Black Gore Creek Total Maximum Daily Load Sediment Source Monitoring 2008 Vail Pass, Colorado. Prepared for: Eagle River Watershed Council

Transcription

1 Black Gore Creek Total Maximum Daily Load Sediment Source Monitoring 2008 Vail Pass, Colorado Prepared for: Eagle River Watershed Council Prepared by: RiverRestoration.org

2 I. Introduction This document presents data results that were collected to support the Black Gore Creek Total Maximum Daily Load sediment source monitoring. Other simultaneous efforts are underway to monitor in channel sediment sizes and biologic indicators of stream health. Data collection and analyses herein represent the fifth annual sediment source monitoring effort. Monitoring data is used to support quantifying the load allocation for the recognized sediment source categories in the annual sediment budget. II. Methods Field data collection was conducted by RiverRestoration.org from September 23-September 26, The Colorado Department of Transportation was in the process of cleaning out Erosion Control Basins along the highway corridor. Sediment source monitoring of the Erosion Control Basins was conducted after the clean-out efforts. The capitol project at mile marker 182.8, The Basin of Last Resort was concurrently removing sediments from the in-channel Erosion Control Basin. As-built surveys of the in-channel Erosion Control Basin need to be gathered and tied into the annual Sediment Source Monitoring surveys; these data are used to monitor the aggradation rate of the reach. Eight sediment source categories were monitored, these include: Erosion Control Basins (ECB); Fill Slope Gullies (FSG); Valley Floors (VF); Photo Monitoring (PM); Bridge Accumulation (BR); Center Median (CM); Cut Slopes (CS); and Fill Slopes (FS). A detailed description of sediment source monitoring procedures is in the BGC Sediment Source Monitoring Field Guide (Total Maximum Daily Load, ). In addition to annual sediment source monitoring, a longitudinal profile and cross sections survey at MM was conducted. The mileage stationing used to identify reference points and locations were based on aerial photographs (digitized in ), as well as CDOT bench marks and Interstate-70 mile markers along the highway. Reference points may vary +/-0.1 mile. A description of the reference points are in the BGC Sediment Source Monitoring Field Guide. Photographic Monitoring (PM) reference points were revisited where they were set in. Colorado Department of Transportation Bar and Cap benchmarks at PM stations 184.5, and had been removed from traffic or plow activity and were not recovered. These photographs were taken from an approximate location. Erosion Control Basins (ECB), Fill Slope Gullies (FSG), Valley Floors (VF) and Center Medians (CM) were monitored with level surveys of cross sections or profiles from established benchmarks. Disturbed Tag Line Posts (TLPs) observed in 2008 were re-established with elevations turned from the associated benchmark. Common causes of the disturbed TLPs are from snow creep, soil creep, and hill slope slumping. Disturbed TLPs with a new elevation established were at: WTP#2 Right Edge Post (REP), ECB REP, FSG #1 LEP, FSG 187.1#1 REP, FSG 187.1#1 LEP, and FSG REP. Bar and Caps stamped RR.org B&C were established at the top of fill slopes at 186.9, 187.0, and at to be used for future benchmarks. The photograph below shows an example of a bent TLP from snow creep. 1-32

3 Photograph 1 Example of bent Tag Line Post The above photograph is of the left end post at cross section 186.8, (186.8 LEP#3). Fill Slope (FS) rill density was measured at the top of the slope. Vegetative cover percentages on the FS were based on visual estimates. Slope angles were estimated in with an inclinometer. Cut Slope (CS) monitoring was performed at all CS to verify if sediment controls, such as sediment basins installed by CDOT, appeared adequate. The distance of a CS was a measure between a culvert (or direct stream input) and the nearest upstream adequate sediment control. Cut Slopes upstream of Black Lakes were not monitored because all sediments transported are currently being retained by Black Lakes. The spillway of Black Lake no.1 and no.2 were visually monitored for sediments to indicate transport from Black Lakes into Black Gore Creek. Bridge Accumulation (BA), and Valley Floors (VF) were monitored by single depth measurements. Single depth measurements were monitored with a sediment probe at a reference post. Sediment probes are also taken at Center Medians (CM), at the invert and at 10 and 30 feet up gradient from the invert. III. Results Photographic Monitoring Photographic Monitoring (PM) stations are placed at representative locations to document general conditions throughout the watershed. These photographs are qualitative data that support load allocations for the recognized sediment source categories, and provide documentation of the 2-32

