DGGS Mat Su rev by HC120619034318


									        Matanuska-Susitna Borough Coastal Management DRAFT Plan
 Department of Natural Resources, Division of Geological & Geophysical Surveys
                      Reviewer: Patty Burns, Geologist III

General Comments
I reviewed the draft plan with regard to Natural Hazard information. Parts of the plan
that I reviewed are packed full of information. It is obvious that much consideration has
gone into thinking about natural hazards. However, the plan could benefit from
significant editing. I found myself wanting to spend more time than I had available
editing the language in the plan. The edits that follow are a bit cumbersome because I
needed to copy text from the plan and paste it into this document in order to make my
comments clear. Due to the fact that the Public Review documents are in .pdf format, the
few editorial comments that I made were more time consuming that necessary. In the
future, reviewers may able to make more meaningful comments if review documents are
in a more editable format such as MS Word which allows editors and reviewers to “track
changes” and insert comments easliy.

The CMP and AMSA cross reference tables were very helpful during my review.

The term “geophysical hazards” is a holdover from the old regulations. The new
regulations refer to “natural hazards”. Consider replacing the old terminology with the
new terminology in Volumes 1 and 2.

In general, the enforceable policies are supported by statements in the Resource
Inventory and Analysis. The policies will be more strongly supported once the
soils/geology language problem (see comment in section 5.3.3 below) is worked out.

Volume 1
Section 4.2.3
p. 5
1) “…slope failure prone areas (landslide/mudslide and avalanche)…” Consider
rewording with the term “slope instability” instead of “slope failure”.

Section 5.3.3
p. 16
“The region has a high amount of seismic activity. For example, on January 27, 2005,
approximately 13 earthquakes occurred in Southcentral Alaska. Of those, seven occurred
in the MSB (Alaska Earthquake Information Center, 2005). Faults that enter and cross
through the District include the Border Range, Eagle River, Bruin Bay, and the Castle
Mountain faults, of which the Castle Mountain Fault is considered an active fault (MSB
Coastal Management Plan, 1984).”

I could be better to describe the seismic activity in broader terms. Rather than citing a
given day, it might be more meaningful to describe seismic activity over a longer period

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of time. It is possible to separate the shallow crustal earthquakes (associated with faults
like the Castle Mountain fault) from the deeper subduction zone erthquakes out of the
data available from Alaska Earthquake Information Center (AEIC). Although the
Aleutian Megathrust (subduction zone) is not mapped at the surface in the Mat-Su
borough, it does pose an earthquake hazard to the Mat-Su.
A good person to discuss seismological data with in more detail is seismologist Natalia
Ratchkovski at the AEIC. natasha@giseis.alaska.edu (907) 474-7472

Fault name correction: Border Ranges

p. 17
“The Glaciolucustrine deposits are abundant in the District lowland area, which is why
there are numerous lakes, wetlands, muskeg, and swamps in that particular portion of the

You may want to reword to read more like the following:
“Glaciolucustrine deposits in the District lowland area contributed to the development of
numerous lakes, wetlands, muskeg, and swamps in that area.”

p. 17
“The glacial unconsolidated deposits have a major influence on the presence of, and
ability to, develop natural resources within the District. Soil types influence the flow,
pattern, and trends of surface and ground water and influence the size and amount of
gravel, sand, silt, and clay deposited throughout the District. The volume and location of
construction materials is dependant on soil composition. Buildings, roads, septic systems,
water availability, and utility lines can be affected by the soils they are built on. The types
and amounts of materials deposited dictate the types and amounts of natural resources
found in a particular area. Deposited materials may also dictate the severity of natural
hazards occurring throughout the MSB. Every development or construction project that
encounters permafrost is affected; however, engineering techniques can be used that
minimize the affects.”
The Paragraph above is confusing. “Glacial unconsolidated deposits” are surficial
geologic units (as opposed to bedrock geologic units). Surficial geologic units are the
parent material for soils. “Soils”, which are surface alteration zones, form on or within
geologic units. The volume and location of construction matierials depends more on the
aerial extent of geologic units such as “gravel” or “glacial outwash” rather than on the
extent of a soil unit that may form on one or more geologic units. (I highlighted the
preceding text because I refer to it again later in this document…in addition to the fact
that it is an important point)

Natural Hazards 5
5.4.1 Earthquakes

p. 17
“Plate tectonics, or movement of continental and oceanic plates, is the theory in which
most geologists think earthquakes occur.”

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This widely accepted scientific theory and can be stated more simply. For example:
Earthquakes occur as a result of plate tectonics, or movement of continental and oceanic

Later in the paragraph cited above the term soil is used improperly. You should replace
the term “soil” with “geology” or “material”.

p. 18
Figures are low resolution and hard to read.
The citation information and text with the Tsunami figure is not readable.

