Written Statement of William E. Weaver, Ph.D. 15 March 2015 Table

INTERNATIONAL COURT OF JUSTICE
CASE CONCERNING THE CONSTRUCTION OF A ROAD IN COSTA RICA ALONG THE SAN JUAN RIVER
NICARAGUA V. COSTA RICA
Written Statement of William E. Weaver, Ph.D.
15 March 2015
Table of Contents
I.
Introduction ......................................................................................................................... 1
II.
Construction and remediation of Route 1856 has not met generally accepted
standards, resulting in avoidable and unacceptable sediment delivery to the Río San
Juan. .................................................................................................................................... 1
III.
A.
The Road was constructed without sufficient planning or engineering design. ......2
B.
Watercourse crossings have not been properly constructed or remediated. ............3
C.
Cut slopes and fill slopes have not been properly constructed or remediated. ......10
D.
Road Drainage and hydrologic connectivity is excessive......................................15
E.
Proper erosion control measures have not been implemented. ..............................17
Additional measures are necessary for proper remediation of Route 1856. ..................... 19
I.
Introduction
1. I have more than 35 years of professional experience in the fields of process
geomorphology, surface water hydrology, watershed management and engineering geology. I
received a Ph.D. in Earth Resources (Geomorphology) from Colorado State University and a
Bachelor’s Degree in Geology from the University of Washington. I am the principal
geomorphologist and co-owner of Pacific Watershed Associates, a professional consulting
firm in northern California. For 13 years, I served as the principal Engineering Geologist at
Redwood National Park, where I was responsible for designing and monitoring the
internationally recognized watershed rehabilitation and erosion control program covering the
park and the 280 square mile Redwood Creek watershed. I have co-authored books and
publications on road planning, design, and construction, and have served on various Advisory
Panels for the state of California regarding forest practices and road construction impacts, and
on best management practices to protect water quality. My expertise lies in the field of
steepland erosion processes, the impacts of road construction on watershed erosion and
sedimentation processes, the effects of land management on watershed sediment yield, and
the design and control of road-related erosion processes in steep, forested environments and
wildland watersheds. I co-authored two expert reports submitted in this case,1 and supported
the preparation of a third.2
II.
Construction and remediation of Route 1856 has not met generally accepted
standards, resulting in avoidable and unacceptable sediment delivery to the Río
San Juan.
2. Costa Rica’s Route 1856 (“Route 1856” or the “Road”) was not subject to proper
planning and design. This contributed to improper construction of the Road in at least five
respects: poor choices in road siting and route location; ineffective and unstable watercourse
crossings; unstable cut slopes and fill slopes; improper drainage; and absent or ineffective
control of surface erosion. These failures have caused the delivery of sediment from the Road
1
G. Mathias Kondolf, Danny Hagans, Bill Weaver and Eileen Weppner, “Environmental Impacts of Juan Rafael
Mora Porras Route 1856, Costa Rica, on the Río San Juan, Nicaragua” (Dec. 2012), submitted as Annex 1 to the
Memorial of Nicaragua (hereinafter “Kondolf, Hagans, Weaver and Weppner (2012)”); Danny Hagans and Dr.
Bill Weaver, “Evaluation of Erosion, Environmental Impacts and Road Repair Efforts at Selected Sites along
Juan Rafael Mora Route 1856 in Costa Rica, Adjacent the Río San Juan, Nicaragua” (Jul. 2014), submitted as
Annex 2 to the Reply of Nicaragua (hereinafter “Hagans and Weaver (2014)”).
2
G. Mathias Kondolf, “Erosion and Sediment Delivery to the Río San Juan from Route 1856” (Jul. 2014),
submitted as Annex 1 to the Reply of Nicaragua (hereinafter “Kondolf (2014)”).
1
to the Río San Juan ( the “River”). Four years after construction commenced, they have not
been adequately mitigated.
A.
The Road was constructed without sufficient planning or engineering
design.
3. Route 1856 was constructed without the benefit of an environmental impact
assessment3 and without sufficient engineering plans and designs. This allowed construction
decisions to be made that violate accepted standards for road construction. which has in turn
resulted in the delivery of hundreds of thousands of cubic meters of sediment to the adjacent
Río San Juan since construction began.4 This ongoing and future delivery of sediment to the
River, and the costs of now-necessary mitigation works, could have been prevented or greatly
reduced had proper planning and design work been undertaken before starting construction.
4. Failure to plan, for instance, resulted in excessive and disorganized earthmoving
works. Contractors began constructing the Road in one location, only to abandon that stretch
and build the Road elsewhere, locally doubling or even tripling the amount of terrain left devegetated, disturbed, exposed and eroding.5
5. Lack of planning also allowed the Road to be built across steep slopes and areas of
weak, unstable soils.6 Over 30 km of the Road has been built across steep hillslopes, many
composed of deeply weathered, unconsolidated, or otherwise weak material that is prone to
erosion and slope failure.7
6. Inadequate planning resulted in construction of the Road inappropriately close to the
Río San Juan in many areas. Thus, 17.9 km of Route 1856 encroaches into the 50 meter
setback required by Costa Rican law, with some sections within as little as five meters of the
River.8 Building the Road within the setbacks heightened the risk and almost assured that
construction and use of the Road would deliver sediment and other pollutants to the River.