4 sediment transport conditions throughout the watershed. In 2008, the PM monitoring at WTP #1 and #2 were changed to new locations. In 2008, a new PM was established at FSG. Below, Table 1 summarizes the PM observations for Table 1 Photographic Monitoring Summary 2008 Reference Point PM Confluence WTP #2 LEP Photo Description Towards US BGC and confluence with Gore Creek Towards WTP #2 REP 9/13-9/ /14-9/ J J 9/14-9/27-9/29 10/16 / pics/i pics\i /23-9/26 Observations Diversion structure constructed in BGC channel. More dense vegetation cover from Newly paved road in. The side channel (behind dead tree ) has been abandoned and vegetated in. WTP #2 CL WTP #1 LEP Center line look downstream Towards WTP #1 REP J pics\i New PM established in Looking downstream from center line of cross section WTP #2. photo shows channel braiding and large lateral bar. Dense vegetation growth from - on lateral bar. Increased willows and bank stability. Paved road in. WTP #1 CL CDOT BM ECB REP ECB #2 LEP Center line look downstream Towards East and center median I-70 Towards ECB LEP Towards ECB #2 REP J J J 26\I \I \I New PM established in Looking downstream from center line of cross section WTP #1. Center median has more dense vegetation cover. There are some invasive weeds. Erosion control logs are buried with sediments. Sedimentation of ECB, more dense vegetation growth. Construction of Basin of Last Resort Project 3-32

5 ECB #1 LEP PM Towards ECB #1 REP Towards westbound I-70 fill slope J J 10-03\I \I Construction of Basin of Last Resort Project No change of fill slope. Good vegetation cover and no slumping or uncontrolled stormwater are evident. PM PM PM BR PM BR Towards failed culvert and FSG Towards DS BGC, 180 US mm183.5 Stand approximately 20 D/S from gage station. From CL look upstream towards gage station pipe. From near BR towards E. abutment S. wing wall east bound I-70 Towards east bound I-70 fill slope Towards east abutment east bound I J J J J 10-03\I \I \I \I \I A new gully has formed down fill slope Photographs show no noticeable change. Slight widening from left bank failure (-2008 front left of photographs). Established in. Photograph shows fines over cobble. Photographs show larger side cast deposits and deep rills. Disturbed PM, no B&C in. PM benchmark reset in East bound shoulder was recently graded in Rills have grown larger and deeper at top of fill slope. Some rills are linked together and forming concentrated drainage down fill slope. Trees are smothered by sediments. In 2008 some dead trees have fallen over. Deposits were surveyed at post. 4-32

6 BR Towards south pier east bound I J 26\I and 2008 photographs are not in archive. PM \I Towards east and 20 westbound I J PM at cut slope ditch PM PM PM G #3 LEP PM Towards eastbound I-70 fill slope From top of FS look down at longitudinal and cross section J 26\I survey reach From top of FS look upstream active beaver dam Towards G #1 REP From CDOT BM towards West and fill slope JP G JP G 10-16\I \I Rills at top of fill slope have concentrated drainage into a gully that is 30' in length. Photographs shows gully degradation. Field notes document freeze/thaw weathering and slope mass failure (large chunks of debris). Uncontrolled cut slope ditch. Exacerbated native slope erosion. No change of fill slope, uncontrolled stormwater, rills at top of fill slope. Field notes documented increased bank erosion 015 Breached beaver dam in Active beaver dam. Increased channel aggradation. Lateral bar growth and drowned trees. Photographs show rill development down slope, gully degradation and delta forming at toe. Increased bank erosion along this reach (notice background of photos). Rills at top of fill slope and smothered vegetation from side cast. No BM in, photograph taken at approximate location. New benchmark established in

7 VF G #3 LEP PM PM VF #2 REP Towards US flow line and deposit Towards G #2 REP Towards downstream BGC and natural right bank erosion Towards East looking at westbound cut slope ditch Towards VF #2 LEP JP G J J JP G J pics\i \I \I \I 2070., / /0 69.JP G \I Increased vegetation cover. A large delta has formed. In, the elevation became high enough that flow now runs to the north of the deposit. Two culverts at are source to VF deposit. Photographs 1997 (taken in during a transport event), and 0107 (2008) is of the delta fan approximately 40 feet upstream from the monitoring post. Photographs show gully degradation. In 2008 the culvert washed to the toe of the fill slope. Photographs show growth of delta at the valley floor Deposition of fines on channel bed Paved shoulder and two subsurface ECB were installed in. Photograph 2071 shows subsurface basin full in. Sediments transport through culvert to VF (See Capital Project Valley Floor Stabilization Other End of the Pipe report). PM shows subsurface basins were clean in and In, crib walls were constructed to stabilize valley floor delta deposits from future transport. Sparse vegetation has established behind crib walls photograph is taken from LEP to REP. VF #1 REP PM Towards VF #1 LEP Towards eastbound US-6 grade and significant slope erosion J J 10-03\I Cross logs were installed in to dissipate energy and trap sediments. Photographs in (front of 2008 photo) shows erosion under the cross logs. Cross section survey shows scour. Vegetation growth (more grass cover and pine sapling growth). 6-32

