allow for additional impervious surface area with State
officials on February 25, 2015.
2. Staff is developing potential amendment(s) to existing regulations requiring
developers to address the comprehensive impact of development with respect to
impervious surface limits and stormwater management.
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Our goal is to offer an option whereby a developer of a subdivision could install
the necessary infrastructure to off -set runoff from roadways and /or developed
parcels thereby relieving future property owners from accepting responsibility for
the installation and maintenance of individual stormwater management controls
on a lot by lot basis. This, in turn, may result in additional impervious surface
allocations for each proposed lot within a subdivision.
We are also looking to establish a policy to address older subdivisions,
developed prior to the adoption of impervious surface limits, where impervious
area within roadways are calculated as being within part of individual lots.
3. Staff is looking for direction from the BOCC on the need to establish impervious
surface limit(s) on those areas of the County not located within a Watershed
Protection Overlay District.
4. In addressing inquiries made by Dr. Janel Sexton at the December 9, 2014
BOCC meeting, the County could:
a. Amend existing impervious surface limits within the various Watershed
Protection Overlay Districts to be consistent with current State allowances
as detailed in Attachment 1.
This would result in a net increase for some residents in the total
cumulative amount of permitted impervious surface area allowed on their
property.
STAFF COMMENT: It would be incumbent on local property
owners to work with staff to record new plats and
declarations of development restrictions to reflect this
increase in allowable impervious surface area.
The property owner would absorb any expense in the
creation of these document(s).
There will be a finite number of property owners who will be
able to take advantage of this provision.
b. Amend the UDO to allow for the placement of additional impervious
surface area on property with the installation /use of a BMP consistent with
State regulations. In staff's opinion this amendment would include, at a
minimum, the following elements:
Consistent with State policy, requiring a property owner to hire an
engineer to complete a stormwater assessment of the current
property identifying its infiltration rates and carrying capacity. This
would include the completion of a comprehensive soil assessment
for the property.
STAFF COMMENT: State officials have previously indicated
soils in our area do not universally lend themselves to being
viable candidates for the installation of a BMP and receiving
additional impervious surface allotments. Lots have to be
reviewed on a case -by -case basis.
5
Even if we implement the program described herein,
opportunities for local property owners to participate in such
a program may be limited.
ii. Have an engineer develop a BMP to `treat' runoff thereby allowing
for additional impervious surface.
STAFF COMMENT: We would recommend the
establishment of a cap on the total amount of additional
impervious surface allowed per Watershed Protection
Overlay District through this method.
For example, we may allow for an additional 50% of
impervious surface area in the University Lake
Protected /Critical Watershed Protection Overlay Districts
beyond the established 6% threshold (i.e. maximum of 9 %).
This translates to a 2 acre parcel of property, normally
allowed 5,227 sq. ft. of impervious surface area (43,560 x 2
x 0.06) to have 7,840 sq. ft. (43,560 x 2 x 0.09).
iii. Establish a maintenance /inspection /certification policy where the
property owner will have to ensure the perpetual viability of the
approved BMP. We would also require documents to be recorded
within the Orange County Registrar of Deeds office detailing same.
STAFF COMMENT: This has the potential to be costly. The
property owner will be required to absorb the cost of:
1. Maintaining the installed BMP,
2. The cost of an engineer's annual /bi- annual
inspection certifying the BMP is working properly,
and
3. The annual /bi- annual inspection by the County as
required within the UDO.
iv. Review the need for the posting of a bond or a letter of credit
allowing for the removal of the system, and excess impervious
surface area, if the property owner fails to properly maintain the
system.
v. Require the property owner to record documents detailing new
impervious surface limits in the Orange County Registrar of Deeds
office (i.e. new subdivision plat(s), impervious surface declaration,
stormwater operational /maintenance agreement, etc.).
STAFF COMMENT: There are subdivisions in the County
with locally established impervious surface limits enforced by
a homeowners association.
Unless these limits are also modified the property owner will
be unable to take advantage of any County approved
increase.
