20051497 Ver 2_Mitigation Plan Review_20090730

Kulz, Eric
From: Kulz, Eric
Sent: Thursday, July 30, 2009 8:33 AM
To: Johnson, Alan
Subject: McAlpine Creek - Mecklenburg Co. (20051497 v2)
Alan;
I reviewed this application and the plans. Looks OK except for concerns about Tributary SR3. They are proposing 370 LF
of Priority 1 restoration on an intermittent stream. This is a very tricky proposition, because by definition, intermittent
streams intersect the water table for a portion of the year. Changing the channel elevation and getting it right is
extremely difficult. Normally, P1 involves bringing up the channel elevation of an incised stream to allow it to access its
floodplain. However, very often, intermittent streams only became intermittent once they cut down to groundwater.
There is the possibility that by doing a P1 on an intermittent stream, you could raise the channel elevation above the
groundwater table, and thus end up with an ephemeral stream.
Confusing me further, looking at the long pro on Sheet SR3-1(27 of 50 in the plans), the existing channel grade is shown
to be approx. four feet higher than the proposed grade!!! Not sure how this could be, as SR3 is described as a
"intermittent gully ........ moderately to highly eroded" (Page 14 of the Mitigation Plan). I wouldn't mind clarification on
this issue.
Let me know if you need anything else or if you have questions about my comments.
Eric
Kulz, Eric
From: Kulz, Eric
Sent: Thursday, July 30, 2009 12:33 PM
To: Johnson, Alan
Subject: RE: McAlpine Creek Again
Cool. I was wondering if you had been out there, and know more about the site than can be gleaned from the plans. I
did notice that on the stream form, they did find dragonfly larvae 9or at least one). That would make it perennial.
From: Johnson, Alan
Sent: Thursday, July 30, 2009 12:07 PM
To: Kulz, Eric
Subject: RE: McAlpine Creek Again
Jarrod will send in additional info about the 12" and 12.5%.... the peizometers are probably to document the 12" and
duration.
The intermittent stream, looked perennial.... I remember the site ...pretty much a butched stream ...but can't remember
the specifics... I think the X Y scale makes it look more pronounced and you're looking at long glides/run between the
small pools. It then just head cuts towards the main channel. The main idea is to pull away from the corner of
apartment building and protect sewer line as well.
From: Kulz, Eric
Sent: Thursday, July 30, 2009 9:02 AM
To: Johnson, Alan
Subject: McAlpine Creek Again
Alan;
I noticed one additional issue. With respect to the wetland monitoring, they say they are going to monitoring hydric soil
formation, hydrophytic vegetation, and wetland hydrology. The table on Page 29 of the plan says they will install
piezometers. What are the success criteria for wetland hydrology? Normally we want to see a specific criterion. e.g.
inundated or saturated within 12" of the ground surface for 12.5% of the growing season in consecutive days.
Eric