In reference to the Castle Mountain fault the plan states that “This fault is the only active
fault within the District boundaries.” You may want to make a more general statement
such as the only active fault mapped within the District boundaries is the Castle Mountain
fault…As I mentioned earlier in my review, the Aleutian Megathrust underlies the
You may want to discuss the postulated blind thrust fault (a buried fault expressed as a
fold at the surface) north of the Castle Mountain Fault with Peter Haeussler, USGS, who
worked in the area for some time. Damaging earthquakes can be generated by blind
thrust faults, 1994 Northridge Earthquake in California is a prime example.
pheuslr@usgs.gov (907) 786-7447

Tsunamis are not necessarily cause by earthquakes. They can be caused by volcanic
eruptions, displacement of the sea floor, or submarine or terrestrial landslides that
displace water.

p. 19
A Point MacKenzie port site would [I suggest substituting “could”] create an area built
Other Tsunami mitigation measures can be taken…without knowing the potential wave
runup heights it is difficult to recommend one mitigation measure over another.

Volcano hazards:

You should check out the Mt. Spurr volcano Hazards report:
2002: Waythomas, C. F., and Nye, C. J., 2002, Preliminary volcano-hazard assessment
for Mount Spurr Volcano, Alaska: U.S. Geological Survey Open-File Report OF 01-
0482, 46 p.
To be thorough, you should take a look at the map in the report above. You can make
stronger statements such as…the district is well beyond the lateral blast and other hazards
as indicated on the map….

You may want to include the inserted map below. If you do, I suggest that you not only
cite AVO 2005, as you have elsewhere, but include the specific URL so that people can
easily get to the online version…Data for each volcano is linked to image on the website.

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I like the following image that you included from the USGS webiste:

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You may want to beef up the caption a little bit and make a statement like…This figure
shows some of the typical hazards associated with Mt Spur and indicate the hazards
relevant to the district.

5.4.4 Slope Failures
p. 21
Consider renaming the section “Unstable slopes”.
It is good that you define the way you are using “landslide” in the plan.

5.4.5 Wildfires
You were wise to include wildfires under the natural hazard section of the plan.
However, wildfires are out of my realm of knowledge. You may want to contact
someone at Division forestry to review this part of the plan if you haven’t done so

Volume II
5.1.4 Geology and Geophysical Hazards
You may want to consider generating more a detailed Natural Hazard area map that
shows the natrual hazard areas described in the text for the Point MacKenzie AMSA.
In your Cook Inlet description you mention structure “…The inlet is located in a
principal structural trough overlying Tertiary rock formations and surrounded by
Quaternary (glacial and recent) deposits of varying densities.” You could mention the
active Cook Inlet structures described by Haeussler (see reference list provided with this

p. 16
Refer to Border Ranges fault, not Border Range fault.
“The other active fault in the near vicinity, the McKinley Strand of the Denali Fault, is
located outside the District boundary.” If you are going make this statement you may
want to mention the 2002 M 7.9 Denali Fault earthquake that ruptured the Denali,
Totschunda and Susitna Glacier Faults. The Susitna Glacier fault was not mapped prior
to the 2002 event…part of the fault may be in your district. I can’t tell from the map
accompanying the draft plan.

“Slope instability” is a better general term than “mass wasting”.
Seismic and non-seismic impacts on slope instability and the current mass wasting
headings could all be addressed under one heading, Slope Instability.

Refer to Bootlegger Cove deposits as “thick”, not “heavy”.

5.2.1 Coastal Habitats
Vegetated Bluffs
p. 19 and 20
I am glad to see the important concepts described in this section; however, the wording is

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p. 32
“The till soils underlying Knik Arm are highly stable and able to stand at deep slopes
such as those of the study area's west channel.”
“Till” is a geologic unit. Soils form on or within till deposits. Please refer to my
comment regarding Volume I, section 5.3.3, p. 17 , above.
Did you mean to say “steep” slopes, not “deep”slopes in the cited passage above?

Natural Hazard Designation Map (Soils.pdf)
See comment regarding soils terminology in Volume 1, section 5.3.3 comments
What is the source of the soil data? (Report, year,publisher)
Where are the soil unit descriptions? Describe how soil types related to hazards.
Mat-Su planners could designate an expanded hazard area with regard to seismic hazards.
See the legal opinion below from Bruce Anders with the department of law regarding
hazard area designations.

The excerpts below are first, a question regarding natural hazard area designations from
ACMP staff and second, the 03/22/05 response is from Bruce Anders with Department of
law. Bruce’s opinion clearly states that he interprets the statute to indicate that a hazard
area must be designated for EACH type of hazard. That said, once any area is designated
as a hazard area (regardless of hazard type), the state standard applies.

Question about designating hazards areas. Do you have to designate for each natural
hazard, or can you designate an area for one hazard, such as earthquakes, but include
policies that address other hazards, such as erosion or wind? (in AW CRSA, the
argument is made that earthquake prone areas are also prone to erosion).

Bruce Anders, Department of Law:
Unfortunately, I believe the plain language of regulations would not allow the AW
approach of a designating natural hazard area to account for more than a single
natural hazard. The first section of 112.210, “Districts “may designate ... natural
processes .. as natural hazards” is not dispositive, as it does not specify the singular or
plural in terms of whether natural process could be a natural hazard. But the
regulation continues, “Such designations must provide the scientific basis for
designating the natural process or adverse condition as a natural hazard in the coastal
area, along with supporting scientific evidence for the designation. (emphasis added).
Since this regulation uses the singular form in tying a “process or adverse condition as
a natural hazard,” it appears that a designated natural hazard area could not account
for more than a single natural hazard.

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