Many of the setback violations occur in the upstream section of the Road that was built in
steep, unstable terrain. There, erosion and slope instability are greater. This is confirmed by
Costa Rica’s 2013 Environmental Diagnostic Assessment (EDA) and its 2015 follow up,
3
Federated Association of Engineers and Architects of Costa Rica, “Report on the Inspection of the [] Border
Road, Northern Area Parallel to the San Juan River CFIA Report” (Jun. 8, 2012), submitted as Annex 4 to the
Memorial of Nicaragua, p. 25.
4
Kondolf (2014), p. 61.
5
Kondolf, Hagans, Weaver and Weppner (2012), p. 21, Figure 7; id. p. 24; Kondolf (2014) p. 6, Figure 4.
6
Ibid., p. 21
7
Ibid., p. 24.
8
Ibid., p. 22.
2
which recommend that Costa Rica evaluate rerouting one very problematic stretch of the
Road inland to a more favorable location to reduce landsliding and slope erosion.9 Of the
41.6 km of road upstream of the Río San Carlos, 12.3 km (30%) is within 50 meters of the
River.10 Based on our experience assessing the impacts of roads and other land-use
disturbances, we consider a minimum of 100 m to be an appropriate buffer distance to protect
a watercourse from road-related erosion on steep terrain.11 A total of 49.5 km of the Road
was built within 100 m of the River, 17.8 km of which lie on steep terrain.12
7. Failure to plan and select an appropriate route violates principles of sound road
construction. There is no technical or environmental reason for the Road to be located where
it was built. Better sites with more stable ground, located a greater distance from the River,
would have resulted in far less environmental impact and over the long run, far less expense
in attempting to maintain a poorly-sited, poorly-constructed road.13
8. Impacts from road construction can occur through multiple types of mass wasting
(e.g., debris slides and slumps) and erosion (e.g., sheet and rill erosion and gullying). These
are distinct processes; the measures that are effective in preventing or minimizing one will
not necessarily be effective with respect to another. The following four sections describe how
these processes have delivered substantial amounts of eroded sediment to the Río San Juan as
a result of the poor construction and lack of proper maintenance and remediation of the Road.
B.
Watercourse crossings have not been properly constructed or remediated.
9. Route 1856 crosses at least 129 streams that flow into the Río San Juan.14 These
watercourse crossings are some of the most environmentally vulnerable locations along the
Road. They must withstand the flow of the water, including during peak flood flows. When a
crossing erodes or fails, the stream transports the resulting eroded sediment directly to the
River. Sediment delivery can occur through constant, gradual erosion, or in large bursts when
9
Cientro Científico Tropical, “Environmental Diagnostic Assessment (EDA), Route 1856 Project - Ecological
Component” (Nov. 2013), submitted as Annex 10 to the Counter-Memorial of Costa Rica, p. 147 (hereinafer
“CCT (2013)”); Centro Científico Tropical, “Follow-up and Monitoring Study Route 1856 Project-EDA
Ecological Component” (Jan. 2015), submitted as Annex 14 to the Rejoinder of Costa Rica, p. 57 (hereinafter
“CCT (2015)”).
10
Kondolf, Hagans, Weaver and Weppner (2012), p. 22
11
Ibid., p. 23.
12
Ibid.; see also Hagans and Weaver (2014), Figure 1.
13
Kondolf, Hagans, Weaver and Weppner (2012), p. 24.
14
Andrews Mende, “Inventory of Slopes and Water Courses related to the Border Road No. 1856 between
Mojón II and Delta Costa Rica: Second Report” (Dec. 2014), submitted as Annex 3 to the Rejoinder of Costa
Rica (hereinafter “Mende (2014)”), p. 26. This figure consists of 127 streams catalogued by Mende and 2
additional streams not catalogued by Mende.
3
the crossing fails entirely. Along the Road, our team has observed numerous poorly located,
designed and constructed watercourse crossings, many of which are not being maintained and
a number of which have already failed or eroded, delivering sediment to the River, sometimes
in large quantities.15
10. Most of the stream crossings were built by filling streambed with earth (fill), with a
culvert placed inside the fill through which the streamflow is intended to pass. These
crossings are cheaper than bridges, but are inherently unstable and prone to erosion,
especially when improperly built, as is the case for many crossings along the Road.16 Figure 1
diagrammatically illustrates a properly
constructed stream crossing built with
fill and a culvert.
11. We observed numerous culverts
that were not designed or installed
properly.
17
Many seem too small to
allow all the water from the stream to
pass during periods of flood flow. Many
also appear to be unprotected from
blockage by sediment and debris; when
these
become
blocked,
water
accumulates behind the fill and can
overtop and completely erode and wash
out the fill, transporting all the eroded
sediment downstream and into the Río
San Juan. Some are installed partway up the fill, above the stream bed, where water from the
stream cannot directly reach the inlet of the culvert. When stream flow cannot immediately
pass through the culvert, it forms a pool on the upstream side of the fill. The fill must then act
as a dam, a role it was not engineered to serve. Eventually, the water is re-directed onto and
erodes adjacent unprotected slopes, or continues to pool until it flows over the top of the road,
eroding the roadbed and the exposed, downstream face of the fill. In the case of a culvert
installed too high in the fill, water passing through will be discharged or flow as a waterfall
15
See, e.g., Kondolf, Hagans, Weaver and Weppner (2012), fig. 16-23; Kondolf (2014), fig. 5, 12-22 fig. 9-16,
36-37 fig. 24-25, Appendix A, Appendix C; Hagans and Weaver (2014), pp. 2-4 fig. 2-5.
16
Kondolf, Hagans, Weaver and Weppner (2012), p. 13.
17
Ibid., pp. 13-14, 30; Hagans and Weaver (2014), pp. 152-156.