8 2065. G LEP PM PM PM Towards DS flow line gully and bike path Towards upstream Black Gore Creek From edge of pavement bike path towards flow line gully and BGC From CDOT BM towards West and median J J J J 10-03\I \I \I \I Right bank mass wasting, large trees have fallen into gully. Site was potential capital project in. In spring of, the beaver dam blew out and sediments have transported downstream. No TLP reference post. New PM benchmark set in Field notes documented increased deposition in channel and gully widening. 113 Increased vegetation cover. Cross Section Monitoring Cross section monitoring conducted at Erosion Control Basins (ECB) show sedimentation. There are two Erosion Control Basins surveyed annually; ECB is a large basin located adjacent to I-70, ECB is a basin in the Black Gore Creek channel. The capital project Basin of Last Resort was implemented in fall of 2008, approximately 26,400 tons of sediments were removed from the in channel basin at (CDOT, draft July-Dec ). An asbuilt survey was conducted by the contractor. RiverRestoration.org performed monitoring survey in October after clean out efforts were complete. Ice prevented cross section survey; however contractor control points, the bank, and monitoring control points were surveyed. Descriptions of the contractors control points need to be uncovered so that the as-built survey can be tied into sediment monitoring control points. Fill Slope Gullies (FSG) show transport through the watershed. These Fill Slope Gullies have formed from dilapidated culverts down fill slopes. The average degradation measured at Fill Slope Gullies is used in calculating the load allocation for the sediment budget. Not all of the Fill Slope Gullies are monitored by cross section surveys. The average degradation measured is 7-32

9 extrapolated for all Fill Slope Gullies. Monitoring observations are presented in Table 2 for surveyed cross sections. Fill Slope Gullies recognized in the load allocation are at: 182.2, 183.0, 185.9, 186.5, 186.6, 186.9, 187.2, 187.6, 187.7, 187.9, 188.2, and An inventory of FSG was conducted in. The gully at formed in, this FSG was added to PM monitoring and the load allocation. The gully at formed in 2008, this FSG is recommended for future PM monitoring and was added to the load allocation. The culvert at was replaced and removed from the FSG load allocation in Figures 1-14 show the surveyed cross sections followed by a brief description. Photograph 2 shows the replaced culvert and repaired FSG at Photographs 3-6 show examples of FSG conditions. Appendix B provides raw and reduced data for cross section surveys. Figure 1 Waste Water Treatment Plant Cross Section #1 Waste Water Treatment Plant In-channel Cross Section # Figure 1: Waste Water Treatment Plant #1 is a cross section survey of the Black Gore Creek channel upstream of the Gore Creek confluence. The Black Gore Creek channel is between stations 30 and 50, a cobble bar is between stations 50 and 70, and a side channel is between stations 70 and 90. The Black Gore Creek channel is beginning to braid in this section. Field notes indicated the channel appears to be coarser and no beaver dams are constructed. There is significant groundwater on the right toe of the fill slope. 8-32

10 Figure 2 Waste Water Treatment Plant Cross Section #2 Waste Water Treatment Plant In-channel Cross Section # Figure 2: Waste Water Treatment Plant #2 is a cross section of the Black Gore Creek channel located approximately 100 upstream of WTP #1. The Black Gore Creek channel is between stations 30 and 70; an island with flow through channels is between stations 70 and 160. In a beaver dam was constructed in the main channel, this created deposition in the main channel. In the beaver dam had washed away; the channel scoured to a new base elevation. Figure 3 Erosion Control Basin Cross Section Erosion Control Basin Figure 3: Cross Section shows aggradation trend and developed flow channels. 9-32

11 Figure 4 Erosion Control Basin Cross Section #1 In-channel Erosion Control Basin # *2008 sediment removal project as-built data needs to be gathered and tied into monitoring survey. Figure 4: Erosion Control Basin #1 is located in the Black Gore Creek channel at the in-channel pond. The in-channel pond serves as a sediment basin. The left side of the channel is a sandy lateral bar. Beavers have built dams that trap these sediments and create bar deposits. The cross section shows approximately 0.5 feet of aggradation from -. Depth probes taken in showed up to 11 feet of deposition on the lateral bar. In 2008, approximately 26,400 tons of sediments were removed from the basin. Figure 5 Erosion Control Basin Cross Section #2 In-channel Erosion Control Basin # *2008 sediment removal project as-built data needs to be gathered and tied into monitoring survey. Figure 5: Erosion Control Basin #2 is located upstream of x-section #1. Beavers have built dams that trap sediments and created the island. The island with flow through channels is between stations 50 and 160. The cross section shows approximately 0.5 feet of aggradation from -. Depth probes taken in showed deposition greater than 15 feet deep on the island

