HomeMy WebLinkAboutcoa.lu.sm.Smuggler Retention Pond.47-83 CASELOAD SUMMARY SHEET
City of Aspen
No. rJ" A/7 —R?
Staff: 7rha/r4'
PROJECT NAME:
APPLICANT: et ,(ir Phone:
REPRESENTATIVE: f / � . Phone: A/ 29.a-
TYPE OF APPLICATION: (Fee)
•
I. GMP /SUBDIVISION /PUD (4 step)
1. Conceptual Submission ($1,840)
2. Preliminary Plat ($1,120)
3. Final Plat ($ 560)
II. SUBDIVISION /PUD (4 step)
1. Conceptual Submission ($1,290)
2. Preliminary Plat ($ 830)
3. Final Plat ($ 560)
III .EXCEPTION /EXEMPTION /REZONING (2 step) ($1,010)
IV. SPECIAL REVIEW (1 step) ($ 465)
1. Special Review
2. Use Determination
3. Conditional Use
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REFERRALS: Date Referred:
Attorney Sanitation District School District
Engineering Dept. Mountain Bell Rocky Mtn. Nat.Ga
Housing Parks State Hgwy. Dept.
Water Holy Cross Electric Fire Chief
City Electric Fire Marshall /Building Dept. Other
FINAL ROUTING: Date Routed: \ 19-13
/
A torney ' Engineering
Building Other
DISPOSITION: l � r`
CITY P &Z REVIEW: d'U (� Y fr v ' F
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Chairman Harvey asked to entertain a motion to "approve Smuggler
Drainage Ditch Stream Margin Review subject to the following
conditions:
1) Water quality of discharge from this ditch to be monitored by
Environmental Health Dept. and the results will be considered in
a thorough engineering evaluation, the results of which will be
incorporated into the Smuggler Area Drainage Plan to eliminate
pollutants at this point by current and future drainage improvements.
2) Discharge point will be relocated immediately upstream from
the proposed point to the natural drainage which lies beyond the
first stand of cottonwood trees.
3) Engineering Department will submit to the Planning & Zoning
Commission and the Planning office a site plan specifying the
drainage area for this ditch. No further flow from City or County
land or private land shall be routed into this ditch without
review and approval by the Planning & Zoning Commission.
4) Environmental Health Dept. shall report the results of moni-
toring to the Planning & Zoning Commission no later than June 30,
1984."
Paul Sheldon made the motion to approve, seconded by Pat Fallin,
all voted in favor, the motion carried.
CITY COUNCIL REVIEW:
Ordinance No.
MEMORANDUM
TO: Aspen Planning and Zoning Commission
FROM: Richard Grice, Planning Office
RE: Stream Margin Review - Smuggler Area Drainage
Project
DATE: October 4, 1983
This application comes from the City Engineering Department and
requests Stream Margin Review approval for a portion of the Smuggler
Area Drainage Plan. This portion involves the construction of a
short ditch from Queen Street to the Roaring Fork River adjacent to
Neal Avenue (see copy of sketch plan included in your packet). The
Engineering Department plans to "rip -rap" the ditch with cobblestones
for erosion protection and to install a small "sedimentation area"
to reduce some of the suspended solids and pollutants. The plan
originally included the construction of a sedimentation pond for a
more effective control of suspended loads and pollutants. The pond
was eliminated from the plan due to its costs and because of the
site's high ground water table.
Criteria established in the City Code (Section 24 -6.3) for the
review of Stream Margin Review applications reads as follows:
"1. No building shall be located so as to be within a flood
hazard area designated by the U.S. Core of Engineers
Flood Plain Report for the Roaring Fork River.
2. In the event there is a trail designated by an approved
trail plan within the development site, such trail shall
be dedicated for public use.
3. All attempts should be made to implement the recommenda-
tions of the Roaring Fork Greenway Plan prepared by the
Roaring Fork Greenway Committee.
4. Vegetation shall not be removed nor any slope grade
changes made that may produce erosion of the stream bank.
5. There shall be permitted no changes to the stream channel
or its capacity, and no activity shall be allowed which
will increase stream sedimentation and suspension loads.
6. All efforts must be made to reduce stream pollution and
interference with the natural changes of the stream, and
to enhance the value of the stream as an important natural
feature."
The attached comments from Bob Nelson, Environmental Health Department,
will provide the Commission with some degree of understanding of
the importance and complexity of identifying, evaluating and effectively
controlling the impacts of the urban runoff anticipated to result
from the construction of this ditch. Runoff from streets is a most
serious form of pollution "with the pollutant strength is milar to
untreated sew9" Drainage from the Smuggler Area in general is
% rather affected by the high cofo..ntration of mine tailings with
known toxic properties. The main thing Bob wanted us to know was that
even though this ditch only amounts to a small component of the total
Smuggler Area Drainage Plan, this discharge point may ultimately be
the only discharge point for Smuggler Aroma and therefore this may be
the only opportunity to review the polution impacts.