4
onto the exposed downstream face of the fill, eroding it and undermining the crossing and the
road.18 One or more of these processes occurred at Sites 9.4, 9.5 and 9.6, discussed below.19
12. In a number of locations, contractors did not even use culverts at all, but instead used
ad hoc materials such as repurposed shipping containers and logs.20 Use of these materials is
not acceptable under common design standards, and such crossings have already failed or
show signs of failure.21
13. In 2012, we conducted a field assessment of approximately 60 stream crossings.22
Nearly all exhibited one or more of the serious design and/or construction deficiencies
described above, making them likely to fail during intense rains or flood flows. At virtually
all the crossings, some volume of sediment had been introduced directly to the receiving
tributary stream and to the Río San Juan during and immediately following construction.
Most of the crossings posed a moderate to high risk of failure due to poor design or
construction, and still do.23 Indeed, CODEFORESA recognizes that at present:
Another factor that is causing soil loss is the watercourses that cross
[Route] 1856. In most of these sites small culverts were placed, which in
some cases became obstructed with branches and trunks, leading to the
formation of blockages which due to the amount of rain destroyed the
passage built and culverts placed. The most troubling is the carrying of
material to the river bank, causing the direct contamination of both the
creek and the river at its mouth and downstream. 24
14. Mende and Astorga conceded the existence of widespread design and construction
problems at stream crossings in 2013, stating that only 10 of the stream crossings at which
construction had been attempted were in “appropriate” condition.25 The report, however,
suggested that at some sites, “technical improvements have been made...and the crossings
will continue to be in an acceptable condition in the medium-term,” and that the road
construction and repair efforts for Route 1856 “can be described as typical during a
18
Kondolf, Hagans, Weaver and Weppner (2012), pp. 13-14, 30; Hagans and Weaver (2014), pp. 2, 5-6. One or
more of these has occurred at Site 9.5
19
See infra paras. 16-19.
20
Kondolf, Hagans, Weaver and Weppner (2012), pp. 32-34 fig. 18, 19, and 22.
21
Ibid., p. 32 fig. 18; see also infra Figure 2.
22
Ibid., p. 5.
23
Ibid.
24
Comisión de Desarrollo Forestal de San Carlos (CODEFORSA), “Restoration and rehabilitation of
ecosystems affected by the construction of the Juan Rafael Mora Porras border road, Route 1856” (Nov. 2014),
submitted as Annex 12 to the Rejoinder of Costa Rica, p. 8 (hereinafter “CODEFORESA (2014) (Annex 12)”).
25
Andreas Menda & Allan Astorga, “Inventory of Slopes and Water Courses related to the Border Road No.
1856 between Mojón II and Delta Costa Rica” (Oct. 2013), submitted as Annex 6 to the Counter-Memorial of
Costa Rica, p. 28 (hereinafter “Mende & Astorga (2013)”).
5
construction period.”26 The 2013 EDA also recognized the existence of “tempora[ry]
structures in poor condition” at stream crossings.27 However, it stated that “a periodic
monitoring effort has been conducted . . . promoting and adequate preventive control of the
structures along the way.”28
15. What our team observed eight months later, in May 2014, cannot be described as
“acceptable” or “typical,” based on our many years of professional experience. Nor did our
team observe measures to stabilize and control erosion at stream crossings that can be called
“adequate” by any reasonable standard. As predicted, the many poorly constructed stream
crossings had begun to fail.29 At the failing sites, there was a nearly total lack of erosion
control efforts or maintenance in the preceding two years.30 Efforts at erosion control were
concentrated along the uppermost 15 km of the Road, a stretch that did not include many of
the worst-eroding sites.31 Even where attempted, they were inadequate; most were superficial
measures designed to limit surface erosion, rather than to fix the instability and fundamental
defects at the crossings.32
16. Our 2014 report reviewed three examples of failing and un-remediated stream
crossings, comparing their status in October 2012 with their status in May 2014. In October
2012, it was apparent that the crossings had been constructed incorrectly, with loose, unengineered fills and culverts placed far too high in the fill to be effective. Landslide and gully
erosion was visible on the faces of the fill, which were exhibiting deformation, and had been
left unprotected and exposed.33 A photograph of the severely eroding sites (“SES” or “Site”),
reflecting their more recent conditions after being partially rebuilt after erosion and slope
failures, is attached as Appendix A.
17. By December 2013, these sites displayed severe erosion. At Site 9.4, a massive gully
had formed in the fill slope, making the crossing impassible. About 1,722 m3 of sediment had
been eroded and transported down the slope, much of it directly into the Río San Juan.34 The
26
Mende & Astorga (2013), p. 28
CCT (2013), p. 30.
28
Ibid.
29
Hagans and Weaver (2014), pp. 2, 4-5, 8-9, 11-12, 15.
30
Ibid., p. 2.
31
Kondolf (2014), p. 39.
32
Ibid., pp. 40-42 fig. 26-27.
33
Hagans and Weaver (2014), p. 2.
34
Ibid., p. 5. The 2014 report by the UCR criticizes the erosion volumes calculated for five Severely Eroding
Sites (8.1, 8.2, 9.4, 9.5, 9.6). See Universidad de Costa Rica, “Second Report on Systematic Field monitoring of
Erosion and Sediment Yield along Route 1856” (Nov. 2014), submitted as Annex 4 to the Rejoinder of Costa
27
6
impact was visible in a large, fresh sediment delta protruding into the River. More had eroded
from other features, for a total of about 3,384 m3.35 Water had ponded above the fill due to a
plugged or improperly-installed culvert and appeared to have overtopped and eroded the fill.