12 Figure 6 Fill Slope Gully Cross Section # Gully # Figure 6: Cross section #1 is at the bottom of the FSG located at mile marker The total gully length is approximately 300 feet. Two defined rills are developing channels on the fill slope; at station 15 and at station 45. The top of the left bank has eroded and filled in the left side of the channel. From -2008, the right bank has eroded approximately 1.0 foot. The 2008 cross section survey shows significant sour of the main channel. The left post is bent and moving with hill slope slumping. Figure 7 Fill Slope Gully Cross Section #2 Gully # Figure 7: Cross Section #2 is located in the middle of the FSG at There is a dilapidated corrugated metal pipe at station 19. In the toe of the channel was eroding on the left side of the pipe. In deposition filled in the left toe of the gully. In the cross section shows left bank erosion and deposition in the channel. In 2008 these deposits had been transported, and the channel widened and soured to a new base elevation

13 Figure 8 Fill Slope Gully Cross Section #3 Gully # Figure 8: Cross Section #3 is located near the top of the FSG at mile marker In a pipe was surveyed at station 16, this pipe was washed away in. A rill is developing a channel at station 5. The cross section shows larger rill development and channel degradation. Figure 9 Fill Slope Gully # Gully # Figure 9: Cross Section 187.1#1 is located near the bottom of the FSG. The total gully length is approximately 220 feet long. The cross section shows hill slope slumping and developed rills at stations 10, 90 and 110. In 2008, the culvert pipe located at station 67 had washed to the toe of the slope. The cross section shows a degradation trend of the gully (see photographs 3-4 at end of section and PM)

14 Figure 10 Fill Slope Gully #2 Gully # Figure 10: Cross Section 187.1#2 is located in the middle of the FSG. The cross section shows significant channel degradation. In 2008, the culvert pipe located at station 18 had transported to the bottom of the gully. Figure 11 Fill Slope Gully 187.1#3 Gully # Figure 11: Cross Section 187.1#3 is located near the top of the FSG. The cross section shows the gully is head cutting

15 Figure 12 Cross Section #1 Valley Floor Vally Floor Gully Cross Section # Elevation As Built Station Figure 12: The Valley Floor at MM has three natural benches. Sediments that have transported through two culverts have built up delta deposits on this VF. Cross Section 187.5#1 is of the gully on the middle bench of the VF. Restoration of the gully in was constructed to stabilize the VF delta deposits. The 2008 survey shows the channel has scoured under the cross logs at station 21. Figure 13 Cross Section 187.5#2 Valley Floor Valley Floor Gully Cross Section # Elevation Station As Built 2008 Figure 13: Cross Section #1 is the gully located near the culvert outflow on the upper bench of the VF delta deposit. Restoration in was constructed to stabilize the delta deposits behind crib walls. Stations located between shows the crib wall deposits

16 Figure 14 Cross Section Fill Slope Gully Gully Figure 14: Cross Section is located near the top of the FSG. The survey shows the channel is shifting and transporting sediments (see photographs 5-6 at end of section and PM). Note: the right post is bent and slumping and needs to be replaced. A control point (RR.org B&C ) was established in 2008; a new REP TLP should be set for future monitoring. Control was performed from the CDOT BM and the left post. Table 2 Fill Slope Gullies Approximate Degradation Cross Section Degradation of Left Third (ft 2 ) Degradation of Center Third (ft 2 ) Degradation of Right Third (ft 2 ) Approximate Degradation (ft 2 ) Notes G # G # G # G # G # Cross section survey shows scour of the gully channel. Cross section shows gully degradation. Cross section shows rill development and degradation of the gully channel. Cross section shows hill slope slumping with rill development 200 feet down slope and continually sloping TLPs. Cross section survey shows significant channel degradation

17 G # G * VF # VF # The failed culvert pipe has washed to the bottom of the fill slope (see PM). Cross section shows hill slope slumping, rills developing down the length of fill slope, and channel degradation. Survey shows the cross section has deposition of sediments. Restoration efforts were conducted in. The right toe of gully cribwall has slightly undercut. Sediment has filled to top of cross logs at grade. The survey shows the gully is stable. On the left toe of the gully some sour has occurred under the cross logs that were installed in 06 restoration efforts. Average Degradation 11.5 * Fill Slope Gully is not stable, cross section data shows deposition. The annual change in the cross section is transported material and is included in the average degradation and FSG load allocation. Photograph 2 Looking up at replaced culvert and repaired FSG at

