HomeMy WebLinkAboutWPO201400092 Correspondence WPO VSMP 2014-09-19 .
�i.r/
1 _�
County of Albemarle
Department of Community Development
Memorandum
To: Engineering Division,Mark Graham
From: Glenn Brooks,County Engineer
Date: 19 Sep 2014
Subject: Lickinghole Basin Board policy implementation
In light of the recent county implementation of the Virginia Stormwater Management Program,I
am re-evaluating our implementation of the policy on Lickinghole Basin for developments within
its watershed. The policy implementation now needs to reflect the use of runoff reduction
methods (RRM) and on-site facilities. Furthermore, considering how stormwater management
has evolved, it is not valid anymore to assume that all water quality requirements in the
watershed are met by this basin.
Licks •hole Basin
4 _
u
d #
NA e°'1 # r 'a
�g� tai . `r f
It has been the practice at the county, based on a Board of Supervisors policy established in 1991
and later amended in 2001, to allow by-right development in this watershed to proceed without
on-site water quality treatment. The board policy, attached for reference, states a pro-rated share
cost,based on the increase in runoff leaving the property during a 10 year storm, shall be paid to
the county in order to recover some (a projected 34%) of the cost of constructing the basin. This
policy had two major implementation hurdles; (1)The policy contains no technical discussion of
• •
Albemarle County Community Development
Lickinghole Basin Policy Implementation
Page 2 of 5
whether on-site facilities will or will not be provided, or what happens if they are. (2)It contains
no instruction on how the increase in runoff is to be computed, or how this correlates to the state
code requirements.
The Board of Supervisors minutes for the policy in 1991 contained a brief exchange by board
members of on-site facilities,item(1). It was noted that this would be a possibility, on a case-by-
case basis. The point of the question was to avoid the county expense in building the basin if on-
site facilities would be cheaper. The basin was a proposed project at the time. (There was no
discussion of how the case-by-case approach would fall short of the target cost recovery, or how
it could be administered.) Subsequent practice has been that the pro-rata share cost is paid in full
regardless of on-site facilities. Initially, this meant no on-site facilities were provided. As
regulations became more stringent, requiring localized detention, adequate channel protection,
and mitigation for buffer disturbances, on-site facilities were often necessary anyway. In
addition, the Board began to get additional facilities with rezonings. However, the Lickinghole.
Basin implementation never changed, and credit has not been given for such facilities.
Computing the pro-rata payment was the main emphasis of the 2001 amendment to the policy,
which gives direction on item (2). I instigated this amendment, in response to inconsistencies in
plan review and pro-rata share payments. The new computation procedure is what we use now.
It looks like this;
Cpost=0.45 from table 4-3 on p.4-20 of VSMH Vol.2
Cpre=0.32 uniform for entire watershed,not based on individual site condition
A=2 acres
Ipre=5.2 tc of 12 min.App.4C VSMH Vol.2
Ipost=6.4 tc of 7 min.
Qpre=Cpre*Ipre*A
Qpost=Cpost*Ipost*A
Qdiff=Qpost-Qpre
Qdiff= 2.4 [Qdiff/A=_1.2,should average around 1.25cfs/acre I
R=456.96$/cfs BOS Policy recovery rate(last updated 16 Jan 2014)
R*(Qdiff)__1111.33$
This computation is performed by county reviewers. With the use of tabulated values, and a
consistent approach, it provided better consistency, and better cost recovery, than was originally
achieved. There are some things it does not do. It does not claim to provide more, or less,
hydrologic accuracy. It does not directly compute velocity or volume as referenced by the policy.
Instead, it computes the related value of a theoretical peak discharge. It does not compute
pollutant loadings.
Even in 2001, staff knew there were significant flaws in the Lickinghole Basin approach to water
quality. Correspondence at the time shows water resources staff had established that there was
not enough nutrient or sediment removal to protect the reservoir. A study by F.X. Browne,Inc.,
of July 1999, was mentioned to indicate 37% to 46% pollutant and sediment removal. This was
when the basin was new. In its present silted state, it is likely lower. Also in 2001,the state
\rv/
Albemarle County Community Development
Lickinghole Basin Policy Implementation
Page 3 of 5
programs were beginning to emphasize that facilities should be built on a scale to protect local
streams and wetlands, such that tributary streams, and Lickinghole Creek leading to the big
basin, were not sacrificed. This trend has continued, such that now facilities in streams are
prohibited and discouraged by state and federal agencies. Furthermore, the South Fork Rivanna
Reservoir is significantly silted in, and a new reservoir has been constructed at Ragged Mountain,
rather than refurbishing the South Fork Rivanna. Through all these changes, the Lickinghole
Basin policy implementation has continued unaltered.