Site 9.5 was impassible as well. The fill had completely eroded and been washed downstream
when a plugged culvert allowed water to pool up and flow over the top of the Road. About
2,860 m3 of sediment from the fill slope was thus eroded and delivered directly to the Río San
Juan where another sediment delta formed.36 At Site 9.6, the gullies beginning to form in
October 2012 had grown immensely due to uncontrolled runoff from the Road and water
overtopping and eroding the fill. By December 2013, none of the sites displayed any
significant visible evidence of efforts to perform preventative surface, rill, gully, or landslide
erosion control measures or slope stabilization.
18. Costa Rica did not appear to make any meaningful effort to control erosion at the
deteriorating sites between December 2013 and May 2014.37 The network of gullies at Site
9.6 continued to grow, and by May 2014 half the road prism had failed, delivering about
8,200 m3 of sediment downslope, a substantial portion of which was delivered directly to the
River.38 The crossings at Sites 9.4 and 9.5 had been partially rebuilt (filled in), but with the
same apparent flaws that had previously led to massive erosion and slope failure. Enough
material to allow a vehicle to pass was bulldozed into the eroded chasm (gully) of the former
fill, but left un-compacted. Culverts were again installed or left high in the fill, leaving it
certain that water would pool upstream of the fill, risking the same failure that had occurred
at Site 9.5. No apparent effort was made to protect the exposed fill material from erosion.
19. In short, the minimal repairs visible at Sites 9.4 and 9.5 appear to have been
implemented solely to provide a narrow and unsafe vehicle route across each failing stream
crossing, not to reduce erosion, or stabilize the sites. The result was to condemn the sites to
fail again, perhaps on an even greater scale; the total volume of the fill is approximately
Rica, p. 25. Its criticisms are unpersuasive. The UCR was only able to perform one volume calculation of its
own at the five severely eroding sites: Site 8.1. The UCR then relies on the different volume they calculated at
that single site to cast doubt on our erosion calculations at the other four sites. Ibid. As the UCR did not actually
conduct individual measurements at these four sites, its criticism of our individual measurement is baseless.
Unfortunately, the UCR did not provide a sufficient description of its methodology to allow us to verify its
calculations.
35
Hagans and Weaver (2014), p. 5.
36
Ibid., p. 8.
37
Ibid., pp. 4, 8, 12.
38
Ibid., pp. 11–12.
7
21,900 m3 at Site 9.4 and 12,000 m3 at Site 9.5.39 Together with the 44,000 m3 fill at Site 9.6,
these sites present a total of 77,900 m3 of unstable and highly erodible soil materials at an
extremely high risk of failure and subsequent transport directly into the River.40
20. The problems at stream crossings are widespread. Even on flat ground, poorly-built
stream crossings have failed, causing both the entirety of the fill material and, in at least one
case, the culvert itself to be washed downstream and into the Río San Juan.41 As of July 2014,
we concluded that a minimum of fifty stream crossings along the Road were so deficient as to
be potentially unsafe for use.42 The deficient construction techniques that make the crossings
unsafe also make them high risk for erosion and sediment delivery to the River. Thus, as of
July 2014, it was apparent that there were many stream crossings along the Road that
required full construction or re-construction utilizing sound geologic, engineering and
compaction standards.43
21. Road-related erosion control and prevention usually requires both heavy equipment
and hand labor treatments. Costa Rica’s efforts with respect to the former have been
undertaken by CONAVI.44 Prof. Thorne states that CONAVI’s mitigation work at
watercourse crossings “is currently on-going, but is scheduled for completion early in
2015.”45 In February-March 2015, however, we observed no recently completed work. There
was also no visible on-going work, other than several local families watering trees planted
along the River and one person planting a slope from a ladder. No earth moving had been
undertaken in the recent past, and we saw no labor crews.
22. The lack of progress is reflected in the 2014 inventory conducted by Dr. Mende, who
determined that of the 103 watercourse crossings that require mitigation, only 28 have been
mitigated. Another 23 are classified as “mitigation in progress, 31 as “mitigation scheduled,
and 21 as “other.”46 Thus, only 27% of the watercourses identified as needing mitigation have
been adequately mitigated to Costa Rica’s own standard in four years.
39
Ibid., pp. 6, 11.
Ibid., p. 11.
41
Kondolf (2014), Appendix C.
42
Kondolf (2014), p. 35.
43
Hagans and Weaver (2014), p. 23.
44
Consejo Nacional de Vialidad (CONAVI), “Works on National Road 1856: Before and After” (Dec. 2014),
submitted as Annex 11 to the Rejoinder of Costa Rica (hereinafter “CONAVI (2014)”).
45
Colin Thorne, “Assessment of the Impact of the Construction of the Border Road in Costa Rica on the San
Juan River: Reply Report” (2015), submitted as Appendix A to the Rejoinder of Costa Rica, para. 7.20
(hereinafter “Thorne (2015)”).
46
Mende (2014), p. 29.
40
8
23. There are sites in clear need of mitigation that were not included in Dr. Mende’s
inventory at all. Figure 2 shows one example, a failed (collapsed) watercourse crossing where
a shipping container was inappropriately used in place of a proper culvert.