18 Photograph 3 Looking up at Fill Slope Gully () Photograph 4 Looking up at Fill Slope Gully (2008) 17-32

19 Photograph 5 Looking up at Fill Slope Gully () Photograph 6 Looking up at Fill Slope Gully (2008) 18-32

20 Longitudinal Profile and Cross Sections at MM In, the Forest Service performed cross section, longitudinal profile and sediment size monitoring of the Black Gore Creek channel at MM In, monitoring efforts discontinued because beavers built a dam that trapped large sediment deposits. RiverRestoration.org performed cross section and a longitudinal profile from The beaver dam was a temporary in-channel sediment basin. Cross section #1 is located near longitudinal station 40, cross section #2 is near station 80, a beaver dam is near station 90, cross section #3 is near station 215, and a second beaver dam is near station 325. From -, Cross sections #1 and #2 show approximately 1.5 channel deposition upstream of the beaver dam. Cross section #3 is located between the beaver dams and the survey shows deposition on the lateral bar. In 2008, the beaver dams had breached and the cross sections and longitudinal profile show the channel has scoured to the base elevation (cobble and boulder substrate). Cross section #1 shows approximately 1.5 of scour, cross section #2 shows approximately 1 of scour, and cross section #3 shows approximately 0.3 of scour in Figures show the monitored cross sections. Figure 18 shows the longitudinal profile

21 Figure 15 Cross Section #1 at Active Beaver Dam Reach BGC x sec#1 elevation (ft) station (ft) USFS RR.org RR.org 2008 RR.org *spring in line with x-sec at toe of fill slope Figure 16 Cross Section #2 at Active Beaver Dam Reach BGC x sec#2 elevation (ft) station (ft) USFS RR.org RR.org 2008 RR.org 20-32

22 Figure 17 Cross Section #3 at Active Beaver Dam Reach BGC x sec #3 elevation (ft) station (ft) USFS RR.org RR.org 2008 RR.org Figure 18 Longitudinal Profile BGC Longitudinal Profile Elevation (ft) RR.org RR.org 2008 RR.org -7 Distance (ft) *Incorrect rod height reading at stations , longitudinal profile data adjusted (-1.2 ) in Adjustment determined from cross section #3 measurements. Single Depth Monitoring Monitoring points that required a single depth measurement, Valley floors (VF) and Bridge Accumulation (BR), are presented in Table 3. Deposits at the monitoring posts indicate transport of sediments through the Valley Floors and Bridges. Measurements taken at the VF and the BR are extrapolated throughout the basin for calculating the load allocation. Most of the accumulation under bridges appears to be from side cast material. This material accumulates over time, and develops rills that transport deposits though the watershed. All of the posts monitored in 2008 at Bridges have sediments deposit. Bridges that do not have monitoring posts are identified in the sediment budget

23 Most of the sediments at Valley Floors are supplied from culverts. Sediment deltas form on the Valley Floors. Posts are set downstream of these deposits to monitor transport. Two of the three Valley Floor posts monitored in 2008 have sediments that have transported to the post. In, the Valley Floor at had deposits approximately 4 upstream; in 2008 these deposits had transported to the post. Valley Floors that do not have monitoring posts are identified in the sediment budget. Table 3 Single Measurement Reference Points Monitoring Reference Point Depth of Deposit (feet) Deposit /TLP (feet) Deposit/ TLP (feet) Deposit/ TLP (feet) 2008 Deposit/ TLP (feet) Notes VF /4.2 0/4.2 0/4.2 0/4.2 No sediments deposit at the post. Three delta deposits are accumulating at toe of the FS up-gradient of this VF post. VF /3.94 0/ /3.82 VF / / /1.25 BR / / / /3.35 New gravel and sand deposits at the post. Coarser deposits of cobble, gravel and sand are at post. Approximately 60% vegetation cover has established on the valley floor delta deposit. Flow has shifted the channel to the right side of valley floor delta deposit, at the toe of fill slope. Sediments deposit is at the post. The Bridge has significant side-cast accumulation and well developed rills. Depth probes of side-cast material over 3 deep. BR / / / /3.25 Sediments deposits are at post. Sediments at post are most likely transported from side cast material. Erosion Control Basins under bridge BR / / /2.8 control I-70 and bike path stormwater