MEMO: Stream Margin Review
Smuggler Area Drainage Project
October 4, 1983
Page Two
Bob Nelson's review comments also indicate that he does not believe
that either a sedimentation pond, which would be located in the
groun3°water table below Queen Street, or the somewhat wider,
deeper channel proposed could be expected to product effluent
at the desired degree of treatment.
Bob's review concluded by noting that this review only encompasses
a small part of the entire plan and by itself will have small
impact on water quality, particularly considering the magnitude of
the drainage problems in the mobile home park. Bob recommended
a thorough engineering evaluation to determine how best to eliminate
po giants at this discharge paint current and future drainage.
The Most effective e ctive pollution control would, in Bob's opinion ', occur
upstream as a part of other segments of the entire drainage project.
The only other issue which we feel should be addressed with respect
to the review criteria required by the Code, is the impact of this
proposal on-_natural vegetation. A visit to the site has led the
writer to be concerned abut potential damage to a stand of
Cottonwood trees along the stream bank. The construction of the
ditch with its discharge point located as proposed would undoubtedly
damage the roots of several large cottonwood trees. The damage
could be avoided by relocating the discharge point to a natural
drainage on the upstream side of the stand of cottonwood trees.
Both Engineering and the Environmental Health Departments agree
that the relocation of this discharge point as described would
be desirable.
The Planning Office recommends approval of this application with
the following motion:
"Move to approve the Smuggler Drainage Ditch Stream Margin
Review subject to the following conditions:
1. The water quality of the discharge from this ditch
will be monitored and the results will be considered
in a thorough engineering evaluation, the results of
which will be incorporated into the Smuggler Area
Drainage Plan to eliminate pollutants at this point
by current and future drainage improvements.
2. The discharge point will be relocated immediately up-
stream from the proposed point to the natural drainage
which lies beyond the first stand of cottonwood trees.
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MEMORANDUM
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TO: Planning and Zoning Commission
THRU: Planning Department
FROM: Bob Wells, Engineering Department
DATE: September 22, 1983
RE: Stream Margin Review - Smuggler Area Drainage
Project
1. The Engineering Department would like to be placed
on the agenda for the next scheduled P &Z meeting. The
purpose would be to present a proposal for a rip - rapped
ditch from approximately Queen Street to the Roaring
Fork River that is subject to Stream Margin Review.
2. Attached is a sketch of the proposed plan and location.
3. This project has been approved by City Council to handle
the drainage from the Smuggler Trailer Park, Gibson Avenue
and Neal Street. The storm drainage from these areas will
be collected and deposited in a rip - rapped ditch which
runs parallel to Neal Street and into the Roaring Fork
River. There will be a headwall at the ditch with a metal
grate and a metal grate at the entrance to the river to
collect large debris.
4. This ditch will not aggrevate the floodplain. There
will be no fill material brought into this area, no change
to the river channel, no work in the river, and no slope changes
which will erode any of the river bank.
5. The ditch will be widened and deepened in one area to
collect as much sedimentation and pollutants as possible.
The Engineering Department is aware that some debris and
pollutants may enter the river; however, this is presently
the case in this area already. This system will not Worsen the
situation and may even make the situation better.
6. The Engineering Department requests your approval to
Perform this work.
BW /co
Enclosures
cc: Wayne Chapman
Dan McArthur
A.T. Zabbia
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ENVIRONMENTAL HEALTH DEPARTMENT
MEMORANDUM
TO: Richard Grice, Planning Office
4 4‘/
FROM: Bob Nelson, Environmental Health Department
DATE: September 28, 1983
RE: Stream Margin Review - Smuggler Area Drainage Project
The aoolication submitted for review is sketchy and only includes
a portion of the information necessary to evaluate the water
quality impacts from the proposed.
As far as the submittal and intent of the stream margin review
and the criteria of Section 24.6 -3 of the Aspen Municipal Code,
it would appear that there should be little permanent impact
on the areas adjacent to the natural water course. Erosion
of the streambank, vegetation removal, and changes in the
channel or its capacity have been addressed and controlled
or are not at issue. The one consideration is the potential
increase in stream sedimentation and suspension loads, which
is more appropriately dealt with as a larger consideration
of the entire drainage plan, and not to be isolated to this
ditch construction.
Several local studies have demonstrated street runoff as a
most serious form of pollution with the pollutant strength
similar to untreated sewage. However, as a matter of Colorado
Department of Health regulations,urban runoff is considered
a nonpoint source of pollution and its discharge,to even
high quality water courses,is not regulated or controlled. As
a result most discharges, including the one proposed,receive
no treatment.