The county is now at a point where it may be easier to develop within the drinking water
watershed and Lickinghole Basin than elsewhere. Outside the watershed, the full state program
is applicable. Inside the watershed, when we exempt development from water quality treatment,
and instead only collect the pro-rata share, the requirements are much less. This has been the
case for some time. However, now the practice must be examined under new code provisions.
The previous code was explicit in its exemption;
"Sec. 17-316 Contribution to regional stormwater management program.
Each stormwater management/BMP plan shall require that the owner contribute to a regional stormwater
management program,as provided herein:
A. If the land development is located within the watershed of a regional stormwater management
program established by the county which requires pro rata share contributions,the owner shall pay a pro
rata share of the cost of the facility in accordance with any ordinance of the county establishing the
program.
B. An owner's payment pursuant to paragraph(A)shall relieve the owner of the requirements of
section 17-314,if the regional program is designed to control the peak rate and velocity of runoff,and/or
the requirements of section 17-315,if the regional program is designed to provide best management
practices.An owner's payment pursuant to paragraph(A)shall not relieve an owner of his responsibility to
comply with any other requirement of this chapter,except as provided in this section."
Section B relieved the owner of on-site requirements, as far as they are covered by the regional
facility. I'm not sure how it came about that Lickinghole Basin was expected to take care of all
water quality compliance, other than common practice. The documentation I can find on
Lickinghole Basin never made that conclusion.
Under the new code, it is stated differently;
"9VAC25-870-69.Offsite compliance options.
A. Offsite compliance options that a VSMP authority may allow an operator to use to meet
required phosphorus nutrient reductions include the following:
1. Offsite controls utilized in accordance with a comprehensive stormwater management
plan adopted pursuant to 9VAC25-870-92 for the local watershed within which a project is located;
2. A locality pollutant loading pro rata share program established pursuant to§ 15.2-2243
of the Code of Virginia or similar local funding mechanism;
3. The nonpoint nutrient offset program established pursuant to§62.1-44.15:35 of the
Code of Virginia;
4. Any other offsite options approved by an applicable state agency or state board;and
5. When an operator has additional properties available within the same HUC or upstream
HUC that the land-disturbing activity directly discharges to or within the same watershed as determined by
Albemarle County Community Development
Lickinghole Basin Policy Implementation
Page 4 of 5
the VSMP authority,offsite stormwater management facilities on those properties may be utilized to meet
the required phosphorus nutrient reductions from the land-disturbing activity."
Development within the Lickinghole Basin watershed falls under section A.2. This in turn
references this section of state code;
§ 15.2-2243.Payment by subdivider of the pro rata share of the cost of certain facilities.
A. A locality may provide in its subdivision ordinance for payment by a subdivider or developer of land
of the pro rata share of the cost of providing reasonable and necessary sewerage,water,and drainage
facilities,located outside the property limits of the land owned or controlled by the subdivider or developer
but necessitated or required,at least in part,by the construction or improvement of the subdivision or
development;however,no such payment shall be required until such time as the governing body or a
designated department or agency thereof has established a general sewer,water,and drainage improvement
program for an area having related and common sewer,water,and drainage conditions and within which the
land owned or controlled by the subdivider or developer is located or the governing body has committed
itself by ordinance to the establishment of such a program.Such regulations or ordinance shall set forth and
establish reasonable standards to determine the proportionate share of total estimated cost of ultimate
sewerage,water,and drainage facilities required to adequately serve a related and common area,when and
if fully developed in accord with the adopted comprehensive plan,that shall be borne by each subdivider or
developer within the area. Such share shall be limited to the amount necessary to protect water quality based
upon the pollutant loading caused by the subdivision or development or to the proportion of such total
estimated cost which the increased sewage flow,water flow,and/or increased volume and velocity of storm
water runoff to be actually caused by the subdivision or development bears to total estimated volume and
velocity of such sewage,water,and/or runoff from such area in its fully developed state.In calculating the
pollutant loading caused by the subdivision or development or the volume and velocity of storm water
runoff, the governing body shall take into account the effect of all on-site storm water facilities or best
management practices constructed or required to be constructed by the subdivider or developer and give
appropriate credit therefor.