24. CONAVI reports having conducted mitigation at a number of sites. However, its 2014
report consists primarily of photographs with no supporting technical information regarding
the construction standards or design criteria employed.47 The same is true of before and after
photos presented by Prof. Thorne as evidence of successful mitigation. On the basis of the
information provided, the short, intermediate, and long term effectiveness of CONAVI’s
mitigation work is unknown, uncertain and cannot be predicted. In any case, that work has
been very limited.48 CONAVI reports performing work on fewer than 20 stream crossings
between 2013 and 2014.49
25. What has been accomplished at sites classified as “mitigation in progress” is in many
places very minimal, and in some cases is even inappropriate for the type of erosion or
instability occurring at the site. Figure 3 shows a site on the banks on the Río San Juan that is
47
CONAVI (2014).
Nicaragua requested design and technical information on February 24. As of the date of this statement, Costa
Rica had not provided any of the requested information. Letter from the Embassy of Nicaragua in the Hague,
(Feb. 23, 2015), submitted on Feb. 24, 2015.
49
See sites presented in CONAVI (2014).
48
9
classified as “mitigation in progress”. It appears that a silt fence or sediment dam was
installed in a stream channel some time ago, but has since failed, and that the mitigation site
has been abandoned and unmaintained since.
26. Finally, Costa Rica has chosen not to remediate some of the worst eroding sites.
These include the stream crossings at Sites 9.4 and 9.5 that have already failed and delivered
massive amounts of sediment to the River, before being rebuilt in the same manner that
caused them to fail in the first instance. The sites have been left “un-mitigated or partially
mitigated so they may continue to serve as control sites for erosion along the road.”50
Moreover, none of the mitigation measures reportedly undertaken by CODEFORSA to
control erosion along Route 1856 have occurred at these or other watercourse crossings.51
C.
Cut slopes and fill slopes have not been properly constructed or
remediated.
27. Where roads are constructed across steep hillslopes, another set of problems can arise
that, unless addressed through proper planning, design and construction, can result in severe
erosion. On steep hillslopes, the typical construction method used by Costa Rica was “cut and
fill,” whereby heavy equipment was used to excavate the hillside on the upslope side of the
50
Universidad de Costa Rica, “Second Report on Systematic Field monitoring of Erosion and Sediment Yield
along Route 1856” (Nov. 2014), submitted as Annex 4 to the Rejoinder of Costa Rica, p. 1.
51
CODEFORESA (2014) (Annex 12), pp. 18–42.
10
Road, creating a flat road surface adjacent to a now-steeper slope (the “cutslope”). The
material that is excavated was placed (bulldozed) onto the downslope side to form the outer
part of the Road (the “fill prism” or “fill slope”). Figure 4, below, illustrates a cut and fill
road built across a hillside.
28. Cutting into and removing rock and soil removes lateral support for the upslope
hillside. Subject to the positive pore pressure produced by flowing and emerging
groundwater, cut slopes can fail; sometimes by
small chunks breaking off, and sometimes in the
form of larger, deeper landslides.52
29. The stability of the fill prism on the outer
half of the road depends largely on how it is
constructed. In the case of Route 1856, the
construction techniques employed on steep slopes
and slopes next to streams and the River were
inappropriate and have left many fill slopes
composed of uncompacted, unstable soil materials
that are prone to erosion and failure. Many fill
slopes show signs of pending failure (e.g., scarps
and slumps), or have already failed. This is because
fill materials were sidecast onto steep, natural
slopes (i.e., simply pushed over the edge of the road
bench and allowed to fall down the slope).
Fillslopes created in this way are inherently
unstable, because they exist at excessively steep
slope angles, and because they consist of loose fill,
without the benefit of compaction.53 We have even
observed dead trees and other debris in the fill
prisms along Route 1856,54 which further weakens
the fill and increases the likelihood of failure as it
decomposes and creates planes of weakness within
52
Kondolf, Hagans, Weaver and Weppner (2012), p. 10.
Ibid., p. 25.
54
Ibid., p. 26.
53
11
the fill over time.
30. The stability of cut slopes also is affected by their angle, with steeper slopes usually
more prone to failure. In many locations, cut slopes were constructed with steeper angles than
specified by proper design standards.55 Road widths often appear excessive for the expected
road design standard, and because of this road cuts are higher and steeper than they would
otherwise have needed to be. As a result, road construction generated excessively large
volumes of waste materials and sidecast debris that were then pushed onto steep hillslopes
below the Road.
31. At least 201 cut slopes and fill slopes were built along the Road, stretching a total of
26.1 km.56 Due to the Road’s proximity to the Río San Juan in many areas, failure of these
slopes can entail the delivery of large volumes of sediment to the River. In 2012, it was
apparent that many of the cut slopes and fill slopes were failing or showing signs of
instability. We observed numerous overly-steep cut slopes that had failed,57 and many
fillslopes that exhibited signs of widespread settlement, failure scarps, and other evidence of
mass movement of material.58
32. Preventing and mitigating damage from instability and mass wasting at fill slopes
requires extensive remedial work. The application of geotextiles, mulch and grass seeding
that cover a slope helps to prevent surface erosion, but does little or nothing to address the
underlying instability caused by lack of compaction and poor construction techniques. To
properly remediate the slopes, the unstable fill material must be excavated and transported to
a stable disposal site. If the site allows, the road may then be re-built to proper engineering
standards.59 Many times, however, the road will need to be relocated to a less hazardous and
more stable location and alignment.
33. In 2013, Costa Rica reported that “mitigation measures [had] been undertaken to
stabilize some of the slopes,”60 and that “significant and substantial engineering works were
carried out at multiple locations along the Road between Marker II and the Rio Infiernito.”61
55
Kondolf, Hagans, Weaver and Weppner (2012), p. 25; Hagans and Weaver (2014), p. 17.