24 Center Medians Four Center Median (CM) profiles are presented in Table 4. In, these monitoring sites had evidence of sediments transporting into the culverts that drain the medians. These sites were randomly chosen to represent all center median areas. In 2008, all of the CM surveys showed sediment transport and deposits 10 and 30 up gradient. The monitoring observations are extrapolated throughout the basin for calculating the CM load allocation. Table 4 Center Median Monitoring Center Median Concurrent Deposits at Invert Deposit Depth 10 /30 Upstream (feet) Deposit Depth 10 /30 Upstream (feet) Deposit Depth 10 /30' Upstream (feet) Deposit Depth 10 /30' Upstream (feet) 2008 Deposit Depth 10 /30' Upstream (feet) CM Yes 2.0/ / / / /1.7 CM No 0.5/ / / / /0.3 CM Yes 1.0/ / / /.05 Overall Change/Notes Gravel and sand are at invert. Coir logs are buried with sediments and 70% vegetation cover has established. No deposits at invert. CDOT B&C was not recovered and buried with sand. 0.3 deposits on top of concrete with vegetation growth. CM No 0.5/ / / / /1.5 No deposits at invert. Fill Slope Monitoring Sediment laden snow side-cast is most likely the significant source of sediments on the FS. Large pieces of asphalt found near the toe of FS was taken as evidence of snow transporting materials down slopes, in addition to fluvial transport of finer materials. Sheet flow down the FS would likely not transport the large pieces of asphalt; however sheet flow develops rills and concentrates flow that is effective at transporting sand size sediments. Most jersey barriers are effective at controlling sheet flow and routing flow to drainages into ECBs or down culverts. However, there are some that have eroded at the toe and are no longer effective, with flow passing under the barriers. Table 5 presents the FS monitoring results. Fill Slopes that have rills 23-32

25 and smothered vegetation are considered to be a sediment source and accounted for in the annual load allocation. Table 5 Fill Slope Monitoring Fill Slope Slope Grade % Rills per 25 feet/ %Veg Cover Rills per 25 feet/ %Veg Cover Rills per 25 feet/ %Veg Cover Rills per 25 feet/ %Veg Cover 2008 Rills per 25 feet/ %Veg Cover FS WB /70 0/75 0/70 0/70 0/70 FS WB /100 0/100 0/90 2/60 N/A FS WB /100 0/100 0/90 0/70 8/70 FS WB /100 0/90 0/90 0/70 0/70 FS WB /70 0/70 0/70 0/60 3/50 FS EB /70 5/70 3/65 3/65 11/60 Notes Jersey barrier with some side cast material down fill slope. Construction road on fill slope for Basin of Last Resort Project. Upstream at there is a berm at top of fill slope with two gullies forming. This berm maybe buried jersey barriers. Jersey barrier between and controls storm water to small ECB. Side cast build-up smothering vegetation down fill slope. Increased buried vegetation from side cast sediments. Swale and ECB at catches sediment upstream of Bridge. Fill slope downstream of Bridge has significant side cast and defined rills down slope. Recently graded at top of fill slope. There are five large rills (forming defined channels) transporting to delta deposits at toe of fill slope. Vegetation cover is dominated by thistle 24-32

26 and cheat grass. Fill slope extends from FS EB /90 4/90 5/70 2/60 0/70 FS EB /80 11/80 15/60 9/80 7/60 FS EB /90 4/70 6/75 4/70 9/75 N/C FS EB /90 8/60 5/70 7/70 5/70 N/C FS EB /60 8/70 7/65 6/70 10/65 N/C FS EB /90 8/70 12/70 12/70 9/75 N/C FS EB /70 8/70 12/70 4/70 17/60 FS EB Recently graded. Vegetation on slope is dominant thistle and cheat grass. Large rills from bike path to BGC channel have caused slope mass failure of fill slope. There are two headcuts that are 30' at top of fill slope and 3.3 in depth. Fill slope gully length is 30' (see PM). Rill development down length of fill slope. Large rills forming two gullies at top of slope. Significant rills at top of fill slope from /80 5/80 8/65 6/70 12/60 FS EB /90 0/90 2/70 5/70 9/40 Increased rills

27 FS EB /100 2/90 7/65 8/65 4/65 FS EB Gully Format ion/ 20 Gully Forma tion/3 0 Gully Format ion/30 Gully Forma tion/ 30 0/75 Jersey barriers have significant side cast with rills and two gullies down fill slope. Sediments deposits behind jersey barrier are almost to top of barrier (barrier extents is ). Gully forming in side cast sediments. Increased vegetation cover in Cut Slope Monitoring Table 6 presents Cut Slope (CS) monitoring findings. These observations recognize where sediments from CS have control basins, adequate basins, or overflowing basins. Most of the Erosion Control Basins (ECBs) were clean in Approximately 4.8 miles of CS were uncontrolled in Cut Slopes are uncontrolled because culverts drain storm water between Erosion Control Basins. Only a couple of ECBs were cleaned between 185 and on east bound I-70. Approximately three miles of CS between mile marker and 185 was uncontrolled because ECBs were not cleaned or non existent. Table 6 Cut Slope Monitoring Cut Slope Culvert Uncontrolled cut slope distance (mile) Notes CS EB CS EB 182.5/ CS WB Two ECBs A&B are small but clean. A large basin at has adequate storage, cross section survey shows aggradation trend. West bound culverts drain to ECBs. East bound stormwater flows down shoulder from the Bridge at down to the culvert at ECB and upstream of the Bridge are full. Two culverts drain east bound shoulder and cut slope. Erosion Control Basin has adequate storage, controls WB stormwater downstream of ECB and EB stormwater downstream culvert and ECB at Site has some transplants from Basin of Last Resort Project. 32