In our conversations with Jay Hammond and Bob Wells, the following
points were made about the need for this project, its current
and future water quality impact and the related control measures
to prevent degredation of water quality in the Roaring Fork.
1. The ditch currently is projected to carry about 8 cubic
feet per second (cfs) from the mobile home park and a
small section of Gibson Avenue for a fifteen (15) minute
peak of a five year, twenty -four hour rainstorm, and about
4 cfs for an average snowmelt situation. This amounts to
only about 16% of the anticipated flows for the project
area when all collection structures are in place. The
total runoff plan analysis is beyond the scope of this
130 South Galena Street Aspen, Colorado 81511 303/925 -2020
Page Two
September 28, 1983
Stream Margin Review - Smuggler Area Drainage Project
office and was not possible in the limited review time.
2. Portions of the upstream catchbasin and manhole structures
are to be built so that ultimate flows could be diverted
to this discharge point with the easily done construction
of curb, gutter and surfaced streets at Neal Street, King
Street, Queen Street and p ossibility Silverking IV.
3. A sedimentation pond was originally proposed for this
project but was eliminated because it would be in
groundwater and was costly.
4. The current runoff from the area is over a bank on Gibson,
although some is retained by percolation or treated by
overland flows through vegetated areas. The new discharge
will concentrate the pollutant loading and increase in the
velocity of the flow to the stream. While control is
desirable to eliminate erosion and nuisance drainage
situations, the City Engineering Department and consultants
are unsure of the net effect of the pollution load to the
Roaring Fork River.
In view of the Water Quality Management Policies (208 Plan)
of the City and County and the expressed concern of the local
citizens to eliminate pollutants from surface waters, we feel
obligated to recommend urban runoff control for this project.
Usual control methods involve limiting impervious surfaces,
controlling runoff rates and avoiding direct discharges.
It is unclear to this department if any other pollutant control
strategies have been incorporated into the drainage project
upstream of the Queen Street manhole. Without some controls,
however, the entire Smuggler runoff management plan could have
a severe impact on this segment of the river, at the point of
discharge created by this proposal. The flows average only
20 to 30 cfs from September through April, limiting the ability
to dilute pollutants. As a result, negative impacts will result
from the addition of heavy metals, sediment, and excessive oxygen
demands. These will exceed the levels established by the Water
Quality Control Division as stream standards for the mainstream
of the Roaring Fork River for fisheries and drinking water.
We feel water quality considerations and established policies
mandate controls in the planning and construction phases of this
project. However, neither a sedimentation pond at the proposed
location in groundwater, or the somewhat wider, deeper channel
proposed, will, in our opinion, produce effluent at the desired
degree of treatment.
The control of pollutants should focus on the elimination or
Page Three
September 28, 1983
Stream Margin Review - Smuggler Area Drainage Project
treatment of all future discharges by providing such structures
as drywells, infiltration trenches, grassed waterways, and debris
basins. Sediment ponds may also prove useful if sized for a
25 year /24 hour storm and are properly baffled and aerated.
Monitoring results from other small sediment ponds in Jenny
Adair Park and on the Rio Grande Trail have shown control ponds
to be fairly ineffective. This could be due to sizing and
detention times, excessive turbulence, small sediment particle
size or the possible inflow of groundwater. We would suggest
if sediment ponds are utilized in runoff control that their
effectiveness be evaluated in the same manner as in the sewage
treatment plants. Continual monitoring results could dictate
further treatment needs by such means as coagulation, slowing
of velocities, or baffling to achieve a better measure of treatment
even after the pond size has been engineered for best results.
Care also must be taken in considering other treatment alternative.
This area needs study to prevent the leaching of toxic metals
from tailings. Further soil sampling and careful siting would
be necessary for all infiltration -type structures considered.
These methods of control may also prove unsatisfactory in some
areas of the drainage basin with a heavy concentration of mine
tailings.
In summary, it is apparent that control efforts to decrease
sediment, heavy metals, oxygen demand, nitrogen and salinity
are desirable if not required. The question of control methods
and the timing of construction will always arise in a project of
this nature, even though this review only encompasses a small
part of the entire plan, and by itself, seems to have a
rather minimal impact on water quality, particularly when weighed
against the magnitude of identified drainage problems in the
mobile home park. We can only continue to recommend a thorough
engineering evaluation to eliminate pollutants at this discharge
point by incorporating controls in current and future drainage
improvements. Most effective control measures, it would appear,
should occur upstream and as parts to other segments of the entire
drainage project, with the emphasis toward infiltration into
suitable soils where possible to eliminate the flows directly
to the river.
BN /co
cc: Jay Hammond
Bob Wells
CITY OF ASPEN fl ab
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