Mende (2014), p. 9.
57
Kondolf, Hagans, Weaver and Weppner (2012), p. 25.
58
Ibid.
59
Ibid.
60
Mende & Astorga (2013), pp. 29-30.
61
Colin Thorne, “Assessment of the Impact of the Construction of the Border Road in Costa Rica on the San
Juan River” (Nov. 2013), submitted as Appendix A to the Counter-Memorial of Costa Rica, para. 11.9.
56
12
However, by 2014, the situation had visibly worsened in many locations.62 This was due in
part to the fact that remedial works had largely been limited to 15 km of the Road, excluding
some of the worst-eroding and most unstable slopes. Where work had been conducted, it
often involved only installing a few culverts and covering the eroding slope with geofabric or
sheets of impermeable “saran” (plastic), rather than addressing the underlying instability.
Covering and concealing the instability does not solve the underlying causes of pending slope
failure.
34. Numerous overly-steep cut slopes and un-compacted fill slopes demonstrated high
levels of erosion and failure.63 For instance, at Site 8.1, large parts of the un-compacted
fillslope had failed and been carried downhill in debris landslides. Large gullies were present
elsewhere in the exposed, un-protected cutslope and fillslope. We estimate that a total of
approximately 4,156 m3 of sediment eroded from the cut and fill slopes at the site within the
first year after its construction.64 Likewise, Site 8.2 displayed landslide scarps on fill slopes
where uncompacted fill had failed and been carried downhill. Other areas of the fillslope
displayed gullying as a result of exposure to runoff. Above the Road, part of the overly-steep
cut slope had collapsed. We estimate the amount of sediment produced by erosion at Site 8.2
to be a minimum of approximately 3,174 m3 per year.65
35. Slope failures and severe erosion occurred in many other locations.66 We identified 34
slopes that were in such poor condition that they were potentially unsafe for vehicle traffic.67
36. Slope remediation and erosion control work along the Road has proceeded extremely
slowly. Reflecting the scale of the problem, Dr. Mende reports that 190 of the 201 slopes
where construction occurred required mitigation in December 2014, four years after
construction began. Of these, mitigation has been completed at only 25, or 13%.68 There are
62
Hagans and Weaver (2014), pp. 17, 18, 21. The worsening conditions along the road are also visible in the
Inventory of Severely Eroding Sites, Appendix A to Kondolf (2014).
63
Hagans and Weaver (2014), p. 17. Nicaragua has requested that Costa Rica provide a description of when
mitigation is scheduled to occur. As of the date of this statement, Costa Rica had not provided any of the
requested information. Letter from the Embassy of Nicaragua in the Hague, (Feb. 23, 2015), submitted on Feb.
24, 2015.
64
Hagans and Weaver (2014), pp. 18-19.
65
Ibid., pp. 21-22.
66
Kondolf (2014), Appendix A.
67
Ibid., Appendix D.
68
Mende (2014), p. 30.
13
also slopes in clear need of remediation that do not appear in Mende’s inventory and have
been left unmitigated.69
37. With respect to the 107 slopes where Dr. Mende reports that mitigation is in progress,
70
we observed no recently completed or ongoing earthmoving or other significant mitigation
work. The measures employed on the slopes were often insufficient and inappropriate for the
type of erosion displayed at the sites. For example, the measures at some sites were limited to
erosion control fabric or silt fencing that, even when properly applied, is inappropriate to
address gullying, landsliding, and slope instability. Many of the slopes appeared to have been
partially and inadequately treated several years ago and have not been touched since then. A
number of slope and channel treatments were falling apart or failing, and had not been
maintained. They were in some stage of progress at one time, but are no longer effective and
have not been worked on or maintained since. Figure 5 shows cut and fill slopes classified as
“mitigation in progress,” where mitigation techniques were improper and the measures are
failing or have already failed.
38. Based on our field observations, we expect erosion will continue or increase on many
slopes classified as “mitigation in progress,” given their present condition and the absence of
meaningful remedial work or maintenance. The same is true for the 58 slopes classified as
“mitigation scheduled,” because these slopes have received no treatment at all.71
69
In our 2015 site visit, the team observed quarries used for mining road materials that have been left
unmitigated and are visibly contributing sediment to the Río San Juan.
70
Mende (2014), p. 30.
71
Ibid. p. 30.
14
D.
Road Drainage and hydrologic connectivity is excessive.
39. Proper road design and construction should ensure that water draining from the road
surface and ditches is dispersed and properly discharged, such that erosion is minimized and
pollution to streams and wetlands is avoided or strictly minimized. Improper drainage can
both damage the road and increase the delivery of sediment to the surrounding environment.
40. Route 1856 has long lengths of bare road surfaces and cutbanks that increase surface
runoff during rainfall events, and thus erosion, because water quickly runs off the compacted
road surface and bare soil areas. In many places, this runoff drains to inboard ditches, which
collect and discharge the concentrated runoff onto adjacent hillslopes, or into nearby stream
channels. When these concentrated flows are discharged onto adjacent fills and native slopes,
severe gullying may result. When they flow into the 129 stream crossings along the Road,
they carry and deliver sediment that has been eroded from the Road and all its adjacent bare
soil areas.
15
41. Lack of proper surface drainage has caused gullying of fill slopes and natural slopes at
a number of locations along the Road. These were apparent in numerous locations in 2012.72
In the absence of meaningful steps taken to address road drainage, gullying due to the
discharge of runoff onto fill slopes had worsened by 2014. There were widespread and
obvious gullies caused by concentrated runoff at both Sites 8.1 and 8.2,73 as well as at other
slopes along the Road.74 We also observed numerous examples of active gullying in our 2015
site visit. Where the Road crosses steep slopes along the banks of the River, the sediment
generated by gully erosion is efficiently delivered downslope to the River.
