Combined Sewer System Long Term Control Plan - DC Water

Selection of Draft LTCP
9.6.5 Non-Monetary Factors
With the exception of Northeast Boundary Flooding, the same non-monetary factors that were
evaluated for the Anacostia River were assessed for Rock Creek
Table 9-16 summarizes the non-monetary evaluations for each alternative.
Table 9-16
Non-Monetary Evaluation Factors: Rock Creek River Final Alternatives
No.
Alternative
A-1 Piney Branch Storage Tunnel; Separate
CSO 059; Reconstruct Regulators for
CSO 031, 033, 036 and 057; Relieve
RCMI to proposed Potomac Tunnel
Public
Acceptance
Ability to
Implement
Reliability
Ease of
Operation
Ease of
Maintenance
Ability to
Upgrade
Good Excellent Excellent Excellent Good Moderate
A-2 Same as A-1, but with LID-R Good Uncertain Uncertain Excellent Uncertain Moderate
B-1
Same as A-1, but with Relief Sewer for
Rock Creek Main Interceptor
Moderate Good Excellent Excellent Good Moderate
B-2 Same as B-2, but with LID-R Good Uncertain Uncertain Excellent Uncertain Moderate
Principle points are described below:
Public Acceptance – Rock Creek Parkway and Piney Branch Parkway are major commuter
thoroughfares. In addition, the walking and biking trails are heavily used throughout the year.
Disruption caused by construction was an important issue for the public. The storage tunnel at
Piney Branch and the regulator reconstructions will minimize disruption. Alternative B-1 entails
constructing a relief sewer parallel to the Rock Creek Main Interceptor. This has the potential to
cause significant disruption and it would have moderate public acceptance. For both the relief a
sewer and the storage tunnel options, issues associated with right of way, construction access,
disruption, and environmental impact would need to be addressed with the National Park Service.
The public also expressed a strong preference for LID-R and inclusion of this is responsive to
public comments.
Ability to implement – Tunnels and regulators have been constructed by WASA and other CSO
communities and are practical. Because of the institutional issues associated with LID-R, the
ability to implement this option has been classified as uncertain.
Reliability – Tunnels for storage can be designed to fill by gravity and their dewatering can be
automated. The Piney Branch storage tunnel can dewater by gravity, eliminating the need for a
pump station making it more reliable. Because the application of LID-R on a large scale for CSO
control has not been attempted before, the long term reliability of these types of controls is
unknown and has been assessed as uncertain.
\\Gh-wash\ENG 1160\LTCP\LTCP Final\Sec 9.doc 9-42 FINAL - July 2002