ATTACHMENT 1 — COUNTY AND STATE
IMPERVIOUS SURFACE LIMITS:
0
Watershed
Overlay District
Impervious Surface Limits —
Residential
Impervious Surface Limits —
Non - residential
State Allowances
University Lake —
6%
6%
Low Density Option:
Protected
Lots existin g p rior to April 2,
Lots existin g p rior to April 2, 1990
6% limit with minimum lot size
(STATE
1990 subject to sliding scale —
subject to sliding scale — See
of 1 acre
Classified WS -II
See Section 4.2.5.2 of UDO
Section 4.2.5.2 of UDO
OR
Watershed Area)
Density n this area is limited to
Y �
Density in this area is limited to 1
Y �
12% limit with minimum lot size
1 dwelling unit for every 5 acres
dwelling unit for every 5 acres of
of 2 acres.
of property.
property.
Certain parcels in existence
Certain parcels in existence prior
High Density Option: 2
prior to October 2, 1989 qualify
to October 2, 1989 qualify for a
If new development exceeds low
for a density bonus of a
density bonus of a maximum of 5
density option, engineered
maximum of 5 dwelling units for
dwelling units for every 2 acres of
stormwater controls required with
every 2 acres of property with
property with any future
development limited to either 24%
any future development being
development being held to the 1
to 30% impervious surface area 3
held to the 1 unit for 5 acre
unit for 5 acre density limit.
density limit.
A maximum of 10% of the
watershed outside of a Critical
Area can be developed up to 70%
impervious with a structural BMP.
University Lake —
6%
6%
SAME AS ABOVE
Critical
Lots existing prior to April 2,
Lots existing prior to April 2, 1990
(STATE
1990 subject to sliding scale —
subject to sliding scale — See
Classified WS -II
See Section 4.2.5.2 of UDO
Section 4.2.5.2 of UDO
Watershed Area)
Density in this area is limited to
Density in this area is limited to 1
1 dwelling unit for every 5 acres
dwelling unit for every 5 acres of
of property.
property.
Certain parcels in existence
Certain parcels in existence prior
prior to October 2, 1989 qualify
to October 12, 1989 qualify for a
for a density bonus of a
density bonus of a maximum of 5
maximum of 5 dwelling units for
dwelling units for every 2 acres of
every 2 acres of property with
property with any future
any future development being
development being held to the 1
held to the 1 unit for 5 acre
unit for 5 acre density limit.
density limit.
1 Property within the University Lake Protected and Critical Watershed Protection Overlay Districts is also located
within the Rural Buffer (RB) general use zoning district. In developing the RB zoning district, which was done prior
to the development and adoption of Watershed Overlay standards, the County chose to require a 2 acre minimum
lot size. We then chose to impose the more restrictive impervious surface limit in an effort to ensure the
protection of the Chapel Hill /Carrboro water source.
z There was a conscious decision made as reflected in the Joint Planning Land Use Plan, Joint Planning Land Use
Plan Agreement, and adopted 2030 Comprehensive Plan to keep the area within the RB zoning district at a low
density. Changing this policy will require the amendment of the aforementioned document(s). Non - residential
development(s) are held to the 6% impervious surface limit.
3 Critical areas, under high density, are limited to 24% while protected areas are limited to 30% impervious surface.
7
Watershed
Overlay District
Impervious Surface Limits —
Residential
Impervious Surface Limits —
Non - residential
State Allowances
Cane Creek —
6%4
12%
Low Density Option:
Protected
Lots existin g p rior to January 1,
Lots existin g p rior to January 1,
6% limit with minimum lot size
(STATE
1994 subject to sliding scale —
1994 sliding scale — See Section
of 1 acre
Classified WS -II
See Section 4.2.5.2 of UDO
4.2.5.2 of UDO
OR
Watershed Area)
Density n this area is limited to
Y �
5 acre minimum lot size
12% limit with minimum lot size
1 dwelling unit for every 5 acres
50% impervious surface limit for all
of 2 acres
of property.
fire stations and solid waste
High Density Option:
Certain parcels in existence
collection centers (with stormwater
prior to October 19, 1999
feature)
If new development exceeds low
qualify for a density bonus of a
density option, engineered
maximum of 5 dwelling units for
stormwater controls required with
every 2 acres of property with
development limited to either 24%
any future development being
to 30% impervious surface area
held to the 1 unit for 5 acre
A maximum of 10% of the
density limit.
watershed outside of a Critical
Area can be developed up to 70%
impervious with a structural BMP.
