HomeMy WebLinkAboutFile Documents.1230 Snowbunny Ln.0166.2018 (25).ARBK
118 W. 6th St, Ste 200 Glenwood Springs, CO 81601 Phone: 970-945-1004 Fax: 970-945-5948
MEMORANDUM
TO: CoA Engineering Dept
FROM: Rick Barth, PE, Senior Engr, SGM; Jordan Kehoe, EI
DATE: July 24, 2020 and August 17, 2020
RE: Engineering Affirmation of drainage design for Valentine Residence, aka 1230
Snowbunny Lane
This memo is to briefly provide our affirmation of the drainage installation for the above residential site.
On July 9th and August 11th I visited the site and toured the drainage elements with the site
superintendent, Jay Smith of Regan Construction and Steve Novy of Greenline Architects. In brief, the
major elements included two small rain gardens and a single drywell, with various surface and
downspout collection devices as well as substantial areas of permeable stone pavers and landscaping.
Initially, a small drywell of unknown size and condition existed just off the driveway to the north (no
records were found). This was essentially a 24” pipe on end a few feet deep. This proved to be
unsuitable therefore a new, up-to-standard drywell (4’ diameter, 10’ feet deep) was installed in the
driveway itself to collect the flows from mainly the southwest side of the parcel, greatly increasing the
capacity. The inverts of the pipe into the drywell still allow for full volumes per drywell calculation
(1.5XWQCV). This drywell and the collection pipe connected to it are shown on the as-builts and a
calculation sheet showing the as-built pipe inverts reveal there is still plenty of volume to satisfy the
requirements.
The two rain gardens were also observed in the excavated state (pre-sand mixture) and later with the
topsoil and adjacent, perimeter berms. With the above notes about general dimensions differing
slightly from design, they both have sufficient volume and in an appropriate location for stormwater
collection. While the back yard rain garden is central, the berm and yard grades will drain to that rain
garden lowpoint, even if only slightly. The designed, small berms of a few inches in height were also
placed, awaiting finishing landscaping but with the topsoil at the time of the second visit. The general
size and geometry of these elements were sufficiently per plan. The designated drainage areas will
clearly drain to these rain gardens through grassed landscaping, as anticipated.
The vast majority of the site is permeable pavers and/or landscaping which should minimize runoff.
Roof drainage is all collected and directed to one of the three elements above, as per plan. Where
surface flows may concentrate, it is evident there will be sufficient grade to direct flows away from the
house to the designed rain gardens, protecting adjacent properties. We submit the construction has
sufficiently satisfied, if not exceeded, in quality and quantity, the drainage requirements of the City of
Aspen’s URMP and our design calculations.
Attached are both the architectural plan (A-10.11) and the Civil drainage plan (C4). Please contact me
if you have any questions regarding this memo at 970-384-9088.
-RLB
118 W. 6th St, Ste 200 Glenwood Springs, CO 81601 Phone: 970-945-1004 Fax: 970-945-5948
Front yard, looking from near front door
toward rain garden area. You can see the
garden depression where the media has been
placed. – 7/24
Photo of corner of driveway. You
can see the heat tubing and
perforated insulation, as per plan.
7/24
118 W. 6th St, Ste 200 Glenwood Springs, CO 81601 Phone: 970-945-1004 Fax: 970-945-5948
Backyard, looking east. You can see the
makings of the detention berm in progress.
7/24
Photo of back yard standing at rain garden,
looking north. You can see the slight contour of
the berm along the treeline. Grade in this area
does drain slightly back to where I am standing. –
8/11
C₀
g
H₀
A₀
-
B
D₀ -
B
I.
D
.
Q
-
B
-
ft
/
s
e
c
²
ft
ft
²
in
.
in
.
cf
s
0.
6
32
.
2
0.
2
5
0.
0
8
6
4.
0
2.
1
0.
0
5
6
Ri
m
78
5
7
.
0
Su
m
p
78
4
5
.
8
In
v
e
r
t
s
78
5
3
.
3
Di
a
m
e
t
e
r
4
fe
e
t
Vo
l
u
m
e
V
=
p
i
*
r
^
2
*
h
94
.
2
5
cu
b
i
c
f
e
e
t
Dr
y
w
e
l
l
S
i
z
i
n
g
**
*
U
s
e
d
S
c
h
e
d
u
l
e
4
0
2
.
0
"
P
V
C
(
2
.
0
6
7
"
I
.
D
.
)
f
o
r
B
a
s
in
B
*
*
*
Ou
t
l
e
t
p
i
p
e
s
i
z
e
d
t
o
r
e
l
e
a
s
e
l
e
s
s
t
h
a
n
1
0
0
-
y
e
a
r
h
i
s
to
r
i
c
f
l
o
w
r
a
t
e
He
a
d
w
a
t
e
r
d
e
p
t
h
c
a
l
c
u
l
a
t
e
d
f
r
o
m
d
e
p
t
h
a
t
1
0
0
-
y
e
a
r
p
on
d
i
n
g
d
e
p
t
h
Ca
l
c
u
l
a
t
e
d
Di
a
m
e
t
e
r
Ac
t
u
a
l
Ou
t
f
l
o
w
Q
-
B
a
s
i
n
B
cf
s
0.
2
0
7
PV
C
Di
a
m
e
t
e
r
Hi
s
t
o
r
i
c
1
0
0
y
e
a
r
F
l
o
w
Ra
t
e
(
Q
)
Di
s
c
h
a
r
g
e
Co
e
f
f
i
c
i
e
n
t
He
a
d
w
a
t
e
r
De
p
t
h
Gr
a
v
i
t
a
t
i
o
n
a
l
C
o
n
s
t
a
n
t
Or
i
f
i
c
e
Ar
e
a