I have added the italics above for emphasis. In this section of code, and in the original board
minutes of 1991, I find a basis for providing, and giving credit for on-site facilities.
Code references to volume and velocity and/or pollutant loading are not new. However, they
have not been directly used in the context of Lickinghole Basin. Historically, velocity and
volume have been computed as they relate to a peak discharge rate (cubic feet per second of
flow). With the new state stormwater program, a pollutant loading computation is required, as
are discharge rates. Volume is also directly reduced in the runoff reduction method through
infiltration practices. These need to be accounted for in the implementation of the Lickinghole
Basin policy.
Volume reductions will be accounted for by multiplying the cost in the original calculation by the
ratio of"runoff reduction (cf)" to"treatment volume (cf)" in the runoff reduction method. For
example, the two acre site had a pro-rata cost of$1,111.33. It might have 1 acre of turf and 1
acre of impervious cover, giving a treatment volume of 4,175cf. With 0.5 acres of impervious
cover draining to a grass channel, and 0.5 acres in permeable pavement(type 2), the runoff
reduction is computed to be 345 cf and 1293 cf. This is a ratio of 0.39. So the final cost is
Lr/
Albemarle County Community Development
Lickinghole Basin Policy Implementation
Page 5 of 5
$1,111.33(1-0.3923) = $675.32. (Refer to the DEQ Runoff Reduction Method, RRM,
spreadsheets for more detail.)
The fact that Lickinghole Basin will not meet current water quality requirements must also be
considered. For purposes of calculation, Lickinghole should be computed at 30% phosphorous
removal. This would apply to the remaining runoff at discharge. There is no runoff reduction,
and no water quantity compliance contribution, directly attributable to Lickinghole Basin.
Furthering the above example, the RRM computes a total phosphorous load (TP) of 2.62 lbs/yr
for the 2 acre site, with a load reduction requirement of 1.80 lbs/yr. Lickinghole could
potentially take care of 30% of the site load but on-site treatment is required first. With the
permeable pavement and grass channel example above, the water quality compliance summary
shows that 1.23 lbs/yr has been treated on-site. 1.40 lbs/yr of the original site load is discharging.
Lickinghole can treat 30% of this, bringing the total treatement volume to 1.23+0.3(1.4) = 1.65
lbs/yr. This is still not quite at the required 1.80 lbs/yr, but getting closer.
The 30% treatment credit from Lickinghole cannot be used for banking credits. Keep in mind
that it is likely 60-70% of the remaining load sent to Lickinghole Basin will not be adequately
treated, but passed on to the reservoir. This is just one way to account for the actual basin
contribution, and give credit for required on-site treatment. The majority of benefit is expected
to come from runoff volume reductions.
I do recognize that there may be much less cost recovered in future when considering on-site
measures as the code directs. However, it is important to consider this in view of the current
program, and the state of Lickinghole Basin, which will not provide water quality protection
equivalent or close to the new state program. On-site facilities may easily provide better
treatment under the new state computation methods, and Lickinghole Basin provides only a
partial treatment as backup for difficult to capture areas. This was arguably its intended purpose,
as added protection in allowing a development area within a drinking water watershed.
Summary
1. Lickinghole Basin pro-rate cost share amounts will be computed with the rational method
peak discharges as before. This is based on the procedure devised in 2001.
2. Credit will be given for on-site facilities by multiplying the cost by the ratio of runoff
reduction to total treatment volume.
3. On-site facilities will be required to meet state water quality pollution (phosphorous load)
treatment requirements, and Lickinghole Basin may be used to account for 30% of pollutant
load leaving the site.
i
3
•
Matthew Wentland
From: Ana Kilmer
Sent: Tuesday,January 26, 2016 10:54 AM
To: Mark Graham; Glenn Brooks
Cc: Max Greene;John Anderson; Matthew Wentland
Subject: Consumer Price Index Information Published January 2016
Attachments: 01262016104712.pdf
In accordance with Board policy, below is the new rate to be used to determine a development's pro-rata share for the
Lickinghole Creek Regional Basin:
Current Rate =471.23/cfs
2015 CPI Percentage Rate=0.1%(per the attached sheet published January 2016)
NEW RATE =471.70
The new rate is effective immediately
Thank you
Ana D. Kilmer
Management Analyst
Community Development Department
401 McIntire Road
Charlottesville,VA 22902
434-296-5832
akilmer@albemarle.org
1
t
t
4Z