CATS NE Corridor Light Rail (3)

Proposed LYNX Blue Line Extension Northeast Corridor Light Rail Project
DWQ Review of Applicant's Response to DWQ's Submittal of Request for Additional
Information
Response Hand Delivered to DWQ 3/15112
Item 1 — Adequately addressed No further information required
Item 2 — Adequately addressed No further information required
Item 3 — Jurisdictional Stream D The relocated channel has been depicted on the plans and
appears to flow into Jurisdictional Stream C The revised plans show some sort of structure
and cross pipe (9) dust west of the last check dam This structure was not on the original
plans It is unknown whether this will impact the stream relocation and how flow will be
maintained in the relocated channel Additionally the profile depicts what appears to be an 8
foot drop from the last cross vane in the relocated channel (Stream D) to the confluence with
Stream C Please provide information on how Stream D will connect to Stream C The
confluence must allow for proper connectivity for low flow of water and aquatic passage
Item 4 — Adequately addressed No further information required
Items 5 and 6 — It appears that impacts in this area have increased from 127 in the original
submittal to 138 in the revised submittal Please explain the increase in impacts A function
box was included in the revised drawings to provide connectivity and reduce energy Did the
reduction of energy in the function box get accounted for when designing the nprap energy
dissipator pad? What are the dimensions of the function box (it is difficult to tell from the profile
drawing)
Item 7 — Adequately addressed No further information required
Item 8 Adequately addressed No further information required
Item 9 Adequately addressed No further information required
Item 10 — The stormwater outfall has been relocated and the pipe size has changed from a 24
RCP to a 30 RCP DWQ remains concerned about streambank destabilization in this area
Based on the profile provided on Figure 15A the installation of the riprap apron requires the
excavation of the existing streambank and it appears to be approximately 2 from the bottom
elevation of the existing stream (assuming what is depicted on the profile is the bed elevation
and not the water surface elevation) Is the apron being installed below the ordinary high water
mark of Little Sugar Creek? Also Class B is proposed for this apron DWQ believes that Little
Sugar Creek rises frequently during storm events and is concerned that Class B in the apron
may be carried downstream in the first large rain event (and subsequent rain events) and no
longer provide the benefits of energy dissipation from the 30 RCP
Item 11 Adequately addressed No further information required
Item 12 Adequately addressed No further information required
Item 13 — The response to DWQ s concern regarding overwidening is that the plunge pool will
be transitioned back into the natural stream dimension Figure 16 does not depict any

transitioning only the installation of a rectangular plunge pool in the stream Please provide
information on how the plunge pool will be transitioned back into the stream
Item 14 Adequately addressed No further information required
Item 15 — A section of stream (21 If) has been identified as impact on the revised drawings
This area was not shaded or identified as impact on the original drawings Table 4 indicates
that the total impact at this location is 77 If Please confirm that all stream impacts at this
location have been accounted for
Item 16 Adequately addressed No further information required
Item 17 Adequately addressed No further information required
Item 18 — The response to DWQ s concern regarding riprap impacts indicate that the riprap
dissipater for the 8 x 6 PBC was extended approximately 20 to the inlet of the dual 72 steel
pipes to protect the channel from erosion and prevent stability issues Are these new impacts
associated with this revised submittal or was the 20 If accounted for in the original submittal?
Item 19 Adequately addressed No further information required
Item 20 Adequately addressed No further information required
Item 21 — Figure 19 depicts the end impact area for Jurisdictional Stream P in a different
location than provided on the original drawings Are there additional impacts in this area? Have
they been accounted for? It was DWQ s understanding that impacts in this area were reduced
by the removal of the multi use path The original plans show 1 173 If of impact and 1 666 If of
impact The narrative included in the response indicates a reduction to 1 488 If of impact
Please clarify Additionally the response includes a statement that the proposed stream will be
a grass channel lined with coconut fiber matting DWQ does not allow grass in Jurisdictional
stream beds However lining the newly created stream channel bed and banks with coir fiber
matting (no plastic netting) is encouraged to promote bed /bank stability
Item 22 — Figure 19d depicts a 30 RCP and a 48 RCP Please explain what is going on in this
location Is the 48 RCP conveying a relocated stream? The profile also depicts a 10 riprap
apron at the end of the 48 RCP Is this necessary? If so was that impact accounted for
(assuming it conveys a Jurisdictional stream)? If it is conveying a stream how will it transition
other structures?
Item 23 — The response indicates an increase in impacts at this site due to stream realignment
Based on our discussion if the applicant can provide natural channel design to provide the
realignment DWQ will not require mitigation for realignment portion of the impact Drawings
must be provided depicting natural channel design to DWQ for review in order to determine
whether mitigation will not be required
Item 24 Adequately addressed No further information required
Item 25 The response indicates that the Jurisdictional stream will be conveyed via a trapezoidal
nprap channel DWQ would prefer that the bottom of the channel be lined with coir fiber matting
(no plastic netting) to promote bed stability

Item 26 Adequately addressed No further information required
Item 27 — See Item 23 above If natural channel design is incorporated as part of the channel
realignment DWQ recommends removing the structure label
Item 28 — The dissipator pad has been revised from the original submittal The western end of
the dissipator pad is located very close to the stream in this location Can the pad be narrowed
(and lengthened if required to narrow it) to be located further from the streambank?
Item 29 Adequately addressed No further information required
Item 30 Adequately addressed No further information required
Item 31 Adequately addressed No further information required
Item 32 Adequately addressed No further information required
Additional Comments
Figure 14E Riprap Plunge Pool detail — The plan view indicates see plan sheet for bank
protection What type of bank protection will provided? DWQ prefers soft stabilization /bank
protection whenever possible This would include live stake plantings and the use of coir fiber
matting (no erosion control matting containing plastic in riparian areas) Please clarify why
Class I riprap is used at the end of the pool Why not use Class II if energy dissipation is a
concern? Also it must be ensured that ALL riprap is buried below the stream bed elevation
DWQ recommends adding a note to the detail stating that all riprap must be buried
A stormwater outfall revision is required as per Page 11 of the response This will also
necessitate the installation of additional nprap in Little Sugar Creek (below the ordinary high
water mark) Please provide drawings /details for the revised stormwater outfall As discussed
please investigate the use of a function box to lower the elevation of the existing stormwater
pipe (currently perched approximately 5 feet above the stream) If riprap impacts are required
that are outside the existing impact area those impacts must be accounted for in the revised
permit application Additionally contact the ACOE to determine whether the jurisdictional
verification and /or associated documents need to be revised to account for this area as it occurs
outside the original project boundaries