42. One of the most insidious and least obvious impacts that occur along poorly planned
and constructed roads is the “hydrologic connectivity” between the Road and nearby streams.
This occurs where erosion of the road bed, the cutbank and the ditch is carried away in
surface runoff and discharged directly into nearby streams, and then to the River. Our
observations suggest that the connectivity is at least 60%, a figure Costa Rica’s experts
accept.75 That is, 60% of the Road's surface and ditch runoff is discharged directly to streams
that drain to the Río San Juan. Figure 6 shows sediment being directed into a stream crossing
culvert inlet that discharges into the River.
43. Some mitigation measures employed by Costa Rica to address road surface drainage
are, in fact, increasing the delivery of sediment to the Río San Juan. A common technique
employed by CONAVI is the construction of concrete-lined ditches like that shown in Figure
72
Kondolf, Hagans, Weaver and Weppner (2012), pp. 42-44.
Hagans and Weaver (2014), pp. 18, 21.
74
See, e.g., Kondolf (2014), p. 41, Figure 26.
75
Instituto Costarricense de Electricidad (ICE), “Second Report on Hydrology and Sediments for the Costa
Rican River Basins draining to the San Juan River” (Dec. 2014), p. 49.
73
16
6.76 This has been rejected under modern construction and design standards, as it greatly
increases the connectedness between the Road and the Río San Juan by increasing the
efficiency with which the ditches carry eroded sediment from the road surface and from
eroding cut banks to culvert inlets at watercourse crossings. The form and magnitude of
sediment pollution from Route 1856 to the Río San Juan due to improper drainage systems is
almost completely preventable and can be almost completely eliminated by implementing
road surface drainage systems designed to disperse surface runoff instead of collecting and
discharging it to streams and to the Río San Juan. It is relatively simple and inexpensive to do
so by shaping the road to disperse road surface runoff (e.g., outsloping) rather than collecting
it, and by installing numerous road drainage structures (e.g., ditch drain culverts and rolling
dips) that discharge surface runoff far away from streams.77
E.
Proper erosion control measures have not been implemented.
44. Proper planning, design, and construction of roads should seek to minimize the impact
of sediment eroded from the surface of the road and from other bare soil areas to the
surrounding environment. To control this erosion, it is standard to apply a covering of mulch,
grass, and/or geotextiles and erosion control fabrics to the exposed faces of cut slopes, fill
slopes, and other areas disturbed by construction.78
45. Very few such measures were applied during or immediately after construction of the
Road. In 2012, most of the observed slopes lacked any cover whatsoever, and where
geotextiles had been installed, they had largely failed.79 A year later, Costa Rica’s expert
reports suggested that the problem of surface erosion from the Road was being addressed. For
example, the UCR reported that “most slopes and fills in the study area have been protected
with geotextile and been subject to re-vegetation or (where possible) re-forestation. . . .”80
46. However, the erosion control measures that were completed between 2012 and 2014
were widely dispersed and limited in extent. The work done by CONAVI, which presented
photos of a handful of sites with newly-installed geotextiles, was limited to 15 km of the
76
E.g., CONAVI (2014), p. 219; Mende (2014), pp. 118, 124, 210.
Pacific Watershed Associates, “Handbook for Forest, Ranch, & Rural Roads” (2015).
78
Kondolf, Hagans, Weaver and Weppner (2012), pp. 5–6. As discussed above, these steps are not a substitute
of other actions necessary to correct problems in watercourse crossing design, slope stability, or drainage. See
supra para 37.
79
Kondolf, Hagans, Weaver and Weppner (2012), pp. 6, 52.
80
University of Costa Rica Centre for Research in Sustainable Development, Department of Civil Engineering,
“Report on Systematic Field monitoring of Erosion and Sediment Yield along Route 1856” (Sept. 2013),
submitted as Annex 1 to the Counter-Memorial of Costa Rica, pp. 1-2.
77
17
Road, and ignored many of the worst-eroding sites.81 In 2014, most of the eroding slopes and
watercourse crossings remained completely exposed, and in many places where erosion
control measures had been installed, they had failed.82 The five severely eroding sites
reviewed in our 2014 report had received limited and inadequate slope stabilization and
erosion control measures.
47. Recent work to control surface erosion along the road alignment has been limited in
scope or will be largely ineffective. CODEFORESA has planted a large number of trees at
sites near the Road,83 but most have been planted on flat or very gently sloping ground along
the River that was undisturbed by road construction. Moreover, most trees were planted on
ground that was already covered by grass and other groundcover.84 That is, the planted areas
were not generating erosion that required remediation. Further, trees, especially when they
are young, are less effective at intercepting surface runoff from upslope areas than surfaces
covered with grass. For this reason, grass and other rapidly growing groundcover species, not
trees, are normally planted for immediate sediment control.
48. Grass plantings, on the other hand, have been minimal. CODEFORSA (2014) has
planted Vetiver grass plugs (a non-native species used for erosion control) on only 12 bare,
eroding cut slopes along the Road, out of over 200 cut slopes identified in Mende (2014).85
Even in those locations, its ultimate success is questionable. CODEFORESA found that the
low soil nutrient content of the cuts required at least four applications of foliar fertilizer
treatments to keep the plants alive and growing.