Cane Creek —
6%
6%
SAME AS ABOVE
Critical
Lots existing prior to April 2,
5 acre minimum lot size
(STATE
1990 subject to sliding scale —
Lots existing prior to April 2, 1990
Classified WS -II
See Section 4.2.5.2 of UDO
subject to sliding scale — See
Watershed Area)
Density in this area is limited to
Section 4.2.5.2 of UDO
1 dwelling unit for every 5 acres
of property.
Certain parcels in existence
prior to October 19, 1999
qualify for a density bonus of a
maximum of 5 dwelling units for
every 2 acres of property with
any future development being
held to the 1 unit for 5 acre
density limit.
4 The Cane Creek Protected Watershed Protection Overlay District originally had a 12% impervious surface limit for
residential developments. It appears to have been changed to be consistent with State standards.
5 There is no High Density Option currently available in the Cane Creek Critical Watershed Protection Overlay
District.
Watershed
Impervious Surface Limits —
Impervious Surface Limits —
State Allowances
Overlay District
Residential
Non - residential
8
Upper Eno —
12% for properties outside of
70 % in Economic Development,
Low Density Option:
Protected 6, '
Transition Areas
Commercial, and Commercial
Industrial Transition Activity Nodes
6% limit with minimum lot size
(STATE
°
30 /° for properties located
with development of a BMP.
of 1 acre
Classified WS -II
within Transition Areas where
OR
Watershed Area)
density exceeds 1 dwelling unit
50% for all fire stations /solid waste
per acre
p
collection centers outside of these
12% limit with minimum lot size
70% for residential land uses
Activity Nodes with development of
of 2 acres
developed at 'high densities'
p g
a BMP
High Density Option:
(R -5, R -8, R -13). A BMP shall
12% for all other non - residential
be required in this scenario
development outside of Activity
If new development exceeds low
Nodes.
density option, engineered
Density in this area is based on
stormwater controls required with
underlying general use zoning
development limited to either 24%
designation
to 30% impervious surface area
A maximum of 10% of the
watershed outside of a Critical
Area can be developed up to 70%
impervious with a structural BMP.
Upper Eno —
6%
6% limit
SAME AS ABOVE
Critical $
Density in this area is limited to
2 acre minimum lot size
(STATE
1 dwelling unit for every 2 acres
Classified WS -II
of property.
Watershed Area)
Lots smaller than 5 acres
existing prior to 6/1/2010
subject to sliding scale — See
Section 4.2.5.2 of UDO
Little River —
6%
2 acre minimum lot size
SAME AS ABOVE
Protected
Lots existing prior to January 1,
50% for all fire stations /solid waste
(STATE
1994 subject to sliding scale —
collection centers outside of these
Classified WS -II
See Section 4.2.5.2 of UDO
Activity Nodes with development of
Watershed Area)
a BMP
Density in this area is limited to
12% for all other non - residential
1 dwelling unit for every 2 acres
development.
of property.
6 Per Section 4.2.4 and 4.2.5 of the UDO a structural BMP is required in some cases where density exceeds 1
dwelling unit per acre.
7 The County chose to institute the High Density Option within the Upper Eno Protected Watershed Protection
Overlay District.