28 CS WB No 0.2 Erosion Control Basin at is clean. Small ECB has heavy sedimentation and does not control stormwater from CS EB CS EB 183.2/183.3/ 183.5/ / / / ECB at is full of sediments with vegetation growth. A culvert drains cut slope and native gully. Uncontrolled cut slope from ECB at is clean. Erosion Control Basin at is full. No ECBs control EB stormwater downstream bridge at to Native drainage at CS WB CS WB 185.1/ CS EB CS WB CS EB CS WB 186.0/186.5/ 186.7/ Erosion Control Basin at 184.6A&B are clean and control WB cut slope from Cut slope is uncontrolled from ECB at 185 down to culvert at Erosion Control Basins at , 185.2, and are clean. Cut slope controlled from culvert at down to ECB ECB and A and B are clean and control EB and WB cut slope and bike path ditches. ECBs at and are clean and control cut slope. Stormwater controlled from to Erosion Control Basin , ECB 185.7, are clean, and has moderate sedimentation. Culverts are at 186 and ECB at is clean. Cut slope controlled ECB and ECB are clean. Cut slope controlled from native drainage at down to ECB Subsurface basins at and are clean. Surface ECB's at 186.9, and are clean. There are culverts at 186.3, and No ECBs are in place to control cut slope stormwater from WB culvert drains to large ECB at CS WB Erosion Control Basins and are clean. Erosion Control Basin has moderate sedimentation, but adequate storage. Culvert is at Cut slope is controlled from

29 CS EB CS WB CS WB CS WB 187.2/187.9/ /188. 0/ / / / / / There are no ECBs that control stormwater on EB cut slopes from to (ECB on Bike path). Erosion Control Basin at is clean. Erosion Control Basin at is clean. Drainage downstream controlled by ECB At two subsurface basins are clean, small ECB at is also clean. Cut slope is controlled from to Reverse drainage to native basin and ECB Culverts at and have coir logs in place from recent fiber optics line construction. Cut slope is not controlled from ECB clean A, 6B are clean. These small basins control ; reverse drainage on westbound cut slope. No sand is stored outside of shed. Bike Path Swale Monitoring At the confluence of Polk Creek, near mile marker 185.5, the Vail Pass bike path runs adjacent to I-70. The swales along the bike path have culverts that transport sediments through the watershed. There are several Erosion Control Basins in place to control sediments that transport through Bike Path Swales. Table 7 presents the BPS monitoring results. Bike Path Swales are monitored similar to cut slopes. The condition of bike path swale Erosion Control Basins and uncontrolled stormwater are monitored. Approximately 1.25 miles of BPS were uncontrolled in Table 7 Bike Path Swale Monitoring Bike Path Swale Culvert Uncontrolled stormwater distance (mile) /186.1/ /188.2/187.9/ Notes Bike path swale controlled from ; ECBs 186.0, and ECB under bridge at are clean with adequate storage. ECB at is clean with adequate storage. Uncontrolled ; ECB at does not catch BPS drainage. Stormwater goes through culvert down FS to VF. Bike path swale not controlled from down to culvert at ECB is clean with good storage and controls sediments downstream of culvert Bike path swale is not controlled down to 28-32

30 culvert at Bike path swale downstream of culvert is controlled by ECB Exacerbated Bank Erosion There are some localized areas of the Black Gore Creek channel that have exacerbated bank erosion. These banks are eroding due to sedimentation and aggradation. For example, a large delta deposit at the outflow of a culvert forces flow to cut into the opposite bank. An inventory of banks with exacerbated erosion was conducted in. Below, photograph 7 shows an example of a bank with exacerbated erosion. Photograph 7 example of exacerbated bank erosion near MM Additional Monitoring The spillways of Black Lakes no.1 and no.2 were visually monitored. There were no signs of sedimentation in the spillway channels. The sand storage shed was visually monitored for sand storage piles. There were no sand piles stored outside of the storage shed. Monitoring and Load Allocation A quantitative sediment yield was calculated for the recognized sediment sources throughout the Black Gore Creek watershed. Table 9 shows the sediment yield results. Information presented 29-32

31 herein is the result of a quantitative analysis (Load Allocation and Sediment Budget, TMDL) which estimates the magnitude of sediments that are recommended to be exported from the basin every year. For the 2009 year the recommended export load is 10,930 tons. The recommend export load is intended to move the stream towards meeting TMDL stream health targets. A minimum export load of 6,400 tons per year is recommend in the TMDL based on the average annual applied traction sand less the transport capacity of BGC (15,000tons/yr less 8,600 tons/yr). The recommend export load for 2008 was 6,400 tons, the actual exported load was 4,619 tons. Colorado Department of Transportation clean up efforts for late summer and fall of 2008 are reported to be 4,619 tons with an additional 26,400 tons of sediments from the Basin Project. This exported load will be included in the 2009 exported load. The Colorado Department of Transportation reports the applied and exported load in June. The month of June is after the winter seasons applied traction sand and before the cleanup efforts are conducted. Clean up efforts are conducted in the summer and fall; these data are reported for the next years removed sediments. The Load Allocation of the sediment sources transported through the watershed is quantified based on the water year in October. Annual monitoring of stream health (macroinvertebrate, residual pool depth, and sediment gradation) is conducted by the U.S. Forest Service. With continued monitoring efforts (Sediment Source and Physical and Biological Stream Health Monitoring) a better estimate of the sediments inputs and controls can be calculated; and the balance between the sediment load and biological and physical stream health can be better determined. Appendix C provides the spread sheet model used to calculate the sediment budget. Table 9 Black Gore Creek 2008 and 2009 Load Allocation and Sediment Budget* SOURCE CATEGORY ZONES LA (Tons/Year) LA (Tons/Year) Applied Traction Sand ,709 Sand Stockpile Erosion Slope Mass Wasting Natural Background Black Lakes Channel Bed Active Storage Fill Slope Gullies 1, Fill Slopes 1, Valley Floors Cut Slopes Accumulation Under Bridges Increased Erosion of Native Slopes Bike path swales 1, Center Medians Increased Bank Erosion Other

32 Sediment Sources TOTAL LA BGC Transport Capacity (TC) BGC Assimilative Capacity (AC) 0 0 Exported Sediment Load 1,2, Recommended Exported Load (2008, 2009) 1,2, * The recommended exported load shall always be equal to, or greater than 6400 tons/year ** Load allocations are estimates based on source monitoring data. See Appendix C for detail. ***Imported and exported load estimates reported by CDOT Draft July-Dec ****Clean up efforts for summer and fall of 2008 are reported to be 4,591 tons with an additional 26,400 tons of sediments from the Basin Project. These sediments removed are the exported load for Recommendations for Future Monitoring There are several Tag Line Posts (TLPs) that need to be replaced due to hill slope slumping, soil creep, or snow creep. These TLPs are located at: LEP #1, REP & LEP #1, and REP. Future monitoring may include a single depth measurement and a transport post near the snow storage site and the native gully. Longitudinal and cross sections surveys, as well as pebble counts should continue at the reach. Monitoring of this site may provide information to better understand beaver activity and storage in Black Gore Creek. This site may show three different transport scenarios; deposits depth behind beaver dams, transport of stored materials when breached, the aggradation rate once beaver dams are re-established. Additional Photographic Monitoring is recommended at the and There are some photographs in the archive of this reach. Monitoring of subsurface bed material is recommended for possible future monitoring in the Black Gore Creek TMDL because it gives a clearer picture of annual sediment transport and is less affected by diurnal and seasonal hydrograph fluctuations. A breached beaver dam with lateral bar deposits at may be a good location for subsurface monitoring. The breached beaver dams at above USGS gage 2190 may also be a good location to establish subsurface monitoring in the future. Fill slope slumping at may be caused from a failed culvert and may result to a gully. This site may be monitored in the future. A delta deposit is forming at the outlet of the culvert into Black Gore Creek, photographs 2087, Fill slope slumping at may be caused from a failed culvert and result to a gully adjacent to the existing failed culvert and FSG at The Fill Slope Gully forming at 183 should be monitored for future conditions of the fill slope and dilapidated culvert

33 Exacerbated bank erosion locations and lengths have not been updated since. Field notes documented exacerbated bank erosion near MM 184.4, and 186.1, but these were not included in the 2008 budget because no measurements were taken. The Field Guide should be updated with elevations that were re-established due to bent or disturbed TLPs; these include G186.8#3 lep, G186.8#1 lep, G187.1#1 lep, G rep, ECB rep, and WTP #1 lep. Abbreviations Black Gore Creek (BGC) Best Management Practice (BMP) Center Median (CM) Corrugated Metal Pipe (CMP) Cut Slopes (CS) East Bound (EB) Erosion Control Basin (ECB) Fill Slopes (FS) Fill Slope Gully (FSG) Gully (G) Large Woody Debris (LWD) Mile Marker (MM) Valley Floor (VF) Waste Water Treatment Plant (WTP) West Bound (WB) Attachments Appendix A: Raw data for Cross Section surveys Appendix B: Photographs Appendix C: Load Allocation Worksheet 32-32