HomeMy WebLinkAbout01-19-2016 Item 14, Hoffman 2it is my understanding that the Council will hold a hearing on the appeal by
developer Jeff Kraft concerning his plans for a building on the lot that stretches
between Buena Vusta and Loomis Avenues.
1 am % ihmittinn to vn» the re-se-arch done by Chris Stier, a rer0ed amorist with
Greenvale Tree Co. regarding the feasibility of planting Oak trees on that lot.
This is very interesting material and important to the project's success because
the Oak trees in question would shield the view of this unconventional building
from travelers coming down the Cuesta Grade.
There is a movement on from Cal Trans (see enclosed) to make the highway
from Atascadero to Pismo Beach a Scenic Highway. Since the building in
question is very visible from higher up on the grade, than shown by Mr. Kraft's
photographs taken from lower down, it would be most desirable to shield it from
view_
I am submitting this report to you early in the hope that that will give you the time
to go over it carefully as it is important information for not only this project but for
others considering landscaping with Oak trees on our hilly slopes.
The success of such landscaping is, in the long run, is very dependent on the
application of this type of research.
Thank you for your attention.
Sincerely, NOV 2 3 2015
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COUNCIL MEETING:
ITEM N(l.:
4
URLEINVALt l dl— l.O1V1fAN Y
Purpose: To explore the feasibility of planting, viability, maintenance and fire safety regarding Oaks to
be planted along the back and sides of a proposed residence on Buena Vista Avenue in San Luis Obispo.
Background:
Local residents in the neighborhood of Buena Vista Avenue are concerned with a proposed residence
that is to be located on a very steep lot. In the proposal it has been stated that large Oak trees are to be
planted to screen views from the back of the residence (toward Loomis) and the sides. Concerns have
arisen about the ability to plant large trees on the slope and the viability and maintenance of them should
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Visihih –Because of the steep slope and the height of where it is to be built the structure will be
highly visible from Highway 101 and the roads and properties below including areas off Monterey Street
and San Luis Drive. There has been some discussion of a 101 scenic highway through the area and some
restrictions concerning buildings along the view corridors as cars approach San Luis Obispo from
Cuesta Grade. Mitigation for this structure was in part to plant trees to screen the residence.
Slone and soil - The lot is extremely steep. Much of it approaches, or perhaps exceeds, 45 degrees. The
soil is loose alluvial soil and not far below this is rock. This type of soil has a high capacity to slip and
erode.
Exposed rock from cuts throughout this area shows signs of underlying serpentine rock. There is very
little organic matter in this soil. Currently the area is grassland with Oaks below along Loomis. There is
one Oak above, very close to Buena Vista Avenue.
Access to the lot – The lot runs between Loomis (below) and Buena Vista. Access for trees and
equipment to be brought onto the property is primarily from Buena Vista as the current plan exists.
There is no driveway but a steel "bridge" linking the garage to the road. Below, on Loomis, there will be
no feasible way up to the area where the trees are to be planted due to the steep terrain. Buena Vista
Avenue is about Wi! lanes at the lot frnntace which makes this area narrow.
Size of trees – Other than "large" trees being planted I have no reference as to what size. I will assume
that large would indicate a boxed tree and 48 -inch would be considered as "large ". For this report, Trees
or Oaks in regard to planting and/or this planned structure are considered to be a 48 -inch box.
The rhizosphere is an area of soil (10 to 16 inches deep) that contain microorganisms such as bacteria,
beneficial fungi and larger organisms such as worms and bugs that break down organic matter. Without a
healthy rhizosphere Oaks are subject to stress, disease and pests. In a practical sense it is the lack of a
suitable rhizosphere, or conditions to create one that limits the viability of an Oak.
The soil on this slope is alluvial with underlying rock. Rock in this area tends to have plentiful
serpentine in it. Serpentine rock/soils tend to have high levels of magnesium and heavy metals and are
low in Calcium. Some plants adapt and some even thrive in serpentine soils. Oaks have adapted to
serpentine soils but these oaks are native coming up from seed. They are also much smaller and more
sparse than oaks that grow on other soils. Also the micro- organisms needed for Oaks tend to fail to
colonize in serpentine soils as heavy metals can be toxic to them.
While the soil here has a loose upper surface there is rock not far below. Two very opposite things are
likely to happen in the establishment of Oaks on this lot due to the underlying rock. The underlying rock
will need to be chipped -away to make a basin for the planting hole. This is a suitable situation when
water can be controlled, But when we have wet years water will pool in the rock planting hole and the
oak will likely die or become stunted due to rot or root asphyxiation. If deeper soil is found where the
planting can be done in loose soil likely the opposite is true. Water will flow through the soil rapidly and
hit the underlying rock where it will then flow downhill. This perennially dry soil will lead to poor
establishment and a Stunted tree
Both the serpentine soil and underlying rock is the reason we find no Oaks growing on this hillside. The
grasses and other annual, shallow rooted plants can survive and grow but establishing an Oak to full
potential and vigor is improbable.
Maintenance
Oaks are wonderful in natural settings but can be a great expense and a big mess in our landscapes.
Constant leaf drop, twig dieback and dropping acorns don't just make a mess they can be fire hazards.
More to the point it is dead leaves and twigs (and sometimes branches) that remain on the tree that can
become fire hazards. Oaks are by nature fire resistant. That is they can recover and re- sprout and in
doing so the fire eliminates the dead and weak branches as well as pests. Near a residence the fire
marshal requires all combustibles within 30 feet of a structure to be removed. Trees "shall" be pruned of
all dead limbs, combustible debris be removed and canopies lifted to prevent fires from coming up from
the ground into the canopy. In general, to meet this requirement oaks will need frequent pruning (every
two to three years).
Because of the type of soil and terrain the oaks should be watered the first three years. In dry years the
Oaks will need supplemental water to survive perhaps on a monthly basis. Failure to maintain the Oaks
through watering can lead to severe dieback, disease and it can become a fire hazard.
Fire Safety