8 The County's Upper Eno Critical Watershed Overlay District is larger than the State recognized critical area.
Watershed
Overlay District
Impervious Surface Limits —
Residential
Impervious Surface Limits —
Non - residential
State Allowances
9
Back Creek —
12% for properties outside of
70 % in Economic Development,
Low Density Option:
Protected
Transition Areas
Commercial, and Commercial
Industrial Transition Activity Nodes
6% limit with minimum lot size
(STATE
°
30 /° for properties located
with development of a BMP.
of 1 acre
Classified WS -II
within Transition Areas where
OR
Watershed Area)
density exceeds 1 dwelling unit
50% for all fire stations /solid waste
per acre
p
collection centers outside of these
12% limit with minimum lot size
70% for residential land uses
Activity Nodes with development of
of 2 acres
developed at 'high densities'
p g
a BMP
High Density Option:
(R -5, R -8, R -13). A BMP shall
12% for all other non - residential
be required in this scenario
development outside of Activity
If new development exceeds low
Nodes.
density option, engineered
Density in this area is based on
stormwater controls required with
underlying general use zoning
development limited to either 24%
designation
to 30% impervious surface area
A maximum of 10% of the
watershed outside of a Critical
Area can be developed up to 70%
impervious with a structural BMP.
Watershed
Overlay District
Impervious Surface Limits —
Residential
Impervious Surface Limits —
Non - residential
State Allowances
10
Flat River —
12%
50% for all fire stations /solid waste
Low Density Option:
Protected
Density in this area is limited to
collection centers
.Density limit of 2 dwelling units
(STATE
1 dwelling unit for every 40,000
12% for all other non - residential
per acre or 20,000 square foot
Classified WS -III
sq. ft. (0.92 acres) of property.
development.
minimum lot excluding roadway
Watershed Area)
right -of -way
OR
• 24% impervious surface limit for
residential /non - residential
developments
High Density Option:
If new development exceeds low
density option, engineered
stormwater controls required with
development limited to 50%
impervious surface area
South Hyco
12%
50% for all fire stations /solid waste
SAME AS ABOVE
Creek —
Density in this area is limited to
collection centers
Protected
1 dwelling unit for every 40,000
12% for all other non - residential
(STATE
sq. ft. (0.92 acres) of property.
development.
Classified WS -III
Watershed Area)
Watershed
Impervious Surface Limits —
Impervious Surface Limits —
State Allowances
Overlay District
Residential
Non - residential
11
Lower Eno —
24% for project with curb and
70 %, with a BMP required when
Low Density Option:
Protected
gutter
an impervious surface exceeds:
• Density limit of 2 dwelling units
(STATE
36% for project without curb
24% for project with curb and
per acre or 20,000 square foot
Classified WS -IV
and gutter
gutter
minimum lot excluding roadway
Watershed Area)
70% for residential land uses
OR
right -of -way
developed at `high densities'
36% for project without curb and
OR
(R -5, R -8, R -13). A BMP shall
be required in this scenario
gutter
. 24% impervious surface limit for
residential /non - residential
Density in this area is based on
development
underlying general use zoning
designation
OR
• 3 dwelling units per acre
OR
• 36% impervious surface limit for
residential /non - residential
development without curb and
gutter street systems
High Density Option:
If new development exceeds low
density option, engineered
stormwater controls required with
development limited to 70%
impervious surface area.
Jordan Lake —
24%
24%
SAME AS ABOVE
Protected
Density in this area is based on
(STATE
underlying general use zoning
Classified WS -IV
designation
Watershed Area)
Haw River —
24%
24%
SAME AS ABOVE
Protected
Density in this area is based on
(STATE
underlying general use zoning
Classified WS -IV
designation
Watershed Area)
Attachment 2
Orange County Watersheds 12
N
pply Watersheds:
Protected
Unprotected
Critical
ver Basin Boundary
atersheds
reams
inicipal Jurisdiction
3 4
Miles
= 2.75 miles
P replaces previous versions.
County Zoning Ordinance
n adopted June 1, 2010
ng & hp-- Dxpartment
ed by I — Colem—
om Sure Plane
rth Amenczn 1983
rims D— November, 2W R—..
2/4/2015