49. Our site visit in February-March 2015 confirmed that many slopes, including many of
the worst-eroding sites, remain largely exposed, with ineffective erosion control materials
present. 86 Erosion at these sites is active and ongoing, and the connectivity of many of them
to the Río San Juan continues to result in preventable, persistent sediment delivery to the
River.
81
Consejo Nacional de Vialidad (CONAVI), “Program for the Consolidation and Continued Improvement of
Route No. 1856” (Oct. 25, 2013), submitted as Annex 8 to the Counter-Memorial of Costa Rica, p. 3.
82
Kondolf (2014), pp. 39-40.
83
Comisión de Desarrollo Forestal de San Carlos (CODEFORSA), “Consulting Services for the Development
and Implementation of an Environmental Plan for the Juan Rafael Mora Porras Border Road” (Nov. 2014),
submitted as Annex 13 to the Rejoinder of Costa Rica (hereinafter “CODEFORSA (2014) (Annex 13)”).
84
CODEFORSA (2014) (Annex 13), page 8, passim.
85
Mende (2014), p. 30.
86
See ibid., pp. 576-578.
18
III.
Additional measures are necessary for proper remediation of Route 1856.
50. Four years after construction of the Road, widespread and effective mitigation is not
apparent. We observed no indication of ongoing or recent earthmoving in February-March
2015. The majority of watercourse crossings, cut slopes and fill slopes remain unstable,
exhibit significant visible erosion, and have not been treated or fully treated with appropriate
stabilization and erosion control measures. The lack of progress is striking, as is the amount
of work that remains to be done. Many sections of the Road appear abandoned and do not
appear to have been touched for several years.87 Although they may be abandoned, some
sections continue to erode and remain hydrologically connected to local streams.
51. What little has been done to address surface erosion and road drainage is being made
ineffective by allowing recreational off-road vehicles to drive on the Road, including during
the wet season, when road damage is greatest and sediment pollution is most likely to result.
In February-March 2015, we observed dozens of motorcycles, ATVs, and SUVs “mudrunning” on Route 1856. Many videos are available online that show such vehicles
destroying the road surface and any erosion control measures that might have been installed.
Sediment delivery to the Río San Juan is greatly increased by this recreational activity.
52. The inadequate planning and design, poor construction, and largely still absent
remediation of the Road and its associated access roads has resulted in the delivery of
116,000-150,000 m3 of eroded sediment to the Río San Juan each year.88 The lower estimate
offered by Costa Rica’s experts, while an acknowledgment that substantial amounts of
sediment are entering the River, is a major underestimate of the amount. It is based on an
inaccurate and ill-conceived erosion rate which is then applied to Dr. Mende’s 2014
Inventory that underrepresents the number of sites delivering eroded sediment to the River.89
Consequently, Dr. Kondolf’s estimate presents the more accurate picture of the impacts to the
Río San Juan.
53. To minimize further impacts to the Río San Juan, the following steps must be taken:
87
This was not only visible during our team’s 2015 field trip, but is also apparent in photographs presented in
Mende’s inventory. See, e.g., pp. 428, 440, 446, 454, 460, 466, 482, 498, 508, 588, 592, 600, 606, 624, and 646.
88
Kondolf (2014), p. 62.
89
See discussion in supra footnote 34 (describing the lack of foundation for the UCR’s criticism of our
calculated erosion rates); see also the discussion at supra paras. 23, 36 (describing sites on ongoing erosion
omitted from Mende (2014)). The errors in Costa Rica’s erosion estimate are discussed in greater detail in Dr.
Kondolf’s written statement.
19
A.
Assess the relocation of portions of the Road built on steep, unstable and
erodible terrain and in close proximity to the Río San Juan, to a more inland,
stable route, as recommended in our 2014 report, and in the 2013 EDA and its
2015 follow up.90
B.
Construct or re-construct all deficient watercourse crossings to accommodate
the 100-year peak storm flow using sound geologic, engineering and
compaction standards, and employing critically important sediment control
techniques, as recommended in our 2014 report.91
C.
Reduce the rate and frequency of road fill failure slumps, debris slides and
debris flows by excavating and removing unstable and potentially unstable fill
materials, especially where the Road crosses steeper hill slopes, and in all
locations where failed or eroded soil materials could be delivered to the Río
San Juan or to other streams, as recommended in our 2014 report.92
D.
Reduce road surface erosion and sediment delivery by improving dispersion of
concentrated road surface runoff and increasing the number and frequency of
road drainage structures, as recommended in our 2014 report,93 by surfacing
the few remaining hydrologically connected road reaches that will then
remain, and by eliminating widespread recreation use of the Road during wet
weather periods.
E.
Reduce and control surface erosion on bare soil areas by remediating erosion
problems on cut slopes and fill slopes, and by applying methods of surface
erosion control on all hydrologically connected bare soil areas, as
recommended in our 2014 report.94
54. These steps should be taken as soon as possible, not only to minimize the amount of
sediment currently being delivered to the Río San Juan, but also to prepare the Road for
future intense rains and storms that could cause even greater erosion.
_______________________________________
William E. Weaver
90
Date: 15 March 2015
CCR (2015), p. 57; Hagans and Weaver (2014), Figure 1; CCR (2013), p. 147.
Hagans and Weaver (2014), pp. 23-24.
92
Ibid., p. 25.
93
Ibid., pp. 25-26.
94
Ibid., pp. 26-27.
91
20
APPENDIX A
Photograph taken from a helicopter on 01 March 2015 at approximately